L9958 datasheet(19/38 Pages) STMICROELECTRONICS

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L9958

Diagnostics and protections

Doc ID 17269 Rev 5

19/38

Diagnostics and protections

A detailed diagnostic of the H-bridge is available through SPI communication. The 16 bits

diagnostic word is sent back to the MCU in return of a command word. The diagnostic word

is used to report two kinds of information:

●

H-Bridge failures:

–

Over-current on each transistor in on-state,

–

Vps under-voltage,

–

Vdd over-voltage,

–

Over-temperature,

–

Open-load in on-state,

–

Off-state diagnostic.

●

H-bridge functional status:

–

Current limitation condition,

–

Current limitation decreasing condition,

–

Disable / Enable status.

5.1

Diagnosis reset strategy

5.1.1

Reset requests

Except "ACT" and "VS_UV" bits, all the others are latched and can only be released by:

●

Transition from "Disable" to "Enable" on DI / EN pins,

●

Diagnostic register read by SPI (see details on each failure release) depending on bit

"DR",

●

Power-On-Reset condition.

When the diagnostic register is reset, the bridge is switched back to normal mode driven by

DIR and PWM. All the settings are kept as before the failure. In case of SPI read, no

additional action on DI / EN is needed.

5.1.2

Diagnosis reset bit

In case of "DR" set to LOW (default value), all the bits of the diagnostic register can be reset

by the three possibilities described in previous section.

In case of "DR" set to HIGH, the over-current, Vdd over-voltage and over-temperature

diagnostic bits can NOT be reset by SPI read and therefore, the bridge is kept in tri-state

until a transition from "Disable" to "Enable" on DI/EN pins or Power-on-Reset condition.

Table 11.

Diagnosis reset strategy

All diagnostic bits reset at each SPI reading (Default)

Over current bits (8..11) + Temp. shutdown TSD bit (6) + Vdd over voltage bit (3) NOT

reset by SPI

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