LM5023 Input voltage dropping

Kuramochi Tadahiko

Guru 28715 points

Other Parts Discussed in Thread: LM5023, UCC24630EVM-636, LM8364

Hi,

My customer is testing the LM5023 as the flyback controller.

They would like to stop operating when the input voltage drops.

Is there any recommended circuits?

Regards,

Kuramochi

over 8 years ago

0 Oliver Pan91 over 8 years ago

TI__Intellectual 2230 points

Hi Kuramochi,

The LM5023 do not have input line brownout function, you may need to add external circuit to realize that, please refer to the UCC24630EVM-636 Schematic in http://www.ti.com/lit/ug/sluub81a/sluub81a.pdf.

Best Regards

Oliver

0 Kuramochi Tadahiko over 8 years ago in reply to Oliver Pan91

Guru 28715 points

Hi Oliver-san,

I got the additional question from the customer.
They're trying to drop the SSpin voltage to stop the operation of LM5023 when the input voltage drop.
Is there any problem on this way?

Best Regard,
Kuramochi

0 Oliver Pan91 over 8 years ago in reply to Kuramochi Tadahiko

TI__Intellectual 2230 points

Hi Kuramochi-san,

There is no problem by putting down the SS when voltage drop, actully the UCC24630EVM-636 is realize UVLO in this way: voltage supervisor device LM8364 is used to accurately set the turn-on voltage of the power supply. The output of LM8364 is high until the voltage on its input exceeds 3 V. This pulls the SS pin on LM5023 low (through Q4 and Q5) and disables startup of the power supply until the input voltage is above brown out recovery voltage.

Best Regards,

Oliver

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LM5023 Input voltage dropping