LTC2172-12/
LTC2171-12/LTC2170-12
12-Bit, 65Msps/40Msps/
25Msps Low Power Quad ADCs
Description
Features
4-Channel Simultaneous Sampling ADC
n 71dB SNR
n 90dB SFDR
n Low Power: 306mW/198mW/160mW Total,
77mW/50mW/40mW per Channel
n Single 1.8V Supply
n Serial LVDS Outputs: One or Two Bits per Channel
n Selectable Input Ranges: 1V
P-P to 2VP-P
n 800MHz Full Power Bandwidth Sample-and-Hold
n Shutdown and Nap Modes
n Serial SPI Port for Configuration
n Pin-Compatible 14-Bit and 12-Bit Versions
n 52-Pin (7mm × 8mm) QFN Package
The LTC®2172-12/LTC2171-12/LTC2170-12 are 4-channel,
simultaneous sampling 12-bit A/D converters designed for
digitizing high frequency, wide dynamic range signals. They
are perfect for demanding communications applications
with AC performance that includes 71dB SNR and 90dB
spurious free dynamic range (SFDR). An ultralow jitter of
0.15psRMS allows undersampling of IF frequencies with
excellent noise performance.
n
DC specifications include ±0.3LSB INL (typ), ±0.1LSB
DNL (typ) and no missing codes over temperature. The
transition noise is a low 0.3LSBRMS.
The digital outputs are serial LVDS to minimize the number of data lines. Each channel outputs two bits at a time
(2-lane mode) or one bit at a time (1-lane mode). The LVDS
drivers have optional internal termination and adjustable
output levels to ensure clean signal integrity.
Applications
n
n
n
n
n
n
Communications
Cellular Base Stations
Software Defined Radios
Portable Medical Imaging
Multichannel Data Acquisition
Nondestructive Testing
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
The ENC+ and ENC – inputs may be driven differentially
or single-ended with a sine wave, PECL, LVDS, TTL or
CMOS inputs. An internal clock duty cycle stabilizer allows high performance at full speed for a wide range of
clock duty cycles.
Typical Application
1.8V
VDD
CHANNEL 2
ANALOG
INPUT
CHANNEL 3
ANALOG
INPUT
CHANNEL 4
ANALOG
INPUT
ENCODE
INPUT
S/H
LTC2172-12, 65Msps,
2-Tone FFT, fIN = 70MHz and 75MHz
OUT1A
12-BIT
ADC CORE
OUT1B
0
–10
S/H
12-BIT
ADC CORE
S/H
12-BIT
ADC CORE
S/H
12-BIT
ADC CORE
DATA
SERIALIZER
OUT2A
–20
OUT2B
–30
OUT3A
OUT3B
OUT4A
OUT4B
DATA
CLOCK
OUT
PLL
FRAME
GND
SERIALIZED
LVDS
OUTPUTS
AMPLITUDE (dBFS)
CHANNEL 1
ANALOG
INPUT
1.8V
OVDD
–40
–50
–60
–70
–80
–90
–100
–110
–120
0
20
10
FREQUENCY (MHz)
30
217212 TA01b
OGND
217212 TA01
21721012fb
1
LTC2172-12/
LTC2171-12/LTC2170-12
Absolute Maximum Ratings
Pin Configuration
(Notes 1 and 2)
OUT1B–
OUT1B+
OUT1A–
OUT1A+
GND
SDO
PAR/SER
VREF
GND
SENSE
VDD
TOP VIEW
VDD
Supply Voltages
VDD , OVDD............................................... –0.3V to 2V
Analog Input Voltage (AIN +, AIN –,
PAR/SER, SENSE) (Note 3)........... –0.3V to (VDD + 0.2V)
Digital Input Voltage (ENC+, ENC–, CS,
SDI, SCK) (Note 4)..................................... –0.3V to 3.9V
SDO (Note 4).............................................. –0.3V to 3.9V
Digital Output Voltage................. –0.3V to (OVDD + 0.3V)
Operating Temperature Range
LTC2172C, LTC2171C, LTC2170C.............. 0°C to 70°C
LTC2172I, LTC2171I, LTC2170I.............–40°C to 85°C
Storage Temperature Range................... –65°C to 150°C
52 51 50 49 48 47 46 45 44 43 42 41
AIN1+ 1
40 OUT2A+
–
2
39 OUT2A–
VCM12 3
38 OUT2B+
AIN1
+
4
37 OUT2B–
–
5
36 DCO+
REFH 6
35 DCO–
AIN2
AIN2
REFH 7
34 OVDD
53
GND
REFL 8
33 OGND
REFL 9
32 FR+
AIN3+ 10
31 FR–
–
AIN3 11
30 OUT3A+
VCM34 12
29 OUT3A–
AIN4+ 13
28 OUT3B+
AIN4– 14
27 OUT3B–
OUT4A+
OUT4A–
OUT4B+
OUT4B–
GND
SDI
SCK
CS
ENC–
ENC+
VDD
VDD
15 16 17 18 19 20 21 22 23 24 25 26
UKG PACKAGE
52-LEAD (7mm × 8mm) PLASTIC QFN
TJMAX = 150°C, θJA = 28°C/W
EXPOSED PAD (PIN 53) IS GND, MUST BE SOLDERED TO PCB
Order Information
LEAD FREE FINISH
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LTC2172CUKG-12#PBF
LTC2172CUKG-12#TRPBF
LTC2172UKG-12
52-Lead (7mm × 8mm) Plastic QFN
0°C to 70°C
LTC2172IUKG-12#PBF
LTC2172IUKG-12#TRPBF
LTC2172UKG-12
52-Lead (7mm × 8mm) Plastic QFN
–40°C to 85°C
LTC2171CUKG-12#PBF
LTC2171CUKG-12#TRPBF
LTC2171UKG-12
52-Lead (7mm × 8mm) Plastic QFN
0°C to 70°C
LTC2171IUKG-12#PBF
LTC2171IUKG-12#TRPBF
LTC2171UKG-12
52-Lead (7mm × 8mm) Plastic QFN
–40°C to 85°C
LTC2170CUKG-12#PBF
LTC2170CUKG-12#TRPBF
LTC2170UKG-12
52-Lead (7mm × 8mm) Plastic QFN
0°C to 70°C
LTC2170IUKG-12#PBF
LTC2170IUKG-12#TRPBF
LTC2170UKG-12
52-Lead (7mm × 8mm) Plastic QFN
–40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/
21721012fb
2
LTC2172-12/
LTC2171-12/LTC2170-12
Converter
Characteristics The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. (Note 5)
LTC2172-12
PARAMETER
CONDITIONS
MIN
LTC2171-12
TYP
MAX
MIN
LTC2170-12
TYP
MAX
MIN
MAX
UNITS
l
12
Integral Linearity Error
Differential Analog Input (Note 6) l
–1
±0.3
1
–1
±0.3
1
–1
±0.3
1
LSB
Differential Linearity Error
Differential Analog Input
l
–0.5
±0.1
0.5
–0.4
±0.1
0.4
–0.4
±0.1
0.4
LSB
Offset Error
(Note 7)
l
–12
±3
12
–12
±3
12
–12
±3
12
mV
Gain Error
Internal Reference
External Reference
–2.5
–1
–1
–2.5
–1
–1
–2.5
–1
–1
0.5
%FS
%FS
Resolution (No Missing Codes)
l
12
TYP
Offset Drift
0.5
12
0.5
Bits
±20
±20
±20
µV/°C
Full-Scale Drift
Internal Reference
External Reference
±35
±25
±35
±25
±35
±25
ppm/°C
ppm/°C
Gain Matching
External Reference
±0.2
±0.2
±0.2
%FS
±3
±3
±3
External Reference
0.32
0.32
0.32
Offset Matching
Transition Noise
mV
LSBRMS
Analog
Input
The l denotes the specifications which apply over the full operating temperature range, otherwise
specifications are at TA = 25°C. (Note 5)
SYMBOL PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
VIN
Analog Input Range (AIN + – AIN –)
1.7V < VDD < 1.9V
l
VIN(CM)
Analog Input Common Mode (AIN + + AIN –)/2
Differential Analog Input (Note 8)
l VCM – 100mV
VSENSE
External Voltage Reference Applied to SENSE
External Reference Mode
l
IIN(CM)
Analog Input Common Mode Current
Per Pin, 65Msps
Per Pin, 40Msps
Per Pin, 25Msps
IIN1
Analog Input Leakage Current (No Encode)
0 < AIN +, AIN – < VDD
l
–1
1
µA
IIN2
PAR/SER Input Leakage Current
0 < PAR/SER < VDD
l
–3
3
µA
IIN3
SENSE Input Leakage Current
0.625 < SENSE < 1.3V
l
–6
6
µA
tAP
Sample-and-Hold Acquisition Delay Time
0
0.15
tJITTER
Sample-and-Hold Acquisition Delay Jitter
CMRR
Analog Input Common Mode Rejection Ratio
BW-3B
Full-Power Bandwidth
Figure 6 Test Circuit
1 to 2
0.625
VP-P
VCM
VCM + 100mV
V
1.250
1.300
V
81
50
31
µA
µA
µA
ns
psRMS
80
dB
800
MHz
21721012fb
3
LTC2172-12/
LTC2171-12/LTC2170-12
Dynamic
Accuracy
The l denotes the specifications which apply over the full operating temperature range,
otherwise specifications are at TA = 25°C. AIN = –1dBFS. (Note 5)
LTC2172-12
SYMBOL
PARAMETER
CONDITIONS
SNR
Signal-to-Noise Ratio
5MHz Input
30MHz Input
70MHz Input
140MHz Input
SFDR
Spurious Free Dynamic Range 5MHz Input
2nd or 3rd Harmonic
30MHz Input
70MHz Input
140MHz Input
Spurious Free Dynamic Range 5MHz Input
4th Harmonic or Higher
30MHz Input
70MHz Input
140MHz Input
S/(N+D)
MIN
l
69.7
l
77
l
85
l
69.1
TYP
MAX
71
71
70.9
70.6
LTC2171-12
MIN
69.5
90
90
89
84
79
90
90
90
90
85
TYP
MAX
70.9
70.8
70.8
70.5
90
90
89
84
LTC2170-12
MIN
69.3
79
90
90
90
90
85
TYP
MAX
UNITS
70.5
70.5
70.5
70.2
dBFS
dBFS
dBFS
dBFS
90
90
89
84
dBFS
dBFS
dBFS
dBFS
90
90
90
90
dBFS
dBFS
dBFS
dBFS
70.5
70.4
70.3
69.9
dBFS
dBFS
dBFS
dBFS
Signal-to-Noise Plus
Distortion Ratio
5MHz Input
30MHz Input
70MHz Input
140MHz Input
Crosstalk, Near Channel
10MHz Input (Note 12)
–90
–90
–90
dBc
Crosstalk, Far Channel
10MHz Input (Note 12)
–105
–105
–105
dBc
70.9
70.9
70.7
70.3
69.4
70.8
70.7
70.6
70.2
69.2
Internal
Reference Characteristics
The l denotes the specifications which apply over the
full operating temperature range, otherwise specifications are at TA = 25°C. AIN = –1dBFS. (Note 5)
PARAMETER
CONDITIONS
VCM Output Voltage
IOUT = 0
MIN
TYP
MAX
0.5 • VDD – 25mV
0.5 • VDD
0.5 • VDD + 25mV
VCM Output Temperature Drift
±25
VCM Output Resistance
–600µA < IOUT < 1mA
VREF Output Voltage
IOUT = 0
VREF Output Temperature Drift
1.250
±25
VREF Output Resistance
–400µA < IOUT < 1mA
VREF Line Regulation
1.7V < VDD < 1.9V
7
0.6
V
ppm/°C
4
1.225
UNITS
Ω
1.275
V
ppm/°C
Ω
mV/V
21721012fb
4
LTC2172-12/
LTC2171-12/LTC2170-12
Digital Inputs And Outputs
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. (Note 5)
SYMBOL PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
ENCODE INPUTS (ENC+, ENC– )
Differential Encode Mode (ENC– Not Tied to GND)
VID
Differential Input Voltage
(Note 8)
VICM
Common Mode Input Voltage
Internally Set
Externally Set (Note 8)
l
1.1
l
0.2
VIN
Input Voltage Range
ENC+, ENC– to GND
RIN
Input Resistance
(See Figure 10)
CIN
Input Capacitance
l
0.2
V
1.2
1.6
V
V
3.6
V
10
kΩ
3.5
pF
Single-Ended Encode Mode (ENC– Tied to GND)
VIH
High Level Input Voltage
VDD = 1.8V
l
VIL
Low Level Input Voltage
VDD = 1.8V
l
VIN
Input Voltage Range
ENC+ to GND
l
RIN
Input Resistance
(See Figure 11)
CIN
Input Capacitance
1.2
V
0
0.6
V
3.6
V
30
kΩ
3.5
pF
DIGITAL INPUTS (CS, SDI, SCK in Serial or Parallel Programming Mode. SDO in Parallel Programming Mode)
VIH
High Level Input Voltage
VDD = 1.8V
l
VIL
Low Level Input Voltage
VDD = 1.8V
l
IIN
Input Current
VIN = 0V to 3.6V
l
CIN
Input Capacitance
1.3
V
–10
0.6
V
10
µA
3
pF
200
Ω
SDO OUTPUT (Serial Programming Mode. Open-Drain Output. Requires 2k Pull-Up Resistor if SDO Is Used)
ROL
Logic Low Output Resistance to GND
VDD = 1.8V, SDO = 0V
IOH
Logic High Output Leakage Current
SDO = 0V to 3.6V
COUT
Output Capacitance
l
–10
10
3
µA
pF
DIGITAL DATA OUTPUTS
VOD
Differential Output Voltage
100Ω Differential Load, 3.5mA Mode
100Ω Differential Load, 1.75mA Mode
l
l
247
125
350
175
454
250
VOS
Common Mode Output Voltage
100Ω Differential Load, 3.5mA Mode
100Ω Differential Load, 1.75mA Mode
l
l
1.125
1.125
1.250
1.250
1.375
1.375
RTERM
On-Chip Termination Resistance
Termination Enabled, OVDD = 1.8V
100
mV
mV
V
V
Ω
21721012fb
5
LTC2172-12/
LTC2171-12/LTC2170-12
Power Requirements
The l denotes the specifications which apply over the full operating temperature
range, otherwise specifications are at TA = 25°C. (Note 9)
LTC2172-12
SYMBOL PARAMETER
CONDITIONS
LTC2171-12
LTC2170-12
MIN
TYP
MAX
MIN
TYP
MAX
MIN
TYP
MAX
UNITS
VDD
Analog Supply Voltage
(Note 10)
l
1.7
1.8
1.9
1.7
1.8
1.9
1.7
1.8
1.9
V
OVDD
Output Supply Voltage
(Note 10)
l
1.7
1.8
1.9
1.7
1.8
1.9
1.7
1.8
1.9
V
IVDD
Analog Supply Current Sine Wave Input
l
154
177
94
111
74
83
mA
IOVDD
Digital Supply Current
l
l
16
30
25
47
28
50
16
29
24
46
27
50
15
28
24
45
26
49
mA
mA
mA
mA
l
l
306
331
322
362
369
409
198
221
212
252
248
290
160
184
176
214
196
238
mW
mW
mW
mW
PDISS
Power Dissipation
1-Lane Mode, 1.75mA Mode
1-Lane Mode, 3.5mA Mode
2-Lane Mode, 1.75mA Mode
2-Lane Mode, 3.5mA Mode
1-Lane Mode, 1.75mA Mode
1-Lane Mode, 3.5mA Mode
2-Lane Mode, 1.75mA Mode
2-Lane Mode, 3.5mA Mode
PSLEEP
Sleep Mode Power
1
1
1
mW
PNAP
Nap Mode Power
75
75
75
mW
PDIFFCLK
Power Increase with Differential Encode Mode Enabled
(No Increase for Sleep Mode)
20
20
20
mW
Timing Characteristics
The l denotes the specifications which apply over the full operating temperature
range, otherwise specifications are at TA = 25°C. (Note 5)
LTC2172-12
SYMBOL
PARAMETER
CONDITIONS
MIN
fS
Sampling Frequency
(Notes 10, 11)
l
5
tENCL
ENC Low Time (Note 8)
Duty Cycle Stabilizer Off
Duty Cycle Stabilizer On
l
l
7.3
2
tENCH
ENC High Time (Note 8)
Duty Cycle Stabilizer Off
Duty Cycle Stabilizer On
l
l
7.3
2
tAP
Sample-and-Hold
Acquisition Delay Time
TYP
LTC2171-12
MAX
MIN
65
5
7.69
7.69
100
100
11.88
2
7.69
7.69
100
100
11.88
2
0
TYP
LTC2170-12
MAX
MIN
40
5
12.5
12.5
100
100
19
2
12.5
12.5
100
100
19
2
0
TYP
MAX
UNITS
25
MHz
20
20
100
100
ns
ns
20
20
100
100
ns
ns
0
ns
21721012fb
6
LTC2172-12/
LTC2171-12/LTC2170-12
Timing Characteristics
The l denotes the specifications which apply over the full operating temperature
range, otherwise specifications are at TA = 25°C. (Note 5)
SYMBOL PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Digital Data Outputs (RTERM = 100Ω Differential, CL = 2pF to GND on Each Output)
1 / (8 • fS)
1 / (7 • fS)
1 / (6 • fS)
1 / (16 • fS)
1 / (14 • fS)
1 / (12 • fS)
s
s
s
s
s
s
tSER
Serial Data Bit Period
2-Lanes, 16-Bit Serialization
2-Lanes, 14-Bit Serialization
2-Lanes, 12-Bit Serialization
1-Lane, 16-Bit Serialization
1-Lane, 14-Bit Serialization
1-Lane, 12-Bit Serialization
tFRAME
FR to DCO Delay
(Note 8)
l
tDATA
DATA to DCO Delay
(Note 8)
l
0.35 • tSER
tPD
Propagation Delay
(Note 8)
l
0.7n + 2 • tSER
tR
Output Rise Time
Data, DCO, FR, 20% to 80%
0.17
ns
tF
Output Fall Time
Data, DCO, FR, 20% to 80%
0.17
ns
DCO Cycle-to-Cycle Jitter
tSER = 1ns
0.35 • tSER
Pipeline Latency
0.5 • tSER
0.65 • tSER
s
0.5 • tSER
0.65 • tSER
s
1.1n + 2 • tSER
1.5n + 2 • tSER
s
60
psP-P
6
Cycles
SPI Port Timing (Note 8)
tSCK
SCK Period
tS
Write Mode
Readback Mode, CSDO = 20pF, RPULLUP = 2k
l
l
40
250
ns
ns
CS to SCK Set-Up Time
l
5
ns
tH
SCK to CS Set-Up Time
l
5
ns
tDS
SDI Set-Up Time
l
5
ns
tDH
SDI Hold Time
l
5
tDO
SCK Falling to SDO Valid
Readback Mode
CSDO = 20pF, RPULLUP = 2k
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2: All voltage values are with respect to GND with GND and OGND
shorted (unless otherwise noted).
Note 3: When these pin voltages are taken below GND or above VDD, they
will be clamped by internal diodes. This product can handle input currents
of greater than 100mA below GND or above VDD without latchup.
Note 4: When these pin voltages are taken below GND they will be
clamped by internal diodes. When these pin voltages are taken above VDD
they will not be clamped by internal diodes. This product can handle input
currents of greater than 100mA below GND without latchup.
Note 5: VDD = OVDD = 1.8V, fSAMPLE = 65MHz (LTC2172),
40MHz (LTC2171), or 25MHz (LTC2170), 2-lane output mode, differential
ENC+/ENC– = 2VP-P sine wave, input range = 2VP-P with differential drive,
unless otherwise noted.
l
ns
125
ns
Note 6: Integral nonlinearity is defined as the deviation of a code from a
best fit straight line to the transfer curve. The deviation is measured from
the center of the quantization band.
Note 7: Offset error is the offset voltage measured from –0.5 LSB when
the output code flickers between 0000 0000 0000 and 1111 1111 1111 in
2’s complement output mode.
Note 8: Guaranteed by design, not subject to test.
Note 9: VDD = OVDD = 1.8V, fSAMPLE = 65MHz (LTC2172), 40MHz
(LTC2171), or 25MHz (LTC2170), 2-lane output mode, ENC+ = singleended 1.8V square wave, ENC– = 0V, input range = 2VP-P with differential
drive, unless otherwise noted. The supply current and power dissipation
specifications are totals for the entire chip, not per channel.
Note 10: Recommended operating conditions.
Note 11: The maximum sampling frequency depends on the speed grade
of the part and also which serialization mode is used. The maximum serial
data rate is 1000Mbps, so tSER must be greater than or equal to 1ns.
Note 12: Near-channel crosstalk refers to Ch. 1 to Ch.2, and Ch.3 to Ch.4.
Far-channel crosstalk refers to Ch.1 to Ch.3, Ch.1 to Ch.4, Ch.2 to Ch.3, and
Ch.2 to Ch.4.
21721012fb
7
LTC2172-12/
LTC2171-12/LTC2170-12
Timing Diagrams
2-Lane Output Mode, 16-Bit Serialization
tAP
ANALOG
INPUT
N+1
N
tENCH
tENCL
ENC–
ENC+
tSER
DCO–
DCO+
tDATA
tFRAME
FR–
FR+
tSER
tPD
tSER
OUT#A–
OUT#A+
OUT#B–
OUT#B+
D3
D1
DX*
0
D11
D9
D7
D5
D3
D1
DX*
0
D11
D9
D2
D0
DY*
0
D10
D8
D6
D4
D2
D0
DY*
0
D10
D8
SAMPLE N-6
SAMPLE N-5
D7
D6
217212 TD01
SAMPLE N-4
*DX AND DY ARE EXTRA NON-DATA BITS FOR COMPLETE SOFTWARE COMPATIBILITY WITH THE 14-BIT
VERSIONS OF THESE A/Ds. DURING NORMAL NON-OVERRANGED OPERATION DX AND DY ARE SET TO
LOGIC 0. SEE THE DATA FORMAT SECTION FOR MORE DETAILS.
2-Lane Output Mode, 14-Bit Serialization
tAP
ANALOG
INPUT
N+2
N+1
N
tENCH
tENCL
ENC–
ENC+
tSER
DCO–
DCO+
tDATA
tFRAME
FR–
FR+
tSER
tPD
tSER
–
OUT#A
OUT#A+
OUT#B–
OUT#B+
D5
D3
D1
DX*
D11
D9
D7
D5
D3
D1
DX* D11
D9
D7
D5
D3
D1
DX*
D11
D9
D7
D4
D2
D0
DY*
D10
D8
D6
D4
D2
D0
DY* D10
D8
D6
D4
D2
D0
DY*
D10
D8
D6
SAMPLE N-6
SAMPLE N-5
SAMPLE N-4
SAMPLE N-3
217212 TD02
NOTE THAT IN THIS MODE, FR+/FR– HAS TWO TIMES THE PERIOD OF ENC+/ENC–
*DX AND DY ARE EXTRA NON-DATA BITS FOR COMPLETE SOFTWARE COMPATIBILITY WITH THE 14-BIT
VERSIONS OF THESE A/Ds. DURING NORMAL NON-OVERRANGED OPERATION DX AND DY ARE SET TO
LOGIC 0. SEE THE DATA FORMAT SECTION FOR MORE DETAILS.
21721012fb
8
LTC2172-12/
LTC2171-12/LTC2170-12
timing DIAGRAMS
2-Lane Output Mode, 12-Bit Serialization
tAP
ANALOG
INPUT
N+1
N
tENCH
tENCL
ENC–
ENC+
tSER
DCO–
DCO+
tDATA
tFRAME
FR+
FR–
tPD
tSER
OUT#A–
OUT#A+
OUT#B–
OUT#B+
tSER
D7
D5
D3
D1
D11
D9
D7
D5
D3
D1
D11
D9
D7
D6
D4
D2
D0
D10
D8
D6
D4
D2
D0
D10
D8
D6
SAMPLE N-6
SAMPLE N-5
217212 TD03
SAMPLE N-4
1-Lane Output Mode, 16-Bit Serialization
tAP
ANALOG
INPUT
N+1
N
tENCH
tENCL
ENC–
ENC+
tSER
DCO–
DCO+
tFRAME
FR–
FR+
tDATA
tSER
tPD
tSER
OUT#A–
OUT#A+
DX*
DY*
0
0
SAMPLE N-6
D11
D10
D9
D8
D7
D6
D5
D4
D3
D2
SAMPLE N-5
D1
D0
DX*
DY*
0
0
D11
D10
SAMPLE N-4
D9
D8
217212 TD04
OUT#B+, OUT#B– ARE DISABLED
*DX AND DY ARE EXTRA NON-DATA BITS FOR COMPLETE SOFTWARE COMPATIBILITY WITH THE 14-BIT
VERSIONS OF THESE A/Ds. DURING NORMAL NON-OVERRANGED OPERATION DX AND DY ARE SET TO
LOGIC 0. SEE THE DATA FORMAT SECTION FOR MORE DETAILS.
21721012fb
9
LTC2172-12/
LTC2171-12/LTC2170-12
timing DIAGRAMS
1-Lane Output Mode, 14-Bit Serialization
tAP
ANALOG
INPUT
N+1
N
tENCH
tENCL
ENC–
ENC+
tSER
DCO–
DCO+
tFRAME
FR–
FR+
OUT#A–
OUT#A+
tDATA
tSER
tPD
D1
D0
DX*
tSER
DY* D11
SAMPLE N-6
D10
D9
D8
D7
D6
D5
D4
D3
D2
D1
D0
DX*
DY*
SAMPLE N-5
D11
D10
D9
D8
217212 TD05
SAMPLE N-4
OUT#B+, OUT#B– ARE DISABLED
*DX AND DY ARE EXTRA NON-DATA BITS FOR COMPLETE SOFTWARE COMPATIBILITY WITH THE 14-BIT
VERSIONS OF THESE A/Ds. DURING NORMAL NON-OVERRANGED OPERATION DX AND DY ARE SET TO
LOGIC 0. SEE THE DATA FORMAT SECTION FOR MORE DETAILS.
1-Lane Output Mode, 12-Bit Serialization
tAP
ANALOG
INPUT
N+1
N
tENCH
tENCL
ENC–
ENC+
tSER
DCO–
DCO+
tFRAME
FR–
FR+
OUT#A–
OUT#A+
tDATA
tSER
tPD
D3
D2
D1
tSER
D0
SAMPLE N-6
D11
D10
SAMPLE N-5
D9
D8
D7
D6
D5
D4
D3
D2
D1
D0
D11
D10
SAMPLE N-4
D9
217212 TD06
OUT#B+, OUT#B– ARE DISABLED
21721012fb
10
LTC2172-12/
LTC2171-12/LTC2170-12
timing DIAGRAMS
SPI Port Timing (Readback Mode)
tDS
tS
tDH
tSCK
tH
CS
SCK
tDO
SDI
SDO
R/W
A6
A5
A4
A3
A2
A1
A0
XX
D7
HIGH IMPEDANCE
XX
D6
XX
D5
XX
D4
XX
D3
XX
D2
XX
XX
D1
D0
SPI Port Timing (Write Mode)
CS
SCK
SDI
SDO
R/W
HIGH IMPEDANCE
A6
A5
A4
A3
A2
A1
A0
D7
D6
D5
D4
D3
D2
D1
D0
217212 TD07
21721012fb
11
LTC2172-12/
LTC2171-12/LTC2170-12
Typical Performance Characteristics
LTC2172-12: Differential
Nonlinearity (DNL)
1.0
1.0
0
0.8
0.8
–10
0.6
0.6
0.4
0.4
0.2
0
–0.2
–0.4
0
–0.2
–0.4
–0.6
–0.8
–0.8
–1.0
–1.0
0
1024
2048
3072
OUTPUT CODE
4096
–30
0.2
–0.6
–60
–70
–80
0
1024
2048
3072
OUTPUT CODE
4096
–110
–120
LTC2172-12: 8k Point FFT,
fIN = 70MHz, –1dBFS, 65Msps
0
–10
–10
–20
–20
–20
–30
–30
–30
–70
–80
0
AMPLITUDE (dBFS)
AMPLITUDE (dBFS)
0
–60
–40
–50
–60
–70
–80
–60
–70
–80
–90
–100
–110
–120
–110
–120
–110
–120
30
0
20
10
FREQUENCY (MHz)
71
14000
12000
10000
COUNT
–40
–50
70
SNR (dBFS)
–30
AMPLITUDE (dBFS)
72
16000
–20
8000
–80
6000
–90
–100
4000
20
10
FREQUENCY (MHz)
30
217212 G07
0
2049
69
68
67
2000
0
30
217212 G06
18000
0
–70
20
10
FREQUENCY (MHz)
LTC2172-12: SNR vs Input
Frequency, –1dBFS, 2V Range,
65Msps
LTC2172-12: Shorted Input
Histogram
–10
–60
0
217212 G05
217212 G04
LTC2172-12: 8k Point 2-Tone FFT,
fIN = 68MHz, 69MHz, –1dBFS,
65Msps
–110
–120
30
LTC2172-12: 8k Point FFT,
fIN = 140MHz, –1dBFS, 65Msps
–40
–90
–100
10
20
FREQUENCY (MHz)
30
–50
–90
–100
0
10
20
FREQUENCY (MHz)
217212 G03
–10
–50
0
217212 G02
LTC2172-12: 8k Point FFT,
fIN = 30MHz, –1dBFS, 65Msps
AMPLITUDE (dBFS)
–40
–50
–90
–100
217212 G01
–40
LTC2172-12: 8k Point FFT,
fIN = 5MHz, –1dBFS, 65Msps
–20
AMPLITUDE (dBFS)
DNL ERROR (LSB)
INL ERROR (LSB)
LTC2172-12: Integral
Nonlinearity (INL)
2050
2051
2052
OUTPUT CODE
2053
217212 G08
66
0
50
100 150 200 250 300
INPUT FREQUENCY (MHz)
350
217212 G09
21721012fb
12
LTC2172-12/
LTC2171-12/LTC2170-12
Typical Performance Characteristics
LTC2172-12: SFDR vs Input
Frequency, –1dBFS, 2V Range,
65Msps
110
100
85
80
75
80
70
dBc
60
60
50
40
30
50
30
20
10
10
0
50
100 150 200 250 300
INPUT FREQUENCY (MHz)
0
–80 –70 –60 –50 –40 –30 –20 –10
INPUT LEVEL (dBFS)
350
LTC2172-12: IVDD vs Sample Rate,
5MHz Sine Wave Input, –1dBFS
155
2-LANE, 3.5mA
40
150
145
IOVDD (mA)
130
–10
70
2-LANE, 1.75mA
20
69
68
125
1-LANE, 1.75mA
10
120
71
1-LANE, 3.5mA
30
0
LTC2172-12: SNR vs SENSE,
fIN = 5MHz, –1dBFS
72
50
135
–40
–30
–20
INPUT LEVEL(dBFS)
217212 G50
IOVDD vs Sample Rate, 5MHz Sine
Wave Input, –1dBFS
160
140
–50
217212 G12
217212 G10
IVDD (mA)
0
–60
0
SNR (dBFS)
65
dBc
40
20
70
dBFS
70
dBFS
90
SFDR (dBc AND dBFS)
SFDR (dBFS)
90
LTC2172-12: SNR vs Input Level,
fIN = 70MHz, 2V Range, 65Msps
80
SNR (dBc AND dBFS)
95
LTC2172-12: SFDR vs Input Level,
fIN = 70MHz, 2V Range, 65Msps
67
115
110
0
10
20
30
40
50
SAMPLE RATE (Msps)
0
60
0
10
20
30
40
50
SAMPLE RATE (Msps)
217212 G53
0.6
LTC2171-12: Differential
Nonlinearity (DNL)
0
0.8
–10
0.6
0.6
0.4
0.4
0
–0.4
0
–0.2
–0.4
–0.6
–0.8
–0.8
–1.0
–1.0
1024
2048
3072
OUTPUT CODE
4096
217212 G21
1.2
1.3
LTC2171-12: 8k Point FFT,
fIN = 5MHz, –1dBFS, 40Msps
–30
0.2
–0.6
0
0.9
1
1.1
SENSE PIN (V)
–20
AMPLITUDE (dBFS)
DNL ERROR (LSB)
1.0
0.8
–0.2
0.8
217212 G15
1.0
0.2
0.7
217212 G51
LTC2171-12: Integral Nonlinearity
(INL)
INL ERROR (LSB)
66
60
–40
–50
–60
–70
–80
–90
–100
0
1024
2048
3072
OUTPUT CODE
4096
217212 G22
–110
–120
0
10
FREQUENCY (MHz)
20
217212 G23
21721012fb
13
LTC2172-12/
LTC2171-12/LTC2170-12
Typical Performance Characteristics
0
LTC2171-12: 8k Point FFT,
fIN = 69MHz, –1dBFS, 40Msps
0
–10
–10
–20
–20
–20
–30
–30
–30
–40
–50
–60
–70
–80
AMPLITUDE (dBFS)
–10
AMPLITUDE (dBFS)
AMPLITUDE (dBFS)
0
LTC2171-12: 8k Point FFT,
fIN = 29MHz, –1dBFS, 40Msps
–40
–50
–60
–70
–80
–40
–50
–60
–70
–80
–90
–100
–90
–100
–90
–100
–110
–120
–110
–120
–110
–120
0
20
10
FREQUENCY (MHz)
0
217212 G24
0
14000
–40
12000
–60
–70
71
70
SNR (dBFS)
–30
COUNT
10000
8000
6000
–90
–100
4000
67
2000
0
0
2049
20
10
FREQUENCY (MHz)
2050
2051
2052
OUTPUT CODE
217212 G27
110
95
100
90
SFDR (dBc AND dBFS)
90
80
75
0
50
100 150 200 250 300
INPUT FREQUENCY (MHz)
LTC2171-12: IVDD vs Sample Rate,
5MHz Sine Wave Input, –1dBFS
100
dBFS
95
80
90
70
60
50
350
217212 G29
LTC2171-12: SFDR vs Input Level,
fIN = 70MHz, 2V Range, 40Msps
dBc
40
85
80
30
20
70
66
2053
217212 G28
LTC2171-12: SFDR vs Input
Frequency, –1dBFS, 2V Range,
40Msps
85
69
68
IVDD (mA)
AMPLITUDE (dBFS)
72
16000
–80
SFDR (dBFS)
217212 G26
18000
–20
20
10
FREQUENCY (MHz)
LTC2171-12: SNR vs Input
Frequency, –1dBFS, 2V Range,
40Msps
LTC2171-12: Shorted Input
Histogram
–10
–50
0
217212 G25
LTC2171-12: 8k Point 2-Tone FFT,
fIN = 68MHz, 69MHz, –1dBFS,
40Msps
–110
–120
20
10
FREQUENCY (MHz)
LTC2171-12: 8k Point FFT,
fIN = 139MHz, –1dBFS, 40Msps
75
10
65
0
50
100 150 200 250 300
INPUT FREQUENCY (MHz)
350
217212 G24a
0
–80 –70 –60 –50 –40 –30 –20 –10
INPUT LEVEL (dBFS)
0
217212 G32
70
0
10
20
30
SAMPLE RATE (Msps)
40
217212 G54
21721012fb
14
LTC2172-12/
LTC2171-12/LTC2170-12
Typical Performance Characteristics
LTC2170-12: Integral Nonlinearity
(INL)
72
71
INL ERROR (LSB)
SNR (dBFS)
70
69
68
67
66
0.6
0.7
0.8
0.9
1
1.1
SENSE PIN (V)
1.2
1.0
1.0
0.8
0.8
0.6
0.6
0.4
0.4
0.2
0
–0.2
–0.4
–0.2
–0.4
–0.6
–0.8
0
1024
2048
3072
OUTPUT CODE
–1.0
4096
0
–10
–20
–20
–20
–30
–30
–30
–70
–80
AMPLITUDE (dBFS)
0
–10
–60
–40
–50
–60
–70
–80
–40
–60
–70
–80
–90
–100
–90
–100
–110
–120
–110
–120
–110
–120
5
FREQUENCY (MHz)
10
0
5
FREQUENCY (MHz)
10
217212 G43
0
18000
–10
–20
–20
–30
–30
14000
–40
12000
–70
16000
–50
COUNT
–60
–60
–70
10000
8000
–80
6000
–90
–100
–90
–100
4000
–110
–120
–110
–120
–80
0
5
FREQUENCY (MHz)
10
217212 G46
10
LTC2170-12: Shorted Input
Histogram
–10
–40
5
FREQUENCY (MHz)
217212 G45
LTC2170-12: 8k Point 2-Tone FFT,
fIN = 68MHz, 69MHz, –1dBFS,
25Msps
LTC2170-12: 8k Point FFT,
fIN = 140MHz, –1dBFS, 25Msps
–50
0
217212 G44
AMPLITUDE (dBFS)
AMPLITUDE (dBFS)
0
4096
–50
–90
–100
0
2048
3072
OUTPUT CODE
LTC2170-12: 8k Point FFT,
fIN = 70MHz, –1dBFS, 25Msps
–10
–50
1024
217212 G42
LTC2170-12: 8k Point FFT,
fIN = 30MHz, –1dBFS, 25Msps
LTC2170-12: 8k Point FFT,
fIN = 5MHz, –1dBFS, 25Msps
–40
0
217212 G41
AMPLITUDE (dBFS)
AMPLITUDE (dBFS)
0
–0.8
217212 G35
0
0.2
–0.6
–1.0
1.3
LTC2170-12: Differential
Nonlinearity (DNL)
DNL ERROR (LSB)
LTC2171-12: SNR vs SENSE,
fIN = 5MHz, –1dBFS
2000
0
5
FREQUENCY (MHz)
0
2049
10
217212 G47
2050
2051
2052
OUTPUT CODE
2053
217212 G48
21721012fb
15
LTC2172-12/
LTC2171-12/LTC2170-12
Typical Performance Characteristics
LTC2170-12: SFDR vs Input
Frequency, –1dBFS, 2V Range,
25Msps
LTC2170-12: SNR vs Input
Frequency, –1dBFS, 2V Range,
25Msps
72
95
71
90
70
85
110
LTC2170-12: SFDR vs Input Level,
fIN = 70MHz, 2V Range, 25Msps
69
68
80
75
67
70
66
65
dBFS
90
SFDR (dBc AND dBFS)
SFDR (dBFS)
SNR (dBFS)
100
80
70
dBc
60
50
40
30
20
10
0
100 150 200 250 300
INPUT FREQUENCY (MHz)
50
350
0
50
100 150 200 250 300
INPUT FREQUENCY (MHz)
217212 G49
LTC2170-12: SNR vs SENSE,
fIN = 5MHz, –1dBFS
DCO Cycle-Cycle Jitter vs Serial
Data Rate
72
350
71
300
PEAK-TO-PEAK JITTER (ps)
80
75
SNR (dBFS)
IVDD (mA)
70
69
68
65
67
60
0
5
10
15
20
SAMPLE RATE (Msps)
25
217212 G55
66
0
217212 G52
217212 G37
LTC2170-12: IVDD vs Sample Rate,
5MHz Sine Wave Input, –1dBFS
70
0
–80 –70 –60 –50 –40 –30 –20 –10
INPUT LEVEL (dBFS)
350
250
200
150
100
50
0.6
0.7
0.8
0.9 1.0 1.1
SENSE PIN (V)
1.2
1.3
217212 G55a
0
0
200
400
600
800
SERIAL DATA RATE (Mbps)
1000
217212 G52
21721012fb
16
LTC2172-12/
LTC2171-12/LTC2170-12
Pin Functions
AIN1+ (Pin 1): Channel 1 Positive Differential Analog
Input.
ENC– (Pin 18): Encode Complement Input. Conversion
starts on the falling edge.
AIN1– (Pin 2): Channel 1 Negative Differential Analog
Input.
CS (Pin 19): In serial programming mode (PAR/SER = 0V),
CS is the serial interface chip select input. When CS is low,
SCK is enabled for shifting data on SDI into the mode
control registers. In parallel programming mode (PAR/SER
= VDD), CS selects two-lane or one-lane output mode. CS
can be driven with 1.8V to 3.3V logic.
VCM12 (Pin 3): Common Mode Bias Output, Nominally
Equal to VDD /2. VCM should be used to bias the common
mode of the analog inputs of channels 1 and 2. Bypass
to ground with a 0.1µF ceramic capacitor.
AIN2+ (Pin 4): Channel 2 Positive Differential Analog
Input.
AIN2– (Pin 5): Channel 2 Negative Differential Analog
Input.
REFH (Pins 6, 7): ADC High Reference. Bypass to Pin 8
and Pin 9 with a 2.2µF ceramic capacitor, and to ground
with a 0.1µF ceramic capacitor.
REFL (Pins 8, 9): ADC Low Reference. Bypass to Pin 6
and Pin 7 with a 2.2µF ceramic capacitor, and to ground
with a 0.1µF ceramic capacitor.
AIN3+ (Pin 10): Channel 3 Positive Differential Analog
Input.
AIN3– (Pin 11): Channel 3 Negative Differential Analog
Input.
VCM34 (Pin 12): Common Mode Bias Output, Nominally
Equal to VDD /2. VCM should be used to bias the common
mode of the analog inputs of channels 3 and 4. Bypass
to ground with a 0.1µF ceramic capacitor.
AIN4+ (Pin 13): Channel 4 Positive Differential Analog
Input.
AIN4– (Pin 14): Channel 4 Negative Differential Analog
Input.
VDD (Pins 15, 16, 51, 52): Analog Power Supply, 1.7V
to 1.9V. Bypass to ground with 0.1µF ceramic capacitors.
Adjacent pins can share a bypass capacitor.
ENC+ (Pin 17): Encode Input. Conversion starts on the
rising edge.
SCK (Pin 20): In serial programming mode (PAR/SER
= 0V), SCK is the serial interface clock input. In parallel
programming mode (PAR/SER = VDD), SCK selects 3.5mA
or 1.75mA LVDS output currents. SCK can be driven with
1.8V to 3.3V logic.
SDI (Pin 21): In serial programming mode (PAR/SER =
0V), SDI is the serial interface data input. Data on SDI
is clocked into the mode control registers on the rising
edge of SCK. In parallel programming mode (PAR/SER =
VDD), SDI can be used to power down the part. SDI can
be driven with 1.8V to 3.3V logic.
GND (Pins 22, 45, 49, Exposed Pad Pin 53): ADC Power
Ground. The exposed pad must be soldered to the PCB
ground.
OGND (Pin 33): Output Driver Ground. Must be shorted
to the ground plane by a very low inductance path. Use
multiple vias close to the pin.
OVDD (Pin 34): Output Driver Supply, 1.7V to 1.9V. Bypass
to ground with a 0.1µF ceramic capacitor.
SDO (Pin 46): In serial programming mode (PAR/SER
= 0V), SDO is the optional serial interface data output.
Data on SDO is read back from the mode control registers and can be latched on the falling edge of SCK.
SDO is an open-drain N-channel MOSFET output that
requires an external 2k pull-up resistor of 1.8V to
3.3V. If readback from the mode control registers is
not needed, the pull-up resistor is not necessary and
SDO can be left unconnected. In parallel programming
mode (PAR/SER = VDD), SDO is an input that enables
internal 100Ω termination resistors on the digital
outputs. When used as an input, SDO can be driven
with 1.8V to 3.3V logic through a 1k series resistor.
21721012fb
17
LTC2172-12/
LTC2171-12/LTC2170-12
Pin Functions
PAR/SER (Pin 47): Programming Mode Selection Pin.
Connect to ground to enable serial programming mode.
CS, SCK, SDI and SDO become a serial interface that controls the A/D operating modes. Connect to VDD to enable
parallel programming mode where CS, SCK, SDI and SDO
become parallel logic inputs that control a reduced set of
the A/D operating modes. PAR/SER should be connected
directly to ground or the VDD of the part and not be driven
by a logic signal.
VREF (Pin 48): Reference Voltage Output. Bypass to ground
with a 1µF ceramic capacitor, nominally 1.25V.
SENSE (Pin 50): Reference Programming Pin. Connecting SENSE to VDD selects the internal reference and a
±1V input range. Connecting SENSE to ground selects
the internal reference and a ±0.5V input range. An external
reference between 0.625V and 1.3V applied to SENSE
selects an input range of ±0.8 • VSENSE.
LVDS Outputs
The following pins are differential LVDS outputs. The
output current level is programmable. There is an optional internal 100Ω termination resistor between the
pins of each LVDS output pair.
OUT4B – /OUT4B + , OUT4A – /OUT4A + (Pins 23/24,
Pins 25/ 26): Serial Data Outputs for Channel 4. In 1-lane
output mode, only OUT4A–/OUT4A+ are used.
OUT3B – /OUT3B + , OUT3A – /OUT3A + (Pins 27/28,
Pins 29/30): Serial Data Outputs for Channel 3. In
1-lane output mode, only OUT3A–/OUT3A+ are used.
FR–/FR+ (Pin 31/Pin 32): Frame Start Output.
DCO–/DCO+ (Pin 35/Pin 36): Data Clock Output.
OUT2B – /OUT2B + , OUT2A – /OUT2A + (Pins 37/38,
Pins 39/40): Serial Data Outputs for Channel 2. In
1-lane output mode, only OUT2A–/OUT2A+ are used.
OUT1B – /OUT1B + , OUT1A – /OUT1A + (Pins 41/42,
Pins 43/44): Serial Data Outputs for Channel 1. In
1-lane output mode, only OUT1A–/OUT1A+ are used.
21721012fb
18
LTC2172-12/
LTC2171-12/LTC2170-12
Functional Block Diagram
ENC+ ENC–
1.8V
1.8V
VDD
CHANNEL 1
ANALOG
INPUT
SAMPLEAND-HOLD
12-BIT
ADC CORE
CHANNEL 2
ANALOG
INPUT
SAMPLEAND-HOLD
12-BIT
ADC CORE
OVDD
OUT1A
PLL
OUT1B
OUT2A
OUT2B
DATA
SERIALIZER
CHANNEL 3
ANALOG
INPUT
OUT3A
12-BIT
ADC CORE
SAMPLEAND-HOLD
OUT3B
OUT4A
CHANNEL 4
ANALOG
INPUT
VREF
1µF
SAMPLEAND-HOLD
12-BIT
ADC CORE
OUT4B
DATA
CLOCK OUT
1.25V
REFERENCE
FRAME
RANGE
SELECT
OGND
REFH
REF
BUF
SENSE
REFL
VDD /2
DIFF
REF
AMP
GND
MODE
CONTROL
REGISTERS
REFH
0.1µF
REFL
VCM12
0.1µF
217212 F01
VCM34
0.1µF
PAR/SER CS SCK SDI SDO
2.2µF
0.1µF
0.1µF
Figure 1. Functional Block Diagram
21721012fb
19
LTC2172-12/
LTC2171-12/LTC2170-12
Applications Information
CONVERTER OPERATION
The LTC2172-12/LTC2171-12/LTC2170-12 are low power,
4-channel, 12-bit, 65Msps/40Msps/25Msps A/D converters that are powered by a single 1.8V supply. The analog
inputs should be driven differentially. The encode input
can be driven differentially for optimal jitter performance,
or single-ended for lower power consumption. The digital
outputs are serial LVDS to minimize the number of data
lines. Each channel outputs two bits at a time (2-lane
mode) or one bit at a time (1-lane mode). Many additional
features can be chosen by programming the mode control
registers through a serial SPI port.
ANALOG INPUT
The analog inputs are differential CMOS sample-and-hold
circuits (Figure 2). The inputs should be driven differentially around a common mode voltage set by the VCM12
RON
25Ω
10Ω
INPUT DRIVE CIRCUITS
Input Filtering
If possible, there should be an RC lowpass filter right
at the analog inputs. This lowpass filter isolates the
drive circuitry from the A/D sample-and-hold switching and limits wideband noise from the drive circuitry.
Figure 3 shows an example of an input RC filter. The RC
component values should be chosen based on the application’s input frequency.
CSAMPLE
3.5pF
RON
25Ω
10Ω
CSAMPLE
3.5pF
CPARASITIC
1.8pF
T1
1:1
25Ω
25Ω
AIN+
LTC2172-12
0.1µF
12pF
25Ω
25Ω
T1: MA/COM MABAES0060
RESISTORS, CAPACITORS
ARE 0402 PACKAGE SIZE
VDD
VCM
0.1µF
0.1µF
ANALOG
INPUT
CPARASITIC
1.8pF
VDD
AIN–
The four channels are simultaneously sampled by a
shared encode circuit (Figure 2).
50Ω
LTC2172-12
VDD
AIN+
or VCM34 output pins, which are nominally VDD /2. For the
2V input range, the inputs should swing from VCM – 0.5V
to VCM + 0.5V. There should be a 180° phase difference
between the inputs.
AIN–
217212 F03
Figure 3. Analog Input Circuit Using a Transformer.
Recommended for Input Frequencies from 5MHz to 70MHz
1.2V
10k
ENC+
ENC–
10k
1.2V
217212 F02
Figure 2. Equivalent Input Circuit. Only One of
the Four Analog Channels Is Shown.
21721012fb
20
LTC2172-12/
LTC2171-12/LTC2170-12
Applications Information
Transformer Coupled Circuits
Amplifier Circuits
Figure 3 shows the analog input being driven by an RF
transformer with a center-tapped secondary. The center
tap is biased with VCM, setting the A/D input at its optimal DC level. At higher input frequencies a transmission
line balun transformer (Figures 4 to 6) has better balance,
resulting in lower A/D distortion.
Figure 7 shows the analog input being driven by a high
speed differential amplifier. The output of the amplifier is
AC-coupled to the A/D so the amplifier’s output common
mode voltage can be optimally set to minimize distortion.
50Ω
At very high frequencies an RF gain block will often have
lower distortion than a differential amplifier. If the gain
block is single-ended, then a transformer circuit (Figures
4 to 6) should convert the signal to differential before
driving the A/D.
50Ω
VCM
VCM
0.1µF
0.1µF
ANALOG
INPUT
0.1µF
0.1µF
+
AIN
T2
T1
25Ω
LTC2172-12
0.1µF
ANALOG
INPUT
AIN+
T2
T1
25Ω
LTC2172-12
0.1µF
4.7pF
0.1µF
25Ω
1.8pF
0.1µF
–
AIN
25Ω
AIN–
217212 F04
217212 F05
T1: MA/COM MABA-007159-000000
T2: MA/COM MABAES0060
RESISTORS, CAPACITORS ARE 0402 PACKAGE SIZE
T1: MA/COM MABA-007159-000000
T2: COILCRAFT WBC1-1LB
RESISTORS, CAPACITORS ARE 0402 PACKAGE SIZE
Figure 4. Recommended Front-End Circuit for Input
Frequencies from 70MHz to 170MHz
Figure 5. Recommended Front-End Circuit for Input
Frequencies from 170MHz to 300MHz
50Ω
VCM
VCM
HIGH SPEED
DIFFERENTIAL
0.1µF
AMPLIFIER
0.1µF
0.1µF
2.7nH
ANALOG
INPUT
25Ω
AIN+
LTC2172-12
0.1µF
ANALOG
INPUT
+
+
–
–
200Ω
200Ω
25Ω
25Ω
2.7nH
AIN–
217212 F06
T1: MA/COM ETC1-1-13
RESISTORS, CAPACITORS
ARE 0402 PACKAGE SIZE
Figure 6. Recommended Front-End Circuit for Input
Frequencies Above 300MHz
AIN+
LTC2172-12
12pF
T1
0.1µF
0.1µF
0.1µF
25Ω
AIN–
217212 F07
Figure 7. Front-End Circuit Using a High Speed
Differential Amplifier
21721012fb
21
LTC2172-12/
LTC2171-12/LTC2170-12
Applications Information
Reference
Encode Input
The LTC2172-12/LTC2171-12/LTC2170-12 has an internal
1.25V voltage reference. For a 2V input range using the
internal reference, connect SENSE to VDD. For a 1V input
range using the internal reference, connect SENSE to
ground. For a 2V input range with an external reference,
apply a 1.25V reference voltage to SENSE (Figure 9).
The signal quality of the encode inputs strongly affects
the A/D noise performance. The encode inputs should
be treated as analog signals—do not route them next to
digital traces on the circuit board. There are two modes
of operation for the encode inputs: the differential encode
mode (Figure 10), and the single-ended encode mode
(Figure 11).
The input range can be adjusted by applying a voltage to
SENSE that is between 0.625V and 1.30V. The input range
will then be 1.6 • VSENSE.
VREF
1µF
The reference is shared by all four ADC channels, so it is
not possible to independently adjust the input range of
individual channels.
The VREF , REFH and REFL pins should be bypassed, as
shown in Figure 8. The 0.1µF capacitor between REFH and
REFL should be as close to the pins as possible (not on
the backside of the circuit board).
1.25V
EXTERNAL
REFERENCE
1.25V
5Ω
1µF
1µF
217212 F09
Figure 9. Using an External 1.25V Reference
LTC2172-12
LTC2172-12
VREF
LTC2172-12
SENSE
1.25V BANDGAP
REFERENCE
VDD
DIFFERENTIAL
COMPARATOR
VDD
0.625V
TIE TO VDD FOR 2V RANGE;
TIE TO GND FOR 1V RANGE;
RANGE = 1.6 • VSENSE FOR
0.625V < VSENSE < 1.300V
0.1µF
15k
RANGE
DETECT
AND
CONTROL
ENC+
ENC–
SENSE
30k
BUFFER
INTERNAL ADC
HIGH REFERENCE
217212 F10
REFH
Figure 10. Equivalent Encode Input Circuit
for Differential Encode Mode
2.2µF
0.1µF
0.1µF
0.8x
DIFF AMP
REFL
LTC2172-12
INTERNAL ADC
LOW REFERENCE
1.8V TO 3.3V
0V
217212 F08
Figure 8. Reference Circuit
ENC+
ENC–
30k
CMOS LOGIC
BUFFER
217212 F11
Figure 11. Equivalent Encode Input Circuit
for Single-Ended Encode Mode
21721012fb
22
LTC2172-12/
LTC2171-12/LTC2170-12
Applications Information
The differential encode mode is recommended for sinusoidal, PECL, or LVDS encode inputs (Figures 12 and 13).
The encode inputs are internally biased to 1.2V through
10k equivalent resistance. The encode inputs can be taken
above VDD (up to 3.6V), and the common mode range
is from 1.1V to 1.6V. In the differential encode mode,
ENC – should stay at least 200mV above ground to avoid
falsely triggering the single-ended encode mode. For
good jitter performance ENC+ should have fast rise and
fall times.
The single-ended encode mode should be used with
CMOS encode inputs. To select this mode, ENC – is connected to ground and ENC+ is driven with a square wave
encode input. ENC+ can be taken above VDD (up to 3.6V)
so 1.8V to 3.3V CMOS logic levels can be used. The
ENC+ threshold is 0.9V. For good jitter performance
ENC+ should have fast rise and fall times.
Clock PLL and Duty Cycle Stabilizer
The encode clock is multiplied by an internal phase-locked
loop (PLL) to generate the serial digital output data. If the
encode signal changes frequency or is turned off, the PLL
requires 25µs to lock onto the input clock.
A clock duty cycle stabilizer circuit allows the duty cycle
of the applied encode signal to vary from 30% to 70%.
In the serial programming mode it is possible to disable
the duty cycle stabilizer, but this is not recommended. In
the parallel programming mode the duty cycle stabilizer
is always enabled.
DIGITAL OUTPUTS
The digital outputs of the LTC2172-12/LTC2171-12/
LTC2170-12 are serialized LVDS signals. Each channel
outputs two bits at a time (2-lane mode) or one bit at a
time (1-lane mode). The data can be serialized with 16-,
14-, or 12-bit serialization (see the Timing Diagrams section for details).
The output data should be latched on the rising and
falling edges of the data clockout (DCO). A data frame
output (FR) can be used to determine when the data
from a new conversion result begins. In the 2-lane, 14bit serialization mode, the frequency of the FR output
is halved.
The maximum serial data rate for the data outputs is
1Gbps, so the maximum sample rate of the ADC will depend on the serialization mode as well as the speed grade
of the ADC (see Table 1). The minimum sample rate for
all serialization modes is 5Msps.
0.1µF
0.1µF
ENC+
T1
50Ω
0.1µF
ENC+
LTC2172-12
PECL OR
LVDS
CLOCK
100Ω
LTC2172-12
0.1µF
ENC–
50Ω
217212 F13
0.1µF
ENC–
Figure 13. PECL or LVDS Encode Drive
217212 F12
T1 = MA/COM ETC1-1-13
RESISTORS AND CAPACITORS
ARE 0402 PACKAGE SIZE
Figure 12. Sinusoidal Encode Drive
21721012fb
23
LTC2172-12/
LTC2171-12/LTC2170-12
Applications Information
Table 1. Maximum Sampling Frequency for All Serialization Modes. Note That These Limits Are for the LTC2172-12. The Sampling
Frequency for the Slower Speed Grades Cannot Exceed 40MHz (LTC2171-12) or 25MHz (LTC2170-12).
SERIALIZATION MODE
MAXIMUM SAMPLING
FREQUENCY, fS (MHz)
DCO FREQUENCY
FR FREQUENCY
SERIAL DATA RATE
2-Lane
16-Bit Serialization
65
4 • fS
fS
8 • fS
2-Lane
14-Bit Serialization
65
3.5 • fS
0.5 • fS
7 • fS
2-Lane
12-Bit Serialization
65
3 • fS
fS
6 • fS
1-Lane
16-Bit Serialization
62.5
8 • fS
fS
16 • fS
1-Lane
14-Bit Serialization
65
7 • fS
fS
14 • fS
1-Lane
12-Bit Serialization
65
6 • fS
fS
12 • fS
By default the outputs are standard LVDS levels: a 3.5mA
output current and a 1.25V output common mode voltage. An external 100Ω differential termination resistor
is required for each LVDS output pair. The termination
resistors should be located as close as possible to the
LVDS receiver.
The outputs are powered by OVDD and OGND which are
isolated from the A/D core power and ground.
Programmable LVDS Output Current
The default output driver current is 3.5mA. This current can
be adjusted by control register A2 in serial programming
mode. Available current levels are 1.75mA, 2.1mA, 2.5mA,
3mA, 3.5mA, 4mA and 4.5mA. In parallel programming
mode the SCK pin can select either 3.5mA or 1.75mA.
Optional LVDS Driver Internal Termination
In most cases, using just an external 100Ω termination
resistor will give excellent LVDS signal integrity. In addition, an optional internal 100Ω termination resistor can
be enabled by serially programming mode control register
A2. The internal termination helps absorb any reflections
caused by imperfect termination at the receiver. When the
internal termination is enabled, the output driver current
is doubled to maintain the same output voltage swing. In
parallel programming mode the SDO pin enables internal
termination. Internal termination should only be used with
1.75mA, 2.1mA or 2.5mA LVDS output current modes.
DATA FORMAT
Table 2 shows the relationship between the analog input
voltage and the digital data output bits. By default the
output data format is offset binary. The 2’s complement
format can be selected by serially programming mode
control register A1.
In addition to the 12 data bits (D11 - D0), two additional
bits (DX and DY) are sent out in the 14-bit and 16-bit
serialization modes. These extra bits are to ensure complete software compatibility with the 14-bit versions of
these A/Ds. During normal operation when the analog
inputs are not overranged, DX and DY are always logic 0.
When the analog inputs are overranged positive, DX and
DY become logic 1. When the analog inputs are overranged negative, DX and DY become logic 0. DX and DY
can also be controlled by the digital output test pattern.
See the Timing Diagrams section for more information.
Table 2. Output Codes vs Input Voltage
AIN+ – AIN–
(2V RANGE)
D11-D0
(OFFSET BINARY)
D11-D0
(2’s COMPLEMENT)
DX, DY
>+1.000000V
1111 1111 1111
0111 1111 1111
11
+0.999512V
1111 1111 1111
0111 1111 1111
00
+0.999024V
1111 1111 1110
0111 1111 1110
00
+0.000488V
1000 0000 0001
0000 0000 0001
00
0.000000V
1000 0000 0000
0000 0000 0000
00
–0.000488V
0111 1111 1111
1111 1111 1111
00
–0.000976V
0111 1111 1110
1111 1111 1110
00
–0.999512V
0000 0000 0001
1000 0000 0001
00
–1.000000V
0000 0000 0000
1000 0000 0000
00
≤–1.000000V
0000 0000 0000
1000 0000 0000
00
21721012fb
24
LTC2172-12/
LTC2171-12/LTC2170-12
Applications Information
Digital Output Randomizer
Interference from the A/D digital outputs is sometimes
unavoidable. Digital interference may be from capacitive or
inductive coupling or coupling through the ground plane.
Even a tiny coupling factor can cause unwanted tones in
the ADC output spectrum. These unwanted tones can be
randomized by randomizing the digital output before it is
transmitted off chip, which reduces the unwanted tone
amplitude.
The digital output is randomized by applying an exclusive-OR logic operation between the LSB and all other
data output bits. To decode, the reverse operation is
applied—an exclusive-OR operation is applied between
the LSB and all other bits. The FR and DCO outputs are
not affected. The output randomizer is enabled by serially
programming mode control register A1.
Digital Output Test Pattern
To allow in-circuit testing of the digital interface to the
A/D, there is a test mode that forces the A/D data outputs
(D11-D0, DX, DY) of all channels to known values. The
digital output test patterns are enabled by serially programming mode control registers A3 and A4. When enabled,
the test patterns override all other formatting modes: 2’s
complement and randomizer.
Output Disable
The digital outputs may be disabled by serially programming mode control register A2. The current drive for all
digital outputs, including DCO and FR, are disabled to save
power or enable in-circuit testing. When disabled, the common mode of each output pair becomes high impedance,
but the differential impedance may remain low.
In nap mode any combination of A/D channels can be
powered down while the internal reference circuits and the
PLL stay active, allowing a faster wake-up than from sleep
mode. Recovering from nap mode requires at least 100
clock cycles. If the application demands very accurate DC
settling, then an additional 50µs should be allowed so the
on-chip references can settle from the slight temperature
shift caused by the change in supply current as the A/D
leaves nap mode. Nap mode is enabled by the mode control
register A1 in the serial programming mode.
DEVICE PROGRAMMING MODES
The operating modes of the LTC2172-12/LTC2171-12/
LTC2170-12 can be programmed by either a parallel
interface or a simple serial interface. The serial interface
has more flexibility and can program all available modes.
The parallel interface is more limited and can only program
some of the more commonly used modes.
Parallel Programming Mode
To use the parallel programming mode, PAR/SER should
be tied to VDD. The CS, SCK, SDI and SDO pins are binary
logic inputs that set certain operating modes. These pins
can be tied to VDD or ground, or driven by 1.8V, 2.5V or
3.3V CMOS logic. When used as an input, SDO should
be driven through a 1k series resistor. Table 3 shows the
modes set by CS, SCK, SDI and SDO.
Table 3. Parallel Programming Mode Control Bits (PAR/SER = VDD)
PIN
DESCRIPTION
CS
2-Lane/1-Lane Selection Bit
0 = 2-Lane, 16-Bit Serialization Output Mode
1 = 1-Lane, 14-Bit Serialization Output Mode
SCK
LVDS Current Selection Bit
Sleep and Nap Modes
0 = 3.5mA LVDS Current Mode
The A/D may be placed in sleep or nap modes to conserve
power. In sleep mode the entire chip is powered down,
resulting in 1mW power consumption. Sleep mode is
enabled by mode control register A1 (serial programming mode), or by SDI (parallel programming mode).
The amount of time required to recover from sleep mode
depends on the size of the bypass capacitors on VREF,
REFH and REFL. For the suggested values in Figure 8, the
A/D will stabilize after 2ms.
1 = 1.75mA LVDS Current Mode
SDI
Power Down Control Bit
0 = Normal Operation
1 = Sleep Mode
SDO
Internal 100Ω Termination Selection Bit
0 = Internal Termination Disabled
1 = Internal Termination Enabled
21721012fb
25
LTC2172-12/
LTC2171-12/LTC2170-12
Applications Information
Serial Programming Mode
To use the serial programming mode, PAR/SER should be
tied to ground. The CS, SCK, SDI and SDO pins become a
serial interface that program the A/D mode control registers.
Data is written to a register with a 16-bit serial word. Data
can also be read back from a register to verify its contents.
Serial data transfer starts when CS is taken low. The data
on the SDI pin is latched at the first 16 rising edges of
SCK. Any SCK rising edges after the first 16 are ignored.
The data transfer ends when CS is taken high again.
The first bit of the 16-bit input word is the R/W bit. The
next seven bits are the address of the register (A6:A0).
The final eight bits are the register data (D7:D0).
If the R/W bit is low, the serial data (D7:D0) will be written to the register set by the address bits (A6:A0). If the
R/W bit is high, data in the register set by the address
bits (A6:A0) will be read back on the SDO pin (see the
Timing Diagrams section). During a readback command
the register is not updated and data on SDI is ignored.
The SDO pin is an open-drain output that pulls to ground
with a 200Ω impedance. If register data is read back
through SDO, an external 2k pull-up resistor is required.
If serial data is only written and readback is not needed,
then SDO can be left floating and no pull-up resistor is
needed. Table 4 shows a map of the mode control registers.
Software Reset
If serial programming is used, the mode control registers
should be programmed as soon as possible after the power
supplies turn on and are stable. The first serial command
must be a software reset which will reset all register data
bits to logic 0. To perform a software reset, bit D7 in the
reset register is written with a logic 1. After the reset SPI
write command is complete, bit D7 is automatically set
back to zero.
Table 4. Serial Programming Mode Register Map (PAR/SER = GND)
REGISTER A0: RESET REGISTER (ADDRESS 00h)
D7
D6
RESET
X
RESET
Bit 7
D5
D4
D3
D2
D1
D0
X
X
X
X
X
X
Software Reset Bit
0 = Not Used
1 = Software Reset. All Mode Control Registers Are Reset to 00h. The ADC is momentarily placed in SLEEP mode. This bit is
automatically set back to zero after the reset is complete at the end of the SPI write command. The reset register is write only.
Bits 6-0
Unused, Don’t Care Bits.
REGISTER A1: POWER-DOWN REGISTER (ADDRESS 01h)
D7
D6
D5
D4
D3
D2
D1
D0
DCSOFF
RAND
TWOSCOMP
SLEEP
NAP_4
NAP_3
NAP_2
NAP_1
Bit 7
Clock Duty Cycle Stabilizer Bit
DCSOFF
0 = Clock Duty Cycle Stabilizer On
1 = Clock Duty Cycle Stabilizer Off. This is Not Recommended.
Bit 6
RAND
Data Output Randomizer Mode Control Bit
0 = Data Output Randomizer Mode Off
1 = Data Output Randomizer Mode On
Bit 5
TWOSCOMP Two’s Complement Mode Control Bit
0 = Offset Binary Data Format
1 = Two’s Complement Data Format
Bits 4-0
SLEEP:NAP_4:NAP_1
Sleep/Nap Mode Control Bits
00000 = Normal Operation
0XXX1 = Channel 1 in Nap Mode
0XX1X = Channel 2 in Nap Mode
0X1XX = Channel 3 in Nap Mode
01XXX = Channel 4 in Nap Mode
1XXXX = Sleep Mode. All Channels Are Disabled
Note: Any Combination of Channels Can Be Placed in Nap Mode.
21721012fb
26
LTC2172-12/
LTC2171-12/LTC2170-12
Applications Information
REGISTER A2: OUTPUT MODE REGISTER (ADDRESS 02h)
D7
ILVDS2
D6
D5
D4
D3
D2
D1
D0
ILVDS1
ILVDS0
TERMON
OUTOFF
OUTMODE2
OUTMODE1
OUTMODE0
Bits 7-5
ILVDS2:ILVDS0 LVDS Output Current Bits
000 = 3.5mA LVDS Output Driver Current
001 = 4.0mA LVDS Output Driver Current
010 = 4.5mA LVDS Output Driver Current
011 = Not Used
100 = 3.0mA LVDS Output Driver Current
101 = 2.5mA LVDS Output Driver Current
110 = 2.1mA LVDS Output Driver Current
111 = 1.75mA LVDS Output Driver Current
Bit 4
TERMON
LVDS Internal Termination Bit
0 = Internal Termination Off
1 = Internal Termination On. LVDS Output Driver Current is 2x the Current Set by ILVDS2:ILVDS0. Internal termination should only be
used with 1.75mA, 2.1mA or 2.5mA LVDS output current modes.
Bit 3
OUTOFF
Output Disable Bit
0 = Digital Outputs are enabled.
1 = Digital Outputs are disabled.
Bits 2-0
OUTMODE2:OUTMODE0 Digital Output Mode Control Bits
000 = 2-Lanes, 16-Bit Serialization
001 = 2-Lanes, 14-Bit Serialization
010 = 2-Lanes, 12-Bit Serialization
011 = Not Used
100 = Not Used
101 = 1-Lane, 14-Bit Serialization
110 = 1-Lane, 12-Bit Serialization
111 = 1-Lane, 16-Bit Serialization
REGISTER A3: TEST PATTERN MSB REGISTER (ADDRESS 03h)
D7
D6
D5
D4
D3
D2
D1
D0
OUTTEST
X
TP11
TP10
TP9
TP8
TP7
TP6
Bit 7
OUTTEST
Digital Output Test Pattern Control Bit
0 = Digital Output Test Pattern Off
1 = Digital Output Test Pattern On
Bit 6
Unused, Don’t Care Bit.
Bits 5-0
TP11:TP6
Test Pattern Data Bits (MSB)
TP11:TP6 Set the Test Pattern for Data Bit 11 (MSB) Through Data Bit 6.
REGISTER A4: TEST PATTERN LSB REGISTER (ADDRESS 04h)
D7
D6
D5
D4
D3
D2
D1
D0
TP5
TP4
TP3
TP2
TP1
TP0
TPX
TPY
Bits 7-2
TP5:TP0
Test Pattern Data Bits (LSB)
TP5:TP0 Set the Test Pattern for Data Bit 5 Through Data Bit 0 (LSB).
Bits 1-0
TPX:TPY
Set the Test Pattern for Extra Bits DX and DY. These Bits are for Compatibility with the 14-Bit Version of the A/D.
21721012fb
27
LTC2172-12/
LTC2171-12/LTC2170-12
Applications Information
GROUNDING AND BYPASSING
The LTC2172-12/LTC2171-12/LTC2170-12 requires a
printed circuit board with a clean unbroken ground plane.
A multilayer board with an internal ground plane in the
first layer beneath the ADC is recommended. Layout for
the printed circuit board should ensure that digital and
analog signal lines are separated as much as possible. In
particular, care should be taken not to run any digital track
alongside an analog signal track or underneath the ADC.
High quality ceramic bypass capacitors should be used at
the VDD, OVDD, VCM, VREF, REFH and REFL pins. Bypass
capacitors must be located as close to the pins as possible.
Of particular importance is the 0.1µF capacitor between
REFH and REFL. This capacitor should be on the same
side of the circuit board as the A/D, and as close to the
device as possible (1.5mm or less). Size 0402 ceramic
capacitors are recommended. The larger 2.2µF capacitor
between REFH and REFL can be somewhat further away.
The traces connecting the pins and bypass capacitors must
be kept short and should be made as wide as possible.
The analog inputs, encode signals and digital outputs
should not be routed next to each other. Ground fill and
grounded vias should be used as barriers to isolate these
signals from each other.
HEAT TRANSFER
Most of the heat generated by the LTC2172-12/LTC2171-12/
LTC2170-12 is transferred from the die through the bottomside exposed pad and package leads onto the printed circuit
board. For good electrical and thermal performance, the
exposed pad must be soldered to a large grounded pad
on the PC board. This pad should be connected to the
internal ground planes by an array of vias.
21721012fb
28
LTC2172-12/
LTC2171-12/LTC2170-12
Typical Applications
Silkscreen Top
Top Side
Inner Layer 2 GND
Inner Layer 3
21721012fb
29
LTC2172-12/
LTC2171-12/LTC2170-12
TYPICAL Applications
Inner Layer 4
Inner Layer 5 Power
Bottom Side
Silkscreen Bottom
21721012fb
30
LTC2172-12/
LTC2171-12/LTC2170-12
TYPICAL Applications
LTC2172 Schematic
SENSE
C17
1µF
PAR/SER
C4
1µF
R14
1k
SDO
VDD
C5
1µF
C3
0.1µF
10
11
AIN3
12
AIN3
13
C59
0.1µF
14
OUT1B–
OUT1B+
OUT1A–
OUT1A+
SDO
GND
PAR/SER
GND
VREF
37
AIN2–
DCO+
REFH
DCO–
LTC2172
OVDD
REFH
35
34
33
REFL
OGND
REFL
FR+
32
AIN3+
FR–
31
AIN3–
OUT3A+
30
VCM34
OUT3A–
29
AIN4+
OUT3B+
28
AIN4–
OUT3B–
27
VDD
AIN4
AIN4
DIGITAL
OUTPUTS
36
C16
0.1µF
OVDD
DIGITAL
OUTPUTS
OUT4A+
9
OUT2B–
OUT4A–
8
AIN2+
OUT4B+
C30
0.1µF
38
OUT4B–
C2
0.1µF
C1
2.2µF
7
OUT2B+
GND
6
VCM12
SDI
AIN2
39
SCK
5
OUT2A–
CS
4
AIN1–
ENC–
AIN2
AIN1
40
ENC+
3
VDD
VDD
2
OUT2A+
+
VDD
C29
0.1µF
AIN1
1
SENSE
52 51 50 49 48 47 46 45 44 43 42 41
AIN1
15 16 17 18 19 20 21 22 23 24 25 26
VDD
C7
0.1µF
C47
0.1µF
ENCODE
CLOCK
C46
0.1µF
ENCODE
CLOCK
SPI BUS
217212 TA02
21721012fb
31
LTC2172-12/
LTC2171-12/LTC2170-12
Package Description
UKG Package
52-Lead Plastic QFN (7mm × 8mm)
(Reference LTC DWG # 05-08-1729 Rev Ø)
7.50 ±0.05
6.10 ±0.05
5.50 REF
(2 SIDES)
0.70 ±0.05
6.45 ±0.05
6.50 REF 7.10 ±0.05 8.50 ±0.05
(2 SIDES)
5.41 ±0.05
PACKAGE OUTLINE
0.25 ±0.05
0.50 BSC
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED
7.00 ± 0.10
(2 SIDES)
0.75 ± 0.05
0.00 – 0.05
R = 0.115
TYP
5.50 REF
(2 SIDES)
51
52
0.40 ± 0.10
PIN 1 TOP MARK
(SEE NOTE 6)
1
2
PIN 1 NOTCH
R = 0.30 TYP OR
0.35 × 45°C
CHAMFER
8.00 ± 0.10
(2 SIDES)
6.50 REF
(2 SIDES)
6.45 ±0.10
5.41 ±0.10
R = 0.10
TYP
TOP VIEW
0.200 REF
0.00 – 0.05
0.75 ± 0.05
(UKG52) QFN REV Ø 0306
0.25 ± 0.05
0.50 BSC
BOTTOM VIEW—EXPOSED PAD
SIDE VIEW
NOTE:
1. DRAWING IS NOT A JEDEC PACKAGE OUTLINE
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.20mm ON ANY SIDE, IF PRESENT
5. EXPOSED PAD SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE TOP AND BOTTOM OF PACKAGE
21721012fb
32
LTC2172-12/
LTC2171-12/LTC2170-12
Revision History
REV
DATE
DESCRIPTION
A
03/10
Changed Sampling Frequency Max for LTC2171-12 from 45MHz to 40MHz in the Timing Characteristics section.
6
Added full part numbers to Grounding and Bypassing and Heat Transfer sections in Applications Information.
28
Revised Descriptions and Comments in the Related Parts section
34
Revised Software Reset paragraph and Table 4 in the Applications Information section.
25
B
07/11
PAGE NUMBER
21721012fb
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
33
LTC2172-12/
LTC2171-12/LTC2170-12
Related Parts
PART NUMBER
DESCRIPTION
COMMENTS
LTC2170-14/LTC217114/LTC2172-14
14-Bit, 25Msps/40Msps/65Msps 1.8V
Quad ADCs, Ultralow Power
162mW/202mW/311mW, 73.7dB SNR, 90dB SFDR, Serial LVDS Outputs,
7mm × 8mm QFN-52
LTC2173-14/LTC217414/LTC2175-14
14-Bit, 80Msps/105Msps/125Msps 1.8V
Quad ADCs, Ultralow Power
376mW/450mW/558mW, 73.4 dB SNR, 88dB SFDR, Serial LVDS Outputs,
7mm × 8mm QFN-52
LTC2173-12/LTC217412/LTC2175-12
12-Bit, 80Msps/105Msps/125Msps
1.8V Quad ADCs, Ultralow Power
369mW/439mW/545mW, 70.6dB SNR, 88dB SFDR, Serial LVDS Outputs,
7mm × 8mm QFN-52
LTC2256-14/LTC225714/LTC2258-14
14-Bit, 25Msps/40Msps/65Msps
1.8V ADCs, Ultralow Power
35mW/49mW/81mW, 74dB SNR, 88dB SFDR, DDR LVDS/DDR CMOS/CMOS
Outputs, 6mm × 6mm QFN-40
LTC2259-14/LTC226014/LTC2261-14
14-Bit, 80Msps/105Msps/125Msps
1.8V ADCs, Ultralow Power
89mW/106mW/127mW, 73.4dB SNR, 85dB SFDR, DDR LVDS/DDR CMOS/CMOS
Outputs, 6mm × 6mm QFN-40
LTC2262-14
14-Bit, 150Msps 1.8V ADC, Ultralow Power 149mW, 72.8dB SNR, 88dB SFDR, DDR LVDS/DDR CMOS/CMOS Outputs,
6mm × 6mm QFN-40
LTC2263-14/LTC226414/LTC2265-14
14-Bit, 25Msps/40Msps/65Msps
1.8V Dual ADCs, Ultralow Power
94mW/113mW/171mW, 73.7dB SNR, 90dB SFDR, Serial LVDS Outputs,
6mm × 6mm QFN-40
LTC2263-12/LTC226412/LTC2265-12
12-Bit, 25Msps/40Msps/65Msps
1.8V Dual ADCs, Ultralow Power
94mW/112mW/167mW, 71dB SNR, 90dB SFDR, Serial LVDS Outputs,
6mm × 6mm QFN-40
LTC2266-14/LTC226714/LTC2268-14
14-Bit, 80Msps/105Msps/125Msps
1.8V Dual ADCs, Ultralow Power
203mW/243mW/299mW, 73.1dB SNR, 88dB SFDR, Serial LVDS Outputs,
6mm × 6mm QFN-40
LTC2266-12/LTC226712/LTC2268-12
12-Bit, 80Msps/105Msps/125Msps
1.8V Dual ADCs, Ultralow Power
200mW/238mW/292mW, 70.6dB SNR, 88dB SFDR, Serial LVDS Outputs,
6mm × 6mm QFN-40
LTC5517
40MHz to 900MHz Direct Conversion
Quadrature Demodulator
High IIP3: 21dBm at 800MHz, Integrated LO Quadrature Generator
LTC5527
400MHz to 3.7GHz High Linearity
Downconverting Mixer
24.5dBm IIP3 at 900MHz, 23.5dBm IIP3 at 1900MHz, NF = 12.5dB,
50Ω Single-Ended RF and LO Ports, 5V Supply
LTC5557
400MHz to 3.8GHz High Linearity
Downconverting Mixer
24dBm IIP3 at 1950MHz, 23.7dBm IIP3 at 2.6GHz, NF = 13.2dB, 3.3V Supply
Operation, Integrated Transformer
LTC5575
800MHz to 2.7GHz Direct Conversion
Quadrature Demodulator
High IIP3: 28dBm at 900MHz, Integrated LO Quadrature Generator, Integrated RF
and LO Transformer
LTC6412
800MHz, 31dB Range, Analog-Controlled
Variable Gain Amplifier
Continuously Adjustable Gain Control, 35dBm OIP3 at 240MHz, 10dB Noise
Figure, 4mm × 4mm QFN-24
LTC6420-20
Dual Low Noise, Low Distortion
Differential ADC Drivers for 300MHz IF
Fixed Gain 10V/V, 2.2nV/√Hz Total Input Referred Noise, 80mA Supply Current per
Amplifier, 46dBm OIP3 at 100MHz, 3mm × 4mm QFN-20
LTC6421-20
Dual Low Noise, Low Distortion
Differential ADC Drivers for 140MHz IF
Fixed Gain 10V/V, 2.2nV/√Hz Total Input Referred Noise, 40mA Supply Current per
Amplifier, 42dBm OIP3 at 100MHz, 3mm × 4mm QFN-20
ADCs
RF Mixers/Demodulators
Amplifiers/Filters
LTC6605-7/ LTC6605-10/ Dual Matched 7MHz/10MHz/14MHz Filters Dual Matched 2nd Order Lowpass Filters with Differential Drivers,
LTC6605-14
with ADC Drivers
Pin-Programmable Gain, 6mm × 3mm DFN-22
Signal Chain Receivers
LTM9002
14-Bit Dual Channel IF/Baseband Receiver Integrated High Speed ADC, Passive Filters and Fixed Gain Differential Amplifiers
Subsystem
21721012fb
34 Linear Technology Corporation
LT 0711 REV B • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507
●
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