ADC08D1020
www.ti.com
SNAS372D – NOVEMBER 2007 – REVISED MARCH 2013
ADC08D1020 Low Power, 8-Bit, Dual 1.0 GSPS or Single 2.0 GSPS A/D Converter
Check for Samples: ADC08D1020
FEATURES
DESCRIPTION
•
•
•
•
The ADC08D1020 is a dual, low power, high
performance, CMOS analog-to-digital converter that
builds upon the ADC08D1000 platform. The
ADC08D1020 digitizes signals to 8 bits of resolution
at sample rates up to 1.3 GSPS. It has expanded
features compared to the ADC08D1000, which
include a test pattern output for system debug, a
clock phase adjust, and selectable output
demultiplexer modes. Consuming a typical 1.6 Watts
in non-demultiplex mode at 1 GSPS from a single 1.9
Volt supply, this device is ensured to have no missing
codes over the full operating temperature range. The
unique folding and interpolating architecture, the fully
differential comparator design, the innovative design
of the internal sample-and-hold amplifier and the
calibration schemes enable a very flat response of all
dynamic parameters beyond Nyquist, producing a
high 7.4 Effective Number of Bits (ENOB) with a 498
MHz input signal and a 1 GHz sample rate while
providing a 10−18 Code Error Rate (C.E.R.) Output
formatting is offset binary and the Low Voltage
Differential Signaling (LVDS) digital outputs are
compatible with IEEE 1596.3-1996, with the
exception of an adjustable common mode voltage
between 0.8V and 1.2V.
1
2
•
•
•
•
•
Single +1.9V ±0.1V Operation
Interleave Mode for 2x Sample Rate
Multiple ADC Synchronization Capability
Adjustment of Input Full-Scale Range, Offset,
and Clock Phase Adjust
Choice of SDR or DDR Output Clocking
1:1 or 1:2 Selectable Output Demux
Second DCLK Output
Duty Cycle Corrected Sample Clock
Test Pattern
APPLICATIONS
•
•
•
•
•
Direct RF Down Conversion
Digital Oscilloscopes
Satellite Set-top Boxes
Communications Systems
Test Instrumentation
KEY SPECIFICATIONS
•
•
•
•
•
•
Resolution: 8 Bits
Max Conversion Rate: 1 GSPS (min)
Code Error Rate: 10−18 (typ)
ENOB @ 498 MHz Input (Normal Mode): 7.4
Bits (typ)
DNL: ±0.15 LSB (typ)
Power Consumption
– Operating in Non-Demux Output: 1.6 W
(typ)
– Operating in 1:2 Demux Output: 1.7 W (typ)
– Power Down Mode: 3.5 mW (typ)
Each converter has a selectable output demultiplexer
which feeds two LVDS buses. If the 1:2
demultiplexed mode is selected, the output data rate
is reduced to half the input sample rate on each bus.
When non-demultiplexed mode is selected, that
output data rate on channels DI and DQ are at the
same rate as the input sample clock. The two
converters can be interleaved and used as a single 2
GSPS ADC.
The converter typically consumes less than 3.5 mW
in the Power Down Mode and is available in a leaded
or lead-free 128-lead, thermally enhanced, exposed
pad, HLQFP and operates over the Industrial (-40°C
≤ TA ≤ +85°C) temperature range.
1
2
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
All trademarks are the property of their respective owners.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2007–2013, Texas Instruments Incorporated
ADC08D1020
SNAS372D – NOVEMBER 2007 – REVISED MARCH 2013
www.ti.com
Block Diagram
VINI+
+
VINI-
-
S/H
8-BIT
8
Selectable
DEMUX
ADC1
DI
LATCH
DId
INPUT
Data Bus Output
16 LVDS Pairs
MUX
VINQ+
+
VINQ-
-
S/H
8-BIT
ADC2
8
DQ
Selectable
DEMUX
DQd
VREF
VBG
CLK+
2
Output
Clock
Generator
CLK/2
CLKDEMUX
Control
Inputs
Serial
Interface
2
Data Bus Output
16 LVDS Pairs
LATCH
Control
Logic
DCLK+
DCLK-
OR/DCLK2
CalRun
3
Submit Documentation Feedback
Copyright © 2007–2013, Texas Instruments Incorporated
Product Folder Links: ADC08D1020
ADC08D1020
www.ti.com
SNAS372D – NOVEMBER 2007 – REVISED MARCH 2013
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
ADC08D1020
Exposed pad bottom side.
(See Note below.)
96
95
94
93
92
91
90
89
88
87
86
85
84
83
82
81
80
79
78
77
76
75
74
73
72
71
70
69
68
67
66
65
DI2+
DI2DI3+
DI3DI4+
DI4DI5+
DI5VDR
DR GND
DI6+
DI6DI7+
DI7DCLK+
DCLKOR-/DCLK2OR+/DCLK2+
DQ7DQ7+
DQ6DQ6+
DR GND
VDR
DQ5DQ5+
DQ4DQ4+
DQ3DQ3+
DQ2DQ2+
VA
Tdiode_p
Tdiode_n
DQd0+
DQd0DQd1+
DQd1VDR
ECE
DR GND
DQd2+
DQd2DQd3+
DQd3DQd4+
DQd4DQd5+
DQd5VDR
DRST_SEL
DR GND
DQd6+
DQd6DQd7+
DQd7DQ0+
DQ0DQ1+
DQ1VDR
NC
DR GND
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
GND
VA
OutV/SCLK
OutEdge/DDR/SDATA
VA
GND
VCMO
VA
GND
VINIVINI+
GND
VA
FSR/ALT_ECE/DCLK_RSTDCLK_RST/DCLK_RST+
VA
VA
CLK+
CLKVA
GND
VINQ+
VINQGND
VA
PD
GND
VA
PDQ
CAL
VBG
REXT
128
127
126
125
124
123
122
121
120
119
118
117
116
115
114
113
112
111
110
109
108
107
106
105
104
103
102
101
100
99
98
97
VA
CalDly/DES/SCS
CalRun
DId0+
DId0DId1+
DId1VDR
NC
DR GND
DId2+
DId2DId3+
DId3DId4+
DId4DId5+
DId5VDR
NC
DR GND
DId6+
DId6DId7+
DId7DI0+
DI0DI1+
DI1VDR
NC
DR GND
Pin Configuration
NOTE
The exposed pad on the bottom of the package must be soldered to a ground plane to
ensure rated performance.
Submit Documentation Feedback
Copyright © 2007–2013, Texas Instruments Incorporated
Product Folder Links: ADC08D1020
3
ADC08D1020
SNAS372D – NOVEMBER 2007 – REVISED MARCH 2013
www.ti.com
Table 1. PIN DESCRIPTIONS AND EQUIVALENT CIRCUITS
Pin Functions
Pin No.
Symbol
Equivalent Circuit
Description
Output Voltage Amplitude and Serial Interface Clock. Tie this
pin high for normal differential DCLK and data amplitude.
Ground this pin for a reduced differential output amplitude
and reduced power consumption. See The LVDS Outputs.
When the extended control mode is enabled, this pin
functions as the SCLK input which clocks in the serial data.
See NORMAL/EXTENDED CONTROL for details on the
extended control mode. See THE SERIAL INTERFACE for
description of the serial interface.
VA
3
OutV / SCLK
29
PDQ
50k
Power Down Pins. A logic high on the PD pin puts the entire
device into the Power Down Mode.
GND
VA
50k
200k
4
OutEdge / DDR /
SDATA
50k
DDR
8 pF
GND
SDATA
DCLK Edge Select, Double Data Rate Enable and Serial Data
Input. This input sets the output edge of DCLK+ at which the
output data transitions. (See OutEdge and Demultiplex
Control Setting). When this pin is floating or connected to 1/2
the supply voltage, DDR clocking is enabled. When the
extended control mode is enabled, this pin functions as the
SDATA input. See NORMAL/EXTENDED CONTROL for
details on the extended control mode. See THE SERIAL
INTERFACE for description of the serial interface.
VA
15
DCLK_RST /
DCLK_RST+
26
PD
DCLK Reset. When single-ended DCLK_RST is selected by
floating or setting pin 52 logic high, a positive pulse on this
pin is used to reset and synchronize the DCLK outputs of
multiple converters. See MULTIPLE ADC
SYNCHRONIZATION for detailed description. When
differential DCLK_RST is selected by setting pin 52 logic low,
this pin receives the positive polarity of a differential pulse
signal used to reset and synchronize the DCLK outputs of
multiple converters.
VA
A logic high on the PDQ pin puts only the "Q" ADC into the
Power Down mode.
CAL
Calibration Cycle Initiate. A minimum 1280 input clock cycles
logic low followed by a minimum of 1280 input clock cycles
high on this pin initiates the calibration sequence. See
Calibration for an overview of calibration and On-Command
Calibration for a description of on-command calibration.
FSR/ALT_ECE/
DCLK_RST-
Full Scale Range Select, Alternate Extended Control Enable
and DCLK_RST-. This pin has three functions. It can
conditionally control the ADC full-scale voltage, enable the
extended control mode, or become the negative polarity
signal of a differential pair in differential DCLK_RST mode. If
pin 52 and pin 41 are floating or at logic high, this pin can be
used to set the full-scale-range or can be used as an
alternate extended control enable pin . When used as the
FSR pin, a logic low on this pin sets the full-scale differential
input range to a reduced VIN input level. A logic high on this
pin sets the full-scale differential input range to a higher VIN
input level. See Converter Electrical Characteristics. To
enable the extended control mode, whereby the serial
interface and control registers are employed, allow this pin to
float or connect it to a voltage equal to VA/2. See
NORMAL/EXTENDED CONTROL for information on the
extended control mode. Note that pin 41 overrides the
extended control enable of this pin. When pin 52 is held at
logic low, this pin acts as the DCLK_RST- pin. When in
differential DCLK_RST mode, there is no pin-controlled FSR
and the full-scale-range is defaulted to the higher VIN input
level.
GND
30
VA
14
50k
50k
GND
4
200k
8 pF
Submit Documentation Feedback
Copyright © 2007–2013, Texas Instruments Incorporated
Product Folder Links: ADC08D1020
ADC08D1020
www.ti.com
SNAS372D – NOVEMBER 2007 – REVISED MARCH 2013
Table 1. PIN DESCRIPTIONS AND EQUIVALENT CIRCUITS (continued)
Pin Functions
Pin No.
Symbol
Equivalent Circuit
Description
Calibration Delay, Dual Edge Sampling and Serial Interface
Chip Select. With a logic high or low on pin 14, this pin
functions as Calibration Delay and sets the number of input
clock cycles after power up before calibration begins (See
Calibration). With pin 14 floating, this pin acts as the enable
pin for the serial interface input and the CalDly value
becomes "0" (short delay with no provision for a long powerup calibration delay). When this pin is floating or connected to
a voltage equal to VA/2, DES (Dual Edge Sampling) mode is
selected where the "I" input is sampled at twice the input
clock rate and the "Q" input is ignored. See Dual-Edge
Sampling.
VA
50k
127
CalDly / DES /
SCS
50k
GND
VA
18
19
CLK+
CLK−
50k
AGND
100
VA
VBIAS
50k
LVDS Clock input pins for the ADC. The differential clock
signal must be a.c. coupled to these pins. The input signal is
sampled on the falling edge of CLK+. See Acquiring the Input
for a description of acquiring the input and THE CLOCK
INPUTS for an overview of the clock inputs.
AGND
VA
50k
11
10
22
23
VINI+
VINI−
VINQ+
VINQ−
AGND
VCMO
100
Control from VCMO
VA
50k
Analog signal inputs to the ADC. The differential full-scale
input range of this input is programmable using the FSR pin
14 in normal mode and the Input Full-Scale Voltage Adjust
register in the extended control mode. Refer to the VIN
specification in the Converter Electrical Characteristics for the
full-scale input range in the normal mode. Refer to
REGISTER DESCRIPTION for the full-scale input range in
the extended control mode.
AGND
VA
VCMO
7
200k
VCMO
8 pF
Enable AC
Coupling
Common Mode Voltage. This pin is the common mode output
in d.c. coupling mode and also serves as the a.c. coupling
mode select pin. When d.c. coupling is used, the voltage
output at this pin is required to be the common mode input
voltage at VIN+ and VIN− when d.c. coupling is used. This pin
should be grounded when a.c. coupling is used at the analog
inputs. This pin is capable of sourcing or sinking 100 μA. See
THE ANALOG INPUT.
GND
Submit Documentation Feedback
Copyright © 2007–2013, Texas Instruments Incorporated
Product Folder Links: ADC08D1020
5
ADC08D1020
SNAS372D – NOVEMBER 2007 – REVISED MARCH 2013
www.ti.com
Table 1. PIN DESCRIPTIONS AND EQUIVALENT CIRCUITS (continued)
Pin Functions
Pin No.
Symbol
31
VBG
126
CalRun
Equivalent Circuit
Description
Bandgap output voltage capable of 100 μA source/sink and
can drive a load up to 80 pF.
VA
Calibration Running indication. This pin is at a logic high
when calibration is running.
GND
VA
32
External bias resistor connection. Nominal value is 3.3 kΩ
(±0.1%) to ground. See Calibration.
V
REXT
GND
Temperature Diode Positive (Anode) and Negative (Cathode).
These pins may be used for die temperature measurements,
however no specified accuracy is implied or ensured. Noise
coupling from adjacent output data signals has been shown
to affect temperature measurements using this feature. See
Thermal Management.
Tdiode_P
34
35
Tdiode_P
Tdiode_N
Tdiode_N
VA
FS (PIN 14)
10k
41
ECE
Extended Control Enable. This pin always enables and
disables Extended Control Enable. When this pin is set logic
high, the extended control mode is inactive and all control of
the device must be through control pins only . When it is set
logic low, the extended control mode is active. This pin
overrides the Extended Control Enable signal set using pin
14.
GND
VA
10k
52
DRST_SEL
GND
6
DCLK_RST select. This pin selects whether the DCLK is
reset using a single-ended or differential signal. When this pin
is floating or logic high, the DCLK_RST operation is singleended and pin 14 functions as FSR/ALT_ECE. When this pin
is logic low, the DCLK_RST operation becomes differential
with functionality on pin 15 (DCLK_RST+) and pin 14
(DCLK_RST-). When in differential DCLK_RST mode, there
is no pin-controlled FSR and the full-scale-range is defaulted
to the higher VIN input level. When pin 41 is set logic low, the
extended control mode is active and the Full-Scale Voltage
Adjust registers can be programmed.
Submit Documentation Feedback
Copyright © 2007–2013, Texas Instruments Incorporated
Product Folder Links: ADC08D1020
ADC08D1020
www.ti.com
SNAS372D – NOVEMBER 2007 – REVISED MARCH 2013
Table 1. PIN DESCRIPTIONS AND EQUIVALENT CIRCUITS (continued)
Pin Functions
Pin No.
Symbol
83 / 78
84 / 77
85 / 76
86 / 75
89 / 72
90 / 71
91 / 70
92 / 69
93 / 68
94 / 67
95 / 66
96 / 65
100 / 61
101 / 60
102 / 59
103 / 58
DI7− / DQ7−
DI7+ / DQ7+
DI6− / DQ6−
DI6+ / DQ6+
DI5− / DQ5−
DI5+ / DQ5+
DI4− / DQ4−
DI4+ / DQ4+
DI3− / DQ3−
DI3+ / DQ3+
DI2− / DQ2−
DI2+ / DQ2+
DI1− / DQ1−
DI1+ / DQ1+
DI0− / DQ0−
DI0+ / DQ0+
104 / 57
105 / 56
106 / 55
107 / 54
111 / 50
112 / 49
113 / 48
114 / 47
115 / 46
116 / 45
117 / 44
118 / 43
122 / 39
123 / 38
124 / 37
125 / 36
DId7− / DQd7−
DId7+ / DQd7+
DId6− / DQd6−
DId6+ / DQd6+
DId5− / DQd5−
DId5+ / DQd5+
DId4− / DQd4−
DId4+ / DQd4+
DId3− / DQd3−
DId3+ / DQd3+
DId2− / DQd2−
DId2+ / DQd2+
DId1− / DQd1−
DId1+ / DQd1+
DId0− / DQd0−
DId0+ / DQd0+
79
80
Equivalent Circuit
Description
I and Q channel LVDS Data Outputs that are not delayed in
the output demultiplexer. Compared with the DId and DQd
outputs, these outputs represent the later time samples.
These outputs should always be terminated with a 100 Ω
differential resistor.
VDR
-
+
+
-
OR+/DCLK2+
OR-/DCLK2-
DR GND
I and Q channel LVDS Data Outputs that are delayed by one
CLK cycle in the output demultiplexer. Compared with the
DI/DQ outputs, these outputs represent the earlier time
sample. These outputs should be terminated with a 100 Ω
differential resistor when enabled. In non-demultiplexed
mode, these outputs are disabled and are high impedance
when enabled. When disabled, these outputs must be left
floating.
Out Of Range output. A differential high at these pins
indicates that the differential input is out of range (outside the
range ±VIN/2 as programmed by the FSR pin in non-extended
control mode or the Input Full-Scale Voltage Adjust register
setting in the extended control mode). DCLK2 is the exact
mirror of DCLK and should output the same signal at the
same rate.
Data Clock. Differential Clock outputs used to latch the output
data. Delayed and non-delayed data outputs are supplied
synchronous to this signal. In 1:2 demultiplexed mode, this
signal is at 1/2 the input clock rate in SDR mode and at 1/4
the input clock rate in the DDR mode. By default, the DCLK
outputs are not active during the termination resistor trim
section of the calibration cycle. If a system requires DCLK to
run continuously during a calibration cycle, the termination
resistor trim portion of the cycle can be disabled by setting
the Resistor Trim Disable (RTD) bit to logic high in the
Extended Configuration Register (address 9h). This disables
all subsequent termination resistor trims after the initial trim
which occurs during the power on calibration. Therefore, this
output is not recommended as a system clock unless the
resistor trim is disabled. When the device is in the nondemultiplexed mode, DCLK can only be in DDR mode and
the signal is at 1/2 the input clock rate.
82
81
DCLK+
DCLK-
2, 5, 8, 13,
16, 17, 20,
25, 28, 33,
128
VA
Analog power supply pins. Bypass these pins to ground.
40, 51, 62,
73, 88, 99,
110, 121
VDR
Output Driver power supply pins. Bypass these pins to DR
GND.
1, 6, 9, 12,
21, 24, 27
GND
Ground return for VA.
Submit Documentation Feedback
Copyright © 2007–2013, Texas Instruments Incorporated
Product Folder Links: ADC08D1020
7
ADC08D1020
SNAS372D – NOVEMBER 2007 – REVISED MARCH 2013
www.ti.com
Table 1. PIN DESCRIPTIONS AND EQUIVALENT CIRCUITS (continued)
Pin Functions
Pin No.
Symbol
42, 53, 64,
74, 87, 97,
108, 119
DR GND
63, 98, 109,
120
NC
Equivalent Circuit
Description
Ground return for VDR.
No Connection. Make no connection to these pins.
These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
8
Submit Documentation Feedback
Copyright © 2007–2013, Texas Instruments Incorporated
Product Folder Links: ADC08D1020
ADC08D1020
www.ti.com
SNAS372D – NOVEMBER 2007 – REVISED MARCH 2013
Absolute Maximum Ratings (1) (2) (3)
Supply Voltage (VA, VDR)
2.2V
Supply Difference
VDR - VA
0V to 100 mV
Voltage on Any Input Pin
(Except VIN+, VIN- )
−0.15V to (VA +0.15V)
Voltage on VIN+, VIN(Maintaining Common Mode)
-0.15 to 2.5V
Ground Difference
|GND - DR GND|
0V to 100 mV
Input Current at Any Pin (4)
±25 mA
Package Input Current (4)
±50 mA
Power Dissipation at TA ≤ 85°C
ESD Susceptibility (5)
2.3 W
Human Body Model
2500V
Machine Model
250V
Charged Device Model
(1)
(2)
(3)
(4)
(5)
1000V
−65°C to +150°C
Storage Temperature
All voltages are measured with respect to GND = DR GND = 0V, unless otherwise specified.
Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. There is no specification of operation at the
Absolute Maximum Ratings. Operating Ratings indicate conditions for which the device is functional, but do not ensure specific
performance limits. For ensured specifications and test conditions, see the Electrical Characteristics. The ensured specifications apply
only for the test conditions listed. Some performance characteristics may degrade when the device is not operated under the listed test
conditions.
If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/ Distributors for availability and
specifications
When the input voltage at any pin exceeds the power supply limits (that is, less than GND or greater than VA), the current at that pin
should be limited to 25 mA. The 50 mA maximum package input current rating limits the number of pins that can safely exceed the
power supplies with an input current of 25 mA to two. This limit is not placed upon the power, ground and digital output pins.
Human body model is 100 pF capacitor discharged through a 1.5 kΩ resistor. Machine model is 220 pF discharged through ZERO
Ohms. Charged device model simulates a pin slowly acquiring charge (such as from a device sliding down the feeder in an automated
assembler) then rapidly being discharged.
Submit Documentation Feedback
Copyright © 2007–2013, Texas Instruments Incorporated
Product Folder Links: ADC08D1020
9
ADC08D1020
SNAS372D – NOVEMBER 2007 – REVISED MARCH 2013
www.ti.com
Operating Ratings (1) (2)
−40°C ≤ TA ≤ +85°C
Ambient Temperature Range
Supply Voltage (VA)
+1.8V to +2.0V
Driver Supply Voltage (VDR)
+1.8V to VA
Common Mode Input Voltage
VCMO ± 50 mV
0V to 2.15V
(100% duty cycle)
0V to 2.5V
(10% duty cycle)
VIN+, VIN− Voltage Range (Maintaining Common Mode)
Ground Difference
(|GND − DR GND|)
0V
CLK Pins Voltage Range
0V to VA
Differential CLK Amplitude
(1)
(2)
0.4VP-P to 2.0VP-P
Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. There is no specification of operation at the
Absolute Maximum Ratings. Operating Ratings indicate conditions for which the device is functional, but do not ensure specific
performance limits. For ensured specifications and test conditions, see the Electrical Characteristics. The ensured specifications apply
only for the test conditions listed. Some performance characteristics may degrade when the device is not operated under the listed test
conditions.
All voltages are measured with respect to GND = DR GND = 0V, unless otherwise specified.
Package Thermal Resistance (1)
(1)
10
Package
θJA
θJC
Top of Package
θJC
Thermal Pad
128-Lead,
HLQFP
26°C / W
10°C / W
2.8°C / W
Soldering process must comply with Reflow Temperature Profile specifications. Refer to www.ti.com/packaging.
Submit Documentation Feedback
Copyright © 2007–2013, Texas Instruments Incorporated
Product Folder Links: ADC08D1020
ADC08D1020
www.ti.com
SNAS372D – NOVEMBER 2007 – REVISED MARCH 2013
Converter Electrical Characteristics
The following specifications apply after calibration for VA = VDR = 1.9V; OutV = 1.9V; VIN FSR (a.c. coupled) = differential 870
mVP-P; CL = 10 pF; Differential, a.c. coupled Sine Wave Input Clock, fCLK = 1 GHz at 0.5 VP-P with 50% duty cycle; VBG =
Floating; Non-Extended Control Mode; SDR Mode; REXT = 3300 Ω ±0.1%; Analog Signal Source Impedance = 100 Ω
Differential; 1:2 Output Demultiplex; Duty Cycle Stabilizer on. Boldface limits apply for TA = TMIN to TMAX. All other limits TA
= 25°C, unless otherwise noted. (1) (2)
Symbol
Parameter
Conditions
Typical
Limits
(3)
Units
(Limits)
(3)
STATIC CONVERTER CHARACTERISTICS
INL
Integral Non-Linearity
(Best fit)
DC Coupled, 1 MHz Sine Wave
Overanged
±0.3
±0.9
LSB (max)
DNL
Differential Non-Linearity
DC Coupled, 1 MHz Sine Wave
Overanged
±0.15
±0.6
LSB (max)
Resolution with No Missing Codes
8
−0.45
VOFF
Offset Error
VOFF_ADJ
Input Offset Adjustment Range
Extended Control Mode
PFSE
Positive Full-Scale Error
See (4)
NFSE
Negative Full-Scale Error
See (4)
FS_ADJ
Full-Scale Adjustment Range
Extended Control Mode
±45
±20
Bits
LSB (min)
LSB (max)
mV
±25
mV (max)
±25
mV (max)
±15
%FS
NORMAL MODE (Non DES) DYNAMIC CONVERTER CHARACTERISTICS, 1:2 DEMUX MODE
FPBW
Full Power Bandwidth
C.E.R.
Code Error Rate
Gain Flatness
ENOB
SINAD
Effective Number of Bits
Signal-to-Noise Plus Distortion
Ratio
SNR
Signal-to-Noise Ratio
THD
Total Harmonic Distortion
2nd Harm
Second Harmonic Distortion
3rd Harm
Third Harmonic Distortion
SFDR
IMD
Spurious-Free dynamic Range
Intermodulation Distortion
Out of Range Output Code
(In addition to OR Output high)
(1)
(2)
(3)
(4)
Normal Mode
2.0
GHz
10−18
Error/Sample
d.c. to 498 MHz
±0.8
dBFS
d.c. to 1 GHz
±1.0
dBFS
fIN = 248 MHz, VIN = FSR − 0.5 dB
7.4
7.0
Bits (min)
fIN = 498 MHz, VIN = FSR − 0.5 dB
7.4
7.0
Bits (min)
fIN = 248 MHz, VIN = FSR − 0.5 dB
46.5
43.9
dB (min)
fIN = 498 MHz, VIN = FSR − 0.5 dB
46.5
43.9
dB (min)
fIN = 248 MHz, VIN = FSR − 0.5 dB
46.8
45.1
dB (min)
fIN = 498 MHz, VIN = FSR − 0.5 dB
46.8
45.1
dB (min)
fIN = 248 MHz, VIN = FSR − 0.5 dB
−58
-50
dB (max)
fIN = 498 MHz, VIN = FSR − 0.5 dB
−58
-50
dB (max)
fIN = 248 MHz, VIN = FSR − 0.5 dB
−63
dB
fIN = 498 MHz, VIN = FSR − 0.5 dB
−63
dB
fIN = 248 MHz, VIN = FSR − 0.5 dB
−65
dB
fIN = 498 MHz, VIN = FSR − 0.5 dB
−65
fIN = 248 MHz, VIN = FSR − 0.5 dB
58
50
dB (min)
fIN = 498 MHz, VIN = FSR − 0.5 dB
58
50
dB (min)
fIN1 = 250 MHz, VIN = FSR − 7 dB
fIN2 = 260 MHz, VIN = FSR − 7 dB
-50
dB
dB
(VIN+) − (VIN−) > + Full Scale
255
(VIN+) − (VIN−) < − Full Scale
0
The analog inputs are protected as shown below. Input voltage magnitudes beyond the Absolute Maximum Ratings may damage this
device. See Figure 1
To ensure accuracy, it is required that VA and VDR be well bypassed. Each supply pin must be decoupled with separate bypass
capacitors. Additionally, achieving rated performance requires that the backside exposed pad be well grounded.
Typical figures are at TA = 25°C, and represent most likely parametric norms. Test limits are specified to TI's AOQL (Average Outgoing
Quality Level).
Calculation of Full-Scale Error for this device assumes that the actual reference voltage is exactly its nominal value. Full-Scale Error for
this device, therefore, is a combination of Full-Scale Error and Reference Voltage Error. See Figure 3. For relationship between Gain
Error and Full-Scale Error, see Specification Definitions for Gain Error.
Submit Documentation Feedback
Copyright © 2007–2013, Texas Instruments Incorporated
Product Folder Links: ADC08D1020
11
ADC08D1020
SNAS372D – NOVEMBER 2007 – REVISED MARCH 2013
www.ti.com
Converter Electrical Characteristics (continued)
The following specifications apply after calibration for VA = VDR = 1.9V; OutV = 1.9V; VIN FSR (a.c. coupled) = differential 870
mVP-P; CL = 10 pF; Differential, a.c. coupled Sine Wave Input Clock, fCLK = 1 GHz at 0.5 VP-P with 50% duty cycle; VBG =
Floating; Non-Extended Control Mode; SDR Mode; REXT = 3300 Ω ±0.1%; Analog Signal Source Impedance = 100 Ω
Differential; 1:2 Output Demultiplex; Duty Cycle Stabilizer on. Boldface limits apply for TA = TMIN to TMAX. All other limits TA
= 25°C, unless otherwise noted.(1)(2)
Symbol
Parameter
Conditions
Typical
(3)
Limits
(3)
Units
(Limits)
NORMAL MODE (Non DES) DYNAMIC CONVERTER CHARACTERISTICS, 1:1 DEMUX MODE
ENOB
Effective Number of Bits
SINAD
Signal-to-Noise Plus Distortion
Ratio
SNR
Signal-to-Noise Ratio
THD
Total Harmonic Distortion
2nd Harm
Second Harmonic Distortion
3rd Harm
Third Harmonic Distortion
SFDR
Spurious-Free dynamic Range
fIN = 248 MHz, VIN = FSR − 0.5 dB
7.3
Bits
fIN = 498 MHz, VIN = FSR − 0.5 dB
7.3
Bits
fIN = 248 MHz, VIN = FSR − 0.5 dB
45.7
dB
fIN = 498 MHz, VIN = FSR − 0.5 dB
45.7
dB
fIN = 248 MHz, VIN = FSR − 0.5 dB
46
dB
fIN = 498 MHz, VIN = FSR − 0.5 dB
46
dB
fIN = 248 MHz, VIN = FSR − 0.5 dB
-57
dB
fIN = 498 MHz, VIN = FSR − 0.5 dB
-57
dB
fIN = 248 MHz, VIN = FSR − 0.5 dB
-63
dB
fIN = 498 MHz, VIN = FSR − 0.5 dB
-63
dB
fIN = 248 MHz, VIN = FSR − 0.5 dB
-64
dB
fIN = 498 MHz, VIN = FSR − 0.5 dB
-64
dB
fIN = 248 MHz, VIN = FSR − 0.5 dB
57
dB
fIN = 498 MHz, VIN = FSR − 0.5 dB
57
dB
INTERLEAVE MODE (DES Pin 127=Float) - DYNAMIC CONVERTER CHARACTERISTICS, 1:4 DEMUX MODE
FPBW
Full Power Bandwidth
Dual Edge Sampling Mode
1.3
ENOB
Effective Number of Bits
fIN = 498 MHz, VIN = FSR − 0.5 dB
7.3
6.7
Bits (min)
GHz
SINAD
Signal to Noise Plus Distortion
Ratio
fIN = 498 MHz, VIN = FSR − 0.5 dB
46
42.1
dB
SNR
Signal to Noise Ratio
fIN = 498 MHz, VIN = FSR − 0.5 dB
46.3
43.8
dB (min)
THD
Total Harmonic Distortion
fIN = 498 MHz, VIN = FSR − 0.5 dB
−58
-47
dB (max)
2nd Harm
Second Harmonic Distortion
fIN = 498 MHz, VIN = FSR − 0.5 dB
−58
3rd Harm
Third Harmonic Distortion
fIN = 498 MHz, VIN = FSR − 0.5 dB
−66
SFDR
Spurious Free Dynamic Range
fIN = 498 MHz, VIN = FSR − 0.5 dB
57
dB
dB
47
dB (min)
ANALOG INPUT AND REFERENCE CHARACTERISTICS
VIN
VCMI
(5)
(6)
12
650
FSR pin 14 High
870
Common Mode Input Voltage
VCMO
580
mVP-P (min)
720
mVP-P (max)
800
mVP-P (min)
940
mVP-P (max)
VCMO −
0.05
V (min)
VCMO +
0.05
V (max)
Analog Input Capacitance,
Normal operation (5) (6)
Differential
0.02
pF
Each input pin to ground
1.6
pF
Analog Input Capacitance,
DES Mode (5) (6)
Differential
0.08
pF
Each input pin to ground
2.2
CIN
RIN
FSR pin 14 Low
Full Scale Analog Differential Input
Range
Differential Input Resistance
100
pF
Ω (min)
Ω (max)
The analog and clock input capacitances are die capacitances only. Additional package capacitances of 0.65 pF differential and 0.95 pF
each pin to ground are isolated from the die capacitances by lead and bond wire inductances.
This parameter is specified by design and is not tested in production.
Submit Documentation Feedback
Copyright © 2007–2013, Texas Instruments Incorporated
Product Folder Links: ADC08D1020
ADC08D1020
www.ti.com
SNAS372D – NOVEMBER 2007 – REVISED MARCH 2013
Converter Electrical Characteristics (continued)
The following specifications apply after calibration for VA = VDR = 1.9V; OutV = 1.9V; VIN FSR (a.c. coupled) = differential 870
mVP-P; CL = 10 pF; Differential, a.c. coupled Sine Wave Input Clock, fCLK = 1 GHz at 0.5 VP-P with 50% duty cycle; VBG =
Floating; Non-Extended Control Mode; SDR Mode; REXT = 3300 Ω ±0.1%; Analog Signal Source Impedance = 100 Ω
Differential; 1:2 Output Demultiplex; Duty Cycle Stabilizer on. Boldface limits apply for TA = TMIN to TMAX. All other limits TA
= 25°C, unless otherwise noted.(1)(2)
Symbol
Parameter
Conditions
Typical
(3)
Limits
(3)
Units
(Limits)
ANALOG OUTPUT CHARACTERISTICS
0.95
V (min)
1.45
V (max)
VCMO
Common Mode Output Voltage
ICMO = ±100 µA
1.26
TC VCMO
Common Mode Output Voltage
Temperature Coefficient
TA = −40°C to +85°C
118
ppm/°C
VCMO_LVL
VCMO input threshold to set DC
Coupling mode
VA = 1.8V
0.60
V
VA = 2.0V
0.66
CLOAD VCMO
Maximum VCMO load Capacitance
VBG
Bandgap Reference Output Voltage IBG = ±100 µA
TC VBG
Bandgap Reference Voltage
Temperature Coefficient
CLOAD VBG
Maximum Bandgap Reference load
Capacitance
V
80
TA = −40°C to +85°C,
IBG = ±100 µA
1.26
pF
1.20
V (min)
1.33
V (max)
28
ppm/°C
80
pF
CHANNEL-TO-CHANNEL CHARACTERISTICS
Offset Match
1
LSB
Positive Full-Scale Match
Zero offset selected in Control
Register
1
LSB
Negative Full-Scale Match
Zero offset selected in Control
Register
1
LSB
Phase Matching (I, Q)
fIN = 1.0 GHz
(VIN-)
0.0V
+VIN/2
Differential Analog Input Voltage (+VIN/2) - (-VIN/2)
Figure 3. Input / Output Transfer Characteristic
Submit Documentation Feedback
Copyright © 2007–2013, Texas Instruments Incorporated
Product Folder Links: ADC08D1020
19
ADC08D1020
SNAS372D – NOVEMBER 2007 – REVISED MARCH 2013
www.ti.com
Timing Diagrams
Sample N
D
Sample N-1
Dd
VIN
Sample N+1
tAD
CLK, CLK
tOD
DId, DI
DQd, DQ
Sample N-18 and
Sample N-17
Sample N-16 and Sample N-15
Sample N-14 and Sample N-13
tOSK
DCLK+, DCLK(OutEdge = 0)
DCLK+, DCLK(OutEdge = 1)
Figure 4. ADC08D1020 Timing — SDR Clocking in 1:2 Demultiplexed Mode
Sample N
D
Sample N-1
Dd
VIN
Sample N+1
tAD
CLK, CLK
tOD
DId, DI
DQd, DQ
Sample N-18 and
Sample N-17
Sample N-16 and Sample N-15
Sample N-14 and Sample N-13
tOSK
DCLK+, DCLK(0° Phase)
tSU
tH
DCLK+, DCLK(90° Phase)
Figure 5. ADC08D1020 Timing — DDR Clocking in 1:2 Demultiplexed and Normal Mode
20
Submit Documentation Feedback
Copyright © 2007–2013, Texas Instruments Incorporated
Product Folder Links: ADC08D1020
ADC08D1020
www.ti.com
SNAS372D – NOVEMBER 2007 – REVISED MARCH 2013
Sample N
Sample N-1
Dd
D
VIN
Sample N+1
tAD
CLK, CLK
tOD
DId, DI
DQd, DQ
Sample N-15
Sample N-13
Sample N-14
Sample N-12
Sample N-11
tOSK
DCLK+, DCLK(0° Phase)
Figure 6. ADC08D1020 Timing — DDR Clocking in Non-Demultiplexed and Normal Mode
Single Register Access
SCS
tSCS
tHCS
tHCS
12
1
13
16
17
32
SCLK
SDATA
Fixed Header Pattern
Register Address
Register Write Data
LSB
MSB
tSH
tSSU
Figure 7. Serial Interface Timing
Synchronizing Edge
CLK
tHR
tSR
DCLK_RSTtOD
DCLK_RST+
tPWR
DCLK+
Figure 8. Clock Reset Timing in DDR Mode
Submit Documentation Feedback
Copyright © 2007–2013, Texas Instruments Incorporated
Product Folder Links: ADC08D1020
21
ADC08D1020
SNAS372D – NOVEMBER 2007 – REVISED MARCH 2013
www.ti.com
Synchronizing Edge
CLK
tHR
tSR
DCLK_RSTtOD
DCLK_RST+
tPWR
DCLK+
OUTEDGE
Figure 9. Clock Reset Timing in SDR Mode with OUTEDGE Low
Synchronizing Edge
CLK
tHR
tSR
DCLK_RSTtOD
DCLK_RST+
tPWR
DCLK+
OUTEDGE
Figure 10. Clock Reset Timing in SDR Mode with OUTEDGE High
tCAL
tCAL
CalRun
tCalDly
CAL
tCAL_H
Calibration Delay
determined by
CalDly Pin (127)
tCAL_L
POWER
SUPPLY
Figure 11. Power-up Calibration and On-Command Calibration Timing
22
Submit Documentation Feedback
Copyright © 2007–2013, Texas Instruments Incorporated
Product Folder Links: ADC08D1020
ADC08D1020
www.ti.com
SNAS372D – NOVEMBER 2007 – REVISED MARCH 2013
Typical Performance Characteristics
VA = VDR = 1.9V, fCLK = 1000 MHz, fIN = 498 MHz, TA= 25°C, I channel, 1:2 Demux Mode (1:1 Demux Mode has similar
performance), unless otherwise stated.
INL
vs.
CODE
INL
vs.
AMBIENT TEMPERATURE
Figure 12.
Figure 13.
DNL
vs.
CODE
DNL
vs.
AMBIENT TEMPERATURE
Figure 14.
Figure 15.
POWER CONSUMPTION
vs.
CLOCK FREQUENCY
ENOB
vs.
AMBIENT TEMPERATURE
Figure 16.
Figure 17.
Submit Documentation Feedback
Copyright © 2007–2013, Texas Instruments Incorporated
Product Folder Links: ADC08D1020
23
ADC08D1020
SNAS372D – NOVEMBER 2007 – REVISED MARCH 2013
www.ti.com
Typical Performance Characteristics (continued)
VA = VDR = 1.9V, fCLK = 1000 MHz, fIN = 498 MHz, TA= 25°C, I channel, 1:2 Demux Mode (1:1 Demux Mode has similar
performance), unless otherwise stated.
24
ENOB
vs.
DIE TEMPERATURE
ENOB
vs.
SUPPLY VOLTAGE
Figure 18.
Figure 19.
ENOB
vs.
CLOCK FREQUENCY
ENOB
vs.
INPUT FREQUENCY
Figure 20.
Figure 21.
SNR
vs.
AMBIENT TEMPERATURE
SNR
vs.
DIE TEMPERATURE
Figure 22.
Figure 23.
Submit Documentation Feedback
Copyright © 2007–2013, Texas Instruments Incorporated
Product Folder Links: ADC08D1020
ADC08D1020
www.ti.com
SNAS372D – NOVEMBER 2007 – REVISED MARCH 2013
Typical Performance Characteristics (continued)
VA = VDR = 1.9V, fCLK = 1000 MHz, fIN = 498 MHz, TA= 25°C, I channel, 1:2 Demux Mode (1:1 Demux Mode has similar
performance), unless otherwise stated.
SNR
vs.
SUPPLY VOLTAGE
SNR
vs.
CLOCK FREQUENCY
Figure 24.
Figure 25.
SNR
vs.
INPUT FREQUENCY
THD
vs.
AMBIENT TEMPERATURE
Figure 26.
Figure 27.
THD
vs.
DIE TEMPERATURE
THD
vs.
SUPPLY VOLTAGE
Figure 28.
Figure 29.
Submit Documentation Feedback
Copyright © 2007–2013, Texas Instruments Incorporated
Product Folder Links: ADC08D1020
25
ADC08D1020
SNAS372D – NOVEMBER 2007 – REVISED MARCH 2013
www.ti.com
Typical Performance Characteristics (continued)
VA = VDR = 1.9V, fCLK = 1000 MHz, fIN = 498 MHz, TA= 25°C, I channel, 1:2 Demux Mode (1:1 Demux Mode has similar
performance), unless otherwise stated.
26
THD
vs.
CLOCK FREQUENCY
THD
vs.
INPUT FREQUENCY
Figure 30.
Figure 31.
SFDR
vs.
AMBIENT TEMPERATURE
SFDR
vs.
DIE TEMPERATURE
Figure 32.
Figure 33.
SFDR
vs.
SUPPLY VOLTAGE
SFDR
vs.
CLOCK FREQUENCY
Figure 34.
Figure 35.
Submit Documentation Feedback
Copyright © 2007–2013, Texas Instruments Incorporated
Product Folder Links: ADC08D1020
ADC08D1020
www.ti.com
SNAS372D – NOVEMBER 2007 – REVISED MARCH 2013
Typical Performance Characteristics (continued)
VA = VDR = 1.9V, fCLK = 1000 MHz, fIN = 498 MHz, TA= 25°C, I channel, 1:2 Demux Mode (1:1 Demux Mode has similar
performance), unless otherwise stated.
SFDR
vs.
INPUT FREQUENCY
GAIN STABILITY
vs.
DIE TEMPERATURE
Figure 36.
Figure 37.
SIGNAL GAIN
vs.
INPUT FREQUENCY
CROSSTALK
vs.
SOURCE FREQUENCY
Figure 38.
Figure 39.
SPECTRAL RESPONSE AT fIN = 248 MHz
SPECTRAL RESPONSE AT fIN = 498 MHz
Figure 40.
Figure 41.
Submit Documentation Feedback
Copyright © 2007–2013, Texas Instruments Incorporated
Product Folder Links: ADC08D1020
27
ADC08D1020
SNAS372D – NOVEMBER 2007 – REVISED MARCH 2013
www.ti.com
FUNCTIONAL DESCRIPTION
The ADC08D1020 is a versatile A/D Converter with an innovative architecture permitting very high speed
operation. The controls available ease the application of the device to circuit solutions. Optimum performance
requires adherence to the provisions discussed here and in the Applications Information Section.
While it is generally poor practice to allow an active pin to float, pins 4, 14 and 127 of the ADC08D1020 are
designed to be left floating without jeopardy. In all discussions throughout this data sheet, whenever a function is
called by allowing a control pin to float, connecting that pin to a potential of one half the VA supply voltage will
have the same effect as allowing it to float.
OVERVIEW
The ADC08D1020 uses a calibrated folding and interpolating architecture that achieves 7.4 effective bits. The
use of folding amplifiers greatly reduces the number of comparators and power consumption. Interpolation
reduces the number of front-end amplifiers required, minimizing the load on the input signal and further reducing
power requirements. In addition to other things, on-chip calibration reduces the INL bow often seen with folding
architectures. The result is an extremely fast, high performance, low power converter.
The analog input signal that is within the converter's input voltage range is digitized to eight bits at speeds of 200
MSPS to 1.3 GSPS, typical. Differential input voltages below negative full-scale will cause the output word to
consist of all zeroes. Differential input voltages above positive full-scale will cause the output word to consist of
all ones. Either of these conditions at either the "I" or "Q" input will cause the OR (Out of Range) output to be
activated. This single OR output indicates when the output code from one or both of the channels is below
negative full scale or above positive full scale.
Each converter has a selectable output demultiplexer which feeds two LVDS buses. If the 1:2 demultiplexed
mode is selected, the output data rate is reduced to half the input sample rate on each bus. When nondemultiplexed mode is selected, that output data rate on channels DI and DQ are at the same rate as the input
sample clock.
The output levels may be selected to be normal or reduced. Using reduced levels saves power but could result in
erroneous data capture of some or all of the bits, especially at higher sample rates and in marginally designed
systems.
Calibration
A calibration is performed upon power-up and can also be invoked by the user upon command. Calibration trims
the 100 Ω analog input differential termination resistor and minimizes full-scale error, offset error, DNL and INL,
resulting in maximizing SNR, THD, SINAD (SNDR) and ENOB. Internal bias currents are also set with the
calibration process. All of this is true whether the calibration is performed upon power up or is performed upon
command. Running the calibration is an important part of this chip's functionality and is required in order to obtain
adequate performance. In addition to the requirement to be run at power-up, an on-command calibration must be
run whenever the sense of the FSR pin is changed. For best performance, we recommend that an on-command
calibration be run 20 seconds or more after application of power and whenever the operating temperature
changes significantly relative to the specific system performance requirements. See On-Command Calibration for
more information. Calibration can not be initiated or run while the device is in the power-down mode. See Power
Down for information on the interaction between Power Down and Calibration.
In normal operation, calibration is performed just after application of power and whenever a valid calibration
command is given, which is holding the CAL pin low for at least tCAL_L clock cycles, then hold it high for at least
another tCAL_H clock cycles as defined in the Converter Electrical Characteristics. The time taken by the
calibration procedure is specified as tCALin Converter Electrical Characteristics. Holding the CAL pin high upon
power up will prevent the calibration process from running until the CAL pin experiences the above-mentioned
tCAL_L clock cycles followed by tCAL_H clock cycles.
CalDly (pin 127) is used to select one of two delay times that apply from the application of power to the start of
calibration. This calibration delay time is depedent on the setting of the CalDly pin and is specified as tCalDly in the
Converter Electrical Characteristics. These delay values allow the power supply to come up and stabilize before
calibration takes place. If the PD pin is high upon power-up, the calibration delay counter will be disabled until the
PD pin is brought low. Therefore, holding the PD pin high during power up will further delay the start of the
power-up calibration cycle. The best setting of the CalDly pin depends upon the power-on settling time of the
power supply.
28
Submit Documentation Feedback
Copyright © 2007–2013, Texas Instruments Incorporated
Product Folder Links: ADC08D1020
ADC08D1020
www.ti.com
SNAS372D – NOVEMBER 2007 – REVISED MARCH 2013
The CAL bit does not reset itself to zero automatically, but must be manually reset before another calibration
event can be initiated. If no further calibration event is desired, the CAL bit may be left high indefinitely, with no
negative consequences. The RTD bit setting is critical for running a calibration event with the Clock Phase Adjust
enabled. If initiating a calibration event while the Clock Phase Adjust is enabled, the RTD bit must be set to high,
or no calibration will occur. If initiating a calibration event while the Clock Phase Adjust is not enabled, a normal
calibration will occur, regardless of the setting of the RTD bit.
Acquiring the Input
In 1:2 demux mode, data is acquired at the falling edge of CLK+ (pin 18) and the digital equivalent of that data is
available at the digital outputs 13 input clock cycles later for the DI and DQ output buses and 14 input clock
cycles later for the DId and DQd output buses. There is an additional internal delay called tOD before the data is
available at the outputs. See the Timing Diagram. The ADC08D1020 will convert as long as the input clock signal
is present. The fully differential comparator design and the innovative design of the sample-and-hold amplifier,
together with calibration, enables a very flat SINAD/ENOB response beyond 1 GHz. The ADC08D1020 output
data signaling is LVDS and the output format is offset binary.
Control Modes
Much of the user control can be accomplished with several control pins that are provided. Examples include
initiation of the calibration cycle, power down mode and full scale range setting. However, the ADC08D1020 also
provides an Extended Control mode whereby a serial interface is used to access register-based control of
several advanced features. The Extended Control mode is not intended to be enabled and disabled dynamically.
Rather, the user is expected to employ either the normal control mode or the Extended Control mode at all times.
When the device is in the Extended Control mode, pin-based control of several features is replaced with registerbased control and those pin-based controls are disabled. These pins are OutV (pin 3), OutEdge/DDR (pin 4),
FSR (pin 14) and CalDly/DES (pin 127). See NORMAL/EXTENDED CONTROL for details on the Extended
Control mode.
The Analog Inputs
The ADC08D1020 must be driven with a differential input signal. Operation with a single-ended signal is not
recommended. It is important that the inputs either be a.c. coupled to the inputs with the VCMO pin grounded, or
d.c. coupled with the VCMO pin left floating. An input common mode voltage equal to the VCMO output must be
provided when d.c. coupling is used.
Two full-scale range settings are provided with pin 14 (FSR). A high on pin 14 causes an input full-scale range
setting of a higher VIN input level, while grounding pin 14 causes an input full-scale range setting of a reduced
VIN input level. The full-scale range setting operates equally on both ADCs.
In the Extended Control mode, programming the Input Full-Scale Voltage Adjust register allows the input fullscale range to be adjusted as described in REGISTER DESCRIPTION and THE ANALOG INPUT.
Clocking
The ADC08D1020 must be driven with an a.c. coupled, differential clock signal. THE CLOCK INPUTS describes
the use of the clock input pins. A differential LVDS output clock is available for use in latching the ADC output
data into whatever device is used to receive the data.
The ADC08D1020 offers input and output clocking options. These options include a choice of Dual Edge
Sampling (DES) or "interleaved mode" where the ADC08D1020 performs as a single device converting at twice
the input clock rate, a choice of which DCLK edge the output data transitions on, and a choice of Single Data
Rate (SDR) or Double Data Rate (DDR) outputs.
The ADC08D1020 also has the option to use a duty cycle corrected clock receiver as part of the input clock
circuit. This feature is enabled by default and provides improved ADC clocking especially in the Dual-Edge
Sampling mode (DES). This circuitry allows the ADC to be clocked with a signal source having a duty cycle ratio
of 20% / 80% (worst case) for both the normal and the Dual Edge Sampling modes.
Submit Documentation Feedback
Copyright © 2007–2013, Texas Instruments Incorporated
Product Folder Links: ADC08D1020
29
ADC08D1020
SNAS372D – NOVEMBER 2007 – REVISED MARCH 2013
www.ti.com
Dual-Edge Sampling
The DES mode allows one of the ADC08D1020's inputs (I or Q Channel) to be sampled by both ADCs. One
ADC samples the input on the positive edge of the input clock and the other ADC samples the same input on the
falling edge of the input clock. A single input is thus sampled twice per input clock cycle, resulting in an overall
sample rate of twice the input clock frequency, or 2 GSPS with a 1 GHz input clock.
In this mode, the outputs must be carefully interleaved to reconstruct the sampled signal. If the device is
programmed into the 1:2 demultiplex mode while in DES mode, the data is effectively demultiplexed 1:4. If the
input clock is 1 GHz, the effective sampling rate is doubled to 2 GSPS and each of the 4 output buses have a
500 MHz output rate. All data is available in parallel. To properly reconstruct the sampled waveform, the four
bytes of parallel data that are output with each clock are in the following sampling order from the earliest to the
latest and must be interleaved as such: DQd, DId, DQ, DI. See Table 2 indicates what the outputs represent for
the various sampling possibilities. If the device is programmed into the non-demultiplex mode, two bytes of
parallel data are output with each edge of the clock in the following sampling order, from the earliest to the latest:
DQ, DI. See Table 3.
In the non-extended mode of operation only the "I" input can be sampled in the DES mode. In the extended
mode of operation, the user can select which input is sampled.
The ADC08D1020 includes an automatic clock phase background adjustment which is used in DES mode to
automatically and continuously adjust the clock phase of the I and Q channel. This feature provides optimal DualEdge Sampling performance.
Table 2. Input Channel Samples Produced at Data Outputs in 1:2 Demultiplexed Mode (1)
Data Outputs
(Always sourced with
respect to fall of DCLK+)
(1)
(2)
Dual-Edge Sampling Mode (DES)
Normal Sampling Mode
I-Channel Selected
Q-Channel Selected (2)
DI
"I" Input Sampled with Fall of CLK 13
cycles earlier.
"I" Input Sampled with Fall of
CLK 13 cycles earlier.
"Q" Input Sampled with Fall of
CLK 13 cycles earlier.
DId
"I" Input Sampled with Fall of CLK 14
cycles earlier.
"I" Input Sampled with Fall of
CLK 14 cycles earlier.
"Q" Input Sampled with Fall of
CLK 14 cycles earlier.
DQ
"Q" Input Sampled with Fall of CLK 13
cycles earlier.
"I" Input Sampled with Rise of
CLK 13.5 cycles earlier.
"Q" Input Sampled with Rise of
CLK 13.5 cycles earlier.
DQd
"Q" Input Sampled with Fall of CLK 14
cycles after being sampled.
"I" Input Sampled with Rise of
CLK 14.5 cycles earlier.
"Q" Input Sampled with Rise of
CLK 14.5 cycles earlier.
Note that, in the non-demultiplexed mode, the DId and DQd outputs are disabled and are high impedance.
Note that, in DES + normal mode, only the I Channel is sampled. In DES + extended control mode, I or Q channel can be sampled.
Table 3. Input Channel Samples Produced at Data Outputs in Non-Demultiplexed Mode
Data Outputs
(Sourced with
respect to fall
of DCLK+)
Normal Mode
DES Mode
DI
"I" Input Sampled with Fall of CLK 13 cycles earlier.
Selected input sampled 13 cycles earlier.
DId
No output.
No output.
DQ
"Q" Input Sampled with Fall of CLK 13 cycles earlier.
Selected input sampled 13.5 cycles earlier.
DQd
No output.
No output.
OutEdge and Demultiplex Control Setting
To help ease data capture in the SDR mode, the output data may be caused to transition on either the positive or
the negative edge of the output data clock (DCLK). In the non-extended control mode, this is chosen with the
OutEdge input (pin 4). A high on the OutEdge input pin causes the output data to transition on the rising edge of
DCLK+, while grounding this input causes the output to transition on the falling edge of DCLK+. See Output
Edge Synchronization. When in the extended control mode, the OutEdge is selected using the OED bit in the
Configuration Register. This bit has two functions. In the single data rate (SDR) mode, the bit functions as
30
Submit Documentation Feedback
Copyright © 2007–2013, Texas Instruments Incorporated
Product Folder Links: ADC08D1020
ADC08D1020
www.ti.com
SNAS372D – NOVEMBER 2007 – REVISED MARCH 2013
OutEdge and selects the DCLK edge with which the data transitions. In the Double Data Rate (DDR) mode, this
bit selects whether the device is in non-demultiplex or 1:2 demultiplex mode. In the DDR case, the DCLK has a
0° phase relationship with the output data independent of the demultiplexer selection. For 1:2 Demux DDR 0°
Mode, there are four, as opposed to three cycles of CLK systematic delay from the Synchronizing Edge to the
start of tOD. See MULTIPLE ADC SYNCHRONIZATIONfor more details.
Single Data Rate and Double Data Rate
A choice of single data rate (SDR) or double data rate (DDR) output is offered. With single data rate the output
clock (DCLK) frequency is the same as the data rate of the two output buses. With double data rate the DCLK
frequency is half the data rate and data is sent to the outputs on both edges of DCLK. DDR clocking is enabled
in non-Extended Control mode by allowing pin 4 to float.
The LVDS Outputs
The data outputs, the Out Of Range (OR) and DCLK, are LVDS. The electrical specifications of the LVDS
outputs are compatible with typical LVDS receivers available on ASIC and FPGA chips; but they are not IEEE or
ANSI communications standards compliant due to the low +1.9V supply used this chip. User is given the choice
of a lower signal amplitude mode with OutV control pin or the OV control register bit. For short LVDS lines and
low noise systems, satisfactory performance may be realized with the OutV input low, which results in lower
power consumption. If the LVDS lines are long and/or the system in which the ADC08D1020 is used is noisy, it
may be necessary to tie the OutV pin high.
The LVDS data output have a typical common mode voltage of 800 mV when the VBG pin is unconnected and
floating. This common mode voltage can be increased to 1.175V by tying the VBG pin to VA if a higher common
mode is required.
IMPORTANT NOTE: Tying the VBG pin to VA will also increase the differential LVDS output voltage by up to 40
mV.
Power Down
The ADC08D1020 is in the active state when the Power Down pin (PD) is low. When the PD pin is high, the
device is in the power down mode. In this power down mode the data output pins (positive and negative) are put
into a high impedance state and the devices power consumption is reduced to a minimal level. The DCLK+/- and
OR +/- are not tri-stated, they are weakly pulled down to ground internally. Therefore when both I and Q are
powered down the DCLK +/- and OR +/- should not be terminated to a DC voltage.
A high on the PDQ pin will power down the "Q" channel and leave the "I" channel active. There is no provision to
power down the "I" channel independently of the "Q" channel. Upon return to normal operation, the pipeline will
contain meaningless information.
If the PD input is brought high while a calibration is running, the device will not go into power down until the
calibration sequence is complete. However, if power is applied and PD is already high, the device will not begin
the calibration sequence until the PD input goes low. If a manual calibration is requested while the device is
powered down, the calibration will not begin at all. That is, the manual calibration input is completely ignored in
the power down state. Calibration will function with the "Q" channel powered down, but that channel will not be
calibrated if PDQ is high. If the "Q" channel is subsequently to be used, it is necessary to perform a calibration
after PDQ is brought low.
Submit Documentation Feedback
Copyright © 2007–2013, Texas Instruments Incorporated
Product Folder Links: ADC08D1020
31
ADC08D1020
SNAS372D – NOVEMBER 2007 – REVISED MARCH 2013
www.ti.com
NORMAL/EXTENDED CONTROL
The ADC08D1020 may be operated in one of two modes. In the simpler standard control mode, the user affects
available configuration and control of the device through several control pins. The "extended control mode"
provides additional configuration and control options through a serial interface and a set of 9 registers. Extended
control mode is selected by setting pin 41 to logic low. If pin 41 is floating and pin 52 is floating or logic high, pin
14 can be used to enable the extended control mode. The choice of control modes is required to be a fixed
selection and is not intended to be switched dynamically while the device is operational.
Table 4 shows how several of the device features are affected by the control mode chosen.
Table 4. Features and Modes
Feature
Normal Control Mode
Extended Control Mode
SDR or DDR Clocking
Selected with pin 4
Selected with nDE in the Configuration Register (Addr-1h;
bit-10).
DDR Clock Phase
Not Selectable (0° Phase Only)
Selected with DCP in the Configuration Register (Addr-1h;
bit-11).
SDR Data transitions with rising or
falling DCLK edge
SDR Data transitions with rising edge of
Selected with OED in the Configuration Register (Addr-1h;
DCLK+ when pin 4 is high and on falling
bit-8).
edge when low.
LVDS output level
Normal differential data and DCLK
amplitude selected when pin 3 is high
and reduced amplitude selected when
low.
Selected with OV in the Configuration Register (Addr-1h; bit9).
Power-On Calibration Delay
Short delay selected when pin 127 is
low and longer delay selected when
high.
Short delay only.
Full-Scale Range
Normal input full-scale range selected
when pin 14 is high and reduced range
when low. Selected range applies to
both channels.
Up to 512 step adjustments over a nominal range specified
in REGISTER DESCRIPTION. Separate range selected for
I- and Q-Channels. Selected using Full Range Registers
(Addr-3h and Bh; bit-7 thru 15).
Input Offset Adjust
Not possible
512 steps of adjustment using the Input Offset register
specified in REGISTER DESCRIPTION for each channel
using Input Offset Registers (Addr-2h and Ah; bit-7 thru 15).
Dual Edge Sampling Selection
Enabled with pin 127 floating
Enabled by programming DES in the Extended
Configuration Register (Addr-9h; bit-13).
Dual Edge Sampling
Input Channel Selection
Only I-Channel Input can be used
Either I- or Q-Channel input may be sampled by both ADCs.
Test Pattern
Not possible
A test pattern can be made present at the data outputs by
setting TPO to 1b in Extended Configuration Register (Addr9h; bit-15).
Resistor Trim Disable
Not possible
The DCLK outputs will continuously be present when RTD is
set to 1b in Extended Configuration Register (Addr-9h; bit14 to 7).
Selectable Output Demultiplexer
Not possible
If the device is set in DDR, the output can be programmed
to be non-demultiplex. When OED in Configuration Register
is set 1b (Addr-1h; bit-8), this selects non-demultiplex. If
OED is set 0b, this selects 1:2 demultiplex.
Second DCLK Output
Not possible
The OR outputs can be programmed to become a second
DCLK output when nSD is set 0b in Configuration Register
(Addr-1h; bit-13).
Sampling Clock Phase Adjust
Not possible
The sampling clock phase can be manually adjusted
through the Coarse and Intermediate Register (Addr-Fh; bit15–7) and Fine Register (Addr-Eh; bit-15 to 8).
The default state of the Extended Control Mode is set upon power-on reset (internally performed by the device)
and is shown in Table 5.
32
Submit Documentation Feedback
Copyright © 2007–2013, Texas Instruments Incorporated
Product Folder Links: ADC08D1020
ADC08D1020
www.ti.com
SNAS372D – NOVEMBER 2007 – REVISED MARCH 2013
Table 5. Extended Control Mode Operation (Pin 41 Logic Low or Pin 14 Floating)
Feature
Extended Control Mode Default State
SDR or DDR Clocking
DDR Clocking
DDR Clock Phase
Data changes with DCLK edge (0° phase)
LVDS Output Amplitude
Higher value indicated in Electrical Table
Calibration Delay
Short Delay
Full-Scale Range
700 mV nominal for both channels
Input Offset Adjust
No adjustment for either channel
Dual Edge Sampling (DES)
Not enabled
Test Pattern
Not present at output
Resistor Trim Disable
Trim enabled, DCLK not continuously present at output
Selectable Output Demultiplexer
1:2 demultiplex
Second DCLK Output
Not present, pins 79 and 80
function as OR+ and OR-
Sampling Clock Phase Adjust
No adjustment for fine, intermediate or coarse
THE SERIAL INTERFACE
IMPORTANT NOTE: During the initial write using the serial interface, all nine registers must be written with
desired or default values. Subsequent writes to single registers are allowed.
The 3-pin serial interface is enabled only when the device is in the Extended Control mode. The pins of this
interface are Serial Clock (SCLK), Serial Data (SDATA) and Serial Interface Chip Select (SCS). Nine write only
registers are accessible through this serial interface.
SCS: This signal should be asserted low while accessing a register through the serial interface. Setup and hold
times with respect to the SCLK must be observed.
SCLK: Serial data input is accepted at the rising edge of this signal. There is no minimum frequency requirement
for SCLK.
SDATA: Each register access requires a specific 32-bit pattern at this input. This pattern consists of a header,
register address and register value. The data is shifted in MSB first. Setup and hold times with respect to the
SCLK must be observed. See the Timing Diagram.
Each Register access consists of 32 bits, as shown in Figure 7 of the Timing Diagrams. The fixed header pattern
is 0000 0000 0001 (eleven zeros followed by a 1). The loading sequence is such that a "0" is loaded first. These
12 bits form the header. The next 4 bits are the address of the register that is to be written to and the last 16 bits
are the data written to the addressed register. The addresses of the various registers are indicated in Table 6.
Refer to the Register Description (REGISTER DESCRIPTION) for information on the data to be written to the
registers.
Subsequent register accesses may be performed immediately, starting with the 33rd SCLK. This means that the
SCS input does not have to be de-asserted and asserted again between register addresses. It is possible,
although not recommended, to keep the SCS input permanently enabled (at a logic low) when using extended
control.
Control register contents are retained when the device is put into power-down mode.
IMPORTANT NOTE: Do not write to the Serial Interface when calibrating the ADC. Doing so will impair the
performance of the device until it is re-calibrated correctly. Programming the serial registers will also reduce
dynamic performance of the ADC for the duration of the register access time.
Submit Documentation Feedback
Copyright © 2007–2013, Texas Instruments Incorporated
Product Folder Links: ADC08D1020
33
ADC08D1020
SNAS372D – NOVEMBER 2007 – REVISED MARCH 2013
www.ti.com
Table 6. Register Addresses
4-Bit Address
Loading Sequence:
A3 loaded after Fixed Header pattern, A0 loaded last
A3
A2
A1
A0
Hex
0
0
0
0
0h
Register Addressed
Calibration
0
0
0
1
1h
Configuration
0
0
1
0
2h
"I" Ch Offset
0
0
1
1
3h
"I" Ch Full-Scale Voltage Adjust
0
1
0
0
4h
Reserved
0
1
0
1
5h
Reserved
0
1
1
0
6h
Reserved
0
1
1
1
7h
Reserved
1
0
0
0
8h
Reserved
1
0
0
1
9h
Extended Configuration
1
0
1
0
Ah
"Q" Ch Offset
1
0
1
1
Bh
"Q" Ch Full-Scale Voltage Adjust
1
1
0
0
Ch
Reserved
1
1
0
1
Dh
Reserved
1
1
1
0
Eh
Sampling Clock Phase Fine Adjust
1
1
1
1
Fh
Sample Clock Phase Intermediate and Coarse Adjust
REGISTER DESCRIPTION
Nine write-only registers provide several control and configuration options in the Extended Control Mode. These
registers have no effect when the device is in the Normal Control Mode. Each register description below also
shows the Power-On Reset (POR) state of each control bit.
Table 7. Calibration Register
Addr: 0h (0000b)
Write only (0x7FFF)
D15
D14
D13
D12
D11
D10
D9
D8
D7
D6
D5
D4
D3
D2
D1
D0
CAL
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
Bit 15
CAL: Calibration Enable. When this bit is set 1b, an on-command calibration cycle is initiated. This function is
exactly the same as issuing an on-command calibration using the CAL pin.
POR State: 0b
Bits 14:0
Must be set to 1b
Table 8. Configuration Register
Addr: 1h (0001b)
Write only (0xB2FF)
D15
D14
D13
D12
D11
D10
D9
D8
D7
D6
D5
D4
D3
D2
D1
D0
1
0
nSD
DCS
DCP
nDE
OV
OED
1
1
1
1
1
1
1
1
Bit 15
Must be set to 1b
Bit 14
Must be set to 0b
Bit 13
nSD: Second DCLK Output Enable. When this bit is 1b, the device only has one DCLK output and one OR
output. When this bit is 0b, the device has two identical DCLK outputs and no OR output.
POR State: 1b
34
Submit Documentation Feedback
Copyright © 2007–2013, Texas Instruments Incorporated
Product Folder Links: ADC08D1020
ADC08D1020
www.ti.com
SNAS372D – NOVEMBER 2007 – REVISED MARCH 2013
Bit 12
DCS: Duty Cycle Stabilizer. When this bit is set to 1b, a duty cycle stabilization circuit is applied to the clock
input. When this bit is set to 0b the stabilization circuit is disabled.
POR State: 1b
Bit 11
DCP: DDR Clock Phase. This bit only has an effect in the DDR mode. When this bit is set to 0b, the DCLK
edges are time-aligned with the data bus edges ("0° Phase"). When this bit is set to 1b, the DCLK edges are
placed in the middle of the data bit-cells ("90° Phase"), using the one-half speed DCLK shown in Figure 5 as
the phase reference.
POR State: 0b
Bit 10
nDE: DDR Enable. When this bit is set to 0b, data bus clocking follows the DDR (Double Data Rate) mode
whereby a data word is output with each rising and falling edge of DCLK. When this bit is set to a 1b, data bus
clocking follows the SDR (single data rate) mode whereby each data word is output with either the rising or
falling edge of DCLK , as determined by the OutEdge bit.
POR State: 0b
Bit 9
OV: Output Voltage. This bit determines the LVDS outputs' voltage amplitude and has the same function as the
OutV pin that is used in the normal control mode. When this bit is set to 1b, the standard output amplitude of
710 mVP-P is used. When this bit is set to 0b, the reduced output amplitude of 510 mVP-P is used.
POR State: 1b
Bit 8
OED: Output Edge and Demultiplex Control. This bit has two functions. When the device is in SDR mode, this
bit selects the DCLK edge with which the data words transition and has the same effect as the OutEdge pin in
the Non-extended control mode. When this bit is set to 1b, the data outputs change with the rising edge of
DCLK+. When this bit is set to 0b, the data output changes with the falling edge of DCLK+. When the device is
in DDR mode, this bit selects the non-demultiplexed mode when set to 1b. When the bit set to 0b, the device is
programmed into the Demultiplexed mode. If the device is in DDR and Non-Demultiplexed Mode, then the
DCLK has a 0° phase relationship with the data; it is not possible to select the 90° phase relationship.
POR State: 0b
Bits 7:0
Must be set to 1b
IMPORTANT NOTE: It is recommended that this register should only be written upon power-up initialization as
writing it may cause disturbance on the DCLK output as this signal's basic configuration is changed.
Table 9. I-Channel Offset
Addr: 2h (0010b)
D15
D14
(MSB)
Bits 15:8
Write only (0x007F)
D13
D12
D11
D10
D9
Offset Value
D8
(LSB)
D7
D6
D5
D4
D3
D2
D1
D0
Sign
1
1
1
1
1
1
1
Offset Value. The input offset of the I-Channel ADC is adjusted linearly and monotonically by the value in this
field. 00h provides a nominal zero offset, while FFh provides a nominal 45 mV of offset. Thus, each code step
provides 0.176 mV of offset.
POR State: 0000 0000 b
Bit 7
Sign bit. 0b gives positive offset, 1b gives negative offset, resulting in total offset adjustment of ±45 mV.
POR State: 0b
Bits 6:0
Must be set to 1b
Submit Documentation Feedback
Copyright © 2007–2013, Texas Instruments Incorporated
Product Folder Links: ADC08D1020
35
ADC08D1020
SNAS372D – NOVEMBER 2007 – REVISED MARCH 2013
www.ti.com
Table 10. I-Channel Full-Scale Voltage Adjust
Addr: 3h (0011b)
D15
D14
Write only (0x807F)
D13
D12
(MSB)
D11
D10
D9
D8
Adjust Value
Bits 15:7
D7
D6
D5
D4
D3
D2
D1
D0
(LSB)
1
1
1
1
1
1
1
Full Scale Voltage Adjust Value. The input full-scale voltage or gain of the I-Channel ADC is adjusted linearly and
monotonically with a 9 bit data value. The adjustment range is ±20% of the nominal 700 mVP-P differential value.
0000 0000 0
560 mVP-P
1000 0000 0
Default Value
700 mVP-P
1111 1111 1
840 mVP-P
For best performance, it is recommended that the value in this field be limited to the range of 0110 0000 0b to
1110 0000 0b. i.e., limit the amount of adjustment to ±15%. The remaining ±5% headroom allows for the ADC's
own full scale variation. A gain adjustment does not require ADC re-calibration.
POR State: 1000 0000 0b (no adjustment)
Bits 6:0
Must be set to 1b
Table 11. Extended Configuration Register
Addr: 9h (1001b)
Write only (0x03FF)
D15
D14
D13
D12
D11
D10
D9
D8
D7
D6
D5
D4
D3
D2
D1
D0
TPO
RTD
DES
IS
0
DLF
1
1
1
1
1
1
1
1
1
1
Bit 15
TPO: Test Pattern Output. When this bit is set 1b, the ADC is disengaged and a test pattern generator is
connected to the outputs including OR. This test pattern will work with the device in the SDR, DDR and the
non-demultiplex output modes.
POR State: 0b
Bit 14
RTD: Resistor Trim Disable. When this bit is set to 1b, the input termination resistor is not trimmed during the
calibration cycle and the DCLK output remains enabled. Note that the ADC is calibrated regardless of this
setting.
POR State: 0b
Bit 13
DES: DES Enable. Setting this bit to 1b enables the Dual Edge Sampling mode. In this mode the ADCs in this
device are used to sample and convert the same analog input in a time-interleaved manner, accomplishing a
sample rate of twice the input clock rate. When this bit is set to 0b, the device operates in the normal dual
channel mode.
POR State: 0b
Bit 12
IS: Input Select. When this bit is set to 0b the "I" input is operated upon by both ADCs. When this bit is set to
1b the "Q" input is operated on by both ADCs.
POR State: 0b
Bit 11
Must be set to 0b
Bit 10
DLF: Low Frequency. When this bit is set 1b, the dynamic performance of the device is improved when the
input clock is less than 900MHz.
POR State: 0b
Bits 9:0
36
Must be set to 1b
Submit Documentation Feedback
Copyright © 2007–2013, Texas Instruments Incorporated
Product Folder Links: ADC08D1020
ADC08D1020
www.ti.com
SNAS372D – NOVEMBER 2007 – REVISED MARCH 2013
Table 12. Q-Channel Offset
Addr: Ah (1010b)
D15
D14
Write only (0x007F)
D13
(MSB)
D12
D11
D10
D9
Offset Value
Bits 15:8
D8
(LSB)
D7
D6
D5
D4
D3
D2
D1
D0
Sign
1
1
1
1
1
1
1
Offset Value. The input offset of the Q-Channel ADC is adjusted linearly and monotonically by the value in this
field. 00h provides a nominal zero offset, while FFh provides a nominal 45 mV of offset. Thus, each code step
provides about 0.176 mV of offset.
POR State: 0000 0000 b
Bit 7
Sign bit. 0b gives positive offset, 1b gives negative offset.
POR State: 0b
Bits 6:0
Must be set to 1b
Table 13. Q-Channel Full-Scale Voltage Adjust
Addr: Bh (1011b)
D15
D14
Write only (0x807F)
D13
D12
(MSB)
D11
D10
D9
D8
Adjust Value
Bits 15:7
D7
D6
D5
D4
D3
D2
D1
D0
(LSB)
1
1
1
1
1
1
1
Full Scale Voltage Adjust Value. The input full-scale voltage or gain of the I-Channel ADC is adjusted linearly
and monotonically with a 9 bit data value. The adjustment range is ±20% of the nominal 700 mVP-P differential
value.
0000 0000 0
560 mVP-P
1000 0000 0
700 mVP-P
1111 1111 1
840 mVP-P
For best performance, it is recommended that the value in this field be limited to the range of 0110 0000 0b to
1110 0000 0b. i.e., limit the amount of adjustment to ±15%. The remaining ±5% headroom allows for the ADC's
own full scale variation. A gain adjustment does not require ADC re-calibration.
POR State: 1000 0000 0b (no adjustment)
Bits 6:0
Must be set to 1b
Table 14. Sample Clock Phase Fine Adjust
Addr: 1110
D15
D14
(MSB)
Bits 15:8
Write only (0x00FF)
D13
D12
D11
D10
D9
Fine Phase Adjust
D8
(LSB)
D7
D6
1
D5
1
D4
1
D3
1
D2
1
D1
1
D0
1
1
Fine Phase Adjust. The phase of the ADC sampling clock is adjusted monotonically by the value in this field.
00h provides a nominal zero phase adjustment, while FFh provides a nominal 50 ps of delay. Thus, each code
step provides approximately 0.2 ps of delay.
POR State: 0000 0000b
Bits 7:0
Must be set to 1b
Submit Documentation Feedback
Copyright © 2007–2013, Texas Instruments Incorporated
Product Folder Links: ADC08D1020
37
ADC08D1020
SNAS372D – NOVEMBER 2007 – REVISED MARCH 2013
www.ti.com
Table 15. Sample Clock Phase Intermediate/Coarse Adjust
Addr: Fh (1111b)
D15
D14
POL
Write only (0x007F)
D13
D12
D11
D10
(MSB) Coarse Phase Adjust
D9
D8
IPA
D7
D6
D5
D4
D3
D2
D1
D0
(LSB)
1
1
1
1
1
1
1
Bit 15
Polarity Select. When this bit is selected, the polarity of the ADC sampling clock is inverted.
POR State: 0b
Bits 14:10
Coarse Phase Adjust. Each code value in this field delays the sample clock by approximately 65 ps. A value of
00000b in this field causes zero adjustment.
POR State: 00000b
Bits 9:7
Intermediate Phase Adjust. Each code value in this field delays the sample clock by approximately 11 ps. A
value of 000b in this field causes zero adjustment. Maximum combined adjustment using Coarse Phase Adjust
and Intermediate Phase adjust is approximately 2.1ns.
POR State: 000b
Bits 6:0
Must be set to 1b
Note Regarding Clock Phase Adjust
This is a feature intended to help the system designer remove small imbalances in clock distribution traces at the
board level when multiple ADCs are used. Please note, however, that enabling this feature will reduce the
dynamic performance (ENOB, SNR, SFDR) some finite amount. The amount of degradation increases with the
amount of adjustment applied. The user is strongly advised to (a) use the minimal amount of adjustment; and (b)
verify the net benefit of this feature in his system before relying on it.
Note Regarding Extended Mode Offset Correction
When using the I or Q channel Offset Adjust registers, the following information should be noted.
For offset values of +0000 0000 and −0000 0000, the actual offset is not the same. By changing only the sign bit
in this case, an offset step in the digital output code of about 1/10th of an LSB is experienced. This is shown
more clearly in the Figure below.
Figure 42. Extended Mode Offset Behavior
38
Submit Documentation Feedback
Copyright © 2007–2013, Texas Instruments Incorporated
Product Folder Links: ADC08D1020
ADC08D1020
www.ti.com
SNAS372D – NOVEMBER 2007 – REVISED MARCH 2013
MULTIPLE ADC SYNCHRONIZATION
The ADC08D1020 has the capability to precisely reset its sampling clock input to DCLK output relationship as
determined by the user-supplied DCLK_RST pulse. This allows multiple ADCs in a system to have their DCLK
(and data) outputs transition at the same time with respect to the shared CLK input that all the ADCs use for
sampling.
The DCLK_RST signal must observe some timing requirements that are shown in Figure 8, Figure 9 and
Figure 10 of the Timing Diagrams. The DCLK_RST pulse must be of a minimum width and its deassertion edge
must observe setup and hold times with respect to the CLK input rising edge. The duration of the DCLK_RST
pulse affects the length of time that the digital output will take before providing valid data again after the end of
the reset condition. Therefore, the DCLK_RST pulse width should be made reasonably short within the system
application constraints. These timing specifications are listed as tRH, tRS, and tPWR in the Converter Electrical
Characteristics.
The DCLK_RST signal can be asserted asynchronous to the input clock. If DCLK_RST is asserted, the DCLK
output is held in a designated state. The state in which DCLK is held during the reset period is determined by the
mode of operation (SDR/DDR) and the setting of the Output Edge configuration pin or bit. (Refer to Figure 8,
Figure 9 and Figure 10 for the DCLK reset state conditions). Therefore, depending upon when the DCLK_RST
signal is asserted, there may be a narrow pulse on the DCLK line during this reset event. When the DCLK_RST
signal is de-asserted in synchronization with the CLK rising edge, there are three or four CLK cycles of
systematic delay and the next CLK falling edge synchronizes the DCLK output with those of other ADC08D1020s
in the system. The DCLK output is enabled again after a constant delay (relative to the input clock frequency)
which is equal to the CLK input to DCLK output delay (tOD). The device always exhibits this delay characteristic in
normal operation. The user has the option of using a single-ended DCLK_RST signal, but a differential
DCLK_RST is strongly recommended due to its superior timing specifications.
As shown in Figure 8, Figure 9, and Figure 10 of the Timing Diagrams, there is a delay from the deassertion of
DCLK_RST to the reappearance of DCLK, which is equal to several cycles of CLK plus tOD. Note that the
deassertion of DCLK_RST is not latched in until the next falling edge of CLK. For 1:2 Demux DDR 0° Mode,
there are four CLK cycles of delay; for all other modes, there are three CLK cycles of delay.
If the device is not programmed to allow DCLK to run continuously, DCLK will become inactive during a
calibration cycle. Therefore, it is strongly recommended that DCLK only be used as a data capture clock and not
as a system clock.
The DCLK_RST pin should NOT be brought high while the calibration process is running (while CalRun is high).
Doing so could cause a digital glitch in the digital circuitry, resulting in corruption and invalidation of the
calibration.
Submit Documentation Feedback
Copyright © 2007–2013, Texas Instruments Incorporated
Product Folder Links: ADC08D1020
39
ADC08D1020
SNAS372D – NOVEMBER 2007 – REVISED MARCH 2013
www.ti.com
ADC TEST PATTERN
To aid in system debug, the ADC08D1020 has the capability of providing a test pattern at the four output ports
completely independent of the input signal. The ADC is disengaged and a test pattern generator is connected to
the outputs including OR. The test pattern output is the same in DES mode and non-DES mode. Each port is
given a unique 8-bit word, alternating between 1's and 0's as described in Table 16 and Table 17.
Table 16. Test Pattern by Output Port in
1:2 Demultiplex Mode
Time
Qd
Id
Q
I
OR
T0
01h
02h
03h
04h
0
T1
FEh
FDh
FCh
FBh
1
T2
01h
02h
03h
04h
0
T3
FEh
FDh
FCh
FBh
1
T4
01h
02h
03h
04h
0
T5
01h
02h
03h
04h
0
T6
FEh
FDh
FCh
FBh
1
T7
01h
02h
03h
04h
0
T8
FEh
FDh
FCh
FBh
1
0
T9
01h
02h
03h
04h
T10
01h
02h
03h
04h
0
T11
...
...
...
...
...
Comments
Pattern Sequence
n
Pattern Sequence
n+1
Pattern Sequence n+2
With the part programmed into the non-demultiplex mode, the test pattern’s order will be as described in
Table 17.
Table 17. Test Pattern by Output Port in
Non-demultiplex Mode
Time
Q
I
OR
T0
01h
02h
0
T1
FEh
FDh
1
T2
01h
02h
0
T3
01h
02h
0
T4
FEh
FDh
1
T5
FEh
FDh
1
T6
01h
02h
0
T7
01h
02h
0
T8
FEh
FDh
1
T9
01h
02h
0
T10
01h
02h
0
T11
FEh
FDh
1
T12
01h
02h
0
T13
01h
02h
0
T14
FEh
FDh
1
T15
...
...
...
Comments
Pattern Sequence
n
Pattern Sequence
n+1
It is possible for the I and the Q channels' test patterns to be not synchronized. Either I and Id or Q and Qd
patterns may be slipped by one DCLK.
To ensure that the test pattern starts synchronously in each port, set DCLK_RST while writing the Test Pattern
Output bit in the Extended Configuration Register. The pattern appears at the data output ports when
DCLK_RST is cleared low. The test pattern will work at speed and will work with the device in the SDR, DDR
and the non-demultiplex output modes.
40
Submit Documentation Feedback
Copyright © 2007–2013, Texas Instruments Incorporated
Product Folder Links: ADC08D1020
ADC08D1020
www.ti.com
SNAS372D – NOVEMBER 2007 – REVISED MARCH 2013
Applications Information
THE REFERENCE VOLTAGE
The voltage reference for the ADC08D1020 is derived from a 1.254V bandgap reference, a buffered version of
which is made available at pin 31, VBG, for user convenience.
This output has an output current capability of ±100 μA and should be buffered if more current than this is
required.
The internal bandgap-derived reference voltage has a nominal value of 650 mV or 870 mV, as determined by the
FSR pin and described in The Analog Inputs.
There is no provision for the use of an external reference voltage, but the full-scale input voltage can be adjusted
through a Configuration Register in the Extended Control mode, as explained in NORMAL/EXTENDED
CONTROL.
Differential input signals up to the chosen full-scale level will be digitized to 8 bits. Signal excursions beyond the
full-scale range will be clipped at the output. These large signal excursions will also activate the OR output for
the time that the signal is out of range. See Out Of Range (OR) Indication.
One extra feature of the VBG pin is that it can be used to raise the common mode voltage level of the LVDS
outputs. The output offset voltage (VOS) is typically 800 mV when the VBG pin is used as an output or left
unconnected. To raise the LVDS offset voltage to a typical value of 1175 mV the VBG pin can be connected
directly to the supply rails.
THE ANALOG INPUT
The analog input is a differential one to which the signal source may be a.c. coupled or d.c. coupled. In the
normal mode, the full-scale input range is selected using the FSR pin as specified in the Converter Electrical
Characteristics. In the Extended Control mode, the full-scale input range is selected by programming the FullScale Voltage Adjust register through the Serial Interface. For best performance when adjusting the input fullscale range in the Extended Control, refer to REGISTER DESCRIPTION for guidelines on limiting the amount of
adjustment
Table 18 gives the input to output relationship with the FSR pin high when the normal (non-extended) mode is
used. With the FSR pin grounded, the millivolt values in Table 18 are reduced to 75% of the values indicated. In
the Enhanced Control Mode, these values will be determined by the full scale range and offset settings in the
Control Registers.
Table 18. Differential Input To Output Relationship
(Non-Extended Control Mode, FSR High)
VIN+
VIN−
Output Code
VCM − 217.5 mV
VCM + 217.5 mV
0000 0000
VCM − 109 mV
VCM + 109 mV
0100 0000
VCM
VCM
0111 1111 /
1000 0000
VCM + 109 mV
VCM − 109 mV
1100 0000
VCM + 217.5 mV
VCM − 217.5 mV
1111 1111
The buffered analog inputs simplify the task of driving these inputs and the RC pole that is generally used at
sampling ADC inputs is not required. If it is desired to use an amplifier circuit before the ADC, use care in
choosing an amplifier with adequate noise and distortion performance and adequate gain at the frequencies used
for the application.
Note that a precise d.c. common mode voltage must be present at the ADC inputs. This common mode voltage,
VCMO, is provided on-chip when a.c. input coupling is used and the input signal is a.c. coupled to the ADC.
When the inputs are a.c. coupled, the VCMO output must be grounded, as shown in Figure 43. This causes the
on-chip VCMO voltage to be connected to the inputs through on-chip 50 kΩ resistors.
Submit Documentation Feedback
Copyright © 2007–2013, Texas Instruments Incorporated
Product Folder Links: ADC08D1020
41
ADC08D1020
SNAS372D – NOVEMBER 2007 – REVISED MARCH 2013
www.ti.com
IMPORTANT NOTE: An Analog input channel that is not used (e.g. in DES Mode) should be connected to acground (ie, capacitors to ground) when the inputs are a.c. coupled. Do not connect an unused analog input
directly to ground.
Ccouple
VIN+
Ccouple
VINVCMO
ADC08D1020
Figure 43. Differential Input Drive
When the d.c. coupled mode is used, a common mode voltage must be provided at the differential inputs. This
common mode voltage should track the VCMO output pin. Note that the VCMO output potential will change with
temperature. The common mode output of the driving device should track this change.
IMPORTANT NOTE: An analog input channel that is not used (e.g. in DES Mode) should be tied to the VCMO
voltage when the inputs are d.c. coupled. Do not connect unused analog inputs to ground.
Full-scale distortion performance falls off rapidly as the input common mode voltage deviates from VCMO.
This is a direct result of using a very low supply voltage to minimize power. Keep the input common
voltage within 50 mV of VCMO.
Performance is as good in the d.c. coupled mode as it is in the a.c. coupled mode, provided the input common
mode voltage at both analog inputs remain within 50 mV of VCMO.
Handling Single-Ended Input Signals
There is no provision for the ADC08D1020 to adequately process single-ended input signals. The best way to
handle single-ended signals is to convert them to differential signals before presenting them to the ADC. The
easiest way to accomplish single-ended to differential signal conversion is with an appropriate balun-connected
transformer, as shown in Figure 44.
a.c. Coupled Input
The easiest way to accomplish single-ended a.c. input to differential a.c. signal is by using an appropriate balun,
as shown inFigure 44.
Ccouple
50:
Source
VIN+
100:
1:2 Balun
Ccouple
VINADC08D1020
Figure 44. Single-Ended to Differential Signal Conversion Using a Balun
Figure 44 is a generic depiction of a single-ended to differential signal conversion using a balun. The circuitry
specific to the balun will depend upon the type of balun selected and the overall board layout. It is recommended
that the system designer contact the manufacturer of the balun they have selected to aid in designing the best
performing single-ended to differential conversion circuit using that particular balun.
42
Submit Documentation Feedback
Copyright © 2007–2013, Texas Instruments Incorporated
Product Folder Links: ADC08D1020
ADC08D1020
www.ti.com
SNAS372D – NOVEMBER 2007 – REVISED MARCH 2013
When selecting a balun, it is important to understand the input architecture of the ADC. There are specific balun
parameters of which the system designer should be mindful. A designer should match the impedance of their
analog source to the ADC081020's on-chip 100Ω differential input termination resistor. The range of this
termination resistor is described in the electrical table as the specification RIN.
Also, the phase and amplitude balance are important. The lowest possible phase and amplitude imbalance is
desired when selecting a balun. The phase imbalance should be no more than ±2.5° and the amplitude
imbalance should be limited to less than 1dB at the desired input frequency range. Finally, when selecting a
balun, the VSWR (Voltage Standing Wave Ratio), bandwidth and insertion loss of the balun should also be
considered. The VSWR aids in determining the overall transmission line termination capability of the balun when
interfacing to the ADC input. The insertion loss should be considered so that the signal at the balun output is
within the specified input range of the ADC as described in the Converter Electrical Characteristics as the
specification VIN.
D.C. Coupled Input
When d.c. coupling to the ADC08D1020 analog inputs is required, single-ended to differential conversion may be
easily accomplished with the LMH6555, as shown in Figure 45. In such applications, the LMH6555 performs the
task of single-ended to differential conversion while delivering low distortion and noise, as well as output balance,
that supports the operation of the ADC08D1020. Connecting the ADC08D1020 VCMO pin to the VCM_REF pin of
the LMH6555, through an appropriate buffer, will ensure that the common mode input voltage is as needed for
optimum performance of the ADC08D1020. The LMV321 was chosen to buffer VCMD for its low voltage operation
and reasonable offset voltage.
Be sure to limit output current from the ADC08D1020 VCMO pin to 100 μA
3.3V
LMH6555
RADJ-
RT2
RG1
50:
VIN100:
+
50:
RT1
RG2
VIN+
50:
50:
50:
RF2
VCM_REF
ADC08D1520
RADJ+
Signal
Input with
dc-coupled
50:
output
impedance
RF1
VCMO
+
LMV321
Figure 45. Example of Servoing the Analog Input with VCMO
In Figure 45, RADJ-and RADJ+ are used to adjust the differential offset that can be measured at the ADC inputs
VIN+ / VIN-with LMH6555's input terminated to ground as shown but not driven and with no RADJ resistors applied.
An unadjusted positive offset with reference to VIN-greater than |15mV| should be reduced with a resistor in the
RADJ-position. Likewise, an unadjusted negative offset with reference to VIN-greater than |15mV| should be
reduced with a resistor in the RADJ+ position. Table 19 gives suggested RADJ-and RADJ+ values for various
unadjusted differential offsets to bring the VIN+ / VIN-offset back to within |15mV|.
Table 19. D.C. Coupled Offset Adjustment
Unadjusted Offset Reading
Resistor Value
0mV to 10mV
no resistor needed
11mV to 30mV
20.0kΩ
31mV to 50mV
10.0kΩ
51mV to 70mV
6.81kΩ
71mV to 90mV
4.75kΩ
91mV to 110mV
3.92kΩ
Submit Documentation Feedback
Copyright © 2007–2013, Texas Instruments Incorporated
Product Folder Links: ADC08D1020
43
ADC08D1020
SNAS372D – NOVEMBER 2007 – REVISED MARCH 2013
www.ti.com
Out Of Range (OR) Indication
When the conversion result is clipped the Out of Range output is activated such that OR+ goes high and ORgoes low. This output is active as long as accurate data on either or both of the buses would be outside the
range of 00h to FFh. Note that when the device is programmed to provide a second DCLK output, the OR
signals become DCLK2. Refer to REGISTER DESCRIPTION
Full-Scale Input Range
As with all A/D Converters, the input range is determined by the value of the ADC's reference voltage. The
reference voltage of the ADC08D1020 is derived from an internal band-gap reference. The FSR pin controls the
effective reference voltage of the ADC08D1020 such that the differential full-scale input range at the analog
inputs is a normal amplitude with the FSR pin high, or a reduced amplitude with FSR pin low as defined by the
specification VIN in the Converter Electrical Characteristics. Best SNR is obtained with FSR high, but better
distortion and SFDR are obtained with the FSR pin low. The LMH6555 of is Figure 45 suitable for any Full Scale
Range.
44
Submit Documentation Feedback
Copyright © 2007–2013, Texas Instruments Incorporated
Product Folder Links: ADC08D1020
ADC08D1020
www.ti.com
SNAS372D – NOVEMBER 2007 – REVISED MARCH 2013
THE CLOCK INPUTS
The ADC08D1020 has differential LVDS clock inputs, CLK+ and CLK−, which must be driven with an a.c.
coupled, differential clock signal. Although the ADC08D1020 is tested and its performance is specified with a
differential 1 GHz clock, it typically will function well with input clock frequencies indicated in the Converter
Electrical Characteristics. The clock inputs are internally terminated and biased. The input clock signal must be
capacitively coupled to the clock pins as indicated in Figure 46.
Operation up to the sample rates indicated in the Converter Electrical Characteristics is typically possible if the
maximum ambient temperatures indicated are not exceeded. Operating at higher sample rates than indicated for
the given ambient temperature may result in reduced device reliability and product lifetime. This is because of the
higher power consumption and die temperatures at high sample rates. Important also for reliability is proper
thermal management . See Thermal Management.
Ccouple
CLK+
Ccouple
CLK-
ADC08D1020
Figure 46. Differential (LVDS) Input Clock Connection
The differential input clock line pair should have a characteristic impedance of 100 Ω and (when using a balun),
be terminated at the clock source in that (100 Ω) characteristic impedance. The input clock line should be as
short and as direct as possible. The ADC08D1020 clock input is internally terminated with an untrimmed 100 Ω
resistor.
Insufficient input clock levels will result in poor dynamic performance. Excessively high clock levels could cause a
change in the analog input offset voltage. To avoid these problems, keep the clock level within the range
specified as VID in the Converter Electrical Characteristics.
The low and high times of the input clock signal can affect the performance of any A/D Converter. The
ADC08D1020 features a duty cycle clock correction circuit which can maintain performance over temperature
even in DES mode. The ADC will meet its performance specification if the input clock high and low times are
maintained within the duty cycle range as specified in the Converter Electrical Characteristics.
High speed, high performance ADCs such as the ADC08D1020 require a very stable input clock signal with
minimum phase noise or jitter. ADC jitter requirements are defined by the ADC resolution (number of bits),
maximum ADC input frequency and the input signal amplitude relative to the ADC input full scale range. The
maximum jitter (the sum of the jitter from all sources) allowed to prevent a jitter-induced reduction in SNR is
found to be
tJ(MAX) = (VINFSR / VIN(P-P)) x (1/(2(N+1) x π x fIN))
(3)
where tJ(MAX) is the rms total of all jitter sources in seconds, VIN(P-P) is the peak-to-peak analog input signal, VINFSR
is the full-scale range of the ADC, "N" is the ADC resolution in bits and fIN is the maximum input frequency, in
Hertz, at the ADC analog input.
Note that the maximum jitter described above is the RSS sum of the jitter from all sources, including that in the
ADC input clock, that added by the system to the ADC input clock and input signals and that added by the ADC
itself. Since the effective jitter added by the ADC is beyond user control, the best the user can do is to keep the
sum of the externally added input clock jitter and the jitter added by the analog circuitry to the analog signal to a
minimum.
Input clock amplitudes above those specified in the Converter Electrical Characteristics may result in increased
input offset voltage. This would cause the converter to produce an output code other than the expected 127/128
when both input pins are at the same potential.
Submit Documentation Feedback
Copyright © 2007–2013, Texas Instruments Incorporated
Product Folder Links: ADC08D1020
45
ADC08D1020
SNAS372D – NOVEMBER 2007 – REVISED MARCH 2013
www.ti.com
CONTROL PINS
Six control pins (without the use of the serial interface) provide a wide range of possibilities in the operation of
the ADC08D1020 and facilitate its use. These control pins provide Full-Scale Input Range setting, Calibration,
Calibration Delay, Output Edge Synchronization choice, LVDS Output Level choice and a Power Down feature.
Full-Scale Input Range Setting
The input full-scale range can be selected with the FSR control input (pin 14) in the normal mode of operation.
The input full-scale range is specified as VIN in the Converter Electrical Characteristics. In the extended control
mode, the input full-scale range may be programmed using the Full-Scale Adjust Voltage register. See THE
ANALOG INPUT for more information.
Calibration
The ADC08D1020 calibration must be run to achieve specified performance. The calibration procedure is run
upon power-up and can be run any time on command. The calibration procedure is exactly the same whether
there is an input clock present upon power up or if the clock begins some time after application of power. The
CalRun output indicator is high while a calibration is in progress. Note that the DCLK outputs are not active
during a calibration cycle by default and therefore are not recommended as system clock unless the Resistor
Trim Disable feature is used (Reg.9h). The DCLK outputs are continuously present at the output only when the
Resistor Trim Disable is active.
Power-On Calibration
Power-on calibration begins after a time delay following the application of power. This time delay is determined
by the setting of CalDly, as described in the Calibration Delay Section, below.
The calibration process will be not be performed if the CAL pin is high at power up. In this case, the calibration
cycle will not begin until the on-command calibration conditions are met. The ADC08D1020 will function with the
CAL pin held high at power up, but no calibration will be done and performance will be impaired. A manual
calibration, however, may be performed after powering up with the CAL pin high. See On-Command Calibration
On-Command Calibration.
The internal power-on calibration circuitry comes up in an unknown logic state. If the input clock is not running at
power up and the power on calibration circuitry is active, it will hold the analog circuitry in power down and the
power consumption will typically be less than 200 mW. The power consumption will be normal after the clock
starts.
On-Command Calibration
To initiate an on-command calibration, bring the CAL pin high for a minimum of tCAL_H input clock cycles after it
has been low for a minimum of tCAL_L input clock cycles. Holding the CAL pin high upon power up will prevent
execution of power-on calibration until the CAL pin is low for a minimum of tCAL_L input clock cycles, then brought
high for a minimum of another tCAL_H input clock cycles. The calibration cycle will begin tCAL_H input clock cycles
after the CAL pin is thus brought high. The CalRun signal should be monitored to determine when the calibration
cycle has completed.
The minimum tCAL_L and tCAL_H input clock cycle sequence is required to ensure that random noise does not
cause a calibration to begin when it is not desired. As mentioned for best performance, a calibration should be
performed 20 seconds or more after power up and repeated when the operating temperature changes
significantly relative to the specific system design performance requirements.
By default, On-Command calibration also includes calibrating the input termination resistance and the ADC.
However, since the input termination resistance, once trimmed at power-up, changes marginally with
temperature, the user has the option to disable the input termination resistor trim, which will ensure that the
DCLK is continuously present at the output during subsequent calibration. The Resistor Trim Disable can be
programmed in register (address: 1h, bit 13) when in the Extended Control mode. Refer to REGISTER
DESCRIPTION for register programming information.
46
Submit Documentation Feedback
Copyright © 2007–2013, Texas Instruments Incorporated
Product Folder Links: ADC08D1020
ADC08D1020
www.ti.com
SNAS372D – NOVEMBER 2007 – REVISED MARCH 2013
Calibration Delay
The CalDly input (pin 127) is used to select one of two delay times after the application of power to the start of
calibration, as described in Calibration. The calibration delay values allow the power supply to come up and
stabilize before calibration takes place. With no delay or insufficient delay, calibration would begin before the
power supply is stabilized at its operating value and result in non-optimal calibration coefficients. If the PD pin is
high upon power-up, the calibration delay counter will be disabled until the PD pin is brought low. Therefore,
holding the PD pin high during power up will further delay the start of the power-up calibration cycle. The best
setting of the CalDly pin depends upon the power-on settling time of the power supply.
Note that the calibration delay selection is not possible in the Extended Control mode and the short delay time is
used.
Output Edge Synchronization
DCLK signals are available to help latch the converter output data into external circuitry. The output data can be
synchronized with either edge of these DCLK signals. That is, the output data transition can be set to occur with
either the rising edge or the falling edge of the DCLK signal, so that either edge of that DCLK signal can be used
to latch the output data into the receiving circuit.
When OutEdge (pin 4) is high, the output data is synchronized with (changes with) the rising edge of the DCLK+
(pin 82). When OutEdge is low, the output data is synchronized with the falling edge of DCLK+.
At the very high speeds of which the ADC08D1020 is capable, slight differences in the lengths of the DCLK and
data lines can mean the difference between successful and erroneous data capture. The OutEdge pin is used to
capture data on the DCLK edge that best suits the application circuit and layout.
Reliable data capture can be achieved by using just one DCLK+/- signal for the full 32 signal data bus. However,
if desired, the user may configure the OR+/- output as the second DCLK+/- output instead.
LVDS Output Level Control
The output level can be set to one of two levels with OutV (pin 3). The strength of the output drivers is greater
with OutV high. With OutV low there is less power consumption in the output drivers, but the lower output level
means decreased noise immunity.
For short LVDS lines and low noise systems, satisfactory performance may be realized with the OutV input low.
If the LVDS lines are long and/or the system in which the ADC08D1020 is used is noisy, it may be necessary to
tie the OutV pin high.
Dual Edge Sampling
The Dual Edge Sampling (DES) feature causes one of the two input pairs to be routed to both ADCs. The other
input pair is deactivated. One of the ADCs samples the input signal on one input clock edge (duty cycle
corrected), the other samples the input signal on the other input clock edge (duty cycle corrected). If the device is
in the 1:2 output demultiplex mode, the result is an output data rate 1/4 that of the interleaved sample rate which
is twice the input clock frequency. Data is presented in parallel on all four output buses in the following order:
DQd, DId, DQ, DI. If the device is the non-demultiplex output mode, the result is an output data rate 1/2 that of
the interleaved sample rate. Data is presented in parallel on two output buses in the following order: DQ, DI.
To use this feature in the non-extended control mode, allow pin 127 to float and the signal at the "I" channel input
will be sampled by both converters. The Calibration Delay will then only be a short delay.
In the extended control mode, either input may be used for dual edge sampling. See Dual-Edge Sampling.
Power Down Feature
The Power Down pins (PD and PDQ) allow the ADC08D1020 to be entirely powered down (PD) or the "Q"
channel to be powered down and the "I" channel to remain active. See Power Down for details on the power
down feature.
The digital data (+/-) output pins are put into a high impedance state when the PD pin for the respective channel
is high. Upon return to normal operation, the pipeline will contain meaningless information and must be flushed.
Submit Documentation Feedback
Copyright © 2007–2013, Texas Instruments Incorporated
Product Folder Links: ADC08D1020
47
ADC08D1020
SNAS372D – NOVEMBER 2007 – REVISED MARCH 2013
www.ti.com
If the PD input is brought high while a calibration is running, the device will not go into power down until the
calibration sequence is complete. However, if power is applied and PD is already high, the device will not begin
the calibration sequence until the PD input goes low. If a manual calibration is requested while the device is
powered down, the calibration will not begin at all. That is, the manual calibration input is completely ignored in
the power down state.
THE DIGITAL OUTPUTS
The ADC08D1020 normally demultiplexes the output data of each of the two ADCs on the die onto two LVDS
output buses (total of four buses, two for each ADC). For each of the two converters, the results of successive
conversions started on the odd falling edges of the CLK+ pin are available on one of the two LVDS buses, while
the results of conversions started on the even falling edges of the CLK+ pin are available on the other LVDS bus.
This means that, the word rate at each LVDS bus is 1/2 the ADC08D1020 input clock rate and the two buses
must be multiplexed to obtain the entire 1 GSPS conversion result.
Since the minimum recommended input clock rate for this device is 200 MSPS (normal non-DES mode), the
effective rate can be reduced to as low as 100 MSPS by using the results available on just one of the the two
LVDS buses and a 200 MHz input clock, decimating the 200 MSPS data by two.
There is one LVDS output clock pair (DCLK+/−) available for use to latch the LVDS outputs on all buses.
However, the user has the option to configure the OR+/- output as a second DCLK+/- pair. Whether the data is
sent at the rising or falling edge of DCLK is determined by the sense of the OutEdge pin, as described in Output
Edge Synchronization.
DDR (Double Data Rate) clocking can also be used. In this mode a word of data is presented with each edge of
DCLK, reducing the DCLK frequency to 1/4 the input clock frequency. See the Timing Diagram section for
details.
The OutV pin is used to set the LVDS differential output levels. See LVDS Output Level Control.
The output format is Offset Binary. Accordingly, a full-scale input level with VIN+ positive with respect to VIN− will
produce an output code of all ones, a full-scale input level with VIN− positive with respect to VIN+ will produce an
output code of all zeros and when VIN+ and VIN− are equal, the output code will vary between codes 127 and
128. A non-multiplexed mode of operation is available for those cases where the digital ASIC is capable of higher
speed operation.
POWER CONSIDERATIONS
A/D converters draw sufficient transient current to corrupt their own power supplies if not adequately bypassed. A
33 µF capacitor should be placed within an inch (2.5 cm) of the A/D converter power pins. A 0.1 µF capacitor
should be placed as close as possible to each VA pin, preferably within one-half centimeter. Leadless chip
capacitors are preferred because they have low lead inductance.
The VA and VDR supply pins should be isolated from each other to prevent any digital noise from being coupled
into the analog portions of the ADC. A ferrite choke, such as the JW Miller FB20009-3B, is recommended
between these supply lines when a common source is used for them.
As is the case with all high speed converters, the ADC08D1020 should be assumed to have little power supply
noise rejection. Any power supply used for digital circuitry in a system where a lot of digital power is being
consumed should not be used to supply power to the ADC08D1020. The ADC supplies should be the same
supply used for other analog circuitry, if not a dedicated supply.
Supply Voltage
The ADC08D1020 is specified to operate with a supply voltage of 1.9V ±0.1V. It is very important to note that,
while this device will function with slightly higher supply voltages, these higher supply voltages may reduce
product lifetime.
No pin should ever have a voltage on it that is in excess of the supply voltage or below ground by more than 150
mV, not even on a transient basis. This can be a problem upon application of power and power shut-down. Be
sure that the supplies to circuits driving any of the input pins, analog or digital, do not come up any faster than
does the voltage at the ADC08D1020 power pins.
48
Submit Documentation Feedback
Copyright © 2007–2013, Texas Instruments Incorporated
Product Folder Links: ADC08D1020
ADC08D1020
www.ti.com
SNAS372D – NOVEMBER 2007 – REVISED MARCH 2013
The Absolute Maximum Ratings should be strictly observed, even during power up and power down. A power
supply that produces a voltage spike at turn-on and/or turn-off of power can destroy the ADC08D1020. The
circuit of Figure 47 will provide supply overshoot protection.
Many linear regulators will produce output spiking at power-on unless there is a minimum load provided. Active
devices draw very little current until their supply voltages reach a few hundred millivolts. The result can be a turnon spike that can destroy the ADC08D1020, unless a minimum load is provided for the supply. The 100 Ω
resistor at the regulator output provides a minimum output current during power-up to ensure there is no turn-on
spiking.
In the circuit of Figure 47, an LM317 linear regulator is satisfactory if its input supply voltage is 4V to 5V . If a
3.3V supply is used, an LM1086 linear regulator is recommended.
Linear
Regulator
VIN
1.9V
to ADC
+
10 PF
210
+
33 PF
100
+
10 PF
110
Figure 47. Non-Spiking Power Supply
The output drivers should have a supply voltage, VDR, that is within the range specified in the Operating Ratings
table. This voltage should not exceed the VA supply voltage.
If the power is applied to the device without an input clock signal present, the current drawn by the device might
be below 200 mA. This is because the ADC08D1020 gets reset through clocked logic and its initial state is
unknown. If the reset logic comes up in the "on" state, it will cause most of the analog circuitry to be powered
down, resulting in less than 100 mA of current draw. This current is greater than the power down current
because not all of the ADC is powered down. The device current will be normal after the input clock is
established.
Thermal Management
The ADC08D1020 is capable of impressive speeds and performance at very low power levels for its speed.
However, the power consumption is still high enough to require attention to thermal management. For reliability
reasons, the die temperature should be kept to a maximum of 130°C. That is, TA (ambient temperature) plus
ADC power consumption times θJA (junction to ambient thermal resistance) should not exceed 130°C. This is not
a problem if the ambient temperature is kept to a maximum of +85°C as specified in the Operating Ratings
section.
Please note that the following are general recommendations for mounting exposed pad devices onto a PCB. This
should be considered the starting point in PCB and assembly process development. It is recommended that the
process be developed based upon past experience in package mounting.
The package of the ADC08D1020 has an exposed pad on its back that provides the primary heat removal path
as well as excellent electrical grounding to the printed circuit board. The land pattern design for lead attachment
to the PCB should be the same as for a conventional HLQFP, but the exposed pad must be attached to the
board to remove the maximum amount of heat from the package, as well as to ensure best product parametric
performance.
To maximize the removal of heat from the package, a thermal land pattern must be incorporated on the PC
board within the footprint of the package. The exposed pad of the device must be soldered down to ensure
adequate heat conduction out of the package. The land pattern for this exposed pad should be at least as large
as the 5 x 5 mm of the exposed pad of the package and be located such that the exposed pad of the device is
entirely over that thermal land pattern. This thermal land pattern should be electrically connected to ground. A
clearance of at least 0.5 mm should separate this land pattern from the mounting pads for the package pins.
Submit Documentation Feedback
Copyright © 2007–2013, Texas Instruments Incorporated
Product Folder Links: ADC08D1020
49
ADC08D1020
SNAS372D – NOVEMBER 2007 – REVISED MARCH 2013
www.ti.com
5.0 mm, min
0.25 mm, typ
0.33 mm, typ
1.2 mm, typ
Figure 48. Recommended Package Land Pattern
Since a large aperture opening may result in poor release, the aperture opening should be subdivided into an
array of smaller openings, similar to the land pattern of Figure 48.
To minimize junction temperature, it is recommended that a simple heat sink be built into the PCB. This is done
by including a copper area of about 2 square inches (6.5 square cm) on the opposite side of the PCB. This
copper area may be plated or solder coated to prevent corrosion, but should not have a conformal coating, which
could provide some thermal insulation. Thermal vias should be used to connect these top and bottom copper
areas. These thermal vias act as "heat pipes" to carry the thermal energy from the device side of the board to the
opposite side of the board where it can be more effectively dissipated. The use of 9 to 16 thermal vias is
recommended.
The thermal vias should be placed on a 1.2 mm grid spacing and have a diameter of 0.30 to 0.33 mm. These
vias should be barrel plated to avoid solder wicking into the vias during the soldering process as this wicking
could cause voids in the solder between the package exposed pad and the thermal land on the PCB. Such voids
could increase the thermal resistance between the device and the thermal land on the board, which would cause
the device to run hotter.
If it is desired to monitor die temperature, a temperature sensor may be mounted on the heat sink area of the
board near the thermal vias. Allow for a thermal gradient between the temperature sensor and the ADC08D1020
die of θJC (Thermal Pad) times typical power consumption = 2.8 x 1.8 = 5°C. Allowing for 6°C, including some
margin for temperature drop from the pad to the temperature sensor, then, would mean that maintaining a
maximum pad temperature reading of 124°C will ensure that the die temperature does not exceed 130°C,
assuming that the exposed pad of the ADC08D1020 is properly soldered down and the thermal vias are
adequate. (The inaccuracy of the temperature sensor is in addition to the above calculation).
LAYOUT AND GROUNDING
Proper grounding and proper routing of all signals are essential to ensure accurate conversion. A single ground
plane should be used, instead of splitting the ground plane into analog and digital areas.
Since digital switching transients are composed largely of high frequency components, the skin effect tells us that
total ground plane copper weight will have little effect upon the logic-generated noise. Total surface area is more
important than is total ground plane volume. Coupling between the typically noisy digital circuitry and the
sensitive analog circuitry can lead to poor performance that may seem impossible to isolate and remedy. The
solution is to keep the analog circuitry well separated from the digital circuitry.
High power digital components should not be located on or near any linear component or power supply trace or
plane that services analog or mixed signal components as the resulting common return current path could cause
fluctuation in the analog input “ground” return of the ADC, causing excessive noise in the conversion result.
Generally, we assume that analog and digital lines should cross each other at 90° to avoid getting digital noise
into the analog path. In high frequency systems, however, avoid crossing analog and digital lines altogether. The
input clock lines should be isolated from ALL other lines, analog AND digital. The generally-accepted 90°
crossing should be avoided as even a little coupling can cause problems at high frequencies. Best performance
at high frequencies is obtained with a straight signal path.
50
Submit Documentation Feedback
Copyright © 2007–2013, Texas Instruments Incorporated
Product Folder Links: ADC08D1020
ADC08D1020
www.ti.com
SNAS372D – NOVEMBER 2007 – REVISED MARCH 2013
The analog input should be isolated from noisy signal traces to avoid coupling of spurious signals into the input.
This is especially important with the low level drive required of the ADC08D1020. Any external component (e.g.,
a filter capacitor) connected between the converter's input and ground should be connected to a very clean point
in the analog ground plane. All analog circuitry (input amplifiers, filters, etc.) should be separated from any digital
components.
DYNAMIC PERFORMANCE
The ADC08D1020 is a.c. tested and its dynamic performance is ensured. To meet the published specifications
and avoid jitter-induced noise, the clock source driving the CLK input must exhibit low rms jitter. The allowable
jitter is a function of the input frequency and the input signal level, as described in THE CLOCK INPUTS.
It is good practice to keep the ADC input clock line as short as possible, to keep it well away from any other
signals and to treat it as a transmission line. Other signals can introduce jitter into the input clock signal. The
clock signal can also introduce noise into the analog path if not isolated from that path.
Best dynamic performance is obtained when the exposed pad at the back of the package has a good connection
to ground. This is because this path from the die to ground is a lower impedance than offered by the package
pins.
USING THE SERIAL INTERFACE
The ADC08D1020 may be operated in the non-extended control (non-Serial Interface) mode or in the extended
control mode. Table 20 and Table 21 describe the functions of pins 3, 4, 14 and 127 in the non-extended control
mode and the extended control mode, respectively.
Non-Extended Control Mode Operation
Non-extended control mode operation means that the Serial Interface is not active and all controllable functions
are controlled with various pin settings. Pin 41 is the primary control of the extended control enable function.
When pin 41 is logic high, the device is in the non-extended control mode. If pin 41 is floating and pin 52 is
floating or logic high, the extended control enable function is controlled by pin 14. The device has functions which
are pin programmable when in the non-extended control mode. An example is the full-scale range is controlled in
the non-extended control mode by setting pin 14 high or low. Table 20 indicates the pin functions of the
ADC08D1020 in the non-extended control mode.
Table 20. Non-Extended Control Mode Operation
(Pin 41 Floating and Pin 52 Floating or Logic High)
Pin
Low
High
Floating
3
Reduced VOD
Normal VOD
n/a
4
OutEdge = Neg
OutEdge = Pos
DDR
127
CalDly Short
CalDly Long
DES
14
Reduced VIN
Normal VIN
Extended Control Mode
Pin 3 can be either high or low in the non-extended control mode. See NORMAL/EXTENDED CONTROL for
more information.
Pin 4 can be high or low or can be left floating in the non-extended control mode. In the non-extended control
mode, pin 4 high or low defines the edge at which the output data transitions. See Output Edge Synchronization
for more information. If this pin is floating, the output clock (DCLK) is a DDR (Double Data Rate) clock (see
Single Data Rate and Double Data Rate) and the output edge synchronization is irrelevant since data is clocked
out on both DCLK edges.
Pin 127, if it is high or low in the non-extended control mode, sets the calibration delay. If pin 127 is floating, the
calibration delay is the same as it would be with this pin low and the converter performs dual edge sampling
(DES).
Submit Documentation Feedback
Copyright © 2007–2013, Texas Instruments Incorporated
Product Folder Links: ADC08D1020
51
ADC08D1020
SNAS372D – NOVEMBER 2007 – REVISED MARCH 2013
www.ti.com
Table 21. Extended Control Mode Operation
(Pin 41 Logic Low or Pin 14 Floating and Pin 52 Floating or Logic High)
Pin
52
Function
3
SCLK (Serial Clock)
4
SDATA (Serial Data)
127
SCS (Serial Interface Chip Select)
Submit Documentation Feedback
Copyright © 2007–2013, Texas Instruments Incorporated
Product Folder Links: ADC08D1020
ADC08D1020
www.ti.com
SNAS372D – NOVEMBER 2007 – REVISED MARCH 2013
COMMON APPLICATION PITFALLS
Failure to write all register locations when using extended control mode. When using the serial interface, all
nine address locations must be written at least once with the default or desired values before calibration and
subsequent use of the ADC.
Driving the inputs (analog or digital) beyond the power supply rails. For device reliability, no input should go
more than 150 mV below the ground pins or 150 mV above the supply pins. Exceeding these limits on even a
transient basis may not only cause faulty or erratic operation, but may impair device reliability. It is not
uncommon for high speed digital circuits to exhibit undershoot that goes more than a volt below ground.
Controlling the impedance of high speed lines and terminating these lines in their characteristic impedance
should control overshoot.
Care should be taken not to overdrive the inputs of the ADC08D1020. Such practice may lead to conversion
inaccuracies and even to device damage.
Incorrect analog input common mode voltage in the d.c. coupled mode. As discussed in The Analog Inputs
and THE ANALOG INPUT, the Input common mode voltage must remain within 50 mV of the VCMO output ,
which has a variability with temperature that must also be tracked. Distortion performance will be degraded if the
input common mode voltage is more than 50 mV from VCMO .
Using an inadequate amplifier to drive the analog input. Use care when choosing a high frequency amplifier
to drive the ADC08D1020 as many high speed amplifiers will have higher distortion than will the ADC08D1020,
resulting in overall system performance degradation.
Driving the VBG pin to change the reference voltage. As mentioned in THE REFERENCE VOLTAGE, the
reference voltage is intended to be fixed by FSR pin or Full-Scale Voltage Adjust register settings. Over driving
this pin will not change the full scale value, but can otherwise upset operation.
Driving the clock input with an excessively high level signal. The ADC input clock level should not exceed
the level described in the Operating Ratings Table or the input offset could change.
Inadequate input clock levels. As described in THE CLOCK INPUTS, insufficient input clock levels can result in
poor performance. Excessive input clock levels could result in the introduction of an input offset.
Using a clock source with excessive jitter, using an excessively long input clock signal trace, or having
other signals coupled to the input clock signal trace. This will cause the sampling interval to vary, causing
excessive output noise and a reduction in SNR performance.
Failure to provide adequate heat removal. As described in Thermal Management, it is important to provide
adequate heat removal to ensure device reliability. This can be done either with adequate air flow or the use of a
simple heat sink built into the board. The backside pad should be grounded for best performance.
Submit Documentation Feedback
Copyright © 2007–2013, Texas Instruments Incorporated
Product Folder Links: ADC08D1020
53
ADC08D1020
SNAS372D – NOVEMBER 2007 – REVISED MARCH 2013
www.ti.com
REVISION HISTORY
Changes from Revision C (March 2013) to Revision D
•
54
Page
Changed layout of National Data Sheet to TI format .......................................................................................................... 53
Submit Documentation Feedback
Copyright © 2007–2013, Texas Instruments Incorporated
Product Folder Links: ADC08D1020
PACKAGE OPTION ADDENDUM
www.ti.com
10-Dec-2020
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
(2)
Lead finish/
Ball material
MSL Peak Temp
Op Temp (°C)
(3)
Device Marking
(4/5)
(6)
ADC08D1020CIYB/NOPB
ACTIVE
HLQFP
NNB
128
60
RoHS & Green
SN
Level-3-260C-168 HR
-40 to 85
ADC08D1020
CIYB
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance
do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may
reference these types of products as "Pb-Free".
RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption.
Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of
工商网监
湘ICP备2023018690号
