LTC1748
14-Bit, 80Msps Low Noise ADC
FEATURES
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DESCRIPTIO
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Sample Rate: 80Msps
76.3dB SNR and 90dB SFDR (3.2V Range)
72.6dB SNR and 90dB SFDR (2V Range)
No Missing Codes
Single 5V Supply
Power Dissipation: 1.4W
Selectable Input Ranges:
±1V
or
±1.6V
240MHz Full Power Bandwidth S/H
Pin Compatible Family
25Msps: LTC1746 (14-Bit), LTC1745 (12-Bit)
50Msps: LTC1744 (14-Bit), LTC1743 (12-Bit)
65Msps: LTC1742 (14-Bit), LTC1741 (12-Bit)
80Msps: LTC1748 (14-Bit), LTC1747 (12-Bit)
48-Pin TSSOP Package
The LTC
®
1748 is an 80Msps, sampling 14-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 LTC1748’s input range to be optimized for a wide
variety of applications.
The LTC1748 is perfect for demanding communications
applications with AC performance that includes 76.3dB
SNR and 90dB spurious free dynamic range. Ultralow jitter
of 0.15ps
RMS
allows undersampling of IF frequencies with
excellent noise performance. DC specs include
±3LSB
INL
and no missing codes.
The digital interface is compatible with 5V, 3V, 2V and
LVDS logic systems. The ENC and ENC inputs may be
driven differentially 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 output power supply can be operated from 0.5V
to 5V, making it easy to connect directly to any low voltage
DSPs or FIFOs.
The TSSOP package with a flow-through pinout simplifies
the board layout.
APPLICATIO S
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Telecommunications
Receivers
Cellular Base Stations
Spectrum Analysis
Imaging Systems
, LTC and LT are registered trademarks of Linear Technology Corporation.
BLOCK DIAGRA
A
IN+
±1V
DIFFERENTIAL
ANALOG INPUT
80Msps, 14-Bit ADC with a 2V Differential Input Range
OV
DD
0.1µF
OF
D13
D0
CLKOUT
0.5V
TO 5V
0.1µF
CORRECTION
LOGIC AND
SHIFT
REGISTER
14
A
IN–
S/H
AMP
14-BIT
PIPELINED ADC
SENSE
BUFFER
RANGE
SELECT
DIFF AMP
1µF
GND
CONTROL LOGIC
1748 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
5V
1µF
MSBINV
OE
W
U
1748fa
1
LTC1748
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
D13
D12
D11
OV
DD
D10
D9
D8
D7
OGND
GND
GND
D6
D5
D4
OV
DD
D3
D2
D1
D0
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
LTC1748C ............................................... 0°C to 70°C
LTC1748I ............................................ – 40°C to 85°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
ORDER PART
NUMBER
LTC1748CFW
LTC1748IFW
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
Offset Tempco
Input Referred Noise (Transition Noise)
The
q
indicates specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. (Note 5)
CONDITIONS
q
(Note 6)
q
(Note 7)
External Reference (SENSE = 1.6V)
Internal Reference
External Reference (SENSE = 1.6V)
SENSE = 1.6V
MIN
14
–3
–1
– 35
– 3.5
TYP
±0.75
±0.5
±8
±1
±40
±20
±20
0.82
MAX
3
1.5
35
3.5
UNITS
Bits
LSB
LSB
mV
%FS
ppm/°C
ppm/°C
µV/°C
LSB
RMS
A ALOG I PUT
SYMBOL
V
IN
I
IN
C
IN
t
ACQ
t
AP
t
JITTER
CMRR
The
q
indicates specifications which apply over the full operating temperature range, otherwise
specifications are at T
A
= 25°C. (Note 5)
PARAMETER
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
CONDITIONS
4.75V
≤
V
DD
≤
5.25V
0 < A
IN+
, A
IN–
< V
DD
Sample Mode ENC < ENC
Hold Mode ENC > ENC
MIN
q
q
TYP
±1
to
±1.6
8
4
5
0
0.15
80
MAX
1
–1
q
6
1.5V < (A
IN–
= A
IN+
) < 3V
UNITS
V
µA
pF
pF
ns
ns
ps
RMS
dB
1748fa
2
U
W
U
U
W W
W
U
U
U
LTC1748
DY A IC ACCURACY
SYMBOL
SNR
PARAMETER
Signal-to-Noise Ratio
SFDR
S/(N + D)
THD
IMD
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
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)
140MHz Input Signal (2V Range)
250MHz Input Signal (2V Range)
MIN
75
74
TYP
72.6
76.3
72.5
76.1
72.2
75.4
71.4
68.9
90
90
94
90
80
85
88
94
85
76
94
77
93
64
89
74.5
72.4
76.0
72.3
75.6
71
71
–90
–90
–90
–85
–78
–74
97
93
240
MAX
UNITS
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dBc
dBc
MHz
Spurious Free Dynamic Range
5MHz Input Signal (2V Range)
5MHz Input Signal (3.2V Range) (2nd and 3rd)
5MHz Input Signal (3.2V Range) (Other)
30MHz Input Signal (2V Range)
30MHz Input Signal (3.2V Range) (2nd and 3rd)
30MHz Input Signal (3.2V Range) (Other)
70MHz Input Signal (2V Range)
70MHz Input Signal (3.2V Range) (2nd and 3rd)
70MHz Input Signal (3.2V Range) (Other)
140MHz Input Signal (2VRange) (2nd and 3rd)
140MHz Input Signal (2V Range) (Other)
250MHz Input Signal (2V Range) (2nd and 3rd)
250MHz Input Signal (2V Range) (Other)
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)
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)
Intermodulation Distortion
Sample-and-Hold Bandwidth
f
IN1
= 2.52MHz, f
IN2
= 5.2MHz (2V Range)
f
IN1
= 2.52MHz, f
IN2
= 5.2MHz (3.2V Range)
R
SOURCE
= 50Ω
U
(Note 5)
MIN
2.30
TYP
2.35
±30
3
4
MAX
2.40
UNITS
V
ppm/°C
mV/V
Ω
1748fa
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LTC1748
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 D13 to D0
Hi-Z Output Capacitance D13 to D0
Output Source Current
Output Sink Current
CONDITIONS
V
DD
= 5.25V, MSBINV and OE
V
DD
= 4.75V, MSBINV and OE
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
4.74
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
q
q
0.5
MIN
4.75
280
1.4
TYP
MAX
5.25
310
1.55
V
DD
UNITS
V
mA
W
V
TI I G CHARACTERISTICS
SYMBOL
t
0
t
1
t
2
t
3
t
4
t
5
t
6
t
7
t
8
t
9
t
10
t
11
t
12
PARAMETER
ENC Period
ENC High
ENC Low
Aperture Delay
ENC to CLKOUT Falling
ENC to CLKOUT Rising
For 80Msps 50% Duty Cycle
ENC to DATA Delay
ENC to DATA Delay (Hold Time)
ENC to DATA Delay (Setup Time)
For 80Msps 50% Duty Cycle
CLKOUT to DATA Delay (Hold Time),
80Msps 50% Duty Cycle
CLKOUT to DATA Delay (Setup Time),
80Msps 50% Duty Cycle
DATA Access Time After OE
BUS Relinquish
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 8)
(Note 8)
(Note 8)
C
L
= 10pF (Note 8)
C
L
= 10pF (Note 8)
C
L
= 10pF (Note 8)
C
L
= 10pF (Note 8)
(Note 8)
C
L
= 10pF (Note 8)
C
L
= 10pF (Note 8)
(Note 8)
C
L
= 10pF (Note 8)
C
L
= 10pF (Note 8)
(Note 8)
q
q
q
5.3
6
2.1
10
10
5
25
25
q
q
q
7.25
2
1.4
q
1
q
q
q
MIN
12.5
6
6
0
2.4
t
1
+ t
4
8.65
4.9
3.4
t
0
– t
6
7.6
10.5
10.25
7.2
4.7
4
TYP
MAX
2000
1000
1000
UNITS
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
cycles
1748fa
4
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U
U
UW
LTC1748
ELECTRICAL CHARACTERISTICS
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 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
.
Note 5:
V
DD
= 5V, f
SAMPLE
= 80MHz, differential ENC/ENC = 2V
P-P
80MHz
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 00 0000 0000 0000 and 11
1111 1111 1111.
Note 8:
Guaranteed by design, not subject to test.
Note 9:
Recommended operating conditions.
TYPICAL PERFOR A CE CHARACTERISTICS
INL, 3.2V Range
2.5
2.0
1.5
1.0
T
A
= 25°C
1.0
0.8
0.6
AMPLITUDE (dBFS)
ERROR (LSB)
0.5
0
–0.5
–1.0
–1.5
–2.0
–2.5
0
4096
8192
12288
OUTPUT CODE
16384
1748 G01
ERROR (LSB)
8192 Point FFT,
Input Frequency = 15.068MHz,
–10dB, 3.2V Range
0
T
A
= 25°C
–10
–20
–30
–40
–50
–60
–70
–80
–90
–100
–110
–120
0
5
10
15 20 25 30
FREQUENCY (MHz)
35
40
AMPLITUDE (dBFS)
AMPLITUDE (dBFS)
–50
–60
–70
–80
–90
–100
–110
–120
0
5
10
15 20 25 30
FREQUENCY (MHz)
35
40
AMPLITUDE (dBFS)
U W
1748 G04
DNL, 3.2V Range
T
A
= 25°C
8192 Point FFT,
Input Frequency = 15.068MHz,
–1dB, 3.2V Range
0
T
A
= 25°C
–10
–20
–30
–40
–50
–60
–70
–80
–90
–100
–110
–120
0.4
0.2
0
–0.2
–0.4
–0.6
–0.8
–1.0
0
4096
12288
8192
OUTPUT CODE
16384
1748 G02
0
5
10
15 20 25 30
FREQUENCY (MHz)
35
40
1748 G03
8192 Point FFT,
Input Frequency = 15.068MHz,
–20dB, 3.2V Range
0
T
A
= 25°C
–10
–20
–30
–40
8192 Point FFT,
Input Frequency = 30.068MHz,
–1dB, 3.2V Range
0
T
A
= 25°C
–10
–20
–30
–40
–50
–60
–70
–80
–90
–100
–110
–120
0
5
10
15 20 25 30
FREQUENCY (MHz)
35
40
1748 G05
1748 G06
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