LMP8358 datasheet(28/32 Pages) NSC

28 / 32 page

Fault Detection Example

Using the fault detection features of the LMP8358 an end

product, such as a scale, can periodically test that no damage

has occurred to the system. A routine can be written that

could, for example, run on start up, that will step through the

fault detection features shown above and compare the output

voltage to a table like that shown in Table 16. Fault Detection

Matrix. If the circuit shown in Figure 7 is used the values

shown in column 2 of Table 16. Fault Detection Matrix would

show that the system is working correctly, the values in the

columns under the Possible Faults heading would show that

there is a potential problem and that operator attention is

needed.

Table 16. Fault Detection Matrix

No Faults

Possible Faults

LMP8358

OUT

Possible Cause

OUT

Possible Cause

OUT

Possible Cause

00 82x

2.5V

OUT < CMVR or

OUT > CMVR

Input is out of

CMVR

V+

+IN shorted to V+ 0V

+IN shorted to

GND

00 C2x

2.5V

OUT < CMVR or

OUT > CMVR

Input is out of

CMVR

V+

−IN shorted to V+ 0V

−IN shorted to

GND

50 00x

0.61V

V+

+IN Open

0.07V

Inputs shorted

50 03x

4.97V

V+

−IN

0.7V

Inputs shorted

50 82x

2.55V

2.65V*

Degraded +IN

line

58 C2x

2.55V

2.55V*

Degraded +IN

line

50 82x

2.55V

2.55V*

Degraded −IN

line

58 C2x

2.55V

2.65V*

Degraded −IN

line

* The values shown for a degraded input line will vary de-

pending on the resistance in the line. This table uses the value

in Figure 12 and Figure 13, 1k

Ω.

LMP8358 Datasheet(PDF) 28 Page - National Semiconductor (TI)

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