LTC1272
12-Bit, 3µs, 250kHz
Sampling A/D Converter
U
FEATURES
DESCRIPTIO
■
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 operation. It uses LTBiCMOSTM switched-capacitor technology to
combine a high speed 12-bit ADC with a fast, accurate
sample-and-hold and a precision reference.
■
■
■
■
■
■
■
■
■
■
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 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 operation, 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 sampleand-hold acquisition time is allowed between conversions.
U
APPLICATIO S
■
■
■
■
High Speed Data Acquisition
Digital Signal Processing (DSP)
Multiplexed Data Acquisition Systems
Single Supply Systems
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.
, 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.
U
TYPICAL APPLICATIO
Single 5V Supply, 3µs, 12-Bit Sampling ADC
10µF
VDD
VREF
+
0.1µF
0
A IN
NC
AGND
+
–20
CS
D10
RD
D9
HBEN
D8
D0/8
D5
D1/9
D4
D2/10
DGND
µP
CONTROL
LINES
D3/11
–60
–80
CLK IN
D6
–40
CLK OUT
D7
S = 72.1
(N+D)
0.1µ F
BUSY
D11 (MSB)
8 OR 12-BIT
PARALLEL
BUS
10 µ F
AMPLITUDE (dB)
2.42V
VREF
OUTPUT
ANALOG INPUT
(0V TO 5V)
1024 Point FFT, fS = 250kHz, fIN = 10kHz
5V
LTC1272
–100
–120
–140
0
20
40
60
80
100
120
FREQUENCY (kHz)
LTC1272 • TA02
LTC1272 • TA01
1272fb
1