MPM3515 for negative rail does not start above about 70°C

Integrated Inductor Power Modules
1

Hello,
I use the MPM3515 supplied by +10V to generate -13V output. The enable is shifted as per buck’s GND. Its output is biased to +0.5V by the load before buck startup. But above 70°C case (thermo cam) the buck does not start even EN is at 2V (max rising threshold is 1.7V). VCC remains OFF. Measurements showed negative voltage (-0.5V) at the (internal) VCC pin. Is there any function inhibiting the VCC regulator’s startup under certain conditions?

Thanks
Ruediger

2

Hi @ruediger.eick,

Can you let me know how are you powering the EN? what is the pull up resistor value? - make sure to have the resistor >= 35k ohm or you’re using an external clock? - the range recommended is 450KHz to 2.2MHz with the pulse width should be below 350ns.

Make sure the Vin is greater than 4.8V at all times to regulate fully. If it falls below that the output decreases.

Are you testing this on the EVB?

Please let us know.
Thanks
Saurabh