designed for digitizing high frequency, wide dynamic range
signals. They are perfect for demanding communications
applications with AC performance that includes 68.5dB
SNR and 90dB spurious free dynamic range (SFDR). The
1.25GHz input bandwidth allows the ADC to achieve high
undersampling ratio with very low attenuation. The latency
is only six clock cycles.
DC specs include ±0.26LSB INL (typ), ±0.16LSB DNL (typ)
and no missing codes over temperature. The transition
noise is 0.54LSB
RMS
.
The digital outputs are double data rate (DDR) LVDS.
The ENC
+
and ENC
–
inputs can be driven differentially with
a sine wave, PECL, LVDS, TTL, or CMOS inputs. An optional
clock duty cycle stabilizer allows 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.
68.5dB SNR
90dB SFDR
Low Power: 628mW/592mW/545mW Total
Single 1.8V Supply
DDR LVDS Outputs
Easy-to-Drive 1.5V
P-P
Input Range
1.25GHz Full-Power Bandwidth S/H
Optional Clock Duty Cycle Stabilizer
Low Power Sleep and Nap Modes
Serial SPI Port for Configuration
Pin Compatible 14-Bit Versions
64-Lead (9mm × 9mm) QFN Package
APPLICATIONS
n
n
n
n
n
n
Communications
Cellular Basestations
Software Defined Radios
Medical Imaging
High Definition Video
Testing and Measurement Instruments
TYPICAL APPLICATION
V
DD
CHANNEL A
ANALOG
INPUT
12-BIT
PIPELINED
ADC CORE
CORRECTION
LOGIC
OUTPUT
DRIVERS
OV
DD
DA10_11
•
•
•
DA0_1
LTC2157-12: 32K Points 2-Tone FFT,
f
IN
= 71MHZ and 69MHz, 250Msps
DDR
LVDS
0
–20
AMPLITUDE (dBFS)
DDR
LVDS
–40
–60
–80
S/H
CLOCK
CLOCK/DUTY
CYCLE
CONTROL
OGND
CHANNEL B
OV
DD
ANALOG
INPUT
S/H
12-BIT
PIPELINED
ADC CORE
GND
CORRECTION
LOGIC
OUTPUT
DRIVERS
DB10_11
•
•
•
DB0_1
–100
–120
0
20
40
60
80
100
FREQUENCY (MHz)
120
21576512 TA01
OGND
21576512 G11
21576512fb
For more information
www.linear.com/LTC2157-12
1
LTC2157-12/
LTC2156-12/LTC2155-12
ABSOLUTE MAXIMUM RATINGS
(Notes 1, 2)
PIN CONFIGURATION
TOP VIEW
V
DD
PAR/SER
CS
SCK
SDI
SDO
GND
DA10_11
+
DA10_11
–
DA8_9
+
DA8_9
–
DA6_7
+
DA6_7
–
DA4_5
+
DA4_5
–
OV
DD
64
63
62
61
60
59
58
57
56
55
54
53
52
51
50
49
48
47
46
45
44
43
42
41
40
39
38
37
36
35
34
33
Supply Voltage
V
DD
, OV
DD
................................................ –0.3V to 2V
Analog Input Voltage
A
INA/B+
, A
INA/B –
, PAR/SER,
SENSE (Note 3)........................ –0.3V to (V
DD
+ 0.2V)
Digital Input Voltage
ENC
+
, ENC
–
(Note 3) ................ –0.3V to (V
DD
+ 0.3V)
CS,
SDI, SCK (Note 4) ........................... –0.3V to 3.9V
SDO (Note 4)............................................. –0.3V to 3.9V
Digital Output Voltage ................ –0.3V to (OV
DD
+ 0.3V)
Operating Temperature Range
LTC2157C, LTC2156C, LTC2155C ............ 0°C to 70°C
LTC2157I, LTC2156I, LTC2155I ............–40°C to 85°C
Storage Temperature Range .................. –65°C to 150°C
V
DD
1
V
DD
2
GND 3
A
INA+
4
A
INA–
5
GND 6
SENSE 7
V
REF
8
GND 9
V
CM
10
GND 11
A
INB–
12
A
INB+
13
GND 14
V
DD
15
V
DD
16
65
GND
OGND
DA2_3
+
DA2_3
–
DA0_1
+
DA0_1
–
NC
NC
CLKOUT
+
CLKOUT
–
DB10_11
+
DB10_11
–
DB8_9
+
DB8_9
–
DB6_7
+
DB6_7
–
OGND
UP PACKAGE
64-LEAD (9mm
×
9mm) PLASTIC QFN
T
JMAX
= 150°C,
θ
JA
= 20°C/W
EXPOSED PAD (PIN 65) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
LTC2157CUP-12#PBF
LTC2157IUP-12#PBF
LTC2156CUP-12#PBF
LTC2156IUP-12#PBF
LTC2155CUP-12#PBF
LTC2155IUP-12#PBF
TAPE AND REEL
LTC2157CUP-12#TRPBF
LTC2157IUP-12#TRPBF
LTC2156CUP-12#TRPBF
LTC2156IUP-12#TRPBF
LTC2155CUP-12#TRPBF
LTC2155IUP-12#TRPBF
PART MARKING*
LTC2157UP-12
LTC2157UP-12
LTC2156UP-12
LTC2156UP-12
LTC2155UP-12
LTC2155UP-12
PACKAGE DESCRIPTION
64-Lead (9mm × 9mm) Plastic QFN
64-Lead (9mm × 9mm) Plastic QFN
64-Lead (9mm × 9mm) Plastic QFN
64-Lead (9mm × 9mm) Plastic QFN
64-Lead (9mm × 9mm) Plastic QFN
64-Lead (9mm × 9mm) Plastic QFN
TEMPERATURE RANGE
0°C to 70°C
–40°C to 85°C
0°C to 70°C
–40°C to 85°C
0°C to 70°C
–40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
For more information on lead free part marking, go to:
http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to:
http://www.linear.com/tapeandreel/
V
DD
GND
ENC
+
ENC
–
GND
OF
–
OF
+
NC
NC
DB0_1
–
DB0_1
+
DB2_3
–
DB2_3
+
DB4_5
–
DB4_5
+
OV
DD
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
21576512fb
2
For more information
www.linear.com/LTC2157-12
LTC2157-12/
LTC2156-12/LTC2155-12
CONVERTER CHARACTERISTICS
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. (Note 5)
CONDITIONS
l
PARAMETER
Resolution (No Missing Codes)
Integral Linearity Error
Differential Linearity Error
Offset Error
Gain Error
Offset Drift
Full-Scale Drift
Transition Noise
LTC2157-12
MIN
TYP MAX
12
–2.3
–0.6
–13
–4
±0.26
±0.16
±5
±1
±20
±30
±10
0.54
2.3
0.8
13
2.2
LTC2156-12
MIN
TYP MAX
12
–2.2
–0.6
–13
–4
±0.30
±0.16
±5
±1
±20
±30
±10
0.54
2.2
0.6
13
2.2
LTC2155-12
MIN
TYP MAX
12
–1.9
–0.6
–13
–4
±0.30
±0.16
±5
±1
±20
±30
±10
0.54
1.9
0.6
13
2.2
UNITS
Bits
LSB
LSB
mV
%FS
µV/°C
ppm/°C
ppm/°C
LSB
RMS
Differential Analog Input (Note 6)
l
Differential Analog Input
(Note 7)
External Reference
Internal Reference
External Reference
l
l
l
ANALOG INPUT
SYMBOL PARAMETER
V
IN
V
IN(CM)
V
SENSE
I
IN1
I
IN2
I
IN3
t
AP
t
JITTER
CMRR
BW-3B
The
l
denotes the specifications which apply over the full operating temperature range, otherwise
specifications are at T
A
= 25°C. (Note 5)
CONDITIONS
1.7V < V
DD
< 1.9V
Differential Analog Input (Note 8)
0 < A
IN+
, A
IN–
< V
DD
, No Encode
0 < PAR/SER < V
DD
1.2V < SENSE < 1.3V
l
l
l
l
l
l
MIN
V
CM
– 20mV
1.200
–1
–1
–1
TYP
1.5
V
CM
1.250
MAX
V
CM
+ 20mV
1.300
1
1
1
UNITS
V
P-P
V
V
µA
µA
µA
ns
ps
RMS
dB
MHz
Analog Input Range (A
IN+
– A
IN–
)
Analog Input Common Mode (A
IN+
+ A
IN–
)/2
Analog Input Leakage Current
PAR/SER Input Leakage Current
SENSE Input Leakage Current
Sample-and-Hold Acquisition Delay Time
Sample-and-Hold Acquisition Delay Jitter
Analog Input Common Mode Rejection Ratio
Full-Power Bandwidth
External Voltage Reference Applied to SENSE External Reference Mode
1
0.15
75
1250
The
l
denotes the specifications which apply over the full operating temperature range,
otherwise specifications are at T
A
= 25°C. A
IN
= –1dBFS. (Note 5)
SYMBOL
SNR
PARAMETER
Signal-to-Noise Ratio
CONDITIONS
15MHz Input
70MHz Input
140MHz Input
LTC2157-12
MIN
TYP MAX
68.5
68.4
68.0
90.6
88
80
98
95
85
68.4
68.3
67.7
–95
LTC2156-12
MIN
TYP MAX
68.5
68.3
67.9
90.1
89
81
98
95
87
68.4
68.3
67.7
–95
LTC2155-12
MIN
TYP MAX
68.5
68.3
67.8
90
88
80
98
95
88
68.4
68.3
67.7
–95
UNITS
dBFS
dBFS
dBFS
dBFS
dBFS
dBFS
dBFS
dBFS
dBFS
dBFS
dBFS
dBFS
dB
DYNAMIC ACCURACY
l
66.9
67.3
67.4
SFDR
Spurious Free Dynamic Range 15MHz Input
2nd or 3rd Harmonic
70MHz Input
140MHz Input
Spurious Free Dynamic Range 15MHz Input
4th Harmonic or Higher
70MHz Input
140MHz Input
l
71
74
75
l
81
82
83
S/(N+D)
Signal-to-Noise Plus
Distortion Ratio
Crosstalk Between Channels
15MHz Input
70MHz Input
140MHz Input
Up to 315MHz Input
l
66.1
66.7
66.8
Crosstalk
21576512fb
For more information
www.linear.com/LTC2157-12
3
LTC2157-12/
LTC2156-12/LTC2155-12
INTERNAL REFERENCE CHARACTERISTICS
PARAMETER
V
CM
Output Voltage
V
CM
Output Temperature Drift
V
CM
Output Resistance
V
REF
Output Voltage
V
REF
Output Temperature Drift
V
REF
Output Resistance
V
REF
Line Regulation
–400µA < I
OUT
< 1mA
1.7V < V
DD
< 1.9V
–1mA < I
OUT
< 1mA
I
OUT
= 0
1.225
CONDITIONS
I
OUT
= 0
The
l
denotes the specifications which apply over the
full operating temperature range, otherwise specifications are at T
A
= 25°C. (Note 5)
MIN
0.435 • V
DD
– 18mV
TYP
0.435 • V
DD
±37
4
1.250
±30
7
0.6
1.275
MAX
0.435 • V
DD
+ 18mV
UNITS
V
ppm/°C
Ω
V
ppm/°C
Ω
mV/V
POWER REQUIREMENTS
SYMBOL PARAMETER
V
DD
OV
DD
I
VDD
I
OVDD
P
DISS
P
SLEEP
P
NAP
Analog Supply Voltage
Output Supply Voltage
Analog Supply Current
Digital Supply Current
Power Dissipation
Sleep Mode Power
Nap Mode Power
CONDITIONS
(Note 9)
(Note 9)
The
l
denotes the specifications which apply over the full operating temperature
range, otherwise specifications are at T
A
= 25°C. (Note 5)
LTC2157-12
MIN
TYP MAX
l
l
l
LTC2156-12
MIN
TYP MAX
1.7
1.7
1.8
1.8
291
38
66
592
643
<5
<5
168
1.9
1.9
320
45
75
657
711
LTC2155-12
MIN
TYP MAX
1.7
1.7
1.8
1.8
266
37
65
545
596
<5
<5
154
1.9
1.9
295
42
74
607
665
UNITS
V
V
mA
mA
mA
mW
mW
mW
mW
mW
1.7
1.7
1.8
1.8
309
40
68
628
679
<5
<5
181
1.9
1.9
345
46
76
704
758
1.75mA LVDS Mode
3.5mA LVDS Mode
1.75mA LVDS Mode
3.5mA LVDS Mode
Clock Disabled
Clocked at f
S(MAX)
Clocked at f
S(MAX)
l
l
l
l
DIGITAL INPUTS AND OUTPUTS
SYMBOL PARAMETER
ENCODE INPUTS (ENC
+
, ENC
–
)
V
ID
V
ICM
R
IN
C
IN
V
IH
V
IL
I
IN
C
IN
R
OL
I
OH
C
OUT
Differential Input Voltage
Common Mode Input Voltage
Input Resistance
Input Capacitance
High Level Input Voltage
Low Level Input Voltage
Input Current
Input Capacitance
Logic Low Output Resistance to GND
Logic High Output Leakage Current
Output Capacitance
(Note 8)
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. (Note 5)
CONDITIONS
l
l
MIN
0.2
1.1
TYP
MAX
UNITS
V
Internally Set
Externally Set (Note 8)
(See Figure 2)
(Note 8)
V
DD
= 1.8V
V
DD
= 1.8V
V
IN
= 0V to 3.6V
(Note 8)
V
DD
= 1.8V, SDO = 0V
SDO = 0V to 3.6V
(Note 8)
1.2
10
2
1.5
V
V
kΩ
pF
V
DIGITAL INPUTS (CS, SDI, SCK)
l
l
l
1.3
0.6
–10
3
200
10
V
µA
pF
Ω
SDO OUTPUT (Open-Drain Output. Requires 2k Pull-Up Resistor if SDO Is Used)
l
–10
4
10
µA
pF
21576512fb
4
For more information
www.linear.com/LTC2157-12
LTC2157-12/
LTC2156-12/LTC2155-12
DIGITAL INPUTS AND OUTPUTS
SYMBOL PARAMETER
DIGITAL DATA OUTPUTS
V
OD
V
OS
R
TERM
Differential Output Voltage
Common Mode Output Voltage
On-Chip Termination Resistance
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. (Note 5)
CONDITIONS
100Ω Differential Load, 3.5mA Mode
100Ω Differential Load, 1.75mA Mode
100Ω Differential Load, 3.5mA Mode
100Ω Differential Load, 1.75mA Mode
Termination Enabled, OV
DD
= 1.8V
l
l
l
l
MIN
247
125
1.125
1.125
TYP
350
175
1.250
1.250
100
MAX
454
250
1.375
1.375
UNITS
mV
mV
V
V
Ω
TIMING CHARACTERISTICS
SYMBOL
f
S
t
L
t
H
PARAMETER
Sampling Frequency
ENC Low Time (Note 8)
ENC High Time (Note 8)
The
l
denotes the specifications which apply over the full operating temperature
range, otherwise specifications are at T
A
= 25°C. (Note 5)
CONDITIONS
(Note 9)
Duty Cycle Stabilizer Off
Duty Cycle Stabilizer On
Duty Cycle Stabilizer Off
Duty Cycle Stabilizer On
MIN
10
1.9
1.5
1.9
1.5
LTC2157-12
TYP MAX
250
2
50
2
50
2
50
2
50
MIN
10
2.26
1.5
2.26
1.5
LTC2156-12
TYP MAX
210
2.38
50
2.38
50
2.38
50
2.38
50
LTC2155-12
MIN
TYP MAX
10
170
2.79 2.94
50
1.5
2.94
50
2.79 2.94
50
1.5
2.94
50
UNITS
MHz
ns
ns
ns
ns
l
l
l
l
l
DIGITAL DATA OUTPUTS
LTC215X-12
SYMBOL
t
D
t
C
t
SKEW
PARAMETER
ENC to Data Delay
ENC to CLKOUT Delay
DATA to CLKOUT Skew
Pipeline Latency
SPI Port Timing (Note 8)
t
SCK
t
S
t
H
t
DS
t
DH
t
DO
SCK Period
CS
to SCK Set-Up Time
SCK to
CS
Hold Time
SDI Set-Up Time
SDI Hold Time
SCK Falling to SDO Valid
Readback Mode, C
SDO
= 20pF R
PULLUP
= 2k
,
Write Mode
Readback Mode C
SDO
= 20pF R
PULLUP
= 2k
,
l
l
l
l
l
l
l
CONDITIONS
C
L
= 5pF (Note 8)
C
L
= 5pF (Note 8)
t
D
– t
C
(Note 8)
MIN
l
l
l
TYP
2
1.6
0.4
MAX
2.3
2
0.55
6
UNITS
ns
ns
ns
Cycles
ns
ns
ns
ns
ns
ns
1.7
1.3
0.3
6
40
250
5
5
5
5
125
ns
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 V
DD
, they
will be clamped by internal diodes. This product can handle input currents
of greater than 100mA below GND or above V
DD
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 V
DD
they will not be clamped by internal diodes. This product can handle input
currents of greater than 100mA below GND without latchup.
Note 5:
V
DD
= OV
DD
= 1.8V, f
SAMPLE
= 250MHz (LTC2157),
210MHz (LTC2156), or 170MHz (LTC2155), differential ENC
+
/ENC
–
= 2V
P-P
sine wave, input range = 1.5V
P-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 –0.5LSB when the
output code flickers between 0000 0000 0000 and 1111 1111 1111 in 2’s
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