Datasheet
+IN
-IN
OUT
1
2
6
V
OUT
= Gain(±IN)/50
V
-
1/50
+
±
+IN
-IN
OUT
1
2
6
V
OUT
= ±Gain(±IN)/50
V
-
1/50
+
±
+IN
-IN
OUT
1
2
6
V
OUT
= Gain(+IN)/50
V
-
1/50
+
±
+IN
-IN
OUT
1
2
6
V
OUT
= ±Gain(+IN)/50
V
-
1/50
+
±
+IN
-IN
OUT
1
2
6
V
OUT
= V
REF
+
±
+IN
-IN
OUT
1
2
6
V
OUT
= V
REF
+
±
LMP8358
SNOSB09B –APRIL 2010–REVISED MARCH 2013
www.ti.com
Table 9. Input Multiplexer and Polarity (Register bits 8:6) (continued)
MUX1 MUX0 Diff Input for POL = 0 Diff Input for POL = 1
0 1
1 0
1 1
Polarity Reversal
When MUX[1:0] = 00b and POL = 0b the LMP8358 has the input of a normal instrumentation amplifier. The input
for the LMP8358 is defined as Gain × (V
+IN
− V
−IN
). When POL = 1b, the input for the LMP8358 is defined as
Gain × (V
−IN
– V
+IN
). Polarity reversal can be used to do system level calibration, for example, to compensate for
thermocouple voltages, residual offset of the LMP8358, or offsets of the sensor or ADC.
Short Inputs
When MUX[1:0] = 01b and POL = 0b both inputs are connected to the +IN pin of the LMP8358. The –IN pin is
left floating. When MUX[1:0] = 01b and POL = 1b both inputs are connected to the -IN pin of the LMP8358. The
+IN pin is left floating.
Compare Input to V-
When MUX[1:0] = 10b or 11b one external input of the LMP8358 is floating. The other external input is divided by
50 as shown in Table 9. The internal instrumentation amplifier input that is not connected to the external pin is
connected to V
−
. With a scale factor of 1/50 this gives an overall gain of 0.2x, 0.4x, 1x, 2x, 4x, 10x, or 20x
depending on what the gain is set to with G[2:0] bits as shown in Table 10.
Table 10. Overall Gain using G[2:0], MUX[1:0] and POL
G[2:0] MUX[1:0] Overall System Gain
POL = 0b POL = 1b
000b 10b or 11b 0.2 −0.2
001b 10b or 11b 0.4 −0.4
010b 10b or 11b 1 −1
011b 10b or 11b 2 −2
100b 10b or 11b 4 −4
101b 10b or 11b 10 −10
110b 10b or 11b 20 −20
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