MP8759 EN resistor for variable input voltage

Hi,

I would like to use MP8759 in an USB type-c device. The USB bus input voltage ranges from 5V ~ 20V as input to MP8759, and then regulated to 5V. EN pin is connected to VIN through resistor so 8759 will auto start when power comes in.

The datasheet gives resistor values for 12V input. However in above application the input voltage varies. How the EN resistor should be selected under this application?

Thank you.

Hello ning.roland,

Please choose a divider that satisfies the EN high threshold of 1.25V. Note the absolute max of this pin is 4.5V. If this is not possible an external source may be required.

Pleas note your design may not be possible with this device due to minimum off time limitations. Toff_min limits your maximum duty cycle and will affect operation when Vin is close to Vout.

Thank you,
Vinh Tran
Field Applications Engineer

Hi Vinh,

thank you for the hint. I just realized that 100% duty cycle may not possible when Vin and Vout are too close.
I’ve got MP8759 EVK for detailed evaluation. I also looked into MP2386. It does not looks much different from 8759 per datasheet. So what is the difference between the two? Which one is more recommended for my targeted application?
Thank you.