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LM5160: Vout ripple at inverting circuit

Takashi Yamaguchi
Genius 11070 points
Part Number: LM5160

Hi team,

My customer is evaluating the LM5160EVM with an inverting circuit configuration.  The customer connects VOUT and GND in reverse to get an inverted output voltage.

Condition : Vin=+12V~+48V, Vout=-5V, Iout=~2A

The customer mentioned that the Vout ripple was observed around 100mVpp at the constant output current. The customer would like to reduce the ripple voltage. Could you tell me how to reduce the ripple voltage, and how much can the ripple voltage be lowered?(e.g. 10mVpp)

The customer uses Type2 configuration, so they added Cff between the FB and Vout. R3(R8 on the EVM) is still 0.47ohm. According to the equation(7), should customer increase the R3 value to reduce the ripple voltage? In that case, customer need to care load transient response because R3 affects to the load transient response? 

Regards,

Yamaguchi

  • 0
    TI__Mastermind 27030 points

    HI 

    increase R3 will increase the ripple at Vout to GND, so customer need to reduce R3 but keep proper injection ripple by equiation 7. if customer need small ripple at inverting  buck boost, I recomand they use type 3 and pls let them know that buckboost ripple related to the output power, Cout and fsw.

    Thanks