L6911D datasheet(8/17 Pages) STMICROELECTRONICS

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L6911D

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Figure 3. High Side driver peak current. Vboot-Vphase=12V (left) Vboot-Vphase=5V (right)

Figure 4. Low Side driver peak current. Vcc=12V (left) Vcc=5V (right)

Monitoring and Protections

The output voltage is monitored by means of pin 1 (VSEN). If it is not within ±12% (typ.) of the programmed

value, the powergood output is forced low.

The device provides overvoltage protection, when the output voltage reaches a value 17% (typ.) grater than the

nominal one. If the output voltage exceeds this threshold, the OVP pin is forced high, triggering an external SCR

to shuts the supply (VIN) down, and also the lower driver is turned on as long as the over-voltage is detected.

To perform the overcurrent protection the device compares the drop across the high side MOS, due to the

RDSON, with the voltage across the external resistor (ROCS) connected between the OCSET pin and drain of

the upper MOS. Thus the overcurrent threshold (IP) can be calculated with the following relationship:

Where the typical value of IOCS is 200µA. To calculate the ROCS value it must be considered the maximum

RDSON (also the variation with temperature) and the minimum value of IOCS. To avoid undesirable trigger of

CH1 = High Side Gate

CH4 = Gate Current

CH1 = Low Side Gate

CH4 = Gate Current

OCS

⋅

DSON

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