MP9486AGN locks up

Hello,

I am in the final stage of replacing our current DCDC converter by MP9486AGN-Z.
we have an input range of 7-60V (nominal 24V) and an output current of max. 1A @ 5V.

I ordered some samples and assembled a test circuit on a breadboard pcb.

R204 = 24k, R205 = 1k

The converter works up to 800mA (no problem - I expect thermal issues on the breadboard pcb)

however. when I make load jumps or short circuit on the output, the DCDC converter does not recover to 5V. It “locks up” at around 2.5V and (around 100mV at the FB pin) and it does not supply much current in this state.

I was only able to resolve this issue by disconnecting and connecting the external voltage. (and also by shorting the FB pin to GND very shortly - of course resulting in an overshoot of the output voltage - I was just curious if this would resolve the issue)

I also replaced the Chip with a new one - same behaviour.

Any ideas what could cause this issue / how to resolve it? The value of C209 seems to influence the behaviour in case of load jumps. But a lock up after a short circuit is not acceptable for the application.

Thanks and BR
Oliver

Hi Oliver,
Thank you for the question.
I will get back to you shortly on this.

Regards,
Yash Shah

Hi Oliver,
Apologies for the delayed response.

I think R205 should be 10k for 5V output. Should be a typo?
For SCP recovery, I think the oscilloscope scale should be longer (~40ms/div). This can bee seen in the datasheet plots.

Also, you can go through the attached document for 5V, 1A application and compare the results of the EVB to your board.
https://www.monolithicpower.com/en/documentview/productdocument/index/version/2/document_type/Datasheet/lang/en/sku/EV9486-N-00A/document_id/3368/

Let me know if you have more questions.

Regards,
Yash Shah

Hello
I am facing similar issue with my MP9486 design.
we have design system for 5V-1A output . followed with reference to

https://www.monolithicpower.com/en/documentview/productdocument/index/version/2/document_type/Datasheet/lang/en/sku/EV9486-N-00A/document_id/3368/

But with Increase in Load DCDC converter Does not recover to 5 V. Out put stays around 2.5V and only be recovered by external power ON/OFF.

Need Support how to resolve this?

Thanks and Regards

Vishal Pawar.

Hello,

I have the same problem, the IC freeze to 2,5 V and no way to exit of this situation.
Using the same value of the EVB the load regulation is very bad, and with input voltage over 16V the chip freeze to 2,5V.
The output current is 30mA at 5V.
Using feedback value of 120K and 10K without forward capacitor the IC work well, if the input voltage rise-up slowly (2s), but with a direct power-on of 24V freeze again.
In this situation I attached a 300mA load, and the regulation work, but is inacceptable the freezing situation to 2,5V.

I need urgent help

Thanks and BR

M. Signorini