1
21421012fa
LTC2142-12/
LTC2141-12/LTC2140-12
TYPICAL APPLICATION
FEATURES
APPLICATIONS
DESCRIPTION
12-Bit, 65Msps/
40Msps/25Msps Low Power
Dual ADCs
n Communications
n Cellular Base Stations
n Software Defined Radios
n Portable Medical Imaging
n Multi-Channel Data Acquisition
n Nondestructive Testing
n 2-Channel Simultaneously Sampling ADC
n 70.8dB SNR
n 89dB SFDR
n Low Power: 92mW/65mW/48mW Total
46mW/33mW/24mW per Channel
n Single 1.8V Supply
n CMOS, DDR CMOS, or DDR LVDS Outputs
n Selectable Input Ranges: 1VP-P to 2VP-P
n 750MHz Full Power Bandwidth S/H
n Optional Data Output Randomizer
n Optional Clock Duty Cycle Stabilizer
n Shutdown and Nap Modes
n Serial SPI Port for Configuration
n 64-Pin (9mm × 9mm) QFN Package
The LTC
®
2142-12/LTC2141-12/LTC2140-12 are 2-channel
simultaneous sampling 12-bit A/D converters designed
for digitizing high frequency, wide dynamic range signals.
They are perfect for demanding communications applica-
tions with AC performance that includes 70.8dB SNR and
89dB spurious free dynamic range (SFDR). Ultralow jitter
of 0.08psRMS 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 0.3LSBRMS.
The digital outputs can be either full rate CMOS, double
data rate CMOS, or double data rate LVDS. A separate
output power supply allows the CMOS output swing to
range from 1.2V to 1.8V.
The ENC+ and ENC– inputs may be driven differentially
or single-ended with a sine wave, PECL, LVDS, TTL, or
CMOS inputs. An optional clock duty cycle stabilizer al-
lows high performance at full speed for a wide range of
clock duty cycles.
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.
2-Tone FFT, fIN = 70MHz and 69MHz
CMOS,
DDR CMOS
OR
DDR LVDS
OUTPUTS
1.8V
VDD
1.8V
OVDD
CLOCK
CONTROL
D1_11
D1_0
21421012 TA01a
CH 1
ANALOG
INPUT
OUTPUT
DRIVERS
t
t
t
GND OGND
S/H 12-BIT
ADC CORE
CH 2
ANALOG
INPUT
S/H 12-BIT
ADC CORE
D2_11
D2_0
t
t
t
65MHz
CLOCK FREQUENCY (MHz)
–100
–110
–120
–70
–60
–80
–90
AMPLITUDE (dBFS)
–50
–30
–40
–20
–10
0
21821012 TA01b
FREQUENCY
(
MHz
)
2
1821012 TA01
b
010 20 30
LTC2142-12/
LTC2141-12/LTC2140-12
2
21421012fa
ABSOLUTE MAXIMUM RATINGS
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
(Notes 1, 2)
PIN CONFIGURATIONS
Digital Output Voltage ................ –0.3V to (OVDD + 0.3V)
Operating Temperature Range
LTC2142C, LTC2141C, LTC2140C ............. 0°C to 70°C
LTC2142I, LTC2141I, LTC2140I ............–40°C to 85°C
Storage Temperature Range .................. –65°C to 150°C
FULL RATE CMOS OUTPUT MODE DOUBLE DATA RATE CMOS OUTPUT MODE
TOP VIEW
UP PACKAGE
64-LEAD (9mm × 9mm) PLASTIC QFN
VDD 1
VCM1 2
GND 3
AIN1+ 4
AIN1– 5
GND 6
REFH 7
REFL 8
REFH 9
REFL 10
PAR/SER 11
AIN2+ 12
AIN2– 13
GND 14
VCM2 15
VDD 16
48 D1_1
47 D1_0
46 DNC*
45 DNC*
44 DNC*
43 DNC*
42 OVDD
41 OGND
40 CLKOUT+
39 CLKOUT–
38 D2_11
37 D2_10
36 D2_9
35 D2_8
34 D2_7
33 D2_6
65
GND
64 VDD
63 SENSE
62 VREF
61 SDO
60 OF1
59 OF2
58 D1_11
57 D1_10
56 D1_9
55 D1_8
54 D1_7
53 D1_6
52 D1_5
51 D1_4
50 D1_3
49 D1_2
VDD 17
ENC+ 18
ENC– 19
CS 20
SCK 21
SDI 22
DNC* 23
DNC* 24
DNC* 25
DNC* 26
D2_0 27
D2_1 28
D2_2 29
D2_3 30
D2_4 31
D2_5 32
TJMAX = 150°C, θJA = 20°C/W
EXPOSED PAD (PIN 65) IS GND, MUST BE SOLDERED TO PCB
TOP VIEW
UP PACKAGE
64-LEAD (9mm × 9mm) PLASTIC QFN
VDD 1
VCM1 2
GND 3
AIN1+ 4
AIN1– 5
GND 6
REFH 7
REFL 8
REFH 9
REFL 10
PAR/SER 11
AIN2+ 12
AIN2– 13
GND 14
VCM2 15
VDD 16
48 D1_0_1
47 DNC
46 DNC*
45 DNC*
44 DNC*
43 DNC*
42 OVDD
41 OGND
40 CLKOUT+
39 CLKOUT–
38 D2_10_11
37 DNC
36 D2_8_9
35 DNC
34 D2_6_7
33 DNC
65
GND
64 VDD
63 SENSE
62 VREF
61 SDO
60 OF2_1
59 DNC
58 D1_10_11
57 DNC
56 D1_8_9
55 DNC
54 D1_6_7
53 DNC
52 D1_4_5
51 DNC
50 D1_2_3
49 DNC
VDD 17
ENC+ 18
ENC– 19
CS 20
SCK 21
SDI 22
DNC* 23
DNC* 24
DNC* 25
DNC* 26
DNC 27
D2_0_1 28
DNC 29
D2_2_3 30
DNC 31
D2_4_5 32
TJMAX = 150°C, θJA = 20°C/W
EXPOSED PAD (PIN 65) IS GND, MUST BE SOLDERED TO PCB
3
21421012fa
LTC2142-12/
LTC2141-12/LTC2140-12
ORDER INFORMATION
LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE
LTC2142CUP-12#PBF LTC2142CUP-12#TRPBF LTC2142UP-12 64-Lead (9mm × 9mm) Plastic QFN 0°C to 70°C
LTC2142IUP-12#PBF LTC2142IUP-12#TRPBF LTC2142UP-12 64-Lead (9mm × 9mm) Plastic QFN –40°C to 85°C
LTC2141CUP-12#PBF LTC2141CUP-12#TRPBF LTC2141UP-12 64-Lead (9mm × 9mm) Plastic QFN 0°C to 70°C
LTC2141IUP-12#PBF LTC2141IUP-12#TRPBF LTC2141UP-12 64-Lead (9mm × 9mm) Plastic QFN –40°C to 85°C
LTC2140CUP-12#PBF LTC2140CUP-12#TRPBF LTC2140UP-12 64-Lead (9mm × 9mm) Plastic QFN 0°C to 70°C
LTC2140IUP-12#PBF LTC2140IUP-12#TRPBF LTC2140UP-12 64-Lead (9mm × 9mm) 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/
PIN CONFIGURATIONS
DOUBLE DATA RATE LVDS OUTPUT MODE
TOP VIEW
UP PACKAGE
64-LEAD (9mm × 9mm) PLASTIC QFN
VDD 1
VCM1 2
GND 3
AIN1+ 4
AIN1– 5
GND 6
REFH 7
REFL 8
REFH 9
REFL 10
PAR/SER 11
AIN2+ 12
AIN2– 13
GND 14
VCM2 15
VDD 16
48 D1_0_1+
47 D1_0_1–
46 DNC*
45 DNC*
44 DNC*
43 DNC*
42 OVDD
41 OGND
40 CLKOUT+
39 CLKOUT–
38 D2_10_11+
37 D2_10_11–
36 D2_8_9+
35 D2_8_9–
34 D2_6_7+
33 D2_6_7–
65
GND
64 VDD
63 SENSE
62 VREF
61 SDO
60 OF2_1+
59 OF2_1–
58 D1_10_11+
57 D1_10_11–
56 D1_8_9+
55 D1_8_9–
54 D1_6_7+
53 D1_6_7–
52 D1_4_5+
51 D1_4_5–
50 D1_2_3+
49 D1_2_3–
VDD 17
ENC+ 18
ENC– 19
CS 20
SCK 21
SDI 22
DNC* 23
DNC* 24
DNC* 25
DNC* 26
D2_0_1– 27
D2_0_1+ 28
D2_2_3– 29
D2_2_3+ 30
D2_4_5– 31
D2_4_5+ 32
TJMAX = 150°C, θJA = 20°C/W
EXPOSED PAD (PIN 65) IS GND, MUST BE SOLDERED TO PCB
LTC2142-12/
LTC2141-12/LTC2140-12
4
21421012fa
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 l1 to 2 VP-P
VIN(CM) Analog Input Common Mode (AIN+ + AIN–)/2 Differential Analog Input (Note 8) l0.7 VCM 1.25 V
VSENSE External Voltage Reference Applied to SENSE External Reference Mode l0.625 1.250 1.300 V
IINCM Analog Input Common Mode Current Per Pin, 65Msps
Per Pin, 40Msps
Per Pin, 25Msps
81
50
31
µA
µA
µA
IIN1 Analog Input Leakage Current (No Encode) 0 < AIN+, AIN– < VDD l–1.5 1.5 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–3 3 µA
tAP Sample-and-Hold Acquisition Delay Time 0 ns
tJITTER Sample-and-Hold Acquisition Delay Jitter Single-Ended Encode
Differential Encode
0.08
0.10
psRMS
psRMS
CMRR Analog Input Common Mode Rejection Ratio 80 dB
BW-3B Full-Power Bandwidth Figure 6 Test Circuit 750 MHz
CONVERTER CHARACTERISTICS
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. (Note 5)
PARAMETER CONDITIONS
LTC2142-12 LTC2141-12 LTC2140-12
UNITSMIN TYP MAX MIN TYP MAX MIN TYP MAX
Resolution (No Missing Codes) l12 12 12 Bits
Integral Linearity Error Differential Analog Input (Note 6) l–0.9 ±0.3 0.9 –0.9 ±0.3 0.9 –0.9 ±0.3 0.9 LSB
Differential Linearity Error Differential Analog Input l–0.5 ±0.1 0.5 –0.5 ±0.1 0.5 –0.5 ±0.1 0.5 LSB
Offset Error (Note 7) l–9 ±1.5 9 –9 ±1.5 9 –9 ±1.5 9 mV
Gain Error Internal Reference
External Reference l–1.7
±1.5
–0.3 1.1 –1.7
±1.5
–0.3 1.1 –1.7
±1.5
–0.3 1.1
%FS
%FS
Offset Drift ±10 ±10 ±10 µV/°C
Full-Scale Drift Internal Reference
External Reference
±30
±10
±30
±10
±30
±10
ppm/°C
ppm/°C
Gain Matching ±0.2 ±0.2 ±0.2 %FS
Offset Matching ±1.5 ±1.5 ±1.5 mV
Transition Noise 0.3 0.3 0.3 LSBRMS
5
21421012fa
LTC2142-12/
LTC2141-12/LTC2140-12
INTERNAL REFERENCE CHARACTERISTICS
The l denotes the specifications which apply over the
full operating temperature range, otherwise specifications are at TA = 25°C. (Note 5)
PARAMETER CONDITIONS MIN TYP MAX UNITS
VCM Output Voltage IOUT = 0 0.5 • VDD – 25mV 0.5 • VDD 0.5 • VDD + 25mV V
VCM Output Temperature Drift ±25 ppm/°C
VCM Output Resistance –600µA < IOUT < 1mA 4
VREF Output Voltage IOUT = 0 1.225 1.250 1.275 V
VREF Output Temperature Drift ±25 ppm/°C
VREF Output Resistance –400µA < IOUT < 1mA 7
VREF Line Regulation 1.7V < VDD < 1.9V 0.6 mV/V
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)
SYMBOL PARAMETER CONDITIONS
LTC2142-12 LTC2141-12 LTC2140-12
UNITSMIN TYP MAX MIN TYP MAX MIN TYP MAX
SNR Signal-to-Noise Ratio 5MHz Input
30MHz Input
70MHz Input
140MHz Input
l69.6
70.8
70.8
70.7
70.5
69.2
70.5
70.5
70.4
70.2
69.7
71
71
70.9
70.7
dBFS
dBFS
dBFS
dBFS
SFDR Spurious Free Dynamic Range
2nd Harmonic
5MHz Input
30MHz Input
70MHz Input
140MHz Input
l78
89
89
88
84
80
89
89
88
84
80
89
89
88
84
dBFS
dBFS
dBFS
dBFS
Spurious Free Dynamic Range
3rd Harmonic
5MHz Input
30MHz Input
70MHz Input
140MHz Input
l80
89
89
88
84
80
89
89
88
84
80
89
89
88
84
dBFS
dBFS
dBFS
dBFS
Spurious Free Dynamic Range
4th Harmonic or Higher
5MHz Input
30MHz Input
70MHz Input
140MHz Input
l85
95
95
95
95
85
95
95
95
95
85
95
95
95
95
dBFS
dBFS
dBFS
dBFS
S/(N+D) Signal-to-Noise Plus
Distortion Ratio
5MHz Input
30MHz Input
70MHz Input
140MHz Input
l69.4
70.7
70.7
70.6
70.2
69.1
70.4
70.4
70.3
69.9
69.6
70.9
70.9
70.8
70.4
dBFS
dBFS
dBFS
dBFS
Crosstalk 10MHz Input –110 –110 –110 dBc
LTC2142-12/
LTC2141-12/LTC2140-12
6
21421012fa
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) l0.2 V
VICM Common Mode Input Voltage Internally Set
Externally Set (Note 8) l1.1
1.2
1.6
V
V
VIN Input Voltage Range ENC+, ENC– to GND l0.2 3.6 V
RIN Input Resistance (See Figure 10) 10 k
CIN Input Capacitance (Note 8) 3.5 pF
Single-Ended Encode Mode (ENC– Tied to GND)
VIH High Level Input Voltage VDD = 1.8V l1.2 V
VIL Low Level Input Voltage VDD = 1.8V l0.6 V
VIN Input Voltage Range ENC+ to GND l0 3.6 V
RIN Input Resistance (See Figure 11) 30 k
CIN Input Capacitance (Note 8) 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 l1.3 V
VIL Low Level Input Voltage VDD = 1.8V l0.6 V
IIN Input Current VIN = 0V to 3.6V l–10 10 µA
CIN Input Capacitance (Note 8) 3 pF
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 200
IOH Logic High Output Leakage Current SDO = 0V to 3.6V l–10 10 µA
COUT Output Capacitance (Note 8) 3 pF
DIGITAL DATA OUTPUTS (CMOS MODES: FULL DATA RATE AND DOUBLE DATA RATE)
OVDD = 1.8V
VOH High Level Output Voltage IO = –500µA l1.750 1.790 V
VOL Low Level Output Voltage IO = 500µA l0.010 0.050 V
OVDD = 1.5V
VOH High Level Output Voltage IO = –500µA 1.488 V
VOL Low Level Output Voltage IO = 500µA 0.010 V
OVDD = 1.2V
VOH High Level Output Voltage IO = –500µA 1.185 V
VOL Low Level Output Voltage IO = 500µA 0.010 V
DIGITAL DATA OUTPUTS (LVDS MODE)
VOD Differential Output Voltage 100 Differential Load, 3.5mA Mode
100 Differential Load, 1.75mA Mode
l247 350
175
454 mV
mV
VOS Common Mode Output Voltage 100 Differential Load, 3.5mA Mode
100 Differential Load, 1.75mA Mode
l1.125 1.250
1.250
1.375 V
V
RTERM On-Chip Termination Resistance Termination Enabled, OVDD = 1.8V 100
7
21421012fa
LTC2142-12/
LTC2141-12/LTC2140-12
POWER REQUIREMENTS
The l denotes the specifications which apply over the full operating temperature
range, otherwise specifications are at TA = 25°C. (Note 9)
SYMBOL PARAMETER CONDITIONS
LTC2142-12 LTC2141-12 LTC2140-12
UNITSMIN TYP MAX MIN TYP MAX MIN TYP MAX
CMOS Output Modes: Full Data Rate and Double Data Rate
VDD Analog Supply Voltage (Note 10) l1.7 1.8 1.9 1.7 1.8 1.9 1.7 1.8 1.9 V
OVDD Output Supply Voltage (Note 10) l1.1 1.8 1.9 1.1 1.8 1.9 1.1 1.8 1.9 V
IVDD Analog Supply Current DC Input
Sine Wave Input
l50.9
51.3
57 35.9
36.2
41 26.9
27
32 mA
mA
IOVDD Digital Supply Current Sine Wave Input, OVDD = 1.2V 3.8 2.4 1.5 mA
PDISS Power Dissipation DC Input
Sine Wave Input, OVDD = 1.2V
l91.6
96.9
103 64.6
68
74 48.4
50.4
57.6 mW
mW
LVDS Output Mode
VDD Analog Supply Voltage (Note 10) l1.7 1.8 1.9 1.7 1.8 1.9 1.7 1.8 1.9 V
OVDD Output Supply Voltage (Note 10) l1.7 1.8 1.9 1.7 1.8 1.9 1.7 1.8 1.9 V
IVDD Analog Supply Current Sine Input, 1.75mA Mode
Sine Input, 3.5mA Mode l
52.6
53.8 61
37.4
38.7 45
28.3
29.5 35.5
mA
mA
IOVDD Digital Supply Current
(0VDD = 1.8V)
Sine Input, 1.75mA Mode
Sine Input, 3.5mA Mode l
30
57.4 67
29.6
57.1 67
29.3
56.8 67
mA
mA
PDISS Power Dissipation Sine Input, 1.75mA Mode
Sine Input, 3.5mA Mode l
149
200 231
121
172 202
104
155 185
mW
mW
All Output Modes
PSLEEP Sleep Mode Power 1 1 1 mW
PNAP Nap Mode Power 10 10 10 mW
PDIFFCLK Power Increase with Differential Encode Mode Enabled
(No Increase for Nap or Sleep Modes)
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)
SYMBOL PARAMETER CONDITIONS
LTC2142-12 LTC2141-12 LTC2140-12
UNITSMIN TYP MAX MIN TYP MAX MIN TYP MAX
fSSampling Frequency (Note 10) l1 65 1 40 1 25 MHz
tLENC Low Time (Note 8) Duty Cycle Stabilizer Off
Duty Cycle Stabilizer On
l
l
7.3
2
7.69
7.69
500
500
11.88
2
12.5
12.5
500
500
19
2
20
20
500
500
ns
ns
tHENC High Time (Note 8) Duty Cycle Stabilizer Off
Duty Cycle Stabilizer On
l
l
7.3
2
7.69
7.69
500
500
11.88
2
12.5
12.5
500
500
19
2
20
20
500
500
ns
ns
tAP Sample-and-Hold
Acquisition Delay Time
000ns
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
Digital Data Outputs (CMOS Modes: Full Data Rate and Double Data Rate)
tDENC to Data Delay CL = 5pF (Note 8) l1.1 1.7 3.1 ns
tCENC to CLKOUT Delay CL = 5pF (Note 8) l1 1.4 2.6 ns
tSKEW DATA to CLKOUT Skew tD – tC (Note 8) l0 0.3 0.6 ns
Pipeline Latency Full Data Rate Mode
Double Data Rate Mode
6
6.5
Cycles
Cycles
LTC2142-12/
LTC2141-12/LTC2140-12
8
21421012fa
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
Digital Data Outputs (LVDS Mode)
tDENC to Data Delay CL = 5pF (Note 8) l1.1 1.8 3.2 ns
tCENC to CLKOUT Delay CL = 5pF (Note 8) l1 1.5 2.7 ns
tSKEW DATA to CLKOUT Skew tD – tC (Note 8) l0 0.3 0.6 ns
Pipeline Latency 6.5 Cycles
SPI Port Timing (Note 8)
tSCK SCK Period Write Mode
Readback Mode, CSDO = 20pF, RPULLUP = 2k
l
l
40
250
ns
ns
tSCS to SCK Setup Time l5ns
tHSCK to CS Setup Time l5ns
tDS SDI Setup Time l5ns
tDH SDI Hold Time l5ns
tDO SCK Falling to SDO Valid Readback Mode, CSDO = 20pF, RPULLUP = 2k l125 ns
TIMING CHARACTERISTICS
The l denotes the specifications which apply over the full operating temperature
range, otherwise specifications are at TA = 25°C. (Note 5)
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 (LTC2142), 40MHz
(LTC2141), or 25MHz (LTC2140), LVDS outputs, differential ENC+/ENC– =
2VP-P sine wave, input range = 2VP-P with differential drive, unless
otherwise noted.
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 = 1.8V, fSAMPLE = 65MHz (LTC2142), 40MHz (LTC2141), or
25MHz (LTC2140), CMOS outputs, ENC+ = single-ended 1.8V square
wave, ENC– = 0V, input range = 2VP-P with differential drive, 5pF load on
each digital output unless otherwise noted. The supply current and power
dissipation specifications are totals for the entire IC, not per channel.
Note 10: Recommended operating conditions.
9
21421012fa
LTC2142-12/
LTC2141-12/LTC2140-12
TYPICAL PERFORMANCE CHARACTERISTICS
LTC2142-12: Integral
Non-Linearity (INL)
LTC2142-12: Differential
Non-Linearity (DNL)
LTC2142-12: 64k Point FFT, fIN =
5MHz, –1dBFS, 65Msps
OUTPUT CODE
0
–1.0
–0.8
–0.6
–0.4
INL ERROR (LSB)
0.2
0.0
1.0
0.6
0.8
0.2
0.4
1024 2048 3072 4096
21421012 G01
OUTPUT CODE
–1.0
–0.4
–0.2
–0.6
–0.8
DNL ERROR (LSB)
0
0.4
0.2
0.6
0.8
1.0
21421012 G02
01024 2048 3072 4096
FREQUENCY (MHz)
–100
–110
–120
–70
–60
–80
–90
AMPLITUDE (dBFS)
–50
–30
–40
–20
–10
0
21421012 G03
010 20 30
LTC2142-12: 64k Point FFT,
fIN = 30MHz, –1dBFS, 65Msps
LTC2142-12: 64k Point FFT,
fIN = 70MHz, –1dBFS, 65Msps
LTC2142-12: 64k Point FFT,
fIN = 140MHz, –1dBFS, 65Msps
LTC2142-12: 64k Point 2-Tone
FFT, fIN = 69MHz, 70MHz,
–7dBFS, 65Msps
LTC2142-12: Shorted Input
Histogram
FREQUENCY (MHz)
–100
–110
–120
–70
–60
–80
–90
AMPLITUDE (dBFS)
–50
–30
–40
–20
–10
0
21421012 G04
LTC2142-12: 64k Point 2-Tone
FFT f
IN
=
69MHz 70MH
z
FREQUENCY
Hz)
21421012
G04
010 20 30
FREQUENCY (MHz)
–100
–110
–120
–70
–60
–80
–90
AMPLITUDE (dBFS)
–50
–30
–40
–20
–10
0
21421012 G05
LT
C
2142-12:
S
horted Input
Histo
g
ram
FREQUENCY
(M
Hz)
21421012
G
0
5
010 20 30
FREQUENCY (MHz)
–100
–110
–120
–70
–60
–80
–90
AMPLITUDE (dBFS)
–50
–30
–40
–20
–10
0
21421012 G06
FREQUENCY
(M
Hz)
21421012
G
0
6
010 20 30
OUTPUT CODE
2043 2044
2000
0
6000
4000
COUNT
8000
10000
18000
16000
14000
12000
2045 2046 2047
21421012 G08
INPUT FREQUENCY (MHz)
0
70
69
68
72
71
SNR (dBFS)
50 100 150 200 250 300
21421012 G09
SINGLE-ENDED
ENCODE
DIFFERENTIAL
ENCODE
LTC2142-12: SNR vs Input
Frequency, –1dBFS, 65Msps,
2V Range
FREQUENCY (MHz)
–100
–110
–120
–70
–60
–80
–90
AMPLITUDE (dBFS)
–50
–30
–40
–20
–10
0
21421012 G07
FREQUENCY
(
MHz
)
21421012
G
0
7
010 20 30
LTC2142-12/
LTC2141-12/LTC2140-12
10
21421012fa
TYPICAL PERFORMANCE CHARACTERISTICS
LTC2142-12: SFDR vs Input Level,
fIN = 70MHz, 65Msps, 2V Range
LTC2142-12: IVDD
vs Sample Rate, 5MHz, –1dBFS
Sine Wave Input on Each Channel
INPUT LEVEL (dBFS)
–80
40
30
20
10
0
60
50
SFDR (dBc AND dBFS)
70
80
110
100
90
–70 –60 –50 –40 –30 –20 –10 0
21421012 G12
dBFS
dBc
SAMPLE RATE (Msps)
0
50
40
45
35
55
IVDD (mA)
10 20 30 40 50 60
21421012 G13
CMOS OUTPUTS
LVDS OUTPUTS
0 50 100 150 200 250 300
INPUT FREQUENCY (MHz)
90
85
80
75
70
65
100
95
2ND AND 3RD HARMONIC (dBFS)
21421012 G10
2ND
3RD
LTC2142-12: 2nd, 3rd Harmonic
vs Input Frequency, –1dBFS,
65Msps, 2V Range
LTC2142-12: IOVDD
vs Sample Rate, 5MHz, –1dBFS,
Sine Wave on Each Channel
LTC2142-12: SNR
vs SENSE, fIN = 5MHz, –1dBFS
LTC2141-12: Integral
Non-Linearity (INL)
LTC2141-12: Differential
Non-Linearity (DNL)
LTC2141-12: 64k Point FFT,
fIN = 5MHz, –1dBFS, 40Msps
SAMPLE RATE (Msps)
0
10
20
0
70
60
50
30
40
IOVDD (mA)
10 20 30 40 50 60
21421012 G14
1.8V CMOS
1.75mA LVDS
3.5mA LVDS
SENSE PIN (V)
0.6
67
66
68
69
72
71
70
SNR (dBFS)
0.7 0.8 0.9 1.1 1.2 1.31
21421012 G15
OUTPUT CODE
0
–1.0
–0.8
–0.6
–0.4
INL ERROR (LSB)
–0.2
0.0
0.2
1.0
0.6
0.8
0.4
1024 2048 3072 4096
21421012 G16
–1.0
–0.4
–0.2
–0.6
–0.8
DNL ERROR (LSB)
0
0.4
0.2
0.6
0.8
1.0
21421012 G17
OUTPUT CODE
01024 2048 3072 4096
FREQUENCY (MHz)
0
–100
–110
–120
–70
–60
–80
–90
AMPLITUDE (dBFS)
–50
–30
–40
–20
–10
0
5 101520
21421012 G18
214
210
12f
FRE
Q
UEN
C
Y (MHz
)
0
5
1
0
15
20
21421012 G1
8
0 50 100 150 200 250 300
INPUT FREQUENCY (MHz)
90
85
80
75
70
65
100
95
2ND AND 3RD HARMONIC (dBFS)
21421012 G11
2ND
3RD
LTC2142-12: 2nd, 3rd Harmonic
vs Input Frequency, –1dBFS,
65Msps, 1V Range
11
21421012fa
LTC2142-12/
LTC2141-12/LTC2140-12
LTC2141-12: 64k Point FFT,
fIN = 140MHz, –1dBFS, 40Msps
TYPICAL PERFORMANCE CHARACTERISTICS
LTC2141-12: 64k Point FFT,
fIN = 30MHz, –1dBFS, 40Msps
FREQUENCY (MHz)
0
–100
–110
–120
–70
–60
–80
–90
AMPLITUDE (dBFS)
–50
–30
–40
–20
–10
0
5 101520
21421012 G19
FREQUENCY (MHz
)
0
5
1
0
1
5
2
0
21421012
G
1
9
LTC2141-12: 64k Point FFT,
fIN = 70MHz, –1dBFS, 40Msps
FREQUENCY (MHz)
0
–100
–110
–120
–70
–60
–80
–90
AMPLITUDE (dBFS)
–50
–30
–40
–20
–10
0
5 101520
21421012 G20
FREQUENCY (MHz
)
0
5
10
15
20
2
1421012
G
2
0
FREQUENCY (MHz)
0
–100
–110
–120
–70
–60
–80
–90
AMPLITUDE (dBFS)
–50
–30
–40
–20
–10
0
5 101520
21421012 G21
LTC2141-12: 64k Point 2-Tone
FFT, fIN = 69MHz, 70MHz,
–7dBFS, 40Msps
FREQUENCY (MHz)
0
–100
–110
–120
–70
–60
–80
–90
AMPLITUDE (dBFS)
–50
–30
–40
–20
–10
0
5 101520
21421012 G22
FREQUENCY
(M
Hz)
0
5
10
1
5 2
0
21421012
G
2
2
OUTPUT CODE
2043 2044
2000
0
6000
4000
COUNT
8000
10000
18000
16000
14000
12000
2045 2046 2047
21421012 G23
LTC2141-12: Shorted Input
Histogram
INPUT FREQUENCY (MHz)
0
69
68
72
71
70
SNR (dBFS)
50 100 150 200 250 300
21421012 G24
SINGLE-ENDED
ENCODE
DIFFERENTIAL
ENCODE
LTC2141-12: SNR
vs Input Frequency, –1dBFS,
40Msps, 2V Range
0 50 100 150 200 250 300
INPUT FREQUENCY (MHz)
90
85
80
75
70
65
100
95
2ND AND 3RD HARMONIC (dBFS)
21421012 G25
2ND
3RD
LTC2141-12: 2nd, 3rd Harmonic
vs Input Frequency, –1dBFS,
40Msps, 2V Range
0 50 100 150 200 250 300
INPUT FREQUENCY (MHz)
90
85
80
75
70
65
100
95
2ND AND 3RD HARMONIC (dBFS)
21421012 G26
2ND
3RD
LTC2141-12: 2nd, 3rd Harmonic
vs Input Frequency, –1dBFS,
40Msps, 1V Range
LTC2141-12: SFDR vs Input Level,
fIN = 70MHz, 40Msps, 2V Range
INPUT LEVEL (dBFS)
–80
40
30
20
10
0
60
50
SFDR (dBc AND dBFS)
70
80
110
100
90
–70 –60 –50 –40 –30 –20 –10 0
21421012 G27
dBFS
dBc
LTC2142-12/
LTC2141-12/LTC2140-12
12
21421012fa
TYPICAL PERFORMANCE CHARACTERISTICS
LTC2140-12: 64k Point FFT,
fIN = 70MHz, –1dBFS, 25Msps
LTC2140-12: 64k Point FFT,
fIN = 140MHz, –1dBFS, 25Msps
LTC2140-12: 64k Point FFT,
fIN = 30MHz, –1dBFS, 25Msps
LTC2141-12: IVDD vs Sample
Rate, 5MHz, –1dBFS Sine Wave
Input on Each Channel
SAMPLE RATE (Msps)
0
35
30
25
40
IVDD (mA)
10 20 30 40
21421012 G28
LVDS OUTPUTS
CMOS OUTPUTS
LTC2141-12: IOVDD vs Sample
Rate, 5MHz, –1dBFS, Sine Wave
Input on Each Channel
LTC2141-12: SNR vs SENSE,
fIN = 5MHz, –1dBFS
LTC2140-12: Integral
Non-Linearity (INL)
LTC2140-12: Differential
Non-Linearity (DNL)
LTC2140-12: 64k Point FFT,
fIN = 5MHz, –1dBFS, 25Msps
SAMPLE RATE (Msps)
10
20
0
70
60
50
30
40
IOVDD (mA)
21421012 G29
0 10203040
1.8V CMOS
1.75mA LVDS
3.5mA LVDS
SENSE PIN (V)
0.6
67
66
68
69
72
71
70
SNR (dBFS)
0.7 0.8 0.9 1.1 1.2 1.31
21421012 G30
OUTPUT CODE
0
–1.0
–0.8
–0.6
–0.4
INL ERROR (LSB)
–0.2
0.0
1.0
0.6
0.8
0.4
1024 2048 3072 4096
21421012 G31
–1.0
–0.4
–0.2
–0.6
–0.8
DNL ERROR (LSB)
0
0.4
0.2
0.6
0.8
1.0
21421012 G32
OUTPUT CODE
01024 2048 3072 4096
FREQUENCY (MHz)
0
–100
–110
–120
–70
–60
–80
–90
AMPLITUDE (dBFS)
–50
–30
–40
–20
–10
0
510
21421012 G33
LT
C2
14
12
:
64
k
Po
in
t
FF
T
F
REQUENCY
Hz)
0
5
10
21421012
G33
FREQUENCY (MHz)
0
–100
–110
–120
–70
–60
–80
–90
AMPLITUDE (dBFS)
–50
–30
–40
–20
–10
0
510
21421012 G36
FREQUENCY (MHz)
0
–100
–110
–120
–70
–60
–80
–90
AMPLITUDE (dBFS)
–50
–30
–40
–20
–10
0
510
21421012 G35
F
REQUENCY
Hz)
0
5
10
21421012
G
3
5
FREQUENCY (MHz)
0
–100
–110
–120
–70
–60
–80
–90
AMPLITUDE (dBFS)
–50
–30
–40
–20
–10
0
510
21421012 G34
FREQUENCY
Hz)
0
5
10
21421012
G34
13
21421012fa
LTC2142-12/
LTC2141-12/LTC2140-12
TYPICAL PERFORMANCE CHARACTERISTICS
LTC2140-12: Shorted Input
Histogram
LTC2140-12: 64k Point 2-Tone FFT,
fIN = 69MHz, 70MHz,
–7dBFS, 25Msps
FREQUENCY (MHz)
0
–100
–110
–120
–70
–60
–80
–90
AMPLITUDE (dBFS)
–50
–30
–40
–20
–10
0
510
21421012 G37
F
REQUENCY
(
MHz
)
0
5
10
21421
0
12
G
3
7
OUTPUT CODE
2050 2051 2053
2000
0
6000
4000
COUNT
8000
10000
18000
16000
14000
12000
2052 2054
21421012 G38
INPUT FREQUENCY (MHz)
0
69
68
72
71
70
SNR (dBFS)
50 100 150 200 250 300
21421012 G39
SINGLE-ENDED
ENCODE
DIFFERENTIAL
ENCODE
LTC2140-12: SNR vs Input
Frequency, –1dBFS, 25Msps,
2V Range
0 50 100 150 200 250 300
INPUT FREQUENCY (MHz)
90
85
80
75
70
65
100
95
2ND AND 3RD HARMONIC (dBFS)
21421012 G40
2ND
3RD
LTC2140-12: 2nd, 3rd Harmonic
vs Input Frequency, –1dBFS,
25Msps, 2V Range
0 50 100 150 200 250 300
INPUT FREQUENCY (MHz)
90
85
80
75
70
65
100
95
2ND AND 3RD HARMONIC (dBFS)
21421012 G41
2ND
3RD
LTC2140-12: 2nd, 3rd Harmonic
vs Input Frequency, –1dBFS,
25Msps, 1V Range
LTC2140-12: SFDR vs Input Level,
fIN = 70MHz, 25Msps, 2V Range
INPUT LEVEL (dBFS)
–80
40
30
20
10
0
60
50
SFDR (dBc AND dBFS)
70
80
110
100
90
–70 –60 –50 –40 –30 –20 –10 0
21421012 G42
dBFS
dBc
LTC2140-12: IVDD vs Sample
Rate, 5MHz, –1dBFS Sine Wave
Input on Each Channel
SAMPLE RATE (Msps)
0
28
22
24
26
20
30
IVDD (mA)
5 10152025
21421012 G43
CMOS OUTPUTS
LVDS OUTPUTS
LTC2140-12: IOVDD vs Sample
Rate, 5MHz, –1dBFS, Sine Wave
on Each Input
LTC2140-12: SNR vs SENSE,
fIN = 5MHz, –1dBFS
SAMPLE RATE (Msps)
10
20
0
60
50
30
40
IOVDD (mA)
21421012 G44
0 5 10 15 20 25
3.5mA LVDS
1.75mA LVDS
1.8V CMOS
SENSE PIN (V)
0.6
67
66
68
69
72
71
70
SNR (dBFS)
0.7 0.8 0.9 1.1 1.2 1.31
21421012 G45
LTC2142-12/
LTC2141-12/LTC2140-12
14
21421012fa
PINS THAT ARE THE SAME FOR ALL DIGITAL
OUTPUT MODES
VDD (Pins 1, 16, 17, 64): Analog Power Supply, 1.7V to
1.9V. Bypass to ground with 0.1µF ceramic capacitors.
Adjacent pins can share a bypass capacitor.
VCM1 (Pin 2): Common Mode Bias Output, Nominally Equal
to VDD/2. VCM1 should be used to bias the common mode
of the analog inputs to channel 1. Bypass to ground with
a 0.1µF ceramic capacitor.
GND (Pins 3, 6, 14): ADC Power Ground.
AIN1+ (Pin 4): Channel 1 Positive Differential Analog
Input.
AIN1– (Pin 5): Channel 1 Negative Differential Analog
Input.
REFH (Pins 7, 9): ADC High Reference. See the Applica-
tions Information section for recommended bypassing
circuits for REFH and REFL.
REFL (Pins 8, 10): ADC Low Reference. See the Applica-
tions Information section for recommended bypassing
circuits for REFH and REFL.
PAR/SER (Pin 11): Programming Mode Selection Pin. Con-
nect 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 VDD and not be driven by a logic signal.
AIN2+ (Pin 12): Channel 2 Positive Differential Analog
Input.
AIN2– (Pin 13): Channel 2 Negative Differential Analog
Input.
VCM2 (Pin 15): Common Mode Bias Output, Nominally
Equal to VDD/2. VCM2 should be used to bias the common
mode of the analog inputs to channel 2. Bypass to ground
with a 0.1µF ceramic capacitor.
ENC+ (Pin 18): Encode Input. Conversion starts on the
rising edge.
ENC– (Pin 19): Encode Complement Input. Conversion
starts on the falling edge. Tie to GND for single-ended
encode mode.
CS (Pin 20): 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 controls the clock duty cycle
stabilizer (see Table 2). CS can be driven with 1.8V to
3.3V logic.
SCK (Pin 21): In Serial Programming Mode, (PAR/SER =
0V), SCK Is the Serial Interface Clock Input. In the parallel
programming mode (PAR/SER = VDD), SCK controls the
digital output mode (see Table 2). SCK can be driven with
1.8V to 3.3V logic.
SDI (Pin 22): 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 together with SDO to power down
the part (see Table 2). SDI can be driven with 1.8V to
3.3V logic.
OGND (Pin 41): 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 42): Output Driver Supply. Bypass to ground
with a 0.1µF ceramic capacitor.
SDO (Pin 61): 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 regis-
ters 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 can
be used together with SDI to power down the part (see
Table 2). When used as an input, SDO can be driven with
1.8V to 3.3V logic through a 1k series resistor.
VREF (Pin 62): Reference Voltage Output. Bypass to
ground with a 2.2µF ceramic capacitor. The output voltage
is nominally 1.25V.
PIN FUNCTIONS
15
21421012fa
LTC2142-12/
LTC2141-12/LTC2140-12
PIN FUNCTIONS
SENSE (Pin 63): 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.
Ground (Exposed Pad Pin 65): The exposed pad must be
soldered to the PCB ground.
DNC* (Pins 23, 24, 25, 26, 43, 44, 45, 46): These pins
are shorted to GND inside the package. For most applica-
tions they should be left unconnected. For pin compat-
ibility with the 14-bit LTC2142-14 or the 16-bit LTC2182
they can be connected as digital outputs to make the bus
width 14 or 16 bits.
FULL RATE CMOS OUTPUT MODE
All Pins Below Have CMOS Output Levels
(OGND to OVDD)
D2_0 to D2_11 (Pins 27, 28, 29, 30, 31, 32, 33, 34, 35,
36, 37, 38): Channel 2 Digital Outputs. D2_11 is the MSB.
CLKOUT– (Pin 39): Inverted Version of CLKOUT+.
CLKOUT+ (Pin 40): Data Output Clock. The digital outputs
normally transition at the same time as the falling edge
of CLKOUT+. The phase of CLKOUT+ can also be delayed
relative to the digital outputs by programming the mode
control registers.
D1_0 to D1_11 (Pins 47, 48, 49, 50, 51, 52, 53, 54,
55, 56, 57, 58): Channel 1 Digital Outputs. D1_11 Is the
MSB.
OF2 (Pin 59): Channel 2 Over/Underflow Digital Output. OF2
is high when an overflow or underflow has occurred.
OF1 (Pin 60): Channel 1 Over/Underflow Digital Output. OF1
is high when an overflow or underflow has occurred.
DOUBLE DATA RATE CMOS OUTPUT MODE
All Pins Below Have CMOS Output Levels
(OGND to OVDD)
D2_0_1 to D2_10_11 (Pins 28, 30, 32, 34, 36, 38):
Channel 2 Double Data Rate Digital Outputs. Two data
bits are multiplexed onto each output pin. The even data
bits (D0, D2, D4, D6, D8, D10) appear when CLKOUT+ is
low. The odd data bits (D1, D3, D5, D7, D9, D11) appear
when CLKOUT+ is high.
DNC (Pins 27, 29, 31, 33, 35, 37, 47, 49, 51, 53, 55,
57, 59): Do not connect these pins.
CLKOUT– (Pin 39): Inverted Version of CLKOUT+.
CLKOUT+ (Pin 40): Data Output Clock. The digital outputs
normally transition at the same time as the falling and
rising edges of CLKOUT+. The phase of CLKOUT+ can also
be delayed relative to the digital outputs by programming
the mode control registers.
D1_0_1 to D1_10_11 (Pins 48, 50, 52, 54, 56, 58):
Channel 1 Double Data Rate Digital Outputs. Two data
bits are multiplexed onto each output pin. The even data
bits (D0, D2, D4, D6, D8, D10) appear when CLKOUT+ is
low. The odd data bits (D1, D3, D5, D7, D9, D11) appear
when CLKOUT+ is high.
OF2_1 (Pin 60): Over/Underflow Digital Output. OF2_1 is
high when an overflow or underflow has occurred. The
over/underflow for both channels are multiplexed onto
this pin. Channel 2 appears when CLKOUT+ is low, and
Channel 1 appears when CLKOUT+ is high.
DOUBLE DATA RATE LVDS OUTPUT MODE
All Pins Below Have LVDS Output Levels. The Output
Current Level Is Programmable. There Is an Optional
Internal 100Ω Termination Resistor Between the Pins
of Each LVDS Output Pair.
D2_0_1–/D2_0_1+ to D2_10_11–/D2_10_11+ (Pins 27/28,
29/30, 31/32, 33/34, 35/36, 37/38): Channel 2 Double
Data Rate Digital Outputs. Two data bits are multiplexed
onto each differential output pair. The even data bits (D0,
D2, D4, D6, D8, D10) appear when CLKOUT+ is low. The
odd data bits (D1, D3, D5, D7, D9, D11) appear when
CLKOUT+ is high.
CLKOUT–/CLKOUT+ (Pins 39/40): Data Output Clock.
The digital outputs normally transition at the same time
as the falling and rising edges of CLKOUT+. The phase of
CLKOUT+ can also be delayed relative to the digital outputs
by programming the mode control registers.
LTC2142-12/
LTC2141-12/LTC2140-12
16
21421012fa
FUNCTIONAL BLOCK DIAGRAM
Figure 1. Functional Block Diagram
D1_0_1–/D1_0_1+ to D1_10_11–/D1_10_11+ (Pins 47/48,
49/50, 51/52, 53/54, 55/56, 57/58): Channel 1 Double
Data Rate Digital Outputs. Two data bits are multiplexed
onto each differential output pair. The even data bits (D0,
D2, D4, D6, D8, D10) appear when CLKOUT+ is low. The
odd data bits (D1, D3, D5, D7, D9, D11) appear when
CLKOUT+ is high.
OF2_1–/OF2_1+ (Pins 59/60): Over/Underflow Digital
Output. OF2_1+ is high when an overflow or underflow
has occurred. The over/underflow for both channels
are multiplexed onto this pin. Channel 2 appears when
CLKOUT+ is low, and Channel 1 appears when CLKOUT+
is high.
DIFF
REF
AMP
REF
BUF
2.2µF
0.1µF 0.1µF
INTERNAL CLOCK SIGNALSREFH REFL
CLOCK/DUTY
CYCLE
CONTROL
RANGE
SELECT
1.25V
REFERENCE
ENC+
REFH REFL ENC–
CORRECTION
LOGIC
SDOCS
OGND
OF1
OVDD
D1_11
CLKOUT–
CLKOUT+
D1_0
21421012 F01
SENSE
VREF
CH 1
ANALOG
INPUT
2.2µF
VCM1
0.1µF
VDD/2
OUTPUT
DRIVERS
MODE
CONTROL
REGISTERS
SCKPAR/SER SDI
•
•
•
GND
S/H 12-BIT
ADC CORE
CH 2
ANALOG
INPUT
S/H 12-BIT
ADC CORE
VCM2
0.1µF
OF2
D2_11
D2_0
•
•
•
VDD
PIN FUNCTIONS
17
21421012fa
LTC2142-12/
LTC2141-12/LTC2140-12
Full Rate CMOS Output Mode Timing
All Outputs Are Single-Ended and Have CMOS Levels
TIMING DIAGRAMS
tH
tD
tC
tL
B – 6 B – 5 B – 4 B – 3 B – 2
tAP
A + 1
A + 2 A + 4
A + 3
A
CH 1
ANALOG
INPUT
ENC–
ENC+
CLKOUT+
CLKOUT–
D2_0 - D2_11, OF2
tAP
B + 1
B + 2 B + 4
B + 3
B
CH 2
ANALOG
INPUT
A – 6 A – 5 A – 4 A – 3 A – 2
D1_0 - D1_11, OF1
21421012 TD01
LTC2142-12/
LTC2141-12/LTC2140-12
18
21421012fa
Double Data Rate CMOS Output Mode Timing
All Outputs Are Single-Ended and Have CMOS Levels
tD
•
•
•
tD
tCtC
tL
BIT 0
A-6
BIT 1
A-6
BIT 0
A-5
BIT 1
A-5
BIT 0
A-4
BIT 1
A-4
BIT 0
A-3
BIT 1
A-3
BIT 0
A-2
BIT 10
A-6
BIT 11
A-6
BIT 10
A-5
BIT 11
A-5
BIT 10
A-4
BIT 11
A-4
BIT 10
A-3
BIT 11
A-3
BIT 10
A-2
ENC–
ENC+
D1_0_1
D1_10_11
•
•
•
BIT 0
B-6
BIT 1
B-6
BIT 0
B-5
BIT 1
B-5
BIT 0
B-4
BIT 1
B-4
BIT 0
B-3
BIT 1
B-3
BIT 0
B-2
BIT 10
B-6
BIT 11
B-6
BIT 10
B-5
BIT 11
B-5
BIT 10
B-4
BIT 11
B-4
BIT 10
B-3
BIT 11
B-3
BIT 10
B-2
OF
B-6
OF
A-6
OF
B-5
OF
A-5
OF
B-4
OF
A-4
OF
B-3
OF
A-3
OF
B-2
D2_0_1
D2_10_11
CLKOUT+
CLKOUT–
OF2_1
21421012 TD02
tH
tAP
A + 1
A + 2 A + 4
A + 3
A
CH 1
ANALOG
INPUT
tAP
B + 1
B + 2 B + 4
B + 3
B
CH 2
ANALOG
INPUT
TIMING DIAGRAMS
19
21421012fa
LTC2142-12/
LTC2141-12/LTC2140-12
TIMING DIAGRAMS
Double Data Rate LVDS Output Mode Timing
All Outputs Are Differential and Have LVDS Levels
tD
•
•
•
tD
tCtC
tL
BIT 0
A-6
BIT 1
A-6
BIT 0
A-5
BIT 1
A-5
BIT 0
A-4
BIT 1
A-4
BIT 0
A-3
BIT 1
A-3
BIT 0
A-2
BIT 10
A-6
BIT 11
A-6
BIT 10
A-5
BIT 11
A-5
BIT 10
A-4
BIT 11
A-4
BIT 10
A-3
BIT 11
A-3
BIT 10
A-2
ENC–
ENC+
D1_0_1+
D1_10_11+
•
•
•
BIT 0
B-6
BIT 1
B-6
BIT 0
B-5
BIT 1
B-5
BIT 0
B-4
BIT 1
B-4
BIT 0
B-3
BIT 1
B-3
BIT 0
B-2
BIT 10
B-6
BIT 11
B-6
BIT 10
B-5
BIT 11
B-5
BIT 10
B-4
BIT 11
B-4
BIT 10
B-3
BIT 11
B-3
BIT 10
B-2
OF
B-6
OF
A-6
OF
B-5
OF
A-5
OF
B-4
OF
A-4
OF
B-3
OF
A-3
OF
B-2
D2_0_1+
D2_10_11+
CLKOUT+
CLKOUT–
OF2_1+
D1_0_1–
D1_10_11–
D2_0_1–
D2_10_11–
OF2_1–
21421012 TD03
tH
tAP
A + 1
A + 2 A + 4
A + 3
A
CH 1
ANALOG
INPUT
tAP
B + 1
B + 2 B + 4
B + 3
B
CH 2
ANALOG
INPUT
A6
tStDS
A5 A4 A3 A2 A1 A0 XX
D7 D6 D5 D4 D3 D2 D1 D0
XX XX XX XX XX XX XX
CS
SCK
SDI R/W
SDO
HIGH IMPEDANCE
SPI Port Timing (Readback Mode)
SPI Port Timing (Write Mode)
tDH
tDO
tSCK tH
A6 A5 A4 A3 A2 A1 A0 D7 D6 D5 D4 D3 D2 D1 D0
21421012 TD04
CS
SCK
SDI R/W
SDO
HIGH IMPEDANCE
LTC2142-12/
LTC2141-12/LTC2140-12
20
21421012fa
CONVERTER OPERATION
The LTC2142-12/LTC2141-12/LTC2140-12 are low
power, 2-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, or single ended for lower
power consumption. The digital outputs can be CMOS,
double data rate CMOS (to halve the number of output
lines), or double data rate LVDS (to reduce digital noise
in the system.) 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 differen-
tially around a common mode voltage set by the VCM1 or
VCM2 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 180° phase difference
between the inputs.
The two channels are simultaneously sampled by a shared
encode circuit (Figure 2).
Single-Ended Input
For applications less sensitive to harmonic distortion, the
AIN+ input can be driven single-ended with a 1VP-P signal
centered around VCM. The AIN– input should be connected
to VCM. With a single-ended input the harmonic distortion
and INL will degrade, but the noise and DNL will remain
unchanged.
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
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
tap is biased with VCM, setting the A/D input at its opti-
mal DC level. At higher input frequencies, a transmission
line balun transformer (Figure 4 to Figure 6) has better
balance, resulting in lower A/D distortion.
CSAMPLE
5pF
RON
15
RON
15
VDD
VDD
LTC2142-12
AIN+
21421012 F02
CSAMPLE
5pF
VDD
AIN–
ENC–
ENC+
1.2V
10k
1.2V
10k
CPARASITIC
1.8pF
CPARASITIC
1.8pF
10
10Ω
25
25 25
25
50
0.1µF
AIN+
AIN–
12pF
0.1µF
VCM
LTC2142-12
ANALOG
INPUT
0.1µF T1
1:1
T1: MA/COM MABAES0060
RESISTORS, CAPACITORS
ARE 0402 PACKAGE SIZE
21421012 F03
Figure 2. Equivalent Input Circuit. Only One of the Two
Analog Channels Is Shown
Figure 3. Analog Input Circuit Using a Transformer.
Recommended for Input Frequencies from 5MHz to 70MHz
APPLICATIONS INFORMATION
21
21421012fa
LTC2142-12/
LTC2141-12/LTC2140-12
APPLICATIONS INFORMATION
Figure 5. Recommended Front-End Circuit for Input
Frequencies from 150MHz to 250MHz
Figure 6. Recommended Front-End Circuit for Input
Frequencies Above 250MHz
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.
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 (Figure 4
to Figure 6) should convert the signal to differential before
driving the A/D.
Figure 4. Recommended Front-End Circuit for Input
Frequencies from 5MHz to 150MHz
Reference
The LTC2142-12/LTC2141-12/LTC2140-12 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 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.
The VREF, REFH and REFL pins should be bypassed, as
shown in Figure 8. A low inductance 2.2µF interdigitated
capacitor is recommended for the bypass between REFH
and REFL. This type of capacitor is available at a low cost
from multiple suppliers.
25
12
12
25
50
0.1µF
AIN+
AIN–
8.2pF
0.1µF
VCM
ANALOG
INPUT
0.1µF
0.1µF
T1
T2
T1: MA/COM MABA-007159-000000
T2: COILCRAFT WBC1-1TL
RESISTORS, CAPACITORS ARE 0402 PACKAGE SIZE
21421012 F04
LTC2142-12
25
25
50
0.1µF
AIN+
AIN–
1.8pF
0.1µF
VCM
ANALOG
INPUT
0.1µF
0.1µF
T1
T2
T1: MA/COM MABA-007159-000000
T2: COILCRAFT WBC1-1TL
RESISTORS, CAPACITORS ARE 0402 PACKAGE SIZE
21421012 F05
LTC2142-12
25
25
50
0.1µF
4.7nH
4.7nH
AIN+
AIN–
0.1µF
VCM
T1: MA/COM ETC1-1-13
RESISTORS, CAPACITORS
ARE 0402 PACKAGE SIZE
21421012 F06
LTC2142-12
ANALOG
INPUT
0.1µF
0.1µF
T1
25
25
200
200
0.1µF AIN+
AIN–
0.1µF
12pF
12pF
VCM
LTC2142-12
21421012 F07
––
++
ANALOG
INPUT
HIGH SPEED
DIFFERENTIAL
AMPLIFIER
0.1µF
Figure 7. Front-End Circuit Using a High Speed
Differential Amplifier
LTC2142-12/
LTC2141-12/LTC2140-12
22
21421012fa
APPLICATIONS INFORMATION
VREF
REFH
REFH
SENSE
C1
TIE TO VDD FOR 2V RANGE;
TIE TO GND FOR 1V RANGE;
3"/(&t7SENSE FOR
0.625V < VSENSE < 1.300V
1.25V
REFL
REFL
INTERNAL ADC
HIGH REFERENCE
BUFFER
21421012 F08a
LTC2142-12
5
0.8x
DIFF AMP
INTERNAL ADC
LOW REFERENCE
C1: 2.2µF LOW INDUCTANCE
INTERDIGITATED CAPACITOR
TDK CLLE1AX7S0G225M
MURATA LLA219C70G225M
AVX W2L14Z225M
OR EQUIVALENT
1.25V BANDGAP
REFERENCE
0.625V
RANGE
DETECT
AND
CONTROL
2.2µF
C2
0.1µF
C3
0.1µF
+
+
–
–
–
–
+
+
Figure 8a. Reference Circuit
SENSE
1.25V
EXTERNAL
REFERENCE
2.2µF
1µF
VREF
21421012 F09
LTC2142-12
Figure 9. Using an External 1.25V Reference
REFH
REFH
REFL
REFL
21421012 F08b
LTC2142-12
CAPACITORS ARE 0402 PACKAGE SIZE
C3
0.1µF
C1
2.2µF
C2
0.1µF
Figure 8b. Alternative REFH/REFL Bypass Circuit
Figure 8c. Recommended Layout for the REFH/REFL
Bypass Circuit in Figure 8a
Alternatively C1 can be replaced by a standard 2.2µF
capacitor between REFH and REFL (see Figure 8b). The
capacitors should be as close to the pins as possible (not
on the back side of the circuit board).
Figure 8c and Figure 8d show the recommended circuit
board layout for the REFH/REFL bypass capacitors. Note
that in Figure 8c, every pin of the interdigitated capacitor
(C1) is connected since the pins are not internally connected
in some vendors’ capacitors. In Figure 8d the REFH and
Figure 8d. Recommended Layout for the REFH/REFL
Bypass Circuit in Figure 8b
Encode Inputs
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 differential encode mode is recommended for si-
nusoidal, PECL, or LVDS encode inputs (Figure 12 and
Figure 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,
REFL pins are connected by short jumpers in an internal
layer. To minimize the inductance of these jumpers they
can be placed in a small hole in the GND plane on the
second board layer.
23
21421012fa
LTC2142-12/
LTC2141-12/LTC2140-12
50Ω
100Ω
0.1µF
T1 = MA/COM ETC1-1-13
RESISTORS AND CAPACITORS
ARE 0402 PACKAGE SIZE
50Ω
LTC2142-12
21421012 F12
ENC–
ENC+
0.1µF
0.1µF
T1
Figure 12. Sinusoidal Encode Drive
ENC+
ENC–
PECL OR
LVDS
CLOCK
0.1µF
0.1µF
21421012 F13
LTC2142-12
Figure 13. PECL or LVDS Encode Drive
VDD
LTC2142-12
21421012 F10
ENC–
ENC+
15k
VDD
DIFFERENTIAL
COMPARATOR
30k
Figure 10. Equivalent Encode Input Circuit
for Differential Encode Mode
30k
ENC+
ENC–
21421012 F11
0V
1.8V TO 3.3V
LTC2142-12
CMOS LOGIC
BUFFER
Figure 11. Equivalent Encode Input Circuit
for Single-Ended Encode Mode
ENC– should stay at least 200mV above ground to avoid
falsely triggering the single ended encode mode. For good
jitter performance ENC+ and 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.
If the encode signal is turned off or drops below approxi-
mately 500kHz, the A/D enters nap mode.
Clock Duty Cycle Stabilizer
For good performance the encode signal should have a
50% (±5%) duty cycle. If the optional clock duty cycle
stabilizer circuit is enabled, the encode duty cycle can
vary from 30% to 70% and the duty cycle stabilizer will
maintain a constant 50% internal duty cycle. If the encode
signal changes frequency, the duty cycle stabilizer circuit
requires one hundred clock cycles to lock onto the input
clock. The duty cycle stabilizer is enabled by mode control
register A2 (serial programming mode), or by CS (parallel
programming mode).
For applications where the sample rate needs to be changed
quickly, the clock duty cycle stabilizer can be disabled. If
the duty cycle stabilizer is disabled, care should be taken to
make the sampling clock have a 50% (±5%) duty cycle. The
duty cycle stabilizer should not be used below 5Msps.
DIGITAL OUTPUTS
Digital Output Modes
The LTC2142-12/LTC2141-12/LTC2140-12 can operate in
three digital output modes: full rate CMOS, double data
rate CMOS (to halve the number of output lines), or double
data rate LVDS (to reduce digital noise in the system.) The
output mode is set by mode control register A3 (serial
programming mode), or by SCK (parallel programming
mode). Note that double data rate CMOS cannot be selected
in the parallel programming mode.
APPLICATIONS INFORMATION
LTC2142-12/
LTC2141-12/LTC2140-12
24
21421012fa
APPLICATIONS INFORMATION
Full Rate CMOS Mode
In full rate CMOS mode the data outputs (D1_0 to D1_11
and D2_0 to D2_11), overflow (OF2, OF1), and the data
output clocks (CLKOUT+, CLKOUT–) have CMOS output
levels. The outputs are powered by OVDD and OGND which
are isolated from the A/D core power and ground. OVDD
can range from 1.1V to 1.9V, allowing 1.2V through 1.8V
CMOS logic outputs.
For good performance, the digital outputs should drive
minimal capacitive loads. If the load capacitance is larger
than 10pF a digital buffer should be used.
Double Data Rate CMOS Mode
In double data rate CMOS mode, two data bits are
multiplexed and output on each data pin. This reduces
the number of digital lines by thirteen, simplifying
board routing and reducing the number of input pins
needed to receive the data. The data outputs (D1_0_1,
D1_2_3, D1_4_5, D1_6_7, D1_8_9, D1_10_11, D2_0_1,
D2_2_3, D2_4_5, D2_6_7, D2_8_9, D2_10_11), overflow
(OF2_1), and the data output clocks (CLKOUT+, CLKOUT–)
have CMOS output levels. The outputs are powered by
OVDD and OGND which are isolated from the A/D core
power and ground. OVDD can range from 1.1V to 1.9V,
allowing 1.2V through 1.8V CMOS logic outputs. Note
that the overflow for both ADC channels is multiplexed
onto the OF2_1 pin.
For good performance, the digital outputs should drive
minimal capacitive loads. If the load capacitance is larger
than 10pF a digital buffer should be used.
Double Data Rate LVDS Mode
In double data rate LVDS mode, two data bits are
multiplexed and output on each differential output
pair. There are six LVDS output pairs per ADC channel
(D1_0_1+/D1_0_1– through D1_10_11+/D1_10_11– and
D2_0_1+/D2_0_1– through D2_10_11+/D2_10_11–) for
the digital output data. Overflow (OF2_1+/OF2_1–) and the
data output clock (CLKOUT+/CLKOUT–) each have an LVDS
output pair. Note that the overflow for both ADC channels
is multiplexed onto the OF2_1+/OF2_1– output pair.
By default the outputs are standard LVDS levels: 3.5mA
output current and a 1.25V output common mode volt-
age. 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. In LVDS
mode, OVDD must be 1.8V.
Programmable LVDS Output Current
In LVDS mode, the default output driver current is 3.5mA.
This current can be adjusted by serially programming mode
control register A3. Available current levels are 1.75mA,
2.1mA, 2.5mA, 3mA, 3.5mA, 4mA and 4.5mA.
Optional LVDS Driver Internal Termination
In most cases, using just an external 100Ω termination
resistor will give excellent LVDS signal integrity. In addi-
tion, an optional internal 100Ω termination resistor can
be enabled by serially programming mode control register
A3. 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.
Overflow Bit
The overflow output bit outputs a logic high when the analog
input is either overranged or underranged. The overflow
bit has the same pipeline latency as the data bits. In full
rate CMOS mode each ADC channel has its own overflow
pin (OF1 for channel 1, OF2 for channel 2). In DDR CMOS
or DDR LVDS mode the overflow for both ADC channels
is multiplexed onto the OF2_1 output.
25
21421012fa
LTC2142-12/
LTC2141-12/LTC2140-12
APPLICATIONS INFORMATION
Phase Shifting the Output Clock
In full rate CMOS mode the data output bits normally
change at the same time as the falling edge of CLKOUT+,
so the rising edge of CLKOUT+ can be used to latch the
output data. In double data rate CMOS and LVDS modes
the data output bits normally change at the same time as
the falling and rising edges of CLKOUT+. To allow adequate
set-up and hold time when latching the data, the CLKOUT+
signal may need to be phase shifted relative to the data
output bits. Most FPGAs have this feature; this is generally
the best place to adjust the timing.
The LTC2142-12/LTC2141-12/LTC2140-12 can also
phase shift the CLKOUT+/CLKOUT– signals by serially
programming mode control register A2. The output
clock can be shifted by 0°, 45°, 90°, or 135°. To use the
phase shifting feature the clock duty cycle stabilizer must
be turned on. Another control register bit can invert the
polarity of CLKOUT+ and CLKOUT–, independently of the
phase shift. The combination of these two features enables
phase shifts of 45° up to 315° (Figure 14).
DATA FORMAT
Table 1 shows the relationship between the analog input
voltage, the digital data output bits and the overflow bit.
By default the output data format is offset binary. The 2’s
complement format can be selected by serially program-
ming mode control register A4.
Table 1. Output Codes vs Input Voltage
AIN+ – AIN–
(2V Range) OF
D11-D0
(OFFSET BINARY)
D11-D0
(2’s COMPLEMENT)
>+1.000000V
+0.999512V
+0.999024V
1
0
0
1111 1111 1111
1111 1111 1111
1111 1111 1110
0111 1111 1111
0111 1111 1111
0111 1111 1110
+0.000488V
0.000000V
–0.000488V
–0.000976V
0
0
0
0
1000 0000 0001
1000 0000 0000
0111 1111 1111
0111 1111 1110
0000 0000 0001
0000 0000 0000
1111 1111 1111
1111 1111 1110
–0.999512V
–1.000000V
≤–1.000000V
0
0
1
0000 0000 0001
0000 0000 0000
0000 0000 0000
1000 0000 0001
1000 0000 0000
1000 0000 0000
CLKOUT+
D0-D11, OF
PHASE
SHIFT
0°
45°
90°
135°
180°
225°
270°
315°
CLKINV
0
0
0
0
1
1
1
1
CLKPHASE1
MODE CONTROL BITS
0
0
1
1
0
0
1
1
CLKPHASE0
0
1
0
1
0
1
0
1
21421012 F14
ENC+
Figure 14. Phase Shifting CLKOUT
LTC2142-12/
LTC2141-12/LTC2140-12
26
21421012fa
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 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 LSB, OF and CLKOUT outputs are
not affected. The output randomizer is enabled by serially
programming mode control register A4.
Alternate Bit Polarity
Another feature that reduces digital feedback on the circuit
board is the alternate bit polarity mode. When this mode
is enabled, all of the odd bits (D1, D3, D5, D7, D9, D11)
are inverted before the output buffers. The even bits (D0,
D2, D4, D6, D8, D10), OF and CLKOUT are not affected.
This can reduce digital currents in the circuit board ground
plane and reduce digital noise, particularly for very small
analog input signals.
When there is a very small signal at the input of the A/D
that is centered around mid-scale, the digital outputs toggle
between mostly 1’s and mostly 0’s. This simultaneous
switching of most of the bits will cause large currents in the
ground plane. By inverting every other bit, the alternate bit
polarity mode makes half of the bits transition high while
half of the bits transition low. This cancels current flow in
the ground plane, reducing the digital noise.
The digital output is decoded at the receiver by inverting
the odd bits (D1, D3, D5, D7, D9, D11). The alternate
bit polarity mode is independent of the digital output
randomizer – either, both or neither function can be on at
the same time. The alternate bit polarity mode is enabled
by serially programming mode control register A4.
APPLICATIONS INFORMATION
CLKOUT CLKOUT
OF
D11/D0
D10/D0
•
•
•
D2/D0
D1/D0
D0
21421012 F15
OF
D11
D10
D2
D1
D0
RANDOMIZER
ON
D11
FPGA
PC BOARD
D10
t
t
t
D2
D1
D0
21421012 F16
D0
D1/D0
D2/D0
D10/D0
D11/D0
OF
CLKOUT
LTC2142-12
Figure 15. Functional Equivalent of Digital Output Randomizer
Figure 16. Unrandomizing a Randomized Digital
Output Signal
27
21421012fa
LTC2142-12/
LTC2141-12/LTC2140-12
slight temperature shift caused by the change in supply
current as the A/D leaves nap mode. Either channel 2 or
both channels can be placed in nap mode; it is not possible
to have channel 1 in nap mode and channel 2 operating
normally.
Sleep mode and nap mode are enabled by mode control
register A1 (serial programming mode), or by SDI and
SDO (parallel programming mode).
DEVICE PROGRAMMING MODES
The operating modes of the LTC2142-12/LTC2141-12/
LTC2140-12 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 2 shows the
modes set by CS, SCK, SDI and SDO.
Table 2. Parallel Programming Mode Control Bits (PAR/SER = VDD)
PIN DESCRIPTION
CS Clock Duty Cycle Stabilizer Control Bit
0 = Clock Duty Cycle Stabilizer Off
1 = Clock Duty Cycle Stabilizer On
SCK Digital Output Mode Control Bit
0 = Full Rate CMOS Output Mode
1 = Double Data Rate LVDS Output Mode
(3.5mA LVDS Current, Internal Termination Off)
SDI/SDO Power Down Control Bit
00 = Normal Operation
01 = Channel 1 in Normal Operation, Channel 2 in Nap Mode
10 = Channel 1 and Channel 2 in Nap Mode
11 = Sleep Mode (Entire Device Powered Down)
APPLICATIONS INFORMATION
Digital Output Test Patterns
To allow in-circuit testing of the digital interface to the
A/D, there are several test modes that force the A/D data
outputs (OF, D11-D0) to known values:
All 1s: All outputs are 1
All 0s: All outputs are 0
Alternating: Outputs change from all 1s to all 0s on
alternating samples.
Checkerboard: Outputs change from 1010101010101
to 0101010101010 on alternating samples.
The digital output test patterns are enabled by serially
programming mode control register A4. When enabled,
the test patterns override all other formatting modes: 2’s
complement, randomizer, alternate bit polarity.
Output Disable
The digital outputs may be disabled by serially program-
ming mode control register A3. All digital outputs including
OF and CLKOUT are disabled. The high impedance disabled
state is intended for in-circuit testing or long periods of
inactivity – it is too slow to multiplex a data bus between
multiple converters at full speed. When the outputs are
disabled both channels should be put into either sleep or
nap mode.
Sleep and Nap Modes
The A/D may be placed in sleep or nap modes to conserve
power. In sleep mode the entire device is powered down,
resulting in 1mW power consumption. 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 Fig. 8, the A/D will stabilize
after 2ms.
In nap mode the A/D core is powered down while the internal
reference circuits 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
LTC2142-12/
LTC2141-12/LTC2140-12
28
21421012fa
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 writ-
ten 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). 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 3 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.
GROUNDING AND BYPASSING
The LTC2142-12/LTC2141-12/LTC2140-12 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.
Size 0402 ceramic capacitors are recommended. The traces
connecting the pins and bypass capacitors must be kept
short and should be made as wide as possible.
Of particular importance is the 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.
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 LTC2142-12/LTC2141-12/
LTC2140-12 is transferred from the die through the bottom-
side 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.
APPLICATIONS INFORMATION
29
21421012fa
LTC2142-12/
LTC2141-12/LTC2140-12
APPLICATIONS INFORMATION
Table 3. Serial Programming Mode Register Map (PAR/SER = GND)
REGISTER A0: RESET REGISTER (ADDRESS 00h)
D7 D6 D5 D4 D3 D2 D1 D0
RESETXXXXXXX
Bit 7 RESET 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. Data Read Back from the
Reset Register Will Be Random.
Bits 6-0 Unused, Don’t Care Bits.
REGISTER A1: POWER-DOWN REGISTER (ADDRESS 01h)
D7 D6 D5 D4 D3 D2 D1 D0
XXXXXXPWROFF1 PWROFF0
Bits 7-2 Unused, Don’t Care Bits.
Bits 1-0 PWROFF1:PWROFF0 Power Down Control Bits
00 = Normal Operation
01 = Channel 1 in Normal Operation, Channel 2 in Nap Mode
10 = Channel 1 and Channel 2 in Nap Mode
11 = Sleep Mode
REGISTER A2: TIMING REGISTER (ADDRESS 02h)
D7 D6 D5 D4 D3 D2 D1 D0
XXXXCLKINV CLKPHASE1 CLKPHASE0 DCS
Bits 7-4 Unused, Don’t Care Bits.
Bit 3 CLKINV Output Clock Invert Bit
0 = Normal CLKOUT Polarity (As Shown in the Timing Diagrams)
1 = Inverted CLKOUT Polarity
Bits 2-1 CLKPHASE1:CLKPHASE0 Output Clock Phase Delay Bits
00 = No CLKOUT Delay (As Shown in the Timing Diagrams)
01 = CLKOUT+/CLKOUT– Delayed by 45° (Clock Period • 1/8)
10 = CLKOUT+/CLKOUT– Delayed by 90° (Clock Period • 1/4)
11 = CLKOUT+/CLKOUT– Delayed by 135° (Clock Period • 3/8)
Note: If the CLKOUT Phase Delay Feature Is Used, the Clock Duty Cycle Stabilizer Must Also Be Turned On
Bit 0 DCS Clock Duty Cycle Stabilizer Bit
0 = Clock Duty Cycle Stabilizer Off
1 = Clock Duty Cycle Stabilizer On
LTC2142-12/
LTC2141-12/LTC2140-12
30
21421012fa
REGISTER A3: OUTPUT MODE REGISTER (ADDRESS 03h)
D7 D6 D5 D4 D3 D2 D1 D0
X ILVDS2 ILVDS1 ILVDS0 TERMON OUTOFF OUTMODE1 OUTMODE0
Bit 7 Unused, Don’t Care Bit.
Bits 6-4 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 3 TERMON LVDS Internal Termination Bit
0 = Internal Termination Off
1 = Internal Termination On. LVDS Output Driver Current is 2 the Current Set by ILVDS2:ILVDS0
Bit 2 OUTOFF Output Disable Bit
0 = Digital Outputs Are Enabled
1 = Digital Outputs Are Disabled and Have High Output Impedance
Note: If the Digital Outputs Are Disabled the Part Should Also Be Put in Sleep or Nap Mode (Both Channels).
Bits 1-0 OUTMODE1:OUTMODE0 Digital Output Mode Control Bits
00 = Full Rate CMOS Output Mode
01 = Double Data Rate LVDS Output Mode
10 = Double Data Rate CMOS Output Mode
11 = Not Used
REGISTER A4: DATA FORMAT REGISTER (ADDRESS 04h)
D7 D6 D5 D4 D3 D2 D1 D0
X X OUTTEST2 OUTTEST1 OUTTEST0 ABP RAND TWOSCOMP
Bit 7-6 Unused, Don’t Care Bits.
Bits 5-3 OUTTEST2:OUTTEST0 Digital Output Test Pattern Bits
000 = Digital Output Test Patterns Off
001 = All Digital Outputs = 0
011 = All Digital Outputs = 1
101 = Checkerboard Output Pattern. OF, D11-D0 Alternate Between 1 0101 0101 0101 and 0 1010 1010 1010
111 = Alternating Output Pattern. OF, D11-D0 Alternate Between 0 0000 0000 0000 and 1 1111 1111 1111
Note: Other Bit Combinations Are Not Used
Bit 2 ABP Alternate Bit Polarity Mode Control Bit
0 = Alternate Bit Polarity Mode Off
1 = Alternate Bit Polarity Mode On. Forces the Output Format to Be Offset Binary
Bit 1 RAND Data Output Randomizer Mode Control Bit
0 = Data Output Randomizer Mode Off
1 = Data Output Randomizer Mode On
Bit 0 TWOSCOMP Two’s Complement Mode Control Bit
0 = Offset Binary Data Format
1 = Two’s Complement Data Format
APPLICATIONS INFORMATION
31
21421012fa
LTC2142-12/
LTC2141-12/LTC2140-12
Silkscreen Top
TYPICAL APPLICATIONS
Top Side
LTC2142-12/
LTC2141-12/LTC2140-12
32
21421012fa
TYPICAL APPLICATIONS
Inner Layer 2 GND
Inner Layer 3
33
21421012fa
LTC2142-12/
LTC2141-12/LTC2140-12
TYPICAL APPLICATIONS
Inner Layer 4
Inner Layer 5 Power
LTC2142-12/
LTC2141-12/LTC2140-12
34
21421012fa
TYPICAL APPLICATIONS
Bottom Side
35
21421012fa
LTC2142-12/
LTC2141-12/LTC2140-12
48
47
46
45
44
43
42
41
40
39
38
37
36
35
34
33
D1_0_1+
D1_0_1–
DNC
DNC
DNC
DNC
OVDD
OGND
CLKOUT+
CLKOUT–
D2_10_11+
D2_10_11–
D2_8_9+
D2_8_9–
D2_6_7+
D2_6_7–
65
PAD
64
63
62
61
60
59
58
57
56
55
54
53
52
51
50
49
VDD
SENSE
VREF
SDO
OF2_1+
OF2_1–
D1_10_11+
D1_10_11–
D1_8_9+
D1_8_9–
D1_6_7+
D1_6_7–
D1_4_5+
D1_4_5–
D1_2_3+
D1_2_3–
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
VDD
ENC+
ENC–
CS
SCK
SDI
DNC
DNC
DNC
DNC
D2_1_0–
D2_1_0+
D2_2_3–
D2_2_3+
D2_4_5–
D2_4_5+
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
C19
0.1µF
SDO
SENSE
VDD
VDD
VCM1
GND
AIN1+
AIN1–
GND
REFH
REFL
REFH
REFL
PAR/SER
AIN2+
AIN2–
GND
VCM2
VDD
C20
0.1µF
C18
0.1µF
VDD
PAR/SER
C17
1µF
C23
2.2µF
C37
0.1µF
DIGITAL
OUTPUTS
DIGITAL
OUTPUTS
OVDD
SPI BUS
C67
0.1µF
C78
0.1µF
C79
0.1µF
R51
100
LTC2142-12
ENCODE
CLOCK
CN1
AIN2+
AIN2–
AIN1+
AIN1–
C15
0.1µF
C21
0.1µF
+
+
–
–
–
–
+
+
21821012 TA02
TYPICAL APPLICATIONS
LTC2142 Schematic
LTC2142-12/
LTC2141-12/LTC2140-12
36
21421012fa
PACKAGE DESCRIPTION
9 .00 ±0.10
(4 SIDES)
NOTE:
1. DRAWING CONFORMS TO JEDEC PACKAGE OUTLINE MO-220 VARIATION WNJR-5
2. ALL DIMENSIONS ARE IN MILLIMETERS
3. 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
4. EXPOSED PAD SHALL BE SOLDER PLATED
5. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE TOP AND BOTTOM OF PACKAGE
6. DRAWING NOT TO SCALE
PIN 1 TOP MARK
(SEE NOTE 5)
0.40 ±0.10
6463
1
2
BOTTOM VIEW—EXPOSED PAD
7.15 ±0.10
7.15 ±0.10
7.50 REF
(4-SIDES)
0.75 ±0.05
R = 0.10
TYP
R = 0.115
TYP
0.25 ±0.05
0.50 BSC
0.200 REF
0.00 – 0.05
(UP64) QFN 0406 REV C
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED
0.70 ±0.05
7.50 REF
(4 SIDES)
7.15 ±0.05
7.15 ±0.05
8.10 ±0.05 9.50 ±0.05
0.25 ±0.05
0.50 BSC
PACKAGE OUTLINE
PIN 1
CHAMFER
C = 0.35
UP Package
64-Lead Plastic QFN (9mm w 9mm)
(Reference LTC DWG # 05-08-1705 Rev C)
Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings.
37
21421012fa
LTC2142-12/
LTC2141-12/LTC2140-12
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 representa-
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
REVISION HISTORY
REV DATE DESCRIPTION PAGE NUMBER
A 07/12 Corrected Channel 1 Data Bus (D1_*) Pin Description to state “Channel 1” 16
LTC2142-12/
LTC2141-12/LTC2140-12
38
21421012fa
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com
© LINEAR TECHNOLOGY CORPORATION 2011
LT 0712 REV A • PRINTED IN USA
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PART NUMBER DESCRIPTION COMMENTS
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14-Bit 65Msps/40Msps/25Msps
1.8V Dual ADCs, Ultralow Power
104mW/68mW/48mW, 73dB SNR, 90dB SFDR, DDR LVDS/DDR CMOS/
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RF Mixers/Demodulators
LTC5517 40MHz to 900MHz Direct Conversion
Quadrature Demodulator
High IIP3: 21dBm at 800MHz, Integrated LO Quadrature Generator
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
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Amplifiers/Filters
LTC6412 800MHz, 31dB Range, Analog-Controlled
Variable Gain Amplifier
Continuously Adjustable Gain Control, 35dBm OIP3 at 240MHz, 10dB Noise Figure,
4mm × 4mm QFN-24
LTC6605-7/LTC6605-10/
LTC6605-14
Dual Matched 7MHz/10MHz/14MHz
Filters with ADC Drivers
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TYPICAL APPLICATIONS
CMOS,
DDR CMOS
OR
DDR LVDS
OUTPUTS
1.8V
VDD
1.8V
OVDD
CLOCK
CONTROL
D1_11
D1_0
21421012 TA01a
CH 1
ANALOG
INPUT
OUTPUT
DRIVERS
t
t
t
GND OGND
S/H 12-BIT
ADC CORE
CH 2
ANALOG
INPUT
S/H 12-BIT
ADC CORE
D2_11
D2_0
t
t
t
65MHz
CLOCK FREQUENCY (MHz)
–100
–110
–120
–70
–60
–80
–90
AMPLITUDE (dBFS)
–50
–30
–40
–20
–10
0
21821012 TA01b
F
REQUENCY
Hz)
2
1821012 TA01
b
010 20 30
2-Tone FFT, fIN = 70MHz and 69MHz