LM25148: Initially design this device for up to a 12A load. But having issues starting up the regulator with a light load. I need a reliable start up with a low power load of 30-40 mA.

Hi Robert,

I reviewed your information and noted that it is generally not recommended to keep PFM/SYNC floating. Either connect this pin to GND for FPWM or to VDDA for PFM operation. Please note section 8.4.2 of the datasheet for more information.

It also looks like the CNFG pin is a bit far from the configuration values provided in Table 8-2 and the ranges given in the EC table under "Configuration." I have included the excerpt in the datasheet below for your convenience:

Please ensure that R27 is within the correct ranges for your desired operation.

If these two items still do not resolve your issue, I have a couple more questions to be answered for us to better assist you:

• Have you tried starting up the device without a load attached, i.e. disconnecting the E-load. In this case does the device properly start up?
• Is this device in isolation? Are there other circuits or schematics connected upstream/downstream of the power supply/load respectively. If this is the case, can you please test the circuit in isolation?
• Can you probe EN and the VCC pin as well when conducting these tests?

Thank you,

Joshua Austria