ADS5542
SBAS308D – MAY 2004 – REVISED FEBRUARY 2007
14-Bit, 80 MSPS
Analog-To-Digital Converter
FEATURES
•
•
•
•
•
•
•
•
•
14-Bit Resolution
80 MSPS Sample Rate
High SNR: 72.9 dBFS at 100 MHz fIN
High SFDR: 88 dBc at 100 MHz fIN
2.3-VPP Differential Input Voltage
Internal Voltage Reference
3.3-V Single-Supply Voltage
Analog Power Dissipation: 545 mW
Serial Programming Interface
•
•
TQFP-64 PowerPAD™ Package
Recommended Amplifiers:
OPA695, OPA847, THS3201, THS3202,
THS4503, THS4509, THS9001
APPLICATIONS
•
•
•
•
•
•
Wireless Communication
– Communication Receivers
– Base Station Infrastructure
Test and Measurement Instrumentation
Single and Multichannel Digital Receivers
Communication Instrumentation
– Radar, Infrared
Video and Imaging
Medical Equipment
DESCRIPTION
The ADS5542 is a high-performance, 14-bit, 80 MSPS analog-to-digital converter (ADC). To provide a complete
converter solution, it includes a high-bandwidth linear sample-and-hold stage (S&H) and internal reference.
Designed for applications demanding the highest speed and highest dynamic performance in little space, the
ADS5542 has excellent power consumption of 545 mW at 3.3-V single-supply voltage. This allows an even
higher system integration density. The provided internal reference simplifies system design requirements.
Parallel CMOS-compatible output ensures seamless interfacing with common logic.
The ADS5542 is available in a 64-pin TQFP PowerPAD package over the industrial temperature range -40°C to
85°C.
ADS5500 PRODUCT FAMILY
80 MSPS
105 MSPS
125 MSPS
12 Bit
ADS5522
ADS5521
ADS5542
14 Bit
ADS5542
ADS5541
ADS5500
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.
PowerPAD is a trademark of Texas Instruments.
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 © 2004–2007, Texas Instruments Incorporated
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SBAS308D – MAY 2004 – REVISED FEBRUARY 2007
AVDD
DRVDD
CLK+
CLK−
Timing Circuitry
14-Bit
Pipeline
ADC
Core
VIN+
S&H
VIN−
CM
Internal
Reference
CLKOUT
Digital
Error
Correction
D0
.
.
.
D13
Output
Control
OVR
DFS
Control Logic
Serial Programming Register
AGND
SEN
SDATA
ADS5542
SCLK
DRGND
This integrated circuit can be damaged by ESD. Texas Instruments recommends that all integrated circuits be handled with
appropriate precautions. Failure to observe proper handling and installation procedures can cause damage.
ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits may be
more susceptible to damage because very small parametric changes could cause the device not to meet its published
specifications.
ORDERING INFORMATION (1)
PRODUCT
PACKAGE-LEAD
ADS5542
HTQFP-64 (2)
PowerPAD
(1)
(2)
PACKAGE
DESIGNATOR
SPECIFIED
TEMPERATURE
RANGE
PACKAGE
MARKING
PAP
–40°C to 85°C
ADS5542I
ORDERING
NUMBER
TRANSPORT
MEDIA, QUANTITY
ADS5542IPAP
Tray, 160
ADS5542IPAPR
Tape and Reel, 1000
For the most current product and ordering information, see the Package Option Addendum at the end of this data sheet.
Thermal pad size: 3,5 mm × 3,5 mm (min), 4 mm x 4 mm (max). θJA = 21.47°C/W and θJC = 2.99°C/W, when used with 2 oz. copper
trace and pad soldered directly to a JEDEC standard, four-layer, 3 in × 3 in PCB.
ABSOLUTE MAXIMUM RATINGS
over operating free-air temperature range (unless otherwise noted) (1)
ADS5500
UNIT
–0.3 to 3.7
V
±0.1
V
–0.3 to minimum (AVDD + 0.3, 3.6)
V
Logic input to DRGND
–0.3 to DRVDD
V
Digital data output to DRGND
–0.3 to DRVDD
V
Operating temperature range
–40 to 85
°C
105
°C
–65 to 150
°C
Supply Voltage
AVDD to AGND, DRVDD to DRGND
AGND to DRGND
Analog input to AGND (2) (3)
Junction temperature
Storage temperature range
(1)
(2)
(3)
2
Stresses above these ratings may cause permanent damage. Exposure to absolute maximum conditions for extended periods may
degrade device reliability. These are stress ratings only, and functional operation of the device at these or any other conditions beyond
those specified is not implied.
If the input signal can exceed 3.6 V, then a resistor greater than or equal to 25 Ω should be added in series with each of the analog
input pins to support input voltages up to 3.8 V. For input voltages above 3.8 V, the device can only handle transients and the duty cycle
of the overshoot should be limited to less than 5% for inputs up to 3.9 V.
The overshoot duty cycle can be defined as the ratio of the total time of overshoot to the total intended device lifetime, expressed as a
percentage. The total time of overshoot is the integrated time of all overshoot occurences over the lifetime of the device.
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SBAS308D – MAY 2004 – REVISED FEBRUARY 2007
RECOMMENDED OPERATING CONDITIONS
MIN
TYP
MAX
UNIT
Analog supply voltage, AVDD
3
3.3
3.6
V
Output driver supply voltage, DRVDD
3
3.3
3.6
V
SUPPLIES
ANALOG INPUT
Differential input range
Input common-mode voltage, VCM
2.3
(1)
1.45
1.55
VPP
1.65
V
DIGITAL OUTPUT
Maximum output load
10
pF
CLOCK INPUT
ADCLK input sample rate (sine wave) 1/tC
2
Clock amplitude, sine wave, differential (2)
1
80
3
Clock duty cycle (3)
VPP
50%
Open free-air temperature range
(1)
(2)
(3)
MSPS
–40
85
°C
Input common-mode should be connected to CM.
See Figure 47 for more information.
See Figure 46 for more information.
ELECTRICAL CHARACTERISTICS
Typical values given at TA = 25°C, min and max specified over the full recommended operating temperature range, AVDD =
DRVDD = 3.3 V, sampling rate = 80 MSPS, 50% clock duty cycle, 3-VPP differential clock, and –1dBFS differential input,
unless otherwise noted
PARAMETER
CONDITIONS
MIN
Resolution
TYP
MAX
UNIT
12
Bits
Analog Inputs
Differential input range
2.3
VPP
Differential input impedance
See Figure 37
6.6
kΩ
Differential input capacitance
See Figure 37
4
pF
200
µA
750
MHz
Analog input common-mode current (per
input)
Analog input bandwidth
Source impedance = 50 Ω
Voltage overload recovery time
4
Clock cycles
Internal Reference Voltages
Reference bottom voltage, VREFM
1.0
Reference top voltage, VREFP
V
2.15
Reference error
–4%
±0.6%
V
4%
1.55 ±0.05
Common-mode voltage output, VCM
V
Dynamic DC Characteristics and Accuracy
No missing codes
Assured
Differential nonlinearity error, DNL
fIN = 10 MHz
-0.9
0.5
1.1
LSB
Integral nonlinearity error, INL
fIN = 10 MHz
–5
±2
5
LSB
±1.5
11
Offset error
-11
Offset temperature coefficient
DC power-supply rejection ratio, DC PSRR
Gain error
∆offset error/∆AVDD from AVDD = 3 V to
AVDD = 3.6 V
(1)
-2
Gain temperature coefficient
(1)
mV
0.02
mV/°C
0.25
mV/V
0.3
–0.02
2
%FS
∆%/°C
Gain error is specified by design and characterization; it is not tested in production.
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SBAS308D – MAY 2004 – REVISED FEBRUARY 2007
ELECTRICAL CHARACTERISTICS (continued)
Typical values given at TA = 25°C, min and max specified over the full recommended operating temperature range, AVDD =
DRVDD = 3.3 V, sampling rate = 80 MSPS, 50% clock duty cycle, 3-VPP differential clock, and –1dBFS differential input,
unless otherwise noted
PARAMETER
CONDITIONS
MIN
TYP
25°C to 85°C
72.7
74.3
Full temp range
71.5
74.0
25°C to 85°C
71.5
73.5
Full temp range
70.0
73
MAX
UNIT
Dynamic AC Characteristics
fIN = 10 MHz
fIN = 55 MHz
Signal-to-noise ratio, SNR
RMS output noise
fIN = 70 MHz
73.7
fIN = 100 MHz
72.9
fIN = 150 MHz
71.9
fIN = 220 MHz
70.7
Input tied to common-mode
fIN = 10 MHz
1.1
25°C
80
92
Full temp range
78
90
fIN = 55 MHz
Spurious-free dynamic range, SFDR
fIN = 70 MHz
25°C
80
87
Full temp range
78
86
88
fIN = 150 MHz
85
fIN = 220 MHz
fIN = 70 MHz
80
92
Full temp range
78
90
25°C
80
87
Full temp range
78
86
88
fIN = 100 MHz
88
fIN = 150 MHz
85
fIN = 220 MHz
77
fIN = 10 MHz
25°C
80
89
Full temp range
78
88
25°C
80
85
Full temp range
78
83
fIN = 55 MHz
Third-harmonic, HD3
fIN = 70 MHz
fIN = 100 MHz
83
fIN = 150 MHz
80
25°C
88
fIN = 70 MHz
25°C
87
25°C to 85°C
72.2
73.8
Full temp range
71
73.5
25°C to 85°C
71
73.2
69.5
72.5
fIN = 55 MHz
Signal-to-noise + distortion, SINAD
4
fIN = 70 MHz
dBc
76
fIN = 10 MHz
fIN = 10 MHz
dBc
79
fIN = 220 MHz
Worst-harmonic/spur (other than HD2 and
HD3)
dBc
77
25°C
fIN = 55 MHz
Second-harmonic, HD2
LSB
88
fIN = 100 MHz
fIN = 10 MHz
dBFS
dBc
73.2
Full temp range
fIN = 100 MHz
72.5
fIN = 150 MHz
71.8
fIN = 220 MHz
69.8
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SBAS308D – MAY 2004 – REVISED FEBRUARY 2007
ELECTRICAL CHARACTERISTICS (continued)
Typical values given at TA = 25°C, min and max specified over the full recommended operating temperature range, AVDD =
DRVDD = 3.3 V, sampling rate = 80 MSPS, 50% clock duty cycle, 3-VPP differential clock, and –1dBFS differential input,
unless otherwise noted
PARAMETER
CONDITIONS
fIN = 10 MHz
MIN
TYP
25°C
78
90
Full temp range
76
Effective number of bits, ENOB
Two-tone intermodulation distortion, IMD
AC power supply rejection ratio, ACPSRR
fIN = 70 MHz
UNIT
88
fIN = 55 MHz
Total harmonic distortion, THD
MAX
83.4
25°C
78
86
Full temp range
76
84
fIN = 100 MHz
83.4
fIN = 150 MHz
81.2
fIN = 220 MHz
75.8
fIN = 70 MHz
11.9
f = 10.1 MHz, 15.1 MHz (–7dBFS each tone)
93.8
f = 50.1 MHz, 55.1 MHz (–7dBFS each tone)
92.4
f = 148.1 MHz, 153.1 MHz (–7dBFS each
tone)
92.6
Supply noise frequency ≤ 100 MHz
dBc
Bits
dBFS
35
dB
Power Supply
Total supply current, ICC
fIN = 70 MHz
204
230
mA
Analog supply current, IAVDD
fIN = 70 MHz
165
180
mA
Output buffer supply current, IDRVDD
fIN = 70 MHz
39
50
mA
Analog only
545
594
Power dissipation
Output buffer power with 10-pF load on
digital output to ground
129
165
Standby power
With Clocks running
180
250
mW
mW
DIGITAL CHARACTERISTICS
Valid over full recommended operating temperature range, AVDD = DRVDD = 3.3 V, unless otherwise noted
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNIT
Digital Inputs
VIH
High-level input voltage
2.4
VIL
Low-level input voltage
0.8
V
IIH
High-level input current
10
µA
IIL
Low-level input current
–10
µA
Input current for RESET
Input capacitance
V
–20
µA
4
pF
Digital Outputs
VOL
Low-level output voltage
CLOAD = 10 pF
VOH
High-level output voltage
CLOAD = 10 pF
Output capacitance
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0.3
2.4
0.4
V
3
V
3
pF
5
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SBAS308D – MAY 2004 – REVISED FEBRUARY 2007
TIMING CHARACTERISTICS (1) (2)
Typical values given at TA = 25°C, min and max specified over the full recommended operating temperature range, AVDD =
DRVDD = 3.3 V, sampling rate = 80 MSPS, 50% clock duty cycle, 3-VPP differential clock, and CLOAD = 10 pF, unless
otherwise noted
PARAMETER
DESCRIPTION
MIN
TYP
MAX
UNIT
Switching Specification
tA
Aperture delay
Input CLK falling edge to data sampling point
Aperture jitter (uncertainty)
Uncertainty in sampling instant
valid (3)
1
ns
300
fs
ns
tSETUP Data setup time
Data
to 50% of CLKOUT rising edge
3.2
4.2
tHOLD
50% of CLKOUT rising edge to data becoming invalid (3)
1.8
3.0
Data hold time
ns
tSTART Input clock to output data valid
start (4) (5)
Input clock rising edge to data valid start delay
tEND
Input clock to output data valid
end
Input clock rising edge to data valid end delay (4) (5)
tJIT
Output clock jitter
Uncertainty in CLKOUT rising edge, peak-to-peak
210
315
psPP
tr
Output clock rise time
Rise time of CLKOUT from 20% to 80% of DRVDD
2.5
2.8
ns
tf
Output clock fall time
Fall time of CLKOUT from 80% to 20% of DRVDD
2.1
2.3
ns
tPDI
Input clock to output clock
delay
Input clock rising edge, zero crossing, to output clock rising
edge 50%
8.0
8.9
ns
tr
Data rise time
Data rise time measured from 20% to 80% of DRVDD
5.8
6.6
ns
tf
Data fall time
Data fall time measured from 80% to 20% of DRVDD
4.4
5.3
Output enable(OE) to data
output delay
Time required for outputs to have stable timings with regard to
input clock (6) after OE is activated
1000
Clock
cycles
Time to valid data after coming out of software power down
1000
Time to valid data after stopping and restarting the clock
1000
Clock
cycles
Wakeup time
Latency
(1)
(2)
(3)
(4)
(5)
(6)
3.8
8.4
7.1
Time for a sample to propagate to the ADC outputs
5.0
11.0
ns
17.5
ns
Clock
cycles
Timing parameters are ensured by design and characterization, and not tested in production.
See Table 5 through Table 6 in the Application Information section for timing information at additional sampling frequencies.
Data valid refers to 2 V for LOGIC HIGH and 0.8 V for LOGIC LOW.
See the Output Information section for details on using the input clock for data capture.
These specifications apply when the CLKOUT polarity is set to rising edge (according to Table 2). Add 1/2 clock period for the valid
number for a falling edge CLKOUT polarity.
Data outputs are available within a clock from assertion of OE; however, it takes 1000 clock cycles to ensure stable timing with respect
to input clock.
Analog
Input
Signal
Sample
N
N + 1
N + 2
N + 3
N + 4
N + 14
N + 15
N + 16
N + 17
tA
Input Clock
tSTART
Output Clock
tPDI
tsu
Data Out
(D0−D11)
N − 17
N − 16
N − 15
tEND
A.
N − 14
N − 13
N−3
N−2
N−1
Data Invalid
17.5 Clock Cycles
N
th
It is recommended that the loading at CLKOUT and all data lines are accurately matched to ensure that the above
timing matches closely with the specified values.
Figure 1. Timing Diagram
6
ns
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SBAS308D – MAY 2004 – REVISED FEBRUARY 2007
RESET TIMING CHARACTERISTICS
Typical values given at TA = 25°C, min and max specified over the full recommended operating temperature range, AVDD =
DRVDD = 3.3 V, and 3-VPP differential clock, unless otherwise noted
PARAMETER
DESCRIPTION
MIN
TYP
MAX
UNIT
Switching Specification
t1
Power-on delay
Delay from power-on of AVDD and DRVDD to RESET pulse
active
10
ms
t2
Reset pulse width
t3
Register write delay
Pulse width of active RESET signal
2
µs
Delay from RESET disable to SEN active
2
Power-up time
Delay from power-up of AVDD and DRVDD to output stable
Power Supply
(AVDD, DRVDD)
µs
40
ms
t1 10 ms
t2 2 ms
t3 2 ms
SEN Active
RESET (Pin 35)
Figure 2. Reset Timing Diagram
SERIAL PROGRAMMING INTERFACE CHARACTERISTICS
The ADS5542 has a three-wire serial interface. The ADS5542 latches serial data SDATA on the falling edge of
serial clock SCLK when SEN is active.
• Serial shift of bits is enabled when SEN is low. SCLK shifts serial data at the falling edge.
• Minimum width of data stream for a valid loading is 16 clocks.
• Data is loaded at every 16th SCLK falling edge while SEN is low.
• In case the word length exceeds a multiple of 16 bits, the excess bits are ignored.
• Data can be loaded in multiples of 16-bit words within a single active SEN pulse.
• The first 4-bit nibble is the address of the register while the last 12 bits are the register contents.
A3
SDATA
A2
A1
A0
D11
D10
ADDRESS
D9
D0
DATA
MSB
Figure 3. DATA Communication is 2-Byte, MSB First
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SBAS308D – MAY 2004 – REVISED FEBRUARY 2007
tSLOADS
SEN
tSLOADH
tWSCLK tWSCLK
tSCLK
SCLK
tsu(D)
SDATA
th(D)
MSB
LSB
MSB
LSB
16 x M
Figure 4. Serial Programming Interface Timing Diagram
Table 1. Serial Programming Interface Timing Characteristics
(1)
SYMBOL
PARAMETER
tSCLK
SCLK period
tWSCLK
SCLK duty cycle
MIN (1)
TYP (1)
MAX (1)
50%
75%
50
25%
UNIT
ns
tSLOADS
SEN to SCLK setup time
8
ns
tSLOADH
SCLK to SEN hold time
6
ns
tDS
Data setup time
8
ns
tDH
Data hold time
6
ns
Min, typ, and max values are characterized, but not production tested.
Table 2. Serial Register Table (1)
A3 A2 A1 A0
D11
D10
D9
TP
TP
D8 D7 D6 D5 D4 D3 D2
D1
D0
DESCRIPTION
Test Mode
1
1
1
0
0
0
0
0
0
0
0
0
0
0
X
0
Normal mode of operation
1
1
1
0
0
0
1
0
0
0
0
0
0
0
X
0
All outputs forced to 0
1
1
1
0
0
1
0
0
0
0
0
0
0
0
X
0
All outputs forced to 1
1
1
1
0
0
1
1
0
0
0
0
0
0
0
X
0
Each output bit toggles between 0 and 1.
PDN
(2) (3)
Power Down
1
1
1
1
0
0
0
0
0
0
0
0
0
0
X
0
Normal mode of operation
1
1
1
1
1
0
0
0
0
0
0
0
0
0
X
0
Device is put in power-down (low-current) mode.
(1)
(2)
(3)
The register contents default to the appropriate setting for normal operation up on RESET.
The patterns given are applicable to the straight offset binary output format. If two's complement output format is selected, the test mode
outputs will be the binary two's complement equivalent of these patterns as described in the Output Information section.
While each bit toggles between 1 and 0 in this mode, there is no assured phase relationship between the data bits D0 through D13. For
example, when D0 is a 1, D1 in not assured to be a 0, and vice versa.
Table 3. Data Format Select (DFS) Table
DFS-PIN VOLTAGE (VDFS)
2
V DFS t
12
CLOCK OUTPUT POLARITY
Straight Binary
Data valid on rising edge
4
12
5
AV DD t V DFS t
12
AV DD
Two's Complement
Data valid on rising edge
7
12
8
AV DD t V DFS t
12
AV DD
Straight Binary
Data valid on falling edge
Two's Complement
Data valid on falling edge
V DFS u
8
AV DD
DATA FORMAT
10
12
AV DD
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SBAS308D – MAY 2004 – REVISED FEBRUARY 2007
PIN CONFIGURATION
54
53
52
51
50
DRVDD
55
DRGND
56
D4
57
D5
58
D7
59
D6
60
D8
D10
61
D9
D11
62
DRGND
D12
63
DRVDD
D13 (MSB)
64
DRGND
OVR
PAP PACKAGE
(TOP VIEW)
49
DRGND
1
48 DRGND
SCLK
2
47 D3
SDATA
3
46 D2
SEN
4
45 D1
AVDD
5
44 D0 (LSB)
AGND
6
43 CLKOUT
AVDD
7
42 DRGND
AGND
8
AVDD
9
ADS5542
PowerPAD
41 OE
40 DFS
19
20
21
22
23
24
25
26
27
28
29
30
31
32
AGND
18
IREF
17
REFM
33 AVDD
REFP
AGND 16
AVDD
34 AVDD
AGND
AVDD 15
AGND
35 RESET
AVDD
AGND 14
AVDD
36 AGND
AGND
AGND 13
AVDD
37 AVDD
AGND
AGND 12
INM
38 AGND
INP
CLKM 11
AGND
39 AVDD
CM
CLKP 10
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SBAS308D – MAY 2004 – REVISED FEBRUARY 2007
PIN CONFIGURATION (continued)
PIN ASSIGNMENTS
TERMINAL
NO. OF
PINS
I/O
AVDD
5, 7, 9, 15, 22,
24, 26, 28, 33,
34, 37, 39
12
I
Analog power supply
AGND
6, 8, 12–14,
16, 18, 21, 23,
25, 27, 32, 36,
38
14
I
Analog ground (PowerPAD is connected to analog ground.)
DRVDD
49, 58
2
I
Output driver power supply
DRGND
1, 42, 48, 50,
57, 59
6
I
Output driver ground
INP
19
1
I
Differential analog input (positive)
INM
20
1
I
Differential analog input (negative)
REFP
29
1
O
Reference voltage (positive); 1-µF capacitor in series with a 1-Ω resistor to GND
REFM
30
1
O
Reference voltage (negative); 1-µF capacitor in series with a 1-Ω resistor to GND
IREF
31
1
I
Current set; 56.2-kΩ resistor to GND; do not connect capacitors
CM
17
1
O
Common-mode output voltage
RESET
35
1
I
Reset (active high), Internal 200-kΩ resistor to AVDD (1)
OE
41
1
I
Output enable (active high) (2)
DFS
40
1
I
Data format and clock out polarity select (3) (2)
CLKP
10
1
I
Data converter differential input clock (positive)
CLKM
11
1
I
Data converter differential input clock (negative)
SEN
4
1
I
Serial interface chip select (2)
SDATA
3
1
I
Serial interface data (2)
SCLK
2
1
I
Serial interface clock (2)
44-47, 51-56,
60-63
14
O
Parallel data output
OVR
64
1
O
Over-range indicator bit
CLKOUT
43
1
O
CMOS clock out in sync with data
NAME
NO.
D0 (LSB) to
D13 (MSB)
(1)
(2)
(3)
10
DESCRIPTION
If unused, the RESET pin should be tied to AGND. See the serial programmine interface section for details.
Pins OE, DFS, SEN, SDATA, and SCLK have internal clamping diodes to the DRVDD supply. Any external circuit driving these pins
must also run off the same supply voltage as DRVDD.
Table 3defines the voltage levels for each mode selectable via the DFS pin.
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DEFINITION OF SPECIFICATIONS
Offset Error
Analog Bandwidth
The analog input frequency at which the power of the
fundamental is reduced by 3 dB with respect to the
low frequency value.
Aperture Delay
The delay in time between the falling edge of the
input sampling clock and the actual time at which the
sampling occurs.
Aperture Uncertainty (Jitter)
The sample-to-sample variation in aperture delay.
Clock Pulse Width/Duty Cycle
The duty cycle of a clock signal is the ratio of the
time the clock signal remains at a logic high (clock
pulse width) to the period of the clock signal. Duty
cycle is typically expressed as a percentage. A
perfect differential sine wave clock results in a 50%
duty cycle.
Maximum Conversion Rate
The maximum sampling rate at which certified
operation is given. All parametric testing is performed
at this sampling rate unless otherwise noted.
Minimum Conversion Rate
The minimum sampling rate at which the ADC
functions.
Differential Nonlinearity (DNL)
An ideal ADC exhibits code transitions at analog
input values spaced exactly 1LSB apart. The DNL is
the deviation of any single step from this ideal value,
measured in units of LSBs.
Integral Nonlinearity (INL)
The offset error is the difference, given in number of
LSBs, between the ADC's actual average idle
channel output code and the ideal average idle
channel output code. This quantity is often mapped
into mV.
Temperature Drift
The temperature drift coefficient (with respect to gain
error and offset error) specifies the change per
degree Celsius of the parameter from TMIN to TMAX. It
is calculated by dividing the maximum deviation of
the parameter across the TMIN to TMAX range by the
difference (TMAX – TMIN).
Signal-to-Noise Ratio (SNR)
SNR is the ratio of the power of the fundamental (PS)
to the noise floor power (PN), excluding the power at
dc and the first eight harmonics.
P
SNR + 10Log 10 S
PN
SNR is either given in units of dBc (dB to carrier)
when the absolute power of the fundamental is used
as the reference or dBFS (dB to Full-Scale) when the
power of the fundamental is extrapolated to the
converter's full-scale range.
Signal-to-Noise and Distortion (SINAD)
SINAD is the ratio of the power of the fundamental
(PS) to the power of all the other spectral
components including noise (PN) and distortion (PD),
but excluding dc.
PS
SINAD + 10Log 10
PN ) PD
(1)
The INL is the deviation of the ADC's transfer
function from a best fit line determined by a least
squares curve fit of that transfer function, measured
in units of LSBs.
SINAD is either given in units of dBc (dB to carrier)
when the absolute power of the fundamental is used
as the reference or dBFS (dB to full-scale) when the
power of the fundamental is extrapolated to the
converter's full-scale range.
Gain Error
Effective Number of Bits (ENOB)
The gain error is the deviation of the ADC's actual
input full-scale range from its ideal value. The gain
error is given as a percentage of the ideal input
full-scale range. Gain error does not account for
variations in the internal reference voltages (see the
Electrical Specifications section for limits on the
variation of VREFP and VREFM).
The ENOB is a measure of a converter's
performance as compared to the theoretical limit
based on quantization noise.
ENOB + SINAD * 1.76
6.02
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Total Harmonic Distortion (THD)
Two-Tone Intermodulation Distortion (IMD3)
THD is the ratio of the power of the fundamental (PS)
to the power of the first eight harmonics (PD).
P
THD + 10Log 10 S
PD
IMD3 is the ratio of the power of the fundamental (at
frequencies f1 and f2) to the power of the worst
spectral component at either frequency 2f1 – f2 or
2f2 – f1. IMD3 is either given in units of dBc (dB to
carrier) when the absolute power of the fundamental
is used as the reference, or dBFS (dB to Full-Scale)
when the power of the fundamental is extrapolated to
the converter's full-scale range.
THD is typically given in units of dBc (dB to carrier).
Spurious-Free Dynamic Range (SFDR)
The ratio of the power of the fundamental to the
highest other spectral component (either spur or
harmonic). SFDR is typically given in units of dBc
(dB to carrier).
DC Power Supply Rejection Ration (DC PSRR)
The DC PSSR is the ratio of the change in offset
error to a change in analog supply voltage. The DC
PSRR is typically given in units of mV/V.
Reference Error
The reference error is the variation of the actual
reference voltage (VREFP - VREFM) from its ideal
value. The reference error is typically given as a
percentage.
Voltage Overload Recovery Time
The voltage overload recovery time is defined as the
time required for the ADC to recover to within 1% of
the full-scale range in response to an input voltage
overload of 10% beyond the full-scale range.
12
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TYPICAL CHARACTERISTICS
Typical values given at TA = 25°C, AVDD = DRVDD = 3.3 V, differential input amplitude = –1dBFS, sampling rate = 80 MSPS
and 3-V differential clock, unless otherwise noted
SPECTRAL PERFORMANCE
(FFT for 4 MHz Input Signal)
SPECTRAL PERFORMANCE
(FFT for 16 MHz Input Signal)
0
0
SFDR = 92.1dBc
SNR = 74.0dBFS
THD = 88.4dBc
SINAD = 73.9dBFS
−40
−60
−80
−100
−60
−80
−120
0
5
10
15
20
25
30
35
0
40
5
10
15
20
25
30
f − Frequency − MHz
f − Frequency − MHz
Figure 5.
Figure 6.
SPECTRAL PERFORMANCE
(FFT for 55 MHz Input Signal)
SPECTRAL PERFORMANCE
(FFT for 70 MHz Input Signal)
0
35
40
0
−40
−60
−80
SFDR = 89.3dBc
SNR = 73.4dBFS
THD = 86.8dBc
SINAD = 73.2dBFS
−20
Magnitude − dB
SFDR = 87.5dBc
SNR = 73.6dBFS
THD = 83.4dBc
SINAD = 73.2dBFS
−20
Magnitude − dB
−40
−100
−120
−100
−40
−60
−80
−100
−120
−120
0
5
10
15
20
25
30
35
40
0
5
10
15
20
25
30
f − Frequency − MHz
f − Frequency − MHz
Figure 7.
Figure 8.
SPECTRAL PERFORMANCE
(FFT for 100 MHz Input Signal)
SPECTRAL PERFORMANCE
(FFT for 125 MHz Input Signal)
0
35
40
35
40
0
−40
−60
−80
−100
SFDR = 83.9dBc
SNR = 72.7dBFS
THD = 81.5dBc
SINAD = 72.2dBFS
−20
Magnitude − dB
SFDR = 87.2dBc
SNR = 72.8dBFS
THD = 83.4dBc
SINAD = 72.5dBFS
−20
Magnitude − dB
SFDR = 92.0dBc
SNR = 73.6dBFS
THD = 88.2dBc
SINAD = 73.5dBFS
−20
Magnitude − dB
Magnitude − dB
−20
−40
−60
−80
−100
−120
−120
0
5
10
15
20
25
30
35
40
0
5
10
15
20
25
f − Frequency − MHz
f − Frequency − MHz
Figure 9.
Figure 10.
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TYPICAL CHARACTERISTICS (continued)
Typical values given at TA = 25°C, AVDD = DRVDD = 3.3 V, differential input amplitude = –1dBFS, sampling rate = 80 MSPS
and 3-V differential clock, unless otherwise noted
SPECTRAL PERFORMANCE
(FFT for 150 MHz Input Signal)
SPECTRAL PERFORMANCE
(FFT for 220 MHz Input Signal)
0
0
Magnitude − dB
−20
−40
−60
−80
SFDR = 78.4dBc
SNR = 70.7dBFS
THD = 75.8dBc
SINAD = 69.8dBFS
−20
Magnitude − dB
SFDR = 88.6dBc
SNR = 71.9dBFS
THD = 81.2dBc
SINAD = 71.8dBFS
−100
−40
−60
−80
−100
−120
−120
0
5
10
15
20
25
30
35
40
0
5
25
Figure 12.
30
35
40
TWO-TONE INTERMODULATION
0
−40
−60
−80
f1 = 10.1MHz (−7dBFS)
f2 = 15.1MHz (−7dBFS)
2−Tone SFDR = 92.8dBc
−20
Magnitude − dB
SFDR = 68.4dBc
SNR = 68.5dBFS
THD = 68.2dBc
SINAD = 65.8dBFS
−20
Magnitude − dB
20
Figure 11.
0
−100
−40
−60
−80
−100
−120
−120
0
5
10
15
20
25
30
35
40
0
5
10
15
20
25
f − Frequency − MHz
f − Frequency − MHz
Figure 13.
Figure 14.
TWO-TONE INTERMODULATION
30
35
40
35
40
TWO-TONE INTERMODULATION
0
0
f1 = 45.1MHz (−7dBFS)
f2 = 50.1MHz (−7dBFS)
2−Tone SFDR = 91.6dBc
−20
f1 = 50.1MHz (−7dBFS)
f2 = 55.1MHz (−7dBFS)
2−Tone SFDR = 91.4dBc
−20
−40
Magnitude − dB
Magnitude − dB
15
f − Frequency − MHz
SPECTRAL PERFORMANCE
(FFT for 300 MHz Input Signal)
−60
−80
−100
−40
−60
−80
−100
−120
−120
0
14
10
f − Frequency − MHz
5
10
15
20
25
30
35
40
0
5
10
15
20
25
f − Frequency − MHz
f − Frequency − MHz
Figure 15.
Figure 16.
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TYPICAL CHARACTERISTICS (continued)
Typical values given at TA = 25°C, AVDD = DRVDD = 3.3 V, differential input amplitude = –1dBFS, sampling rate = 80 MSPS
and 3-V differential clock, unless otherwise noted
DIFFERENTIAL NONLINEARITY
INTEGRAL NONLINEARITY
1.0
2.0
f IN = 10MHz
AIN = −0.5dBFS
0.8
0.6
1.0
INL − LSB
DNL − LSB
0.4
0.2
0
−0.2
−0.4
0.5
0
−0.5
−1.0
−0.6
−1.5
−0.8
−1.0
−2.0
0
2048
4096
6144
8192 10240 12288 14336 16384
0
2048
4096
Figure 17.
Figure 18.
SPURIOUS-FREE DYNAMIC RANGE
vs INPUT FREQUENCY
SIGNAL-TO-NOISE RATIO
vs INPUT FREQUENCY
75
90
74
SNR − dBFS
95
85
80
75
70
73
72
71
70
69
65
68
60
67
0
50
100
150
200
250
300
0
50
Frequency − MHz
100
150
200
250
300
Frequency − MHz
Figure 19.
Figure 20.
AC PERFORMANCE
vs ANALOG SUPPLY VOLTAGE
AC PERFORMANCE
vs ANALOG SUPPLY VOLTAGE
100
98
fIN = 150MHz
SFDR − dBc
SFDR − dBc
8192 10240 12288 14336 16384
Code
76
95
90
SFDR
85
fIN = 70MHz
94
SFDR
90
86
82
72
SNR − dBFS
80
SNR − dBFS
6144
Code
100
SFDR − dBc
f IN = 10MHz
AIN = −0.5dBFS
1.5
SNR
70
65
60
48
SNR
74
70
66
3.0
3.1
3.2
3.3
3.4
3.5
3.6
3.0
3.1
3.2
3.3
3.4
AVDD − Analog Supply Voltage − V
AVDD − Analog Supply Voltage − V
Figure 21.
Figure 22.
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3.6
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TYPICAL CHARACTERISTICS (continued)
Typical values given at TA = 25°C, AVDD = DRVDD = 3.3 V, differential input amplitude = –1dBFS, sampling rate = 80 MSPS
and 3-V differential clock, unless otherwise noted
AC PERFORMANCE
vs DIGITAL SUPPLY VOLTAGE
AC PERFORMANCE
vs DIGITAL SUPPLY VOLTAGE
95
fIN = 150MHz
SFDR
SFDR − dBc
SFDR − dBc
95
90
85
85
80
75
SNR − dBFS
SNR − dBFS
80
fIN = 70MHz
SFDR
90
SNR
70
65
SNR
75
70
65
3.0
3.1
3.2
3.3
3.4
3.5
3.6
3.0
3.1
3.2
3.3
3.4
3.5
DVDD − Digital Supply Voltage − V
DVDD − Digital Supply Voltage − V
Figure 23.
Figure 24.
POWER DISSIPATION
vs SAMPLE RATE
POWER DISSIPATION
vs SAMPLE RATE
0.75
0.75
fIN = 70MHz
fIN = 150MHz
0.70
Power Dissipation − W
Power Dissipation − W
0.70
0.65
0.60
0.55
0.50
0.45
20
30
40
50
60
70
80
0.55
0.50
10
40
50
60
Figure 25.
Figure 26.
AC PERFORMANCE
vs TEMPERATURE
AC PERFORMANCE
vs INPUT AMPLITUDE
f IN = 70MHz
AC Performance − dB
SFDR
90
85
80
SNR
75
70
65
60
−15
30
Sample Rate − MSPS
95
−40
20
Sample Rate − MSPS
100
SFDR − dBc
0.60
0.40
10
SNR − dBFS
0.65
0.45
0.40
+10
+35
+60
+85
70
100
90
SNR (dBFS)
80
70
60
50
40
SFDR (dBc)
30
20
SNR (dBc)
10
0
−10
fIN = 70MHz
−20
−30
−100 −90 −80 −70 −60 −50 −40 −30 −20 −10
Temperature − _C
Input Amplitude − dBFS
Figure 27.
16
3.6
Figure 28.
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TYPICAL CHARACTERISTICS (continued)
Typical values given at TA = 25°C, AVDD = DRVDD = 3.3 V, differential input amplitude = –1dBFS, sampling rate = 80 MSPS
and 3-V differential clock, unless otherwise noted
AC PERFORMANCE
vs INPUT AMPLITUDE
100
90
SNR (dBFS)
80
70
60
50
40
SFDR (dBc)
30
20
SNR (dBc)
10
0
−10
−20
fIN = 150MHz
−30
−100 −90 −80 −70 −60 −50 −40 −30 −20 −10 0
90
70
60
50
40
30
SFDR (dBc)
20
10
SNR (dBc)
0
−10
−20
fIN = 220MHz
−30
−100 −90 −80 −70 −60 −50 −40
Input Amplitude − dBFS
Figure 29.
Figure 30.
OUTPUT
NOISE HISTOGRAM
AC PERFORMANCE
vs CLOCK AMPLITUDE
−10
0
SFDR − dBc
95
35
30
25
20
fIN = 70MHz
90
SFDR
85
SNR − dBFS
80
15
10
8215
75
SNR
70
65
8216
8214
8212
8213
8210
8211
8208
8209
8207
8205
8206
8203
0
8204
5
0
0.5
1.0
1.5
2.0
2.5
3.0
Differential Clock Amplitude − V
Code
Figure 31.
Figure 32.
WCDMA
CARRIER
AC PERFORMANCE
vs CLOCK DUTY CYCLE
0
100
SFDR − dBc
fS = 76.8MSPS
fIN = 170MHz
−20
−40
−60
fIN = 20MHz
SFDR
95
90
85
−80
SNR − dBFS
Amplitude − dB
−30 −20
Input Amplitude − dBFS
40
Occurrence − %
SNR (dBFS)
80
AC Performance − dB
AC Performance − dB
AC PERFORMANCE
vs INPUT AMPLITUDE
−100
−120
−140
80
75
SNR
70
65
0
5
10
15
20
25
30
35
40
40
45
50
f − Frequency − MHz
Clock Duty Cycle − %
Figure 33.
Figure 34.
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TYPICAL CHARACTERISTICS
Typical values given at TA = 25°C, AVDD = DRVDD = 3.3 V, differential input amplitude = -1dBFS, and 3-V differential clock,
unless otherwise noted
SIGNAL-TO-NOISE RATIO (SNR)
74
100
70
74
69
90
72
73
80
71
72
60
70
74
69
50
68
71
73
72
66
70
40
69
68
66
65
67
30
66
74
71
20
72
73
68
70
64
65
67
69
66
63
10
50
100
150
200
Input Frequency (MHz)
Figure 35.
18
64
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300
62
SNR (dBFS)
Sampling Rate (MSPS)
70
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TYPICAL CHARACTERISTICS (continued)
Typical values given at TA = 25°C, AVDD = DRVDD = 3.3 V, differential input amplitude = -1dBFS, and 3-V differential clock,
unless otherwise noted
SPURIOUS-FREE DYNAMIC RANGE (SFDR)
87
81
85
85
90
87
79
87
Sampling Rate (MSPS)
80
87
60
71
73
79
87
85
85
87
89
85
69
77
81
83
85
71
77
81
85
40
87
75
81
75
79
87
30
69
71
83
80
73
85
91
91
79
75
83
89 87
50
81
85
91
20
85
85
89
70
90
67
75
87
91
81
81
SFDR (dBc)
100
73
77
87
70
85
89
75
81
85
81
83
79
73
77
71
10
50
100
150
200
Input Frequency (MHz)
250
65
300
Figure 36.
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APPLICATION INFORMATION
THEORY OF OPERATION
The ADS5542 is a low-power, 14-bit, 80 MSPS, CMOS, switched capacitor, pipeline ADC that operates from a
single 3.3-V supply. The conversion process is initiated by a falling edge of the external input clock. Once the
signal is captured by the input S&H, the input sample is sequentially converted by a series of small resolution
stages, with the outputs combined in a digital correction logic block. Both the rising and the falling clock edges
are used to propagate the sample through the pipeline every half clock cycle. This process results in a
datalatency of 17.5 clock cycles, after which the output data is available as a 14-bit parallel word, coded in either
straight offset binary or binary two's complement format.
INPUT CONFIGURATION
The analog input for the ADS5542 consists of a differential sample-and-hold architecture implemented using the
switched capacitor technique shown in Figure 37.
S3a
L1
R1a
C1a
INP
S1a
CP1
CP3
S2
R3
CA
L2
R1b
INM
S1b
C1b
VINCM
1V
CP2
CP4
L1, L2: 6 nH − 10 nH effective
R1a, R1b: 5W − 8W
C1a, C1b: 2.2 pF − 2.6 pF
CP1, CP2: 2.5 pF − 3.5 pF
CP3, CP4: 1.2 pF − 1.8 pF
CA: 0.8 pF − 1.2 pF
R3: 80 W − 120 W
Swithches: S1a, S1b: On Resistance: 35 W − 50 W
S2: On Resistance: 7.5 W − 15 W
S3a, S3b: On Resistance: 40 W − 60 W
All switches OFF Resistance: 10 GW
A.
All Switches are ON in sampling phase which is approximately one half of a clock period.
Figure 37. Analog Input Stage
20
S3b
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This differential input topology produces a high level of ac-performance for high sampling rates. It also results in
a very high usable input bandwidth, especially important for high intermediate-frequency (IF) or undersampling
applications. The ADS5542 requires each of the analog inputs (INP, INM) to be externally biased around the
common-mode level of the internal circuitry (CM, pin 17). For a full-scale differential input, each of the differential
lines of the input signal (pins 19 and 20) swings symmetrically between CM + 0.575 V and CM – 0.575 V. This
means that each input is driven with a signal of up to CM ± 0.575 V, so that each input has a maximum
differential signal of 1.15 VPP for a total differential input signal swing of 2.3 VPP. The maximum swing is
determined by the two reference voltages, the top reference (REFP, pin 29), and the bottom reference (REFM,
pin 30).
The ADS5542 obtains optimum performance when the analog inputs are driven differentially. The circuit shown
in Figure 38 shows one possible configuration using an RF transformer.
R0
50 W
Z0
50 W
25 W
INP
1:1
R
50 W
25 W
AC Signal
Source
ADS5542
INM
ADT1−1WT
CM
10 W
1nF
0.1mF
Figure 38. Transformer Input to Convert Single-Ended Signal to Differential Signal
The single-ended signal is fed to the primary winding of an RF transformer. Since the input signal must be
biased around the common-mode voltage of the internal circuitry, the common-mode voltage (VCM) from the
ADS5542 is connected to the center-tap of the secondary winding. To ensure a steady low-noise VCM reference,
best performance is obtained when the CM (pin 17) output is filtered to ground with 0.1 µF and 0.001-µF
low-inductance capacitors.
Output VCM (pin 17) is designed to directly drive the ADC input. When providing a custom CM level, be aware
that the input structure of the ADC sinks a common-mode current in the order of 400 µA (200 µA per input) at 80
MSPS. Equation 2 describes the dependency of the common-mode current and the sampling frequency:
400mA f S (in MSPS)
80 MSPS
(2)
Where:
fS > 2MSPS.
This equation helps to design the output capability and impedance of the driving circuit accordingly.
When it is necessary to buffer or apply a gain to the incoming analog signal, it is possible to combine
single-ended operational amplifiers with an RF transformer, or to use a differential input/output amplifier without
a transformer, to drive the input of the ADS5542. Texas Instruments offers a wide selection of single-ended
operational amplifiers (including the THS3201, THS3202, OPA695, and OPA847) that can be selected
depending on the application. An RF gain block amplifier, such as Texas Instruments THS9001, can also be
used with an RF transformer for high input frequency applications. The THS4503 is a recommended differential
input/output amplifier. Table 4 lists the recommended amplifiers.
When using single-ended operational amplifiers (such as the THS3201, THS3202, OPA695, or OPA847) to
provide gain, a three-amplifier circuit is recommended with one amplifier driving the primary of an RF
transformer and one amplifier in each of the legs of the secondary driving the two differential inputs of the
ADS5542. These three amplifier circuits minimize even-order harmonics. For high frequency inputs, an RF gain
block amplifier can be used to drive a transformer primary; in this case, the transformer secondary connections
can drive the input of the ADS5542 directly, as shown in Figure 38, or with the addition of the filter circuit shown
in Figure 39.
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Figure 39 illustrates how RIN and CIN can be placed to isolate the signal source from the switching inputs of the
ADC and to implement a low-pass RC filter to limit the input noise in the ADC. It is recommended that these
components be included in the ADS5542 circuit layout when any of the amplifier circuits discussed previously
are used. The components allow fine-tuning of the circuit performance. Any mismatch between the differential
lines of the ADS5542 input produces a degradation in performance at high input frequencies, mainly
characterized by an increase in the even-order harmonics. In this case, special care should be taken to keep as
much electrical symmetry as possible between both inputs.
Another possible configuration for lower-frequency signals is the use of differential input/output amplifiers that
can simplify the driver circuit for applications requiring dc-coupling of the input. Flexible in their configurations
(see Figure 40), such amplifiers can be used for single-ended-to-differential conversion signal amplification.
Table 4. Recommended Amplifiers to Drive the Input of the ADS5542
INPUT SIGNAL FREQUENCY
RECOMMENDED AMPLIFIER
TYPE OF AMPLIFIER
DC to 20 MHz
THS4503
Differential In/Out Amp
No
DC to 50 MHz
OPA847
Operational Amp
Yes
DC to 100 MHz
THS4509
Differential In/Out Amp
No
OPA695
Operational Amp
Yes
THS3201
Operational Amp
Yes
THS3202
Operational Amp
Yes
THS9001
RF Gain Block
Yes
10 MHz to 120 MHz
Over 100 MHz
USE WITH TRANSFORMER?
+5V -5V
RS
100 W
VIN
0.1mF
RIN
1:1
OPA695
INP
RT
100 W
1000pF
R1
400 W
25 W
CIN
ADS5542
INM
RIN
CM
25 W
AV = 8V/V
(18dB)
R2
57.5 W
10 W
0.1mF
Figure 39. Converting a Single-Ended Input Signal to a Differential Signal Using an RF Transformer
RS
RG
RF
+5V
RT
+3.3V
10mF
0.1mF
RIN
VOCM
1mF
RIN
THS4503
10mF
INP ADS5542
14-Bit / 80 MSPS
INM
CM
0.1mF
10 W
RG
-5V
RF
0.1mF
Figure 40. Using the THS4503 with the ADS5542
22
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SBAS308D – MAY 2004 – REVISED FEBRUARY 2007
POWER-SUPPLY SEQUENCE
The preferred power-up sequence is to ramp AVDD first, followed by DRVDD, including a simultaneous ramp of
AVDD and DRVDD. In the event that DRVDD ramps up first in the system, care must be taken to ensure that AVDD
ramps up within 10 ms. Optionally, it is recommended to put a 2-kΩ resistor from REFP (pin 29) to AVDD as
shown in Figure 41. This helps to make the device more robust to power supply ramp-up timings.
28
AVDD
29
REFP
2 kW
1W
1 mF
Figure 41.
POWER-DOWN
The device enters power-down in one of two ways: either by reducing the clock speed or by setting the PDN bit
throught the serial programming interface. Using the reduced clock speed, power-down may be initiated for clock
frequency below 2 MSPS. The exact frequency at which the power down occurs varies from device to device.
Using the serial interface PDN bit to power down the device places the outputs in a high-impedance state and
only the internal reference remains on to reduce the power-up time. The power-down mode reduces power
dissipation to approximately 180 mW.
REFERENCE CIRCUIT
The ADS5542 has built-in internal reference generation, requiring no external circuitry on the printed circuit
board (PCB). For optimum performance, it is best to connect both REFP and REFM to ground with a 1-µF
decoupling capacitor (the 1-Ω resistor shown in Figure 42 is optional). In addition, an external 56.2-kΩ resistor
should be connected from IREF (pin 31) to AGND to set the proper current for the operation of the ADC, as
shown in Figure 42. No capacitor should be connected between pin 31 and ground; only the 56.2-kΩ resistor
should be used.
1W
29
R EF P
30
R EF M
31
IR EF
1 mF
1W
1 mF
56.2 kW
Figure 42. REFP, REFM, and IREF Connections for Optimum Performance
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SBAS308D – MAY 2004 – REVISED FEBRUARY 2007
CLOCK INPUT
The ADS5542 clock input can be driven with either a differential clock signal or a single-ended clock input, with
little or no difference in performance between both configurations. The common-mode voltage of the clock inputs
is set internally to CM (pin 17) using internal 5-kΩ resistors that connect CLKP (pin 10) and CLKM (pin 11) to
CM (pin 17), as shown in Figure 43.
CM
CM
5 kW
5 kW
CLKM
CLKP
6 pF
3 pF
3 pF
Figure 43. Clock Inputs
When driven with a single-ended CMOS clock input, it is best to connect CLKM (pin 11) to ground with a
0.01-µF capacitor, while CLKP is ac-coupled with a 0.01-µF capacitor to the clock source, as shown in
Figure 44.
Square Wave
or Sine Wave
(3VPP)
0.01mF
CLKP
ADS5542
CLKM
0.01mF
Figure 44. AC-Coupled, Single-Ended Clock Input
The ADS5542 clock input can also be driven differentially, reducing susceptibility to common-mode noise. In this
case, it is best to connect both clock inputs to the differential input clock signal with 0.01-µF capacitors, as
shown in Figure 45.
0.01mF
CLKP
Differential Square Wave
or Sine Wave
(3VPP)
ADS5542
0.01mF
CLKM
Figure 45. AC-Coupled, Differential Clock Input
For high input frequency sampling, it is recommended to use a clock source with low jitter. Additionally, the
internal ADC core uses both edges of the clock for the conversion process. This means that, ideally, a 50% duty
cycle should be provided. Figure 46 shows the performance variation of the ADC versus clock duty cycle.
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SBAS308D – MAY 2004 – REVISED FEBRUARY 2007
SFDR − dBc
100
fIN = 20MHz
95
SFDR
90
85
SNR − dBFS
80
75
SNR
70
65
60
35
40
45
50
55
60
65
Clock Duty Cycle − %
Figure 46. AC Performance vs Clock Duty Cycle
Bandpass filtering of the source can help produce a 50% duty cycle clock and reduce the effect of jitter. When
using a sinusoidal clock, the clock jitter further improves as the amplitude is increased. In that sense, using a
differential clock allows for the use of larger amplitudes without exceeding the supply rails and absolute
maximum ratings of the ADC clock input. Figure 47 shows the performance variation of the device versus input
clock amplitude. For detailed clocking schemes based on transformer or PECL-level clocks, see the
ADS55xxEVM User's Guide (SLWU010), available for download from www.ti.com.
SFDR − dBc
95
fIN = 70MHz
90
SFDR
85
SNR − dBFS
80
75
SNR
70
65
60
0
0.5
1.0
1.5
2.0
2.5
3.0
Differential Clock Amplitude − V
Figure 47. AC Performance vs Clock Amplitude
OUTPUT INFORMATION
The ADC provides 14 data outputs (D13 to D0, with D13 being the MSB and D0 the LSB), a data-ready signal
(CLKOUT, pin 43), and an out-of-range indicator (OVR, pin 64) that equals one when the output reaches the
full-scale limits.
Two different output formats (straight offset binary or two's complement) and two different output clock polarities
(latching output data on rising or falling edge of the output clock) can be selected by setting DFS (pin 40) to one
of four different voltages. Table 3 details the four modes. In addition, output enable control (OE, pin 41, active
high) is provided to put the outputs into a high-impedance state.
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In the event of an input voltage overdrive, the digital outputs go to the appropriate full scale level. For a positive
overdrive, the output code is 0x3FFF in straight offset binary output format, and 0x1FFF in 2's complement
output format. For a negative input overdrive, the output code is 0x0000 in straight offset binary output format
and 0x2000 in two's complement output format. These outputs to an overdrive signal are ensured through
design and characterization
The output circuitry of the ADS5542, by design, minimizes the noise produced by the data switching transients,
and, in particular, its coupling to the ADC analog circuitry. Output D4 (pin 51) senses the load capacitance and
adjusts the drive capability of all the output pins of the ADC to maintain the same output slew rate described in
the timing diagram of Figure 1. Care should be taken to ensure that all output lines (including CLKOUT) have
nearly the same load as D4 (pin 51). This circuit also reduces the sensitivity of the output timing versus supply
voltage or temperature. Placing external resistors in series with the outputs is not recommended.
The timing characteristics of the digital outputs change for sampling rates below the 80 MSPS maximum
sampling frequency. Table 5 and Table 6 show the values of various timing parameters for lower sampling
frequenies.
To use the input clock as the data capture clock, it is necessary to delay the input clock by a delay, td, that
results in the desired setup or hold time. Use either of the following equations to calculate the value of td.
Desired setup time = td – tSTART
Desired hold time = tEND – td
Table 5. Timing Characteristics at Additional Sampling Frequencies
tSETUP (ns)
tHOLD (ns)
tSTART (ns)
tEND (ns)
tr (ns)
tf (ns)
fS
(MSPS)
MIN
TYP
MIN
TYP
TYP
MAX
MIN
TYP
TYP
MAX
TYP
MAX
65
4.3
5.7
2
3
2.8
4.5
8.3
11.8
6.6
7.2
5.5
6.4
40
8.5
11
2.6
3.5
–1
1.5
8.9
14.5
7.5
8
7.3
7.8
20
17
25.7
2.5
4.7
–9.8
2
9.5
21.6
7.5
8
7.6
8
10
27
51
4
6.5
-30
-3
11.5
31
2
284
370
8
19
185
320
515
576
50
82
75
150
MAX
MAX
MIN
MAX
MIN
MIN
Table 6. Timing Characteristics at Additional Sampling Frequencies
fS
(MSPS)
CLKOUT, Rise Time
tr (ns)
MIN
TYP
MAX
65
3.1
40
4.8
20
CLKOUT Jitter,
Peak-to-Peak
tJIT (ps)
CLKOUT, Fall Time
tf (ns)
MIN
TYP
MAX
3.5
2.6
5.3
4
8.3
9.5
31
52
MIN
Input-to-Output Clock Delay
tPDI (ns)
TYP
MAX
MIN
2.9
260
380
7.8
8.5
9.4
4.4
445
650
9.5
10.4
11.4
7.6
8.2
800
1200
13
15.5
18
16
20.7
25.5
36
65
2610
4400
537
551
567
10
2
TYP
MAX
SERIAL PROGRAMMING INTERFACE
The ADS5542 has internal registers for the programming of some of the modes described in the previous
sections. The registers should be reset after power-up by applying a 2 us (minimum) high pulse on RESET (pin
35); this also resets the entire ADC and sets the data outputs to low. This pin has a 200-kΩ internal pullup
resistor to AVDD. The programming is done through a three-wire interface. The timing diagram and serial register
setting in the Serial Programing Interface section describe the programming of this register.
Table 2 shows the different modes and the bit values to be written to the register to enable them.
Note that some of these modes may modify the standard operation of the device and possibly vary the
performance with respect to the typical data shown in this data sheet.
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Applying a RESET signal is absolutely essential to set the internal registers to their default states for normal
operation. If the hardware RESET function is not used in the system, the RESET pin must be tied to ground and
it is necessary to write the default values to the internal registers through the serial programming interface. The
following registers must be written in this order.
Write 9000h (Address 9, Data 000)
Write A000h (Address A, Data 000)
Write B000h (Address B, Data 000)
Write C000h (Address C, Data 000)
Write D000h (Address D, Data 000)
Write E000h (Address E, Data 804)
Write 0000h (Address 0, Data 000)
Write 1000h (Address 1, Data 000)
Write F000h (Address F, Data 000)
NOTE:
This procedure is only required if a RESET pulse is not provided to the device.
PowerPAD PACKAGE
The PowerPAD package is a thermally enhanced standard size IC package designed to eliminate the use of
bulky heatsinks and slugs traditionally used in thermal packages. This package can be easily mounted using
standard printed circuit board (PCB) assembly techniques and can be removed and replaced using standard
repair procedures.
The PowerPAD package is designed so that the lead frame die pad (or thermal pad) is exposed on the bottom
of the IC. This provides a low thermal resistance path between the die and the exterior of the package. The
thermal pad on the bottom of the IC can then be soldered directly to the printed circuit board (PCB), using the
PCB as a heatsink.
Assembly Process
1. Prepare the PCB top-side etch pattern including etch for the leads as well as the thermal pad as
illustrated in the Mechanical Data section. The recommended thermal pad dimension is 8 mm x 8 mm.
2. Place a 5-by-5 array of thermal vias in the thermal pad area. These holes should be 13 mils in diameter.
The small size prevents wicking of the solder through the holes.
3. It is recommended to place a small number of 25 mil diameter holes under the package, but outside the
thermal pad area to provide an additional heat path.
4. Connect all holes (both those inside and outside the thermal pad area) to an internal copper plane (such
as a ground plane).
5. Do not use the typical web or spoke via connection pattern when connecting the thermal vias to the
ground plane. The spoke pattern increases the thermal resistance to the ground plane.
6. The top-side solder mask should leave exposed the terminals of the package and the thermal pad area.
7. Cover the entire bottom side of the PowerPAD vias to prevent solder wicking.
8. Apply solder paste to the exposed thermal pad area and all of the package terminals.
For more detailed information regarding the PowerPAD package and its thermal properties, see either the
application brief SLMA004B (PowerPAD Made Easy) or technical brief SLMA002 (PowerPAD Thermally
Enhanced Package).
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Table 7. Revision History
Added notes regarding the input voltage overstress requirements in the absolute maximum ratings table
Changed minimum recommended sampling rate to 2 MSPS.
Added timing parameters - output clock jitter, wakeup time, output clock rise and fall time, Tpdi and timings across Fs.
Clarified output capture test modes.
Pin table info added - RESET pin, note on OE, SEN, SDATA and SCLK pins
Updated the definitions section.
Removed the input voltage stress section - notes added in absolute maximum ratings table
Updated the Power Down section to reflect the newly specified 2 MSPS minimum sampling rate.
Note added in Power supply sequence section for robust power supply ramp-up.
Note on mandatory RESET added
Rev D
Added min/max specs for Offset and Gain errors.
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PACKAGE OPTION ADDENDUM
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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)
Device Marking
(3)
(4/5)
(6)
ADS5542IPAP
ACTIVE
HTQFP
PAP
64
160
RoHS & Green
NIPDAU
Level-3-260C-168 HR
-40 to 85
ADS5542I
(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
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