Datasheet

10
LTC1446/LTC1446L
TYPICAL APPLICATIONS N
U
An Autoranging 8-Channel ADC with Shutdown
LTC1296
V
CC
50k
74HC04
5V
5V
CS
22µF
µP
CLK
8 ANALOG
INPUT CHANNELS
D
OUT
D
IN
CH0
COM
SSO REF
–
CH7
REF
+
50k
0.1µF
100Ω
100Ω
LTC1446
CS/LD
CLK
D
OUT
D
IN
V
OUT B
GND
V
CC
1446/46L F03
V
OUT A
0.1µF
0.1µF
+
2N3906
This circuit shows how to use one LTC1446 to make an
autoranging ADC. The microprocessor sets the reference
span and the Common pin for the analog input by loading
the appropriate digital code into the LTC1446. V
OUT A
controls the Common pin for the analog inputs to the
LTC1296 and V
OUT B
controls the reference span by setting
the REF
+
pin on the LTC1296. The LTC1296 has a Shut-
down pin that goes low in shutdown mode. This will turn
off the PNP transistor supplying power to the LTC1446.
The resistor and capacitor on the LTC1446 outputs act as
a lowpass filter for noise.