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TPS53355 OCP issue

Yanhong Zhu
Prodigy 50 points
Other Parts Discussed in Thread: TPS53355

Hello. In our project, we have two TPS53355 application. One application is converting from 12V  to 3.3V, the other application is converting from 12V to 1.15V.

And the trip resister is 147k.

When implementing OCP test, The OCP of the 3.3V circuit is above 30A, while the OCP of the 1.15V circuit is only about 24A.

When test the OCP of 1.15V circuit, the load is cut, only add electrical load to the 1.15V circuit.

Could you help me to why there's the difference?

  • 0
    Genius 3295 points
    Equation (2) on page 17 of the TPS53355 data sheet shows that the Iocp is dependent on the inductor ripple current -Iind(ripple). If you have the same trip resistor and the same output inductor for each converter your results make sense. This is because the inductor ripple current is a function of the difference between the input voltage, (Vin - Vout) * Vout/Vin, as shown in Equation (2). Therefore, the 1.15 V converter will have a lower inductor ripple current and the IOCP is lower (1.039 A for the 1.15V output vs. 2.39 A for the 3.3V output). You either need to modify the trip resistor or the output inductor according to Equation (2).