LM25117 Diode Emulation Mode

Kuramochi Tadahiko

Guru 28715 points

Other Parts Discussed in Thread: LM25117

Hi,

My customer is evaluating LM25117.

They are using the Diode Emulation Mode.

When the critical conduction mode, Vout is unstable.

The waveform of the Vout is following.

Have you ever seen such wave ?

Can you expect the reason that Vout is unstable?

Thanks

Kuramochi

over 10 years ago

0 EricLee over 10 years ago

TI__Guru 58171 points

Hi Kuramochi
Please try smaller Rramp or Cramp. This might help a little.
If you tie DEMB pin to VCC, there will be no such a issue.
Regards,
EL

0 Kuramochi Tadahiko over 10 years ago in reply to EricLee

Guru 28715 points

Hi Eric-san,

Thank you for your advice.

I told this information to my customer .

By the way, DEMB pin is tied to VCC on the circuit of my customer.

What is this meaning?

Thanks and Regards,

Kuramochi

0 EricLee over 10 years ago in reply to Kuramochi Tadahiko

TI__Guru 58171 points

Hi
In FPWM mode, there is no critical conduction. The converter works in CCM always.
Please check the board is working in FPWM mode or not.
Regards,
EL

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LM25117 Diode Emulation Mode