MPM3840 Fails to Start


I use MPM3840 in my project, please check the scematic below. PCB was designed as recommended bu MPS User Manual.

Incoming 5 V is tested OK, but there is only about 500 mV output voltage, which does not depend on EN input level.
I have 2 MPM3840 in my circuit, with the same problem.
Please help me to solve the issue.

With regards,

Hi bigdeal2000,

Thanks for posting on the MPSNow Forum.
Can you provide some scope shots of the following? Vin, SW, EN, PG, Vout


Hi cindy,yu!

I checked those pins with a scope:
Vin == 5 V constantly
SW == 0.6 V constantly
EN == 0.6 V when floating and about 4V during test
PG == 0.6 V
Vout == 0.6 V
There is not pulse/spikes/waves, which can be treated as DC/DC start-up attempts. Just stable voltage.

Thank you!
With regards,

Everything is Ok, there was a hard-to-find soldering problem - Vin did not actually apllied to IC pin.

Thanks for your attention.
With regards,