Hi Experts,
My customer wishes to use UCC28740 in charger design but need additional OTP circuit for protection. Could you suggest which pin should we use to shutdown the controller?
Do we have any reference circuit for this function?
Best Regards,
Wei-Hao
CS pin can be used as below.
When the primary MOSFET is on, D2 is off, so the added D2 and Rt1 have no effect. When the primary MOSFET is off, D2 is on, when temperature increases to cause RT1 decrease, and cause CS-pin voltage to increase, and when CS-pin voltage reaches 1.5V, the device enters protection due to CS-pin 1.5V fault and the converter will be in operation of hiccup.
This external circuit is simple for hiccup type of OTP with possible two components addition.
Since when the MOSFET is off, AUX output voltage is regulated by the Vout, so AUX output voltage in nature is a constant voltage during the MOSFET off. This nature helps good tolerance for OTP threshold.
