Datasheet

100 PA
+
-
+5V
1k
1k
1k
1k
+IN
-IN
OUT
+5V
V
+
5V or GND
+5V
GND
+
-
+5V
1k
1k
1k
1k
+IN
-IN
OUT
+5V
V
+
5V
100 PA
+
-
+5V
1k
1k
1k
1k
+IN
-IN
OUT
+5V
V
+
LMP8358
www.ti.com SNOSB09B –APRIL 2010–REVISED MARCH 2013
Open Input
Figure 56 shows an example of an open input fault. To sense this type of fault use the 1/50 feature by setting
MUX[1:0] to 10b to test the +IN pin or to 11b to test the −IN pin, POL to 0b, PIN to 1b to test the −IN pin, and
G[2:0] to 010b for a gain of 50, and inject 100µA current by setting CUR[2:0] = 101b (5082x or 58C2x). Since the
input is open the input pin will be pulled to V+. With an overall gain of 1 the output will read 5V for open input.
Figure 56. Open Input
Input Shorted to V+ or V−
Figure 57 shows an example of an input pin shorted to V+ or V−. To sense this fault, use the 1/50 feature by
setting MUX[1:0] to 10b to test the +IN pin or to 11b to test the −IN pin, POL to 0b, and G[2:0] to 010b for a gain
of 50 (0082x or 00C2x). This will give an overall gain of 1 and the output will read either V+ or V− depending on
whether the input pin is shorted to V+ or V−.
Figure 57. Input Shorted to V+ or V−
Shorted Inputs
Figure 58 shows the inputs of the LMP8358 shorted. To detect this fault set CUR[2:0] = 101b to inject a 100µA
current and set the gain to 10× (5000x). The LMP8358 is set up with normal differential inputs. The output will
read about 0.07V because of the voltage drop across the internal ESD resistor, which has a value between 60Ω
to 90Ω. If the gain is set to 100× with an injected current of 100µA the output will be about 0.7V.
Figure 58. Shorted Inputs
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