LMP8358MA NSC [National Semiconductor], LMP8358MA Datasheet - Page 27

• Manufacturer Part Number: LMP8358MA
• Description: Zero-Drift, Programmable Instrumentation Amplifier with Diagnostics
• Manufacturer: NSC [National Semiconductor]

Shorted Inputs
Figure 11
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 nor-
mal differential inputs. The output will read about 0.07V be-
Degraded Input Line
Figure 12
tween the bridge and the +IN pin of the LMP8358. This fault
is shown by the 1 kΩ resistor placed between the bridge and
the LMP8358. To detect this fault use the 1/50 feature by set-
ting MUX[1:0] to 10b to test the +IN pin, POL to 0b, and G[2:0]
shows the inputs of the LMP8358 shorted. To detect
shows an example of a degraded connection be-
FIGURE 12. Degraded Input Line, Step 1
FIGURE 13. Degraded Input Line, Step 2
FIGURE 11. Shorted Inputs
27
cause 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.
to 010b for a gain of 50. This will give an overall gain of 1. Set
CUR[2:0] = 101b to inject a 100µA current and read the output
voltage (5082x). Next set MUX[1:0] to 11b and PIN to 1b to
test the −IN pin as shown in
(58C2x). If the voltages of these two measurements are dif-
ferent a degraded input fault exists.
300454c0
300454c1
300454b9
Figure 13
and read the output
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