Datasheet

LTC2302/LTC2306
13
23026fa
APPLICATIONS INFORMATION
Figure 1a. Example MUX Confi gurations
Figure 1b. Changing the MUX Assignment “On the Fly”
and Control section). The input data word for the LTC2306
is defi ned as follows:
S/D O/S X X UNI X
S/D = SINGLE-ENDED/DIFFERENTIAL BIT
O/S = ODD/SIGN BIT
UNI = UNIPOLAR/BIPOLAR BIT
X = DON’ T CARE
For the LTC2302, the input data word is defi ned as:
X O/S X X UNI X
Analog Input Multiplexer
The analog input MUX is programmed by the S/D and O/S
bits of the D
IN
word for the LTC2306 and the O/S bit of the
D
IN
word for the LTC2302. Table 1 and Table 2 list MUX
confi gurations for all combinations of the confi guration
bits. Figure 1a shows several possible MUX confi gurations
and Figure 1b shows how the MUX can be reconfi gured
from one conversion to the next.
Driving the Analog Inputs
The analog inputs of the LTC2302/LTC2306 are easy to
drive. Each of the analog inputs of the LTC2306 (CH0
and CH1) can be used as a single-ended input relative
to GND or as a differential pair. The analog inputs of the
LTC2302 (IN
+
, IN
–
) are always confi gured as a differential
pair. Regardless of the MUX confi guration, the “+” and “–”
inputs are sampled at the same instant. Any unwanted
signal that is common to both inputs will be reduced by
the common mode rejection of the sample-and-hold cir-
cuit. The inputs draw only one small current spike while
CH0
CH1
(–) GND
2 Single-Ended
+
1 Differential
+ (
–
)
+
LTC2306 LTC2306
23026 F01a
–
(
+
)
{
CH0
CH1
1 Differential
+ (
–
)
LTC2302
–
(
+
)
{
IN
+
IN
–
CH0
CH1
(–) GND
LTC2306
2nd Conversion
+
1st Conversion
+
+
23026 F01b
–
{
CH0
CH1
LTC2306
S/D
0
0
1
1
O/S
0
1
0
1
CH0
+
–
+
CH1
–
+
+
WITH RESPECT
TO GND
NOTE: UNIPOLAR MODE SHOULD BE USED
FOR SINGLE-ENDED OPERATION, SINCE INPUT
SIGNALS ARE ALWAYS REFERENCED TO GND
Table 1. Channel Configuration
for the LTC2306
O/S
0
1
IN
+
+
–
IN
–
–
+
Table 2. Channel Configuration
for the LTC2302