LTC1272
12-Bit, 3µs, 250kHz
Sampling A/D Converter
FEATURES
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DESCRIPTIO
AD7572 Pinout
12-Bit Resolution
3µs and 8µs Conversion Times
On-Chip Sample-and-Hold
Up to 250kHz Sample Rates
5V Single Supply Operation
No Negative Supply Required
On-Chip 25ppm/°C Reference
75mW (Typ) Power Consumption
24-Pin Narrow DIP and SOL Packages
ESD Protected on All Pins
The LTC1272 is a 3µs, 12-bit, successive approximation
sampling A/D converter. It has the same pinout as the
industry standard AD7572 and offers faster conversion
time, on-chip sample-and-hold, and single supply opera-
tion. It uses LTBiCMOS
TM
switched-capacitor technology to
combine a high speed 12-bit ADC with a fast, accurate
sample-and-hold and a precision reference.
The LTC1272 operates with a single 5V supply but can also
accept the 5V/–15V supplies required by the AD7572 (Pin
23, the negative supply pin of the AD7572, is not connected
on the LTC1272). The LTC1272 has the same 0V to 5V input
range as the AD7572 but, to achieve single supply opera-
tion, it provides a 2.42V reference output instead of the
– 5.25V of the AD7572. It plugs in for the AD7572 if the
reference capacitor polarity is reversed and a 1µs sample-
and-hold acquisition time is allowed between conversions.
The output data can be read as a 12-bit word or as two
8-bit bytes. This allows easy interface to both 8-bit and
higher processors. The LTC1272 can be used with a
crystal or an external clock and comes in speed grades of
3ms and 8ms.
APPLICATIO S
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High Speed Data Acquisition
Digital Signal Processing (DSP)
Multiplexed Data Acquisition Systems
Single Supply Systems
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
LTBiCMOS is a trademark of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
TYPICAL APPLICATIO
LTC1272
2.42V
V
REF
OUTPUT
ANALOG INPUT
(0V TO 5V)
A
IN
V
REF
10µF
AGND
D11 (MSB)
D10
D9
D8
D7
8 OR 12-BIT
PARALLEL
BUS
D6
D5
D4
DGND
Single 5V Supply, 3µs, 12-Bit Sampling ADC
5V
1024 Point FFT, f
S
= 250kHz, f
IN
= 10kHz
0
V
DD
NC
BUSY
CS
RD
HBEN
CLK OUT
CLK IN
D0/8
D1/9
D2/10
D3/11
10
µ
F
+
0.1µF
+
–20
0.1
µ
F
–40
µ
P
CONTROL
LINES
AMPLITUDE (dB)
–60
–80
–100
–120
–140
0
20
40
60
80
100
120
LTC1272 • TA02
LTC1272 • TA01
U
S = 72.1
(N+D)
FREQUENCY (kHz)
1272fb
U
U
1
LINER [ LINEAR TECHNOLOGY ]
