LTC2175-12/
LTC2174-12/LTC2173-12
12-Bit, 125Msps/105Msps/
80Msps Low Power Quad ADCs
Features
n
n
n
n
n
n
n
n
n
n
n
n
Description
4-Channel Simultaneous Sampling ADC
70.6dB SNR
88dB SFDR
Low Power: 545mW/439mW/369mW Total,
136mW/110mW/92mW per Channel
Single 1.8V Supply
Serial LVDS Outputs: 1 or 2 Bits per Channel
Selectable Input Ranges: 1VP-P to 2VP-P
800MHz Full Power Bandwidth S/H
Shutdown and Nap Modes
Serial SPI Port for Configuration
Pin Compatible 14-Bit and 12-Bit Versions
52-Pin (7mm × 8mm) QFN Package
The LTC®2175-12/LTC2174-12/LTC2173-12 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 70.6dB SNR and
88dB spurious free dynamic range (SFDR). Ultralow jitter
of 0.15psRMS allows undersampling of IF frequencies with
excellent noise performance.
DC specs 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). At lower sampling rates there is a one bit
per channel option (1-lane mode). The LVDS drivers have
optional internal termination and adjustable output levels
to ensure clean signal integrity.
Applications
Communications
Cellular Base Stations
n Software Defined Radios
n Portable Medical Imaging
n Multichannel Data Acquisition
n Nondestructive Testing
n
n
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 1
ANALOG
INPUT
LTC2175-12, 125Msps,
2-Tone FFT, fIN = 70MHz and 75MHz
1.8V
OVDD
S/H
12-BIT
ADC CORE
OUT1A
0
OUT1B
–10
CHANNEL 2
ANALOG
INPUT
S/H
12-BIT
ADC CORE
OUT2A
CHANNEL 3
ANALOG
INPUT
S/H
12-BIT
ADC CORE
S/H
12-BIT
ADC CORE
CHANNEL 4
ANALOG
INPUT
ENCODE
INPUT
–20
OUT3A
OUT3B
OUT4A
OUT4B
DATA
CLOCK
OUT
PLL
FRAME
SERIALIZED
LVDS
OUTPUTS
AMPLITUDE (dBFS)
DATA
SERIALIZER
–30
OUT2B
–40
–50
–60
–70
–80
–90
–100
–110
–120
0
10
20
30
40
FREQUENCY (MHz)
50
60
217512 TA01b
GND
OGND
217512 TA01
21754312fa
1
LTC2175-12/
LTC2174-12/LTC2173-12
Absolute Maximum Ratings
Pin ConfigurationS
(Notes 1, 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
LTC2175C, 2174C, 2173C.......................... 0°C to 70°C
LTC2175I, 2174I, 2173I.........................–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+
–
27 OUT3B–
AIN4 14
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
LTC2175CUKG-12#PBF
LTC2175CUKG-12#TRPBF
LTC2175UKG-12
52-Lead (7mm × 8mm) Plastic QFN
0°C to 70°C
LTC2175IUKG-12#PBF
LTC2175IUKG-12#TRPBF
LTC2175UKG-12
52-Lead (7mm × 8mm) Plastic QFN
–40°C to 85°C
LTC2174CUKG-12#PBF
LTC2174CUKG-12#TRPBF
LTC2174UKG-12
52-Lead (7mm × 8mm) Plastic QFN
0°C to 70°C
LTC2174IUKG-12#PBF
LTC2174IUKG-12#TRPBF
LTC2174UKG-12
52-Lead (7mm × 8mm) Plastic QFN
–40°C to 85°C
LTC2173CUKG-12#PBF
LTC2173CUKG-12#TRPBF
LTC2173UKG-12
52-Lead (7mm × 8mm) Plastic QFN
0°C to 70°C
LTC2173IUKG-12#PBF
LTC2173IUKG-12#TRPBF
LTC2173UKG-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.
Consult LTC Marketing for information on non-standard lead based finish parts.
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/
21754312fa
2
LTC2175-12/
LTC2174-12/LTC2173-12
Converter
Characteristics l denotes the specifications which apply over the full operating
The
temperature range, otherwise specifications are at TA = 25°C. (Note 5)
LTC2175-12
PARAMETER
CONDITIONS
MIN
LTC2174-12
TYP
MAX
MIN
LTC2173-12
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
–0.4
±0.1
0.4
–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
–2.8
–1.3
–1.3
–2.8
–1.3
–1.3
–2.8
–1.3
–1.3
0.2
%FS
%FS
Resolution (No Missing Codes)
l
Offset Drift
12
TYP
0.2
12
0.2
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
mV
External Reference
0.3
0.3
0.3
LSBRMS
Offset Matching
Transition Noise
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(CM)
Analog Input Range (AIN+ – AIN–)
Analog Input Common Mode (AIN+ + AIN–)/2
VSENSE
External Voltage Reference Applied to SENSE External Reference Mode
IINCM
Analog Input Common Mode Current
Per Pin, 125Msps
Per Pin, 105Msps
Per Pin, 80Msps
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
tJITTER
Sample-and-Hold Acquisition Delay Jitter
0.15
CMRR
Analog Input Common Mode Rejection Ratio
BW-3B
Full-Power Bandwidth
VIN
1.7V < VDD < 1.9V
l
Differential Analog Input (Note 8)
l
VCM – 100mV
VCM
VCM + 100mV
V
l
0.625
1.250
1.300
V
Figure 6 Test Circuit
1 to 2
VP-P
155
130
100
µA
µA
µA
ns
psRMS
80
dB
800
MHz
21754312fa
3
LTC2175-12/
LTC2174-12/LTC2173-12
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)
LTC2175-12
SYMBOL
PARAMETER
CONDITIONS
SNR
Signal-to-Noise Ratio
5MHz Input
70MHz Input
140MHz Input
SFDR
S/(N+D)
MAX
LTC2174-12
MAX
LTC2173-12
MIN
TYP
MIN
TYP
MIN
TYP
l
69.3
70.6
70.6
70.3
69.2
70.6
70.5
70.3
69.3
70.6
70.5
70.3
MAX
UNITS
dBFS
dBFS
dBFS
Spurious Free Dynamic Range 5MHz Input
2nd or 3rd Harmonic
70MHz Input
140MHz Input
l
74
88
85
82
74
88
85
82
76
88
85
82
dBFS
dBFS
dBFS
Spurious Free Dynamic Range 5MHz Input
4th Harmonic or Higher
70MHz Input
140MHz Input
l
84
90
90
90
84
90
90
90
85
90
90
90
dBFS
dBFS
dBFS
l
68.6
70.6
70.4
70
68.7
70.6
70.4
70
68.9
70.6
70.4
70
dBFS
dBFS
dBFS
Signal-to-Noise Plus
Distortion Ratio
5MHz 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
Internal
Reference Characteristics l denotes the specifications which apply over the
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
21754312fa
4
LTC2175-12/
LTC2174-12/LTC2173-12
Digital
Inputs and Outputs l denotes the specifications which apply over the full operating
The
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)
l
0.2
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
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
0.6
0
3.6
V
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 2kΩ 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
21754312fa
5
LTC2175-12/
LTC2174-12/LTC2173-12
Power
Requirements l denotes the specifications which apply over the full operating temperature
The
range, otherwise specifications are at TA = 25°C. (Note 9)
LTC2175-12
SYMBOL PARAMETER
LTC2173-12
MIN
TYP
MAX
MIN
TYP
MAX
MIN
TYP
(Note 10)
l
1.7
1.8
1.9
1.7
1.8
1.9
1.7
1.8
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
Analog Supply Current
Sine Wave Input
l
276
300
218
240
180
196
mA
IOVDD
Digital Supply Current
2-Lane Mode, 1.75mA Mode
2-Lane Mode, 3.5mA Mode
l
l
27
49
31
54
26
48
31
53
25
47
29
52
mA
mA
PDISS
Power Dissipation
2-Lane Mode, 1.75mA Mode
2-Lane Mode, 3.5mA Mode
l
l
545
585
596
637
439
479
488
527
369
409
405
446
mW
mW
PSLEEP
Sleep Mode Power
1
1
1
mW
PNAP
Nap Mode Power
85
85
85
mW
PDIFFCLK
Power Increase With Differential Encode Mode Enabled
(No Increase for Sleep Mode)
20
20
20
mW
VDD
Analog Supply Voltage
OVDD
IVDD
CONDITIONS
LTC2174-12
MAX UNITS
1.9
V
Timing
Characteristics
The
l denotes the specifications which apply over the full operating temperature
range, otherwise specifications are at TA = 25°C. (Note 5)
LTC2175-12
SYMBOL
PARAMETER
CONDITIONS
fS
Sampling Frequency
(Notes 10,11)
l
MIN
5
tENCL
ENC Low Time (Note 8)
Duty Cycle Stabilizer Off
Duty Cycle Stabilizer On
l
l
3.8
2
tENCH
ENC High Time (Note 8)
Duty Cycle Stabilizer Off
Duty Cycle Stabilizer On
l
l
3.8
2
tAP
Sample-and-Hold
Acquisition Delay Time
SYMBOL
PARAMETER
TYP
LTC2174-12
MAX
MIN
125
5
4
4
100
100
4.52
2
4
4
100
100
4.52
2
0
TYP
LTC2173-12
MAX
MIN
105
5
4.76
4.76
100
100
5.93
2
4.76
4.76
100
100
5.93
2
0
CONDITIONS
MIN
TYP
MAX
MHz
6.25
6.25
100
100
ns
ns
6.25
6.25
100
100
ns
ns
0
TYP
UNITS
80
ns
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
0.35 • tSER
0.5 • tSER
0.65 • tSER
s
tDATA
DATA to DCO Delay
(Note 8)
l
0.35 • tSER
0.5 • tSER
0.65 • tSER
s
tPD
Propagation Delay
(Note 8)
l
tR
Output Rise Time
tF
Output Fall Time
DCO Cycle-Cycle Jitter
tSER = 1ns
Pipeline Latency
0.7n + 2 • tSER 1.1n + 2 • tSER 1.5n + 2 • tSER
s
Data, DCO, FR, 20% to 80%
0.17
ns
Data, DCO, FR, 20% to 80%
0.17
ns
60
psP-P
6
Cycles
21754312fa
6
LTC2175-12/
LTC2174-12/LTC2173-12
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
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 Setup Time
l
5
ns
tH
SCK to CS Setup Time
l
5
ns
tDS
SDI Setup Time
l
5
ns
tDH
SDI Hold Time
l
5
ns
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 = 125MHz (LTC2175), 105MHz
(LTC2174), or 80MHz (LTC2173), 2-lane output mode, differential ENC+/
ENC– = 2VP-P sine wave, input range = 2VP-P with differential drive, unless
otherwise noted.
l
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 = 125MHz (LTC2175), 105MHz
(LTC2174), or 80MHz (LTC2173), 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.
21754312fa
7
LTC2175-12/
LTC2174-12/LTC2173-12
Timing Diagrams
2-Lane Output Mode, 16-Bit Serialization
tAP
ANALOG
INPUT
N+1
N
tENCH
ENC–
tENCL
ENC+
tSER
DCO–
DCO+
tFRAME
FR–
FR+
tDATA
tSER
tPD
OUT#A–
OUT#A+
OUT#B–
OUT#B+
tSER
D3
D1
DX*
0
D11 D9
D7
D5
D3
D1 DX*
0
D11 D9
D7
D2
D0
DY*
0
D10 D8
D6
D4
D2
D0 DY*
0
D10 D8
D6
SAMPLE N-6
SAMPLE N-5
SAMPLE N-4
217512 TD01
*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
tENCH
ENC–
N+1
tENCL
ENC+
tSER
DCO–
DCO+
tFRAME
FR–
FR+
OUT#A–
OUT#A+
OUT#B–
OUT#B+
tDATA
tSER
tPD
tSER
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
217512 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.
21754312fa
8
LTC2175-12/
LTC2174-12/LTC2173-12
timing DIAGRAMS
2-Lane Output Mode, 12-Bit Serialization
tAP
ANALOG
INPUT
N
N+1
tENCH
ENC–
tENCL
ENC+
tSER
DCO–
DCO+
tFRAME
FR+
FR–
OUT#A–
OUT#A+
OUT#B–
OUT#B+
tDATA
tPD
tSER
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
SAMPLE N-4
217512 TD03
1-Lane Output Mode, 16-Bit Serialization
tAP
ANALOG
INPUT
N+1
N
tENCH
ENC–
tENCL
ENC+
tSER
DCO–
DCO+
tFRAME
FR–
FR+
OUT#A–
OUT#A+
tDATA
tSER
tPD
DX* DY*
SAMPLE N-6
0
tSER
0
D11 D10 D9
D8
D7
D6
D5
D4
D3
D2
D1
D0 DX* DY*
SAMPLE N-5
0
0
D11 D10 D9
SAMPLE N-4
D8
217512 TD05
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.
21754312fa
9
LTC2175-12/
LTC2174-12/LTC2173-12
timing DIAGRAMS
One-Lane Output Mode, 14-Bit Serialization
tAP
ANALOG
INPUT
N+1
N
tENCH
ENC–
tENCL
+
ENC
tSER
DCO–
+
DCO
tFRAME
FR–
FR+
OUT#A–
OUT#A+
tDATA
tSER
tPD
D1
D0
tSER
DX* DY* D11 D10 D9
SAMPLE N-6
D8
D7
D6
D5
D4
D3
D2
D1
D0 DX* DY* D11 D10 D9
SAMPLE N-5
SAMPLE N-4
D8
217512 TD06
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.
One-Lane Output Mode, 12-Bit Serialization
tAP
ANALOG
INPUT
N+1
N
tENCH
ENC–
tENCL
ENC+
tSER
DCO–
DCO+
tFRAME
FR–
FR+
OUT#A–
OUT#A+
tDATA
tSER
tPD
D3
D2
D1
SAMPLE N-6
tSER
D0 D11 D10 D9
D8
D7
D6
D5
D4
D3
D2
D1
D0 D11 D10 D9
SAMPLE N-5
SAMPLE N-4
217512 TD07
OUT#B+, OUT#B– ARE DISABLED
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
XX
D6
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
217512 TD04
21754312fa
10
LTC2175-12/
LTC2174-12/LTC2173-12
Typical Performance Characteristics
LTC2175-12: Differential
Nonlinearity (DNL)
LTC2175-12: 8k Point FFT, fIN = 5MHz
–1dBFS, 125Msps
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
1024
2048
3072
OUTPUT CODE
4096
–30
0.2
–0.6
0
–20
AMPLITUDE (dBFS)
DNL ERROR (LSB)
INL ERROR (LSB)
LTC2175-12: Integral
Nonlinearity (INL)
–60
–70
–80
–90
–100
0
1024
2048
3072
OUTPUT CODE
217512 G01
4096
–110
–120
LTC2175-12: 8k Point FFT, fIN = 70MHz
–1dBFS, 125Msps
–20
–20
–20
–30
–30
–30
–70
–80
AMPLITUDE (dBFS)
0
–10
AMPLITUDE (dBFS)
0
–10
–60
–40
–50
–60
–70
–80
–60
–70
–80
–90
–100
–110
–120
–110
–120
–110
–120
20
30
40
FREQUENCY (MHz)
50
60
0
10
20
30
40
FREQUENCY (MHz)
50
LTC2175-12: 8k Point 2-Tone FFT,
fIN = 70MHz, 75MHz, –1dBFS,
125Msps
10000
8000
–80
6000
–90
–100
4000
20
30
40
FREQUENCY (MHz)
50
60
217512 G07
0
2041
69
68
67
2000
10
60
70
SNR (dBFS)
COUNT
AMPLITUDE (dBFS)
12000
–40
0
50
71
14000
–30
–70
20
30
40
FREQUENCY (MHz)
72
16000
–20
–60
10
LTC2175-12: SNR vs Input
Frequency, –1dB, 2V Range,
125Msps
18000
0
–50
0
217512 G06
LTC2175-12: Shorted Input
Histogram
–10
–110
–120
60
217512 G05
217512 G04
60
–40
–90
–100
10
50
–50
–90
–100
0
20
30
40
FREQUENCY (MHz)
LTC2175-12: 8k Point FFT, fIN = 140MHz
–1dBFS, 125Msps
0
–50
10
217512 G03
–10
–40
0
217512 G02
LTC2175-12: 8k Point FFT, fIN = 30MHz
–1dBFS, 125Msps
AMPLITUDE (dBFS)
–40
–50
2042
2044
2043
OUTPUT CODE
2045
217512 G08
66
0
50
100 150 200 250 300
INPUT FREQUENCY (MHz)
350
217512 G09
21754312fa
11
LTC2175-12/
LTC2174-12/LTC2173-12
Typical Performance Characteristics
LTC2175-12: SFDR vs Input
Frequency, –1dB, 2V Range,
125Msps
95
110
90
80
dBFS
100
80
75
80
70
dBc
60
60
SNR (dBc AND dBFS)
85
50
40
30
40
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
217512 G10
2-LANE, 3.5mA
71
40
270
IOVDD (mA)
230
70
1-LANE, 3.5mA
30
2-LANE, 1.75mA
20
69
68
1-LANE, 1.75mA
10
67
220
210
0
25
50
75
100
SAMPLE RATE (Msps)
0
125
0
25
50
75
100
SAMPLE RATE (Msps)
0.6
1.0
0
0.8
0.8
–10
0.6
0.6
0.4
0.4
–0.2
–0.4
0
–0.2
–0.4
–0.6
–0.8
–0.8
–1.0
–1.0
1024
2048
3072
OUTPUT CODE
4096
217512 G21
1.2
1.3
–30
0.2
–0.6
0
0.9
1
1.1
SENSE PIN (V)
–20
AMPLITUDE (dBFS)
0
0.8
LTC2174-12: 8k Point FFT, fIN = 5MHz
–1dBFS, 105Msps
1.0
0.2
0.7
217512 G15
LTC2174-12: Differential
Nonlinearity (DNL)
DNL ERROR (LSB)
INL ERROR (LSB)
66
125
217512 G51
217512 G53
LTC2174-12: Integral Nonlinearity
(INL)
0
72
280
240
–10
LTC2175-12: SNR vs SENSE,
fIN = 5MHz, –1dB
50
250
–40
–30
–20
INPUT LEVEL (dBFS)
217512 G50
IOVDD vs Sample Rate, 5MHz Sine
Wave Input, –1dB
290
260
–50
217512 G12
LTC2175-12: IVDD vs Sample Rate,
5MHz Sine Wave Input, –1dB
IVDD (mA)
0
–60
0
SNR (dBFS)
65
dBc
50
20
70
dBFS
70
90
SFDR (dBc AND dBFS)
SFDR (dBFS)
LTC2175-12: SNR vs Input Level,
fIN = 70MHz, 2V Range, 125Msps
LTC2175-12: SFDR vs Input Level,
fIN = 70MHz, 2V Range, 125Msps
–40
–50
–60
–70
–80
–90
–100
0
1024
2048
3072
OUTPUT CODE
4096
217512 G22
–110
–120
0
10
20
30
40
FREQUENCY (MHz)
50
217512 G23
21754312fa
12
LTC2175-12/
LTC2174-12/LTC2173-12
Typical Performance Characteristics
LTC2174-12: 8k Point FFT, fIN = 70MHz
–1dBFS, 105Msps
LTC2174-12: 8k Point FFT, fIN = 140MHz
–1dBFS, 105Msps
0
0
–10
–10
–20
–20
–20
–30
–30
–30
–40
–50
–60
–70
–80
AMPLITUDE (dBFS)
0
–10
AMPLITUDE (dBFS)
AMPLITUDE (dBFS)
LTC2174-12: 8k Point FFT, fIN = 30MHz
–1dBFS, 105Msps
–40
–50
–60
–70
–80
–40
–50
–60
–70
–80
–90
–100
–90
–100
–90
–100
–110
–120
–110
–120
–110
–120
0
10
20
30
40
FREQUENCY (MHz)
50
0
10
20
30
40
FREQUENCY (MHz)
217512 G24
70
–60
–70
SNR (dBFS)
12000
–40
–50
COUNT
10000
8000
–80
6000
–90
–100
4000
67
2000
10
20
30
40
FREQUENCY (MHz)
0
2044
50
2045
2046
2047
OUTPUT CODE
LTC2174-12: SFDR vs Input
Frequency, –1dB, 2V Range,
105Msps
110
100
90
SFDR (dBc AND dBFS)
80
75
80
70
60
50
100 150 200 250 300
INPUT FREQUENCY (MHz)
350
217512 G23a
350
220
210
dBc
50
40
200
190
180
30
170
10
0
100 150 200 250 300
INPUT FREQUENCY (MHz)
230
dBFS
20
70
50
LTC2174-12: IVDD vs Sample Rate,
5MHz Sine Wave Input, –1dB
90
85
0
217512 G29
LTC2174-12: SFDR vs Input Level,
fIN = 70MHz, 2V Range, 105Msps
95
SFDR (dBFS)
66
2048
217512 G28
217512 G27
65
69
68
IVDD (mA)
AMPLITUDE (dBFS)
71
14000
–30
50
72
16000
–20
20
30
40
FREQUENCY (MHz)
217512 G26
18000
0
10
LTC2174-12: SNR vs Input
Frequency, –1dB, 2V Range,
105Msps
LTC2174-12: Shorted Input
Histogram
–10
0
0
217512 G25
LTC2174-12: 8k Point 2-Tone FFT,
fIN = 70MHz, 75MHz, –1dBFS,
105Msps
–110
–120
50
0
–80 –70 –60 –50 –40 –30 –20 –10
INPUT LEVEL (dBFS)
0
217512 G32
160
0
25
50
75
SAMPLE RATE (Msps)
100
217512 G54
21754312fa
13
LTC2175-12/
LTC2174-12/LTC2173-12
Typical Performance Characteristics
LTC2174-12: SNR vs SENSE,
fIN = 5MHz, –1dB
LTC2173-12: Integral Nonlinearity
(INL)
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
–0.2
–0.4
–0.6
–0.8
–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
AMPLITUDE (dBFS)
0
–60
–40
–50
–60
–70
–80
–40
–60
–70
–80
–90
–100
–90
–100
–110
–120
–110
–120
–110
–120
10
20
30
FREQUENCY (MHz)
40
0
10
20
30
FREQUENCY (MHz)
0
–10
–20
–20
–30
–30
–60
–70
14000
12000
–40
–50
–60
–70
10000
8000
6000
–90
–100
4000
–110
–120
–110
–120
10
20
30
FREQUENCY (MHz)
40
217512 G46
40
16000
–80
0
20
30
FREQUENCY (MHz)
18000
–90
–100
–80
10
LTC2173-12: Shorted Input
Histogram
COUNT
AMPLITUDE (dBFS)
AMPLITUDE (dBFS)
0
–10
–40
0
217512 G45
LTC2173-12: 8k Point 2-Tone FFT,
fIN = 70MHz, 75MHz, –1dBFS,
80Msps
LTC2173-12: 8k Point FFT, fIN = 140MHz
–1dBFS, 80Msps
–50
40
217512 G44
217512 G43
4096
–50
–90
–100
0
2048
3072
OUTPUT CODE
LTC2173-12: 8k Point FFT, fIN = 70MHz
–1dBFS, 80Msps
–10
–50
1024
217512 G42
LTC2173-12: 8k Point FFT, fIN = 30MHz
–1dBFS, 80Msps
LTC2173-12: 8k Point FFT, fIN = 5MHz
–1dBFS, 80Msps
–40
0
217512 G41
217512 G35
AMPLITUDE (dBFS)
0.2
–0.6
–1.0
1.3
DNL ERROR (LSB)
72
LTC2173-12: Differential
Nonlinearity (DNL)
2000
0
10
20
30
FREQUENCY (MHz)
40
217512 G47
0
2052
2053
2054
2055
OUTPUT CODE
2056
217512 G48
21754312fa
14
LTC2175-12/
LTC2174-12/LTC2173-12
Typical Performance Characteristics
LTC2173-12: SFDR vs Input
Frequency, –1dB, 2V Range,
80Msps
95
71
90
70
85
69
LTC2173-12: SFDR vs Input Level,
fIN = 70MHz, 2V Range, 80Msps
110
100
80
68
75
67
70
66
65
dBFS
90
SFDR (dBc AND dBFS)
72
SFDR (dBFS)
SNR (dBFS)
LTC2173-12: SNR vs Input
Frequency, –1dB, 2V Range,
80Msps
80
70
dBc
60
50
40
30
20
10
0
50
100 150 200 250 300
INPUT FREQUENCY (MHz)
350
0
50
100 150 200 250 300
INPUT FREQUENCY (MHz)
217512 G35a
217512 G49
LTC2173-12: IVDD vs Sample Rate,
5MHz Sine Wave Input, –1dB
DCO Cycle-Cycle Jitter vs Serial
Data Rate
72
350
71
300
PEAK-TO-PEAK JITTER (ps)
180
SNR (dBFS)
IVDD (mA)
70
160
69
68
150
140
67
0
20
40
60
SAMPLE RATE (Msps)
80
217512 G55
66
0
217512 G52
LTC2173-12: SNR vs SENSE,
fIN = 5MHz, –1dB
190
170
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
217512 G55a
0
0
200
400
600
800
SERIAL DATA RATE (Mbps)
1000
217512 G52a
21754312fa
15
LTC2175-12/
LTC2174-12/LTC2173-12
Pin Functions
AIN1+ (Pin 1): Channel 1 Positive Differential Analog
Input.
AIN1– (Pin 2): Channel 1 Negative Differential Analog Input.
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.
SCK (Pin 20): In serial programming mode, (PAR/SER =
0V), SCK is the serial interface clock input. In the 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 the 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.
REFH (Pins 6,7): ADC High Reference. Bypass to pins 8, 9
with a 2.2µF ceramic capacitor and to ground with a 0.1µF
ceramic capacitor.
GND (Pins 22, 45, 49, Exposed Pad Pin 53): ADC Power
Ground. The exposed pad must be soldered to the PCB
ground.
REFL (Pins 8,9): ADC Low Reference. Bypass to pins 6, 7
with a 2.2µF ceramic capacitor and to ground with a 0.1µF
ceramic capacitor.
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.
AIN3+ (Pin 10): Channel 3 Positive Differential Analog Input.
OVDD (Pin 34): Output Driver Supply, 1.7V to 1.9V. Bypass
to ground with a 0.1µF ceramic capacitor.
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.
ENC– (Pin 18): Encode Complement Input. Conversion
starts on the falling edge.
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 the parallel programming mode (PAR/
SER = VDD), CS selects 2-lane or 1-lane output mode. CS
can be driven with 1.8V to 3.3V logic.
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 NMOS output that requires an external
2k pull-up resistor to 1.8V – 3.3V. If read back from the
mode control registers is not needed, the pull-up resistor
is not necessary and SDO can be left unconnected. In the
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.
PAR/SER (Pin 47): Programming Mode Selection Pin.
Connect to ground to enable the serial programming mode.
CS, SCK, SDI, SDO become a serial interface that control
the A/D operating modes. Connect to VDD to enable the
parallel programming mode where CS, SCK, SDI, 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.
21754312fa
16
LTC2175-12/
LTC2174-12/LTC2173-12
Pin Functions
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
All pins in this section 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.
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+ (Pins 31/32): Frame Start Outputs.
DCO–/DCO+ (Pins 35/36): Data Clock Outputs.
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.
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.
21754312fa
17
LTC2175-12/
LTC2174-12/LTC2173-12
Functional Block Diagram
1.8V
1.8V
ENC+
VDD
ENC–
OVDD
CHANNEL 1
ANALOG INPUT+
CHANNEL 1
ANALOG INPUT–
OUT1A+
OUT1A–
12-BIT
ADC CORE
S/H
OUT1B+
PLL
OUT1B–
CHANNEL 2
ANALOG INPUT+
CHANNEL 2
ANALOG INPUT–
12-BIT
ADC CORE
S/H
OUT2A+
DATA
SERIALIZER
OUT2A–
OUT2B+
OUT2B–
CHANNEL 3
ANALOG INPUT+
CHANNEL 3
ANALOG INPUT–
OUT3A+
12-BIT
ADC CORE
S/H
OUT3A–
OUT3B+
OUT3B–
CHANNEL 4
ANALOG INPUT+
CHANNEL 4
ANALOG INPUT–
OUT4A+
12-BIT
ADC CORE
S/H
OUT4A–
OUT4B+
OUT4B–
DATA
CLOCK OUT+
VREF
1µF
DATA
CLOCK OUT–
1.25V
REFERENCE
FRAME+
FRAME–
RANGE
SELECT
OGND
SENSE
REFH
REF
BUF
REFL
MODE
CONTROL
REGISTERS
VDD/2
DIFF
REF
AMP
REFH
GND
REFL
VCM12
VCM34
CS
SCK
SDI
SDO
217512 F01
0.1µF
0.1µF
2.2µF
0.1µF
PAR/SER
0.1µF
0.1µF
Figure 1. Functional Block Diagram
21754312fa
18
LTC2175-12/
LTC2174-12/LTC2173-12
Applications Information
CONVERTER OPERATION
The LTC2175-12/LTC2174-12/LTC2173-12 are low power,
4-channel, 12-bit, 125Msps/105Msps/80Msps 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). At lower sampling rates there is a one bit
per channel option (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
or VCM34 output pins, which are nominally VDD/2. For the
LTC2175-12
VDD
AIN+
RON
25Ω
10Ω
AIN–
INPUT DRIVE CIRCUITS
Input Filtering
If possible, there should be an RC low pass filter right at
the analog inputs. This lowpass filter isolates the drive
circuitry from the A/D sample-and-hold switching, and also
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.
Transformer Coupled Circuits
Figure 3 shows the analog input being driven by an RF
transformer with a center-tapped secondary. The center
50Ω
VCM
0.1µF
0.1µF
RON
25Ω
10Ω
The four channels are simultaneously sampled by a shared
encode circuit (Figure 2).
CSAMPLE
3.5pF
CPARASITIC
1.8pF
VDD
2V input range, the inputs should swing from VCM – 0.5V
to VCM + 0.5V. There should be 180° phase difference
between the inputs.
CSAMPLE
3.5pF
ANALOG
INPUT
T1
1:1
25Ω
25Ω
AIN+
LTC2175-12
0.1µF
12pF
CPARASITIC
1.8pF
25Ω
VDD
25Ω
T1: MA/COM MABAES0060
RESISTORS, CAPACITORS
ARE 0402 PACKAGE SIZE
AIN–
217512 F03
1.2V
Figure 3. Analog Input Circuit Using a Transformer.
Recommended for Input Frequencies from 5MHz to 70MHz.
10k
ENC+
ENC–
10k
1.2V
217512 F02
Figure 2. Equivalent Input Circuit. Only One of the Four
Analog Channels Is Shown.
21754312fa
19
LTC2175-12/
LTC2174-12/LTC2173-12
Applications Information
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.
Amplifier Circuits
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.
Reference
The LTC2175-12/LTC2174-12/LTC2173-12 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
50Ω
VCM
0.1µF
0.1µF
0.1µF
ANALOG
INPUT
T1
0.1µF
AIN+
T2
25Ω
LTC2175-12
0.1µF
25Ω
HIGH SPEED
DIFFERENTIAL
0.1µF
AMPLIFIER
AIN+
25Ω
LTC2175-12
0.1µF
1.8pF
0.1µF
25Ω
AIN–
217512 F06
VCM
VCM
0.1µF
T1
2.7nH
Figure 6. Recommended Front End Circuit for Input
Frequencies Above 300MHz
Figure 4. Recommended Front End Circuit for Input
Frequencies from 70MHz to 170MHz
T2
25Ω
T1: MA/COM ETC1-1-13
RESISTORS, CAPACITORS
ARE 0402 PACKAGE SIZE
T1: MA/COM MABA-007159-000000
T2: MA/COM MABAES0060
RESISTORS, CAPACITORS ARE 0402 PACKAGE SIZE
0.1µF
LTC2175-12
T1
217512 F04
ANALOG
INPUT
AIN+
0.1µF
25Ω
0.1µF
AIN–
50Ω
2.7nH
ANALOG
INPUT
4.7pF
0.1µF
VCM
AIN–
ANALOG
INPUT
+
+
–
–
200Ω
200Ω
25Ω
0.1µF
AIN+
LTC2175-12
12pF
0.1µF
25Ω
AIN–
217512 F07
217512 F05
T1: MA/COM MABA-007159-000000
T2: COILCRAFT WBC1-1LB
RESISTORS, CAPACITORS ARE 0402 PACKAGE SIZE
Figure 7. Front End Circuit Using a High Speed
Differential Amplifier
Figure 5. Recommended Front End Circuit for Input
Frequencies from 170MHz to 300MHz
21754312fa
20
LTC2175-12/
LTC2174-12/LTC2173-12
Applications Information
ground. For a 2V input range with an external reference,
apply a 1.25V reference voltage to SENSE (Figure 9).
and REFL should be as close to the pins as possible (not
on the backside of the circuit board).
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.
Encode Input
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
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).
LTC2175-12
LTC2175-12
VREF
1.25V
5Ω
1.25V BANDGAP
REFERENCE
1µF
VDD
DIFFERENTIAL
COMPARATOR
VDD
0.625V
15k
TIE TO VDD FOR 2V RANGE;
TIE TO GND FOR 1V RANGE;
RANGE = 1.6 • VSENSE FOR
0.65V < VSENSE < 1.300V
RANGE
DETECT
AND
CONTROL
ENC+
ENC–
SENSE
30k
BUFFER
INTERNAL ADC
HIGH REFERENCE
0.1µF
217512 F10
REFH
Figure 10. Equivalent Encode Input Circuit for
Differential Encode Mode
2.2µF
0.1µF
0.1µF
0.8x
DIFF AMP
REFL
LTC2175-12
INTERNAL ADC
LOW REFERENCE
1.8V TO 3.3V
0V
217512 F08
Figure 8. Reference Circuit
1.25V
EXTERNAL
REFERENCE
ENC–
30k
CMOS LOGIC
BUFFER
217512 F11
Figure 11. Equivalent Encode Input Circuit for
Single-Ended Encode Mode
VREF
1µF
ENC+
LTC2175-12
SENSE
1µF
217512 F09
Figure 9. Using an External 1.25V Reference
21754312fa
21
LTC2175-12/
LTC2174-12/LTC2173-12
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
0.1µF
ENC+
T1
50Ω
0.1µF
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.
0.1µF
LTC2175-12
PECL OR
LVDS
CLOCK
100Ω
50Ω
0.1µF
is 0.9V. For good jitter performance ENC+ should have fast
rise and fall times.
ENC–
LTC2175-12
0.1µF
ENC–
217512 F13
217512 F12
T1 = MA/COM ETC1-1-13
RESISTORS AND CAPACITORS
ARE 0402 PACKAGE SIZE
ENC+
Figure 13. PECL or LVDS Encode Drive
Figure 12. Sinusoidal Encode Drive
21754312fa
22
LTC2175-12/
LTC2174-12/LTC2173-12
Applications Information
DIGITAL OUTPUTS
The digital outputs of the LTC2175-12/LTC2174-12/
LTC2173-12 are serialized LVDS signals. Each channel
outputs two bits at a time (2-lane mode). At lower sampling rates there is a one bit per channel option (1-lane
mode). The data can be serialized with 16, 14, or 12-bit
serialization (see timing diagrams for details).
The output data should be latched on the rising and falling
edges of the data clock out (DCO). A data frame output
(FR) can be used to determine when the data from a new
conversion result begins. In the 2-lane, 14-bit 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.
By default the outputs are standard LVDS levels: 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 the serial programming mode. Available current levels are 1.75mA,
2.1mA, 2.5mA, 3mA, 3.5mA, 4mA and 4.5mA. In the
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 the
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.
Table 1. Maximum Sampling Frequency for All Serialization Modes. Note That These Limits Are for the LTC2175-12. The Sampling
Frequency for the Slower Speed Grades Cannot Exceed 105MHz (LTC2174-12) or 80MHz (LTC2173-12).
SERIALIZATION MODE
MAXIMUM SAMPLING
FREQUENCY, fS (MHz)
DCO FREQUENCY
FR FREQUENCY
SERIAL DATA RATE
2-Lane
16-Bit Serialization
125
4 • fS
fS
8 • fS
2-Lane
14-Bit Serialization
125
3.5 • fS
0.5 • fS
7 • fS
2-Lane
12-Bit Serialization
125
3 • fS
fS
6 • fS
1-Lane
16-Bit Serialization
62.5
8 • fS
fS
16 • fS
1-Lane
14-Bit Serialization
71.4
7 • fS
fS
14 • fS
1-Lane
12-Bit Serialization
83.3
6 • fS
fS
12 • fS
21754312fa
23
LTC2175-12/
LTC2174-12/LTC2173-12
Applications Information
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)
>+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
DX, DY
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
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. By randomizing the digital
output before it is transmitted off chip, these unwanted
tones can be randomized which reduces the unwanted
tone amplitude.
The digital output is randomized by applying an exclusiveOR 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.
Sleep and Nap Modes
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.
21754312fa
24
LTC2175-12/
LTC2174-12/LTC2173-12
Applications Information
In nap mode any combination of A/D channels can be
powered down while the internal reference circuits and the
PLL stay active, allowing faster wakeup 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 mode control
register A1 in the serial programming mode.
Serial Programming Mode
DEVICE PROGRAMMING MODES
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).
The operating modes of the LTC2175-12/LTC2174-12/
LTC2173-12 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.
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.
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 sections). During a read back 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 read back 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.
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
0 = 3.5mA LVDS Current Mode
1 = 1.75mA LVDS Current Mode
SDI
Power Down Control Bit
0 = Normal Operation
1 = Sleep Mode
SDO
Internal Termination Selection Bit
0 = Internal Termination Disabled
1 = Internal Termination Enabled
21754312fa
25
LTC2175-12/
LTC2174-12/LTC2173-12
Applications Information
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.
GROUNDING AND BYPASSING
The LTC2175-12/LTC2174-12/LTC2173-12 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 LTC2175-12/LTC2174-12/
LTC2173-12 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.
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 at the End of the SPI Write Command.
The Reset Register is Write Only.
Bits 6-0
Unused, Don’t Care Bits.
REGISTER A1: FORMAT AND POWER-DOWN REGISTER (ADDRESS 01h)
D7
DCSOFF
D6
D5
D4
D3
D2
D1
D0
RAND
TWOSCOMP
SLEEP
NAP_4
NAP_3
NAP_2
NAP_1
Bit 7
DCSOFF
Clock Duty Cycle Stabilizer Bit
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
21754312fa
26
LTC2175-12/
LTC2174-12/LTC2173-12
Applications Information
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.
REGISTER A2: OUTPUT MODE REGISTER (ADDRESS 02h)
D7
D6
D5
D4
D3
D2
D1
D0
ILVDS2
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
TP5
D6
D5
D4
D3
D2
D1
D0
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).
Bit 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.
21754312fa
27
LTC2175-12/
LTC2174-12/LTC2173-12
Typical Applications
Silkscreen Top
Top Side
21754312fa
28
LTC2175-12/
LTC2174-12/LTC2173-12
TYPICAL Applications
Inner Layer 2 GND
Inner Layer 3
Inner Layer 4
Inner Layer 5 Power
21754312fa
29
LTC2175-12/
LTC2174-12/LTC2173-12
TYPICAL Applications
Bottom Side
Silkscreen Bottom
21754312fa
30
LTC2175-12/
LTC2174-12/LTC2173-12
TYPICAL Applications
LTC2175 Schematic
SENSE
R14
1k
C17
1µF
PAR/SER
C4
1µF
SDO
VDD
C5
1µF
10
11
R93
100
AIN3
12
AIN3
13
C59
0.1µF
AIN4
14
R94
100
OUT1B–
OUT1B+
OUT1A–
OUT1A+
SDO
GND
PAR/SER
GND
VREF
AIN2
REFH
DCO–
LTC2175
35
34
REFH
OVDD
REFL
OGND
REFL
FR+
32
AIN3+
FR–
31
AIN3–
OUT3A+
30
VCM34
OUT3A–
29
33
AIN4
+
OUT3B+
28
AIN4–
OUT3B–
27
AIN4
DIGITAL
OUTPUTS
36
C16
0.1µF
OVDD
DIGITAL
OUTPUTS
OUT4A+
9
C3
0.1µF
37
DCO+
OUT4A–
8
OUT2B–
–
OUT4B+
7
C30
0.1µF
AIN2+
VDD
C2
0.1µF
C1
2.2µF
38
OUT4B–
6
OUT2B+
GND
AIN2
VCM12
SDI
5
39
SCK
4
R92
100
AIN1
CS
AIN2
40
OUT2A–
–
ENC–
3
OUT2A+
AIN1+
ENC+
2
VDD
1
C29
0.1µF
AIN1
VDD
VDD
R8
100
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
217512 TA02
21754312fa
31
LTC2175-12/
LTC2174-12/LTC2173-12
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
21754312fa
32
LTC2175-12/
LTC2174-12/LTC2173-12
Revision History
REV
DATE
DESCRIPTION
PAGE NUMBER
A
6/11
Corrected part numbers in Description.
1
Revised Software Reset paragraph and Table 4 in Applications Information section.
26
Added VDD to LTC2175 Schematic in Typical Applications section.
31
21754312fa
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
LTC2175-12/
LTC2174-12/LTC2173-12
Related Parts
PART NUMBER
DESCRIPTION
COMMENTS
ADCs
LTC2170-14/LTC2171-14/ 14-Bit, 25Msps/40Msps/65Msps
LTC2172-14
1.8V Quad ADCs, Ultralow Power
178mW/234mW/360mW, 73.4dB SNR, 85dB SFDR, Serial LVDS Outputs,
7mm × 8mm QFN-52
LTC2170-12/LTC2171-12/ 12-Bit, 25Msps/40Msps/65Msps
LTC2172-12
1.8V Quad ADCs, Ultralow Power
178mW/234mW/360mW, 70.5dB SNR, 85dB SFDR, Serial LVDS Outputs,
7mm × 8mm QFN-52
LTC2173-14/LTC2174-14/ 14-Bit, 80Msps/105Msps/125Msps
LTC2175-14
1.8V Quad ADCs, Ultralow Power
373mW/445mW/551mW, 73.2 dB SNR, 88dB SFDR, Serial LVDS Outputs,
7mm × 8mm QFN-52
LTC2256-14/LTC2257-14/ 14-Bit, 25Msps/40Msps/65Msps
LTC2258-14
Msps1.8V ADCs, Ultralow Power
35mW/49mW/81mW, 74dB SNR, 88dB SFDR, DDR LVDS/DDR CMOS/CMOS
Outputs, 6mm × 6mm QFN-36
LTC2259-14/LTC2260-14/ 14-Bit, 80Msps/105Msps/125Msps
LTC2261-14
1.8V ADCs, Ultralow Power
89mW/106mW/127mW, 73.4dB SNR, 85dB SFDR, DDR LVDS/DDR CMOS/CMOS
Outputs, 6mm × 6mm QFN-36
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-36
LTC2263-14/LTC2264-14/ 14-Bit, 25Msps/40Msps/65Msps
LTC2265-14
1.8V Dual ADCs, Ultralow Power
99mW/126mW/191mW, 73.4dB SNR, 85dB SFDR, Serial LVDS Outputs,
6mm × 6mm QFN-36
LTC2263-12/LTC2264-12/ 12-Bit, 25Msps/40Msps/65Msps
LTC2265-12
1.8V Dual ADCs, Ultralow Power
99mW/126mW/191mW, 70.5dB SNR, 85dB SFDR, Serial LVDS Outputs,
6mm × 6mm QFN-36
LTC2266-14/LTC2267-14/ 14-Bit, 80Msps/105Msps/125Msps
LTC2268-14
1.8V Dual ADCs, Ultralow Power
216mW/250mW/293mW, 73.4dB SNR, 85dB SFDR, Serial LVDS Outputs,
6mm × 6mm QFN-36
LTC2266-12/LTC2267-12/ 12-Bit, 80Msps/105Msps/125Msps
LTC2268-12
1.8V Dual ADCs, Ultralow Power
216mW/250mW/293mW, 70.5dB SNR, 85dB SFDR, Serial LVDS Outputs,
6mm × 6mm QFN-36
RF Mixers/Demodulators
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 3.5GHz, NF = 12.5dB,
50Ω Single-Ended RF and LO Ports
LTC5557
400MHz to 3.8GHz High Linearity
Downconverting Mixer
23.7dBm IIP3 at 2.6GHz, 23.5dBm IIP3 at 3.5GHz, 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
1.8GHz Dual Low Noise, Low Distortion
Differential ADC Drivers for 300MHz IF
Fixed Gain 10V/V, 1nV/√Hz Total Input Noise, 80mA Supply Current per Amplifier,
3mm × 4mm QFN-20
LTC6421-20
1.3GHz Dual Low Noise, Low Distortion
Differential ADC Drivers
Fixed Gain 10V/V, 1nV/√Hz Total Input Noise, 40mA Supply Current per Amplifier,
3mm × 4mm QFN-20
LTC6605-7/ LTC6605-10/
LTC6605-14
Dual Matched 7MHz/10MHz/14MHz Filters Dual Matched 2nd Order Lowpass Filters with Differential Drivers,
with ADC Drivers
Pin-Programmable Gain, 6mm × 3mm DFN-22
Amplifiers/Filters
Receiver Subsystems
LTM9002
14-Bit Dual Channel IF/Baseband Receiver Integrated High Speed ADC, Passive Filters and Fixed Gain Differential Amplifiers
Subsystem
21754312fa
34 Linear Technology Corporation
LT 0611 REV A • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507
●
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