L9945 datasheet(134/151 Pages) STMICROELECTRONICS

134 / 151 page

•

HS diagnostics

–

Vout > VOL indicates a STB (see Figure 36)

–

VLVT < Vout < VOL indicates an OL

–

Vout < VLVT is a normal condition for HS configuration

Refer to Table 36 for the diagnostic codes corresponding to the STB/STG and OL faults.

Refer to Section 6.4.2 for the VOL and VLVT thresholds value.

When an OL or STB/STG fault is detected, the corresponding diagnostic code is latched, but no action is taken on

the outputs.

Note:

Vout corresponds to DRNx pin for LS NMOS and HS PMOS configurations, while it's SNGPx pin for HS NMOS

configuration.

6.4.1

Settling and deglitch filter times

A filter time tDIAG has been implemented to allow settling of the output node voltage (Vout) before the comparison

to the diagnostic thresholds.

When an output is switched OFF, the tDIAG filter time is started. When the filter expires, Vout is compared to the

VLVT and VOL thresholds to determine the output diagnostic status (see Figure 36).

The filter time tDIAG can be programmed as follows:

Table 43. Diagnostic filter time selection for OFF state

tdiag_config_xx

Value

Unit

Values available for all configurations

25.6

µs

61.2

µs

105.6

µs

150

µs

Additional values available for H-Bridge configuration (refer to H-Bridge OFF state diagnostic timings)

11.2

µs

28.9

µs

51.2

µs

While in the OFF state, the tDIAG filter is reset and restarts if one of the following condition occurs:

•

LS configuration

–

VLVT crossed with a negative slope (possible STG),

–

VOL crossed with a negative slope (possible OL),

•

HS configuration

–

VLVT crossed with a positive slope (possible OL),

–

VOL crossed with a positive slope (possible STB).

To avoid glitches on threshold crossing, a deglitch filter with tFIL_OFF timeout has been implemented. The deglitch

filter time tFIL_OFF is fixed (see Figure 36):

L9945

OFF state diagnostics

DS12275 - Rev 8

page 134/151

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