L9958 datasheet(22/38 Pages) STMICROELECTRONICS

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Diagnostics and protections

L9958

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Doc ID 17269 Rev 5

Figure 17.

Battery voltage monitoring

5.2.7

Vdd over-voltage detection

Although the Vdd input pin and all I/O's are able to withstand up to 19 V, an over-voltage

circuitry is implemented to ensure that the bridge is kept in tri-state when the Vdd voltage is

higher than the Vdd overvoltage threshold "Vdd_ov_off" for duration longer than

"Tov_Vdd". The information is detected and stored into the SPI register in a bit called

"VDD_OV". The bridge is kept in tri-state as long as an appropriate reset is not requested

(see Section 5.1).

5.2.8

Vdd under-voltage detection

When the Vdd voltage falls below the under-voltage detection threshold "Vdd_uv_off" for

duration longer than "Tuv_vdd", the bridge is switched to tri-state. In such a condition, the

L9958 is going in sleep mode. When the voltage increases above the threshold (hysteresis

implemented), the L9958 starts with all the settings reset to their default values (Power On

Reset).

5.2.9

Output short protection

The L9958 can sustain short on the outputs. In case of short to GND, short to battery or

short between outputs the battery voltage cannot exceed 18 V. The connection of a 100 µF

decoupling capacitor as close as possible to Vs pin and the GND connection of the slug or of

the exposed pad is mandatory to improve the robustness.

Table 13.

Vs under-voltage

VS_UV

Comments

Bridge state

FSI

Vs < Vs_uv_off

Hi Z

1 (not latched)

0 (default)

Vs > Vs_uv_on

Table 14.

Vdd over-voltage detection

VDD_OV

Comments

Bridge state

FSI

Vdd > Vdd_ov_off

Hi-Z

1 (latched)

0 (default)

Vdd < Vdd_ov_on

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