S12ZVML charge pump capacitor value size selection problem

[yq1]

hello
I encountered a problem in selecting charge pump capacitance when applying S12ZVML chip, please help me guide. As shown in the figure below, currently Ccp1 chooses 10nF and Ccp2 chooses 100nF, and it is found that the driving capacity is a little insufficient, and the VCP voltage drop after loading is large. Can I change Ccp1 to 68pF without changing the CP frequency? Will there be any disadvantages in doing so? Because the instruction manual recommends Ccp1*10=Ccp2

thanks

[lama · Accepted solution]

Hi,

Our recommendation is to recalculate the bootstrap capacitor to match the Qg requirement of the FETs you are using. Another thing is to check the DC bus voltage for a large voltage drop. (solution = increase Cdc) Our MCU is not designed to only use the Charge pump to switch the FETs and is only a "support" circuit when the duty cycle causes the Cbs to not be sufficiently charged.

Of course you can try also to increase value of Ccp1 as you wanted.

I have added an additional material for consideration.

Best regards,

Ladislav