I'm looking on the datasheet of the BQ25798 (Buck Boost Lipo Charger) and was wondering which task the Zener Diode and the 294 Ohms Resistor has.

I had an idea that the resistor is maybe limiting the switching speeds of the two mosfets and therefor limiting inrush current? (I think I read it somewhere) But why has it to be this abstract 294 Ohms value? would 300 Ohms be also ok?

For the zener diode I haven't found any information and I have no clue for what it could be used. maybe someone could give me some hints.

Here is a typical application schematic of the ic with the two mosfets and the diode Typical Application

for reference, in a dev kit they used a 12V Zener Diode. dev kit


1 Answer 1


The Zener diode sets the maximum gate voltage to a specific and repeatable value. In this case 12V.

In order to achieve the Zener voltage, an appropriate current must be supplied to the Zener. The 294 ohm resistor limits the current to the correct amount. The value chosen depends on the required tolerance. If 5% variation is acceptable then any value from 270 to 330 is acceptable.


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