LTC1285/LTC1288
3V Micropower Sampling
12-Bit A/D Converters in
SO-8 Packages
U
DESCRIPTION
FEATURES
TheLTC®1285/LTC1288are3Vmicropower, 12-bit, suc-
cessive approximation sampling A/D converters. They
typically draw only 160µA of supply current when con-
verting and automatically power down to a typical supply
currentof1nAwhenevertheyarenotperformingconver-
sions. They are packaged in 8-pin SO packages and
operate on 3V to 6V supplies. These 12-bit, switched-
capacitor, successive approximation ADCs include
sample-and-holds. The LTC1285 has a single differential
analog input. The LTC1288 offers a software selectable
2-channel MUX.
■
12-Bit Resolution
■
8-Pin SO Plastic Package
■
Low Cost
■
Low Supply Current: 160µA Typ
■
Auto Shutdown to 1nA Typ
■
Guaranteed ±3/4LSB Max DNL
■
Single Supply 3V to 6V Operation
■
Differential Inputs (LTC1285)
■
2-Channel MUX (LTC1288)
■
On-Chip Sample-and-Hold
■
100µs Conversion Time
■
Sampling Rates:
On-chip serial ports allow efficient data transfer to a wide
rangeofmicroprocessorsandmicrocontrollersoverthree
wires.This,coupledwithmicropowerconsumption,makes
remote location possible and facilitates transmitting data
through isolation barriers.
7.5ksps (LTC1285)
6.6ksps (LTC1288)
■
I/O Compatible withU SPI, Microwire, etc.
APPLICATIONS
These circuits can be used in ratiometric applications or
with an external reference. The high impedance analog
inputs and the ability to operate with reduced spans (to
1.5V full scale) allow direct connection to sensors and
transducersinmanyapplications, eliminatingtheneedfor
gain stages.
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Pen Screen Digitizing
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Battery-Operated Systems
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Remote Data Acquisition
■
Isolated Data Acquisition
Battery Monitoring
■
■
Temperature Measurement
, LTC and LT are registered trademarks of Linear Technology Corporation.
U
TYPICAL APPLICATIONS N
12µW, S0-8 Package, 12-Bit ADC
Supply Current vs Sample Rate
Samples at 200Hz and Runs Off a 3V Supply
1000
T
= 25°C
A
V
V
= 2.7V
CC
REF
CLK
1µF
3V
= 2.5V
f
= 120kHz
100
10
1
MPU
(e.g., 8051)
1
2
3
4
8
V
V
P1.4
P1.3
P1.2
REF
CC
7
6
5
+IN
CLK
ANALOG INPUT
0V TO 3V RANGE
LTC1285
–IN
D
OUT
SERIAL DATA LINK
GND
CS/SHDN
LTC1285/88 • TA01
0.1
1
10
100
SAMPLE FREQUENCY (kHz)
LTC1285/88 • TA02
1