L6911E datasheet(8/20 Pages) STMICROELECTRONICS

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L6911E

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Figure 3. High Side driver peak current.

Vboot-Vphase=12V (left) Vboot-Vphase=5V (right) CH1 = High Side Gate CH4 = Inductor Current

Figure 4. Low Side driver peak current.

Vcc=12V (left) Vcc=5V (right)CH1 = Low Side Gate CH4 = Inductor Current

Monitor and Protection

The output voltage is monitored by means of pin 1 (VSEN). If it is not within

±10% (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.) greater than

the nominal one. If the output voltage exceed this threshold, the OVP pin is forced high (5V) and the lower driver

is turned on as long as the over-voltage is detected. The OVP pin is capable to deliver up to 60mA (min) in order

to trigger an external SCR connected to burn the input fuse. The low-side mosfet turn-on implement this function

when the SCR is not used and helps in keeping the ouput low.

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

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 overcurrent protection this relationship must be

satisfied:

OCS

⋅

DSON

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