AN2115 datasheet(17/33 Pages) STMICROELECTRONICS

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AN2115

Synchronization

Doc ID 11165 Rev 5

17/33

Equation 9

Thanks to the very low FB leakage current (25 nA), high R3 and R2 values can be chosen

(hundreds of k

Ω) which increase system efficiency at very low load.

5.4

OVP (overvoltage protection)

The device is equipped with an internal overvoltage protection circuit to protect the load. If

the voltage at the feedback pin goes higher than an internal threshold set at 10% (typ.)

higher than the reference voltage, the low side MOSFET is turned on until the feedback

voltage goes lower than the reference voltage. During overvoltage circuit intervention, the

zero crossing comparator is disabled so that the device is also able to sink current.

5.5

Thermal shutdown

The device also has thermal shutdown protection, which is activated when the junction

temperature reaches 155 °C. In this case both the high and low side MOSFETs are turned

off.

Once the junction temperature goes back below 95 °C, the device resumes normal

operation.

out

0.6

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