L9958 datasheet(21/38 Pages) STMICROELECTRONICS

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L9958

Diagnostics and protections

This disable the turning on of the low-side drivers during current recirculation. The current

flows through the body diode of the low-side MOS for a fixed time. At the end of this fixed

time the Vout voltage is sampled and the possible open load condition detected (see

Figure 16).

Figure 16. Open load in on state - Low-side current recirculation

5.2.5

Over-temperature

When Twarn is reached, thermal current reduction is activated, and the information is stored

and latched. When Tsd is reached, the “TSD” bit is set and all output transistors are put in

tri-state conditions as long as a reset is applied.

5.2.6

Vs under-voltage shutdown

If the supply-voltage at the VS pins falls below the under-voltage detection threshold

Vs_uv_off, the outputs are set to tri-state and the error bit "Undervoltage at VS" is set.

A filtering time "Tuv_Vs" is implemented to avoid unwanted detection due to parasitic

glitches. The information is transferred into the SPI register in a bit called "VS_UV". This bit

is NOT latched. As soon as the voltage rises again above the Vs under-voltage threshold

(hysteresis implemented), the bridge is switched back to normal mode driven by DIR and

PWM. All the settings are kept as before the under-voltage event.

Table 12. Over-temperature

TSD

Comments

Bridge state

FSI

Tj > TSD

Tri-state-

0 (default)

Tj < TSD

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