LTC1745
Low Noise,12-Bit, 25Msps ADC
FEATURES
s
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DESCRIPTIO
Sample Rate: 25Msps
72.5dB SNR and 91dB SFDR (3.2V Range)
71dB SNR and 96dB SFDR (2V Range)
No Missing Codes
Single 5V Supply
Low Power Dissipation: 380mW
Selectable Input Ranges:
±1V
or
±1.6V
240MHz Full Power Bandwidth S/H
Pin Compatible Family
25 Msps: LTC1746 (14-Bit), LTC1745 (12-Bit)
50 Msps: LTC1744 (14-Bit), LTC1743 (12-Bit)
65 Msps: LTC1742 (14-Bit), LTC1741 (12-Bit)
80 Msps: LTC1748 (14-Bit), LTC1747 (12-Bit)
The LTC
®
1745 is a 25Msps, sampling 12-bit A/D con-
verter designed for digitizing high frequency, wide dy-
namic range signals. Pin selectable input ranges of
±1V
and
±1.6V
along with a resistor programmable mode
allow the LTC1745’s input range to be optimized for a wide
variety of applications.
The LTC1745 is perfect for demanding communications
applications with AC performance that includes 72.5dB
SNR and 91dB spurious free dynamic range. Ultralow jitter
of 0.3ps
RMS
allows undersampling with excellent noise
performance. DC specs include
±1LSB
INL maximum and
±0.75LSB
DNL over temperature.
The digital interface is compatible with 5V, 3V and 2V logic
systems. The ENC and ENC inputs may be driven differen-
tially from PECL, GTL and other low swing logic families or
from single-ended TTL or CMOS. The low noise, high gain
ENC and ENC inputs may also be driven by a sinusoidal
signal without degrading performance. A separate digital
output power supply can be operated from 0.5V to 5V,
making it easy to connect directly to low voltage DSPs
or FIFOs.
The TSSOP package with a flow-through pinout simplifies
the board layout.
APPLICATIO S
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Telecommunications
Medical Imaging
Receivers
Base Stations
Spectrum Analysis
Imaging Systems
, LTC and LT are registered trademarks of Linear Technology Corporation.
BLOCK DIAGRA
A
IN
±1V
DIFFERENTIAL
ANALOG INPUT
+
25Msps, 12-Bit ADC with a
±1V
Differential Input Range
OV
DD
OF
D11
D0
CLKOUT
0.1µF
0.5V TO 5V
0.1µF
A
IN–
S/H
AMP
12-BIT
PIPELINED ADC
12
SENSE
BUFFER
RANGE
SELECT
DIFF AMP
GND
CONTROL LOGIC
1745 BD
V
CM
4.7µF
2.35V
REF
REFLB
0.1µF
1µF
REFHA
4.7µF
REFLA
REFHB
ENC
ENC
0.1µF
1µF
DIFFERENTIAL
ENCODE INPUT
U
OUTPUT
LATCHES
•
•
•
OGND
V
DD
1µF
1µF
1µF
5V
MSBINV
OE
W
U
1745f
1
LTC1745
ABSOLUTE
MAXIMUM
RATINGS
OV
DD
= V
DD
(Notes 1, 2)
PACKAGE/ORDER INFORMATION
TOP VIEW
SENSE
V
CM
GND
A
IN+
A
IN–
GND
V
DD
V
DD
GND
REFLB
REFHA
GND
GND
REFLA
REFHB
GND
V
DD
V
DD
GND
V
DD
GND
MSBINV
ENC
ENC
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
FW PACKAGE
48-LEAD PLASTIC TSSOP
48
47
46
45
44
43
42
41
40
39
38
37
36
35
34
33
32
31
30
29
28
27
26
25
OF
OGND
D11
D10
D9
OV
DD
D8
D7
D6
D5
OGND
GND
GND
D4
D3
D2
OV
DD
D1
D0
NC
NC
OGND
CLKOUT
OE
Supply Voltage (V
DD
) ............................................. 5.5V
Analog Input Voltage (Note 3) .... – 0.3V to (V
DD
+ 0.3V)
Digital Input Voltage (Note 4) ..... – 0.3V to (V
DD
+ 0.3V)
Digital Output Voltage ................. – 0.3V to (V
DD
+ 0.3V)
OGND Voltage ..............................................– 0.3V to 1V
Power Dissipation ............................................ 2000mW
Operating Temperature Range
LTC1745C ............................................... 0°C to 70°C
LTC1745I ............................................ – 40°C to 85°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
ORDER PART
NUMBER
LTC1745CFW
LTC1745IFW
T
JMAX
= 150°C,
θ
JA
= 35°C/W
Consult LTC Marketing for parts specified with wider operating temperature ranges.
CO VERTER CHARACTERISTICS
PARAMETER
Resolution (No Missing Codes)
Integral Linearity Error
Differential Linearity Error
Offset Error
Gain Error
Full-Scale Tempco
The
q
indicates specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. (Note 5)
CONDITIONS
q
MIN
12
–1
–0.75
– 30
– 2.5
q
q
TYP
±0.4
±0.2
±5
±1
±40
MAX
1
0.75
30
2.5
UNITS
Bits
LSB
LSB
mV
%FS
ppm/°C
(Note 6)
(Note 7)
External Reference (SENSE = 1.6V)
I
OUT(REF)
= 0
q
q
A ALOG I PUT
SYMBOL
V
IN
I
IN
C
IN
t
ACQ
t
AP
t
JITTER
CMRR
PARAMETER
The
q
indicates specifications which apply over the full operating temperature range, otherwise
specifications are at T
A
= 25°C. (Note 5)
CONDITIONS
4.75V
≤
V
DD
≤
5.25V
Sample Mode ENC < ENC
Hold Mode ENC > ENC
q
q
q
MIN
–1
TYP
±1
to
±1.6
MAX
1
UNITS
V
µA
pF
pF
Analog Input Range (Note 8)
Analog Input Leakage Current
Analog Input Capacitance
Sample-and-Hold Acquisition Time
Sample-and-Hold Acquisition Delay Time
Sample-and-Hold Acquisition Delay Time Jitter
Analog Input Common Mode Rejection Ratio
8
4
15
0
0.3
18
ps
RMS
dB
1745f
1.0V < (A
IN–
= A
IN+
) < 3.5V
80
2
U
W
U
U
W W
W
U
U
U
ns
ns
LTC1745
DY A IC ACCURACY
SYMBOL
SNR
PARAMETER
Signal-to-Noise Ratio
The
q
indicates specifications which apply over the full operating temperature range,
otherwise specifications are at T
A
= 25°C. A
IN
= –1dBFS. (Note 5)
CONDITIONS
5MHz Input Signal (2V Range)
5MHz Input Signal (3.2V Range)
30MHz Input Signal (2V Range)
30MHz Input Signal (3.2V Range)
70MHz Input Signal (2V Range)
70MHz Input Signal (3.2V Range)
SFDR
Spurious Free Dynamic Range
5MHz Input Signal (2V Range)
5MHz Input Signal (3.2V Range)
30MHz Input Signal (2V Range)
30MHz Input Signal (3.2V Range)
70MHz Input Signal (2V Range)
70MHz Input Signal (3.2V Range)
S/(N + D)
Signal-to-(Noise + Distortion) Ratio
5MHz Input Signal (2V Range)
5MHz Input Signal (3.2V Range)
30MHz Input Signal (2V Range)
30MHz Input Signal (3.2V Range)
70MHz Input Signal (2V Range)
70MHz Input Signal (3.2V Range)
THD
Total Harmonic Distortion
5MHz Input Signal, First 5 Harmonics (2V Range)
5MHz Input Signal, First 5 Harmonics (3.2V Range)
30MHz Input Signal, First 5 Harmonics (2V Range)
30MHz Input Signal, First 5 Harmonics (3.2V Range)
70MHz Input Signal, First 5 Harmonics (2V Range)
70MHz Input Signal, First 5 Harmonics (3.2V Range)
IMD
Intermodulation Distortion
Sample-and-Hold Bandwidth
f
IN1
= 4MHz, f
IN2
= 5.1MHz (2V Range)
f
IN1
= 4MHz, f
IN2
= 5.1MHz (3.2V Range)
R
SOURCE
= 50Ω
q
q
q
I TER AL REFERE CE CHARACTERISTICS
PARAMETER
V
CM
Output Voltage
V
CM
Output Tempco
V
CM
Line Regulation
V
CM
Output Resistance
CONDITIONS
I
OUT
= 0
I
OUT
= 0
4.75V
≤
V
DD
≤
5.25V
1mA
≤ I
OUT
≤
1mA
U
W U
U
MIN
71
TYP
71
72.5
71
72
70
71.5
MAX
UNITS
dBFS
dBFS
dBFS
dBFS
dBFS
dBFS
dB
dB
dB
dB
dB
dB
dBFS
dBFS
dBFS
dBFS
dBFS
dBFS
dB
dB
dB
dB
dB
dB
dBc
dBc
MHz
78
96
91
93.5
87
79
70.5
71
71
72.5
71
72
69.5
68.5
– 92
– 90
– 91.5
– 86.5
–77.5
–70
85
84
240
U
(Note 5)
MIN
2.29
TYP
2.35
±30
3
4
MAX
2.41
UNITS
V
ppm/°C
mV/V
Ω
1745f
3
LTC1745
DIGITAL I PUTS A D DIGITAL OUTPUTS
SYMBOL
V
IH
V
IL
I
IN
C
IN
V
OH
V
OL
I
OZ
C
OZ
I
SOURCE
I
SINK
PARAMETER
High Level Input Voltage
Low Level Input Voltage
Digital Input Current
Digital Input Capacitance
High Level Output Voltage
Low Level Output Voltage
Hi-Z Output Leakage D11 to D0
Hi-Z Output Capacitance D11 to D0
Output Source Current
Output Sink Current
CONDITIONS
V
DD
= 5.25V
V
DD
= 4.75V
V
IN
= 0V to V
DD
MSBINV and OE Only
OV
DD
= 4.75V
OV
DD
= 4.75V
V
OUT
= 0V to V
DD
, OE = High
OE = High (Note 8)
V
OUT
= 0V
V
OUT
= 5V
I
O
= –10µA
I
O
= – 200µA
I
O
= 160µA
I
O
= 1.6mA
q
q
q
q
q
q
q
The
q
indicates specifications which apply over the full
operating temperature range, otherwise specifications are at T
A
= 25°C. (Note 5)
MIN
2.4
0.8
±10
1.5
4.74
4
0.05
0.1
0.4
±10
15
– 50
50
TYP
MAX
UNITS
V
V
µA
pF
V
V
V
V
µA
pF
mA
mA
POWER REQUIRE E TS
SYMBOL
V
DD
I
DD
P
DIS
OV
DD
PARAMETER
Positive Supply Voltage
Positive Supply Current
Power Dissipation
Digital Output Supply Voltage
The
q
indicates specifications which apply over the full operating temperature
range, otherwise specifications are at T
A
= 25°C. (Note 5)
CONDITIONS
2V Range, Full-Scale Input
2V Range, Full-Scale Input
q
q
TI I G CHARACTERISTICS
SYMBOL
f
SAMPLE
t
1
t
2
t
3
t
4
t
5
t
6
t
7
t
8
PARAMETER
Sampling Frequency
ENC Low Time
ENC High Time
Aperture Delay of Sample-and-Hold
ENC to Data Delay
ENC to CLKOUT Delay
CLKOUT to Data Delay
DATA Access Time After OE
↓
BUS Relinquish Time
Data Latency
The
q
indicates specifications which apply over the full operating temperature
range, otherwise specifications are at T
A
= 25°C. (Note 5)
CONDITIONS
(Note 9)
(Note 9)
(Note 9)
C
L
= 10pF (Note 8)
C
L
= 10pF (Note 8)
C
L
= 10pF (Note 8)
C
L
= 10pF (Note 8)
(Note 8)
q
q
q
q
q
q
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2:
All voltage values are with respect to ground with GND
(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. This product can handle input currents of
>100mA below GND without latchup. These pins are not clamped to V
DD
.
4
U W
U
U
MIN
4.75
TYP
76
380
MAX
5.25
91
455
V
DD
UNITS
V
mA
mW
V
0.5
UW
MIN
1
19
19
1.4
0.5
0
TYP
20
20
0
4
2
2
10
10
5
MAX
25
1000
1000
10
5
25
25
UNITS
MHz
ns
ns
ns
ns
ns
ns
ns
ns
cycles
Note 5:
V
DD
= 5V, f
SAMPLE
= 25MHz, differential ENC/ENC = 2V
P-P
25MHz
sine wave, input range =
±1.6V
differential, unless otherwise specified.
Note 6:
Integral nonlinearity is defined as the deviation of a code from a
straight line passing through the actual endpoints of the transfer curve.
The deviation is measured from the center of the quantization band.
Note 7:
Bipolar offset is the offset voltage measured from – 0.5 LSB
when the output code flickers between 0000 0000 0000 and
1111 1111 1111.
Note 8:
Guaranteed by design, not subject to test.
Note 9:
Recommended operating conditions.
1745f
LTC1745
TYPICAL PERFOR A CE CHARACTERISTICS
Typical INL
1.0
0.5
DNL ERROR (LSB)
INL ERROR (LSB)
AMPLITUDE (dB)
0
–0.5
–1.0
0
1000
2000
CODE
3000
4000
1745 G01
Nonaveraged, 32768 Point FFT,
Input Frequency = 5MHz,
2V Range
0
–10
–20
–30
AMPLITUDE (dB)
AMPLITUDE (dB)
–40
–50
–60
–70
–80
–90
–100
–110
–120
0
2
4
8
6
FREQUENCY (MHz)
10
12
1745 G04
–50
–60
–70
–80
–90
–100
–110
–120
0
2
4
8
6
FREQUENCY (MHz)
10
12
1745 G05
AMPLITUDE (dB)
Nonaveraged, 32768 Point FFT,
Input Frequency = 70MHz,
2V Range
0
–10
–20
–30
AMPLITUDE (dB)
AMPLITUDE (dB)
–40
–50
–60
–70
–80
–90
–100
–110
–120
0
2
4
8
6
FREQUENCY (MHz)
10
12
1745 G07
–50
–60
–70
–80
–90
–100
–110
–120
0
2
4
8
6
FREQUENCY (MHz)
10
12
1745 G08
AMPLITUDE (dB)
U W
Typical DNL
1.0
0
–10
–20
Nonaveraged, 32768 Point FFT,
Input Frequency = 5MHz,
3.2V Range
0.5
–30
–40
–50
–60
–70
–80
–90
–100
–110
0
–0.5
–1.0
0
1000
2000
CODE
3000
4000
1745 G02
–120
0
2
4
8
6
FREQUENCY (MHz)
10
12
1745 G03
Nonaveraged, 32768 Point FFT,
Input Frequency = 30MHz,
3.2V Range
0
–10
–20
–30
–40
0
–10
–20
–30
–40
–50
–60
–70
–80
–90
–100
–110
–120
Nonaveraged, 32768 Point FFT,
Input Frequency = 30MHz,
2V Range
0
2
4
8
6
FREQUENCY (MHz)
10
12
1745 G06
Nonaveraged, 32768 Point
2-Tone FFT, Input Frequency =
4MHz and 5.1MHz, 3.2V Range
0
–10
–20
–30
–40
0
–10
–20
–30
–40
–50
–60
–70
–80
–90
–100
–110
–120
Nonaveraged, 32768 Point
2-Tone FFT, Input Frequency =
4MHz and 5.1MHz, 2V Range
0
2
4
8
6
FREQUENCY (MHz)
10
12
1745 G09
1745f
5
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