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LM5002: Can the LM5002 handle Vin > Vout?

Leo Potjewijd
Prodigy 90 points
Part Number: LM5002

In my application, I need 20V (minimum) at some 45mA; the input can vary from 6 to 30V.
Because space is extremely limited I would like to avoid a Sepic configuration.

The circuit requiring the 20V can handle the excess 10V without any problem so poor regulation is no issue.

Can I just use diodes to 'or' the input with the output or do I need some form of shutdown circuitry for the LM5002?

  • 0
    TI__Guru* 78060 points
    In a boost, if Vin>Vout, the PWM controller will stop switching and the Vin will pass through to Vout, and produce Vout = Vin -VF -Vdrop, where VF is the forward drop of the rectifier diode, and Vdrop is the voltage drop across the boost inductor and other resistances along the current flow path. Therefore, the LM5002 can handle Vin>Vout, and Vout will be determined by above equation.