LM5143-Q1EVM-2100: Abnormal output when Vout = 6.6V(single output, dual phase)

Roy Chou1

Genius 16055 points

Part Number: LM5143-Q1EVM-2100

Hi Team,

I modified the EVM and met some problem. Please see below image.

Sometimes, output =5V when I set Vout = 6.6V and I tried to re-power up the system and the Vout can be 6.6V.

Regards,

Roy

over 3 years ago

0 Timothy Hegarty over 3 years ago

TI__Guru 73112 points

Hi Roy,

The Thevenin resistance at FB must be greater than 5kΩ. Try increasing the FB resistances.

Regards,

Tim

0 Roy Chou1 over 3 years ago in reply to Timothy Hegarty

TI__Genius 16055 points

Hi Tim,

Thank you for your comments. The issue can be fixed. In addition, can you share why feedback resistor needs to > 5kohm? Thank you.

Regards,

Roy

0 Timothy Hegarty over 3 years ago in reply to Roy Chou1

TI__Guru 73112 points

Hi Roy,

It's mentioned in the datasheet. If the effective resistance at FB is less than 5k, then it will be detected as a fixed 5V output (this is checked at startup where FB low or high designates fixed 5V or 3.3V, respectively).

Regards,

Tim

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LM5143-Q1EVM-2100: Abnormal output when Vout = 6.6V(single output, dual phase)