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 60

Ω

to 90

Ω. 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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