L9945 datasheet(122/151 Pages) STMICROELECTRONICS

122 / 151 page

Figure 27. NDIS/DIS release before NRES release: tCC is selected as watchdog starting timer value. Then,

CC timer switches to tCC.

typ 132ms

NRES

DIS

NDIS

CC function

CC timing

disabled

enabled

110...165ms

55...80ms

GAPG0102161058CFT

The distinction between tCC and tCC_INIT applies only at the beginning of CC. After the first valid SPI frame, CC

always operates with tCC deadline.

In case of no valid communication the CC timer will expire and disable all related outputs. With the next valid

communication the outputs are enabled. Each correct communication restarts the CC timer. If a CC failure is

detected, all channels except 7 and 8 are actively turned off and the CC_LATCH is set high (cleared on SPI

readout).

The CC can be deactivated by programming the CONFIG_CC field via SPI. By default CC is active. CC status

can be monitored by reading the config_CC_STATE SPI bit.

Note:

When configured as H-Bridge, channels 7 and 8 are handled like other channels and are disabled in case of CC

failure.

Table 35. CC timings

Symbol

Parameter

Min. Max. Unit

tCC

Communication Timeout

tCC_INIT

Deadline for the first communication engagement in case DIS/NDIS are released before NRES

release.

110

165

6.2

Diagnostics overview

The device performs two types of diagnostics for each output channel:

•

ON state diagnostics: overcurrent (OC) detection;

•

OFF state diagnostics: open load (OL), short to ground (STG), and short to battery (STB) detection.

Diagnostic can be enabled/disabled by programming the ENABLE_DIAGNOSTIC bit.

The AN "L9945_Diagnostics_Explained" covers all the main aspects of diagnostics and helps choosing the

correct values for the tblank_oc and tdiag filter times.

Diagnostic report for all channels is readable via SPI, after having issued the 0x9AAA0001 frame. The diagnostic

status of each channel is encoded in 3 bit (diag_xx[2-0]), as shown in the table below.

L9945

Diagnostics overview

DS12275 - Rev 8

page 122/151

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