RE: nPM1300 evaluation kit LDO mode questions

Tomi Koskela — Fri, 29 Aug 2025 07:00:01 GMT

Hello,

1. 2. 3. In LDO mode the minimum input voltage is 2.6V

4. LDO operates in sampled mode when buck is in PFM mode and no charging enabled. This sampling can cause some ripple on the output voltage. You could check if this ripple you see goes away if you start charging for example. Then LDOs are in continuous mode and you should not see the LDO reference refresh caused ripple anymore.

This ripple can be also caused by the buck converter operating in PFM mode depending how you are powering LDOs etc. and what is the load of the buck. Care should be taken also how to ground the oscilloscope probe to avoid GND bounce affecting the measurement. You can experiment forcing buck to PWM mode to see how it effects the ripple.

5. Yes there can be high current pulse on the startup to charge the output capacitors. No damage to the nPM1300 will be caused by it, the behavior is normal.

RE: nPM1300 evaluation kit LDO mode questions

Poki Huang — Wed, 27 Aug 2025 04:23:21 GMT

Add question 5

At LDO mode, we set VOUTLDO1 1.8V

When we turn on LDO1, there is a inrush current as below pic.

The max current value is ~222mA and the duration time is ~200us

The 222mA is over LDO spec. 50mA, so will it damage nPM1300?

Or it is a normal situation for nPM1300 LDO?

Thank you

Poki