Start-up issue with MP9486A

DC-DC Power Converters
1

Hallo
In my project we used the MP9486A in a similar circuit like the Eval. board.

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We observed a similar problem like some others had observed as well
( MP9486AGN locks up ]
is there any solution yet?
My PCB starts up when input voltage rises slowly >3ms but goes to some strange state if the input Voltage turns on rapidly.
The Eval board works perfectly now what did i do wrong?

2

Hi @torge.hinz,

Can you please tell me about your input specs and how are you supplying the input? At the output how much current do you want? 1A?

Can you please elaborate “Strange state” ? When the Vin is rapidly turned on, what is the inrush current? Can you try enabling the device using the EN pin, under the same conditions?

Please let us know.

Thank you
Saurabh

3

Hallo @MPSNow_Saurabh

We made the system work.
But we are not vary sure if it will stably work under all circumstances.
It is most likely that the inrush current is the Problem. But I don’t know how to measure.
To reduce it we removed the two nearest 100uF Capacitors and increased the Coil inductance to 68uH.

We supply the DCDC with a 2m long cable from the truck battery which is huge.
The Voltage varies according to the truck type.

The “strange state” is that the DCDC outputs a voltage of 1-2V and stays like this even if EN is triggered.
The output current is not fix minimum we need 300mA but in some system configuration up to 1.5A would be possible.

We would like to increase the Capacitance to make the Output voltage more stable but that ends up in the old failure.

Kind regards
Torge

4

To all people that might have some instability problems with this chip, I have built a project using this MP9486 chip and applied some modifications. it works stable and flawlessly. Just follow my design and PCB and embed this board on your mainboard PCB

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More info: https://www.youtube.com/watch?v=_oljkEE9LmQ

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