Post Go back to editing

LT3080 Dropout Voltage

A customer asks concerning the LT3080:  "We operate at: Vin = 3.3V Vout = 3V, Vcontrol = 5V, output current max. = 200mA. Is this ok?"

This is a common question so I will answer it myself in a REPLY post.

  • The customer's VCONTROL is high enough above VOUT that there is no dropout voltage concern for VCONTROL.

    The image below shows how the specification for VIN Dropout Voltage from the datasheet Electrical Characteristics table relates to the Dropout Voltage (Minimum IN Voltage) curve.  The Electrical Characteristics specification essentially adds some margin to the Dropout Voltage (Minimum IN Voltage) curve.  The customer's 200mA IOUT with 300mV IN - OUT condition should be o.k. for regulation because the customer's conditions do not violate the margin imposed by the Electrical Characteristics specification.

    In general, noise and PSRR performance get worse when the IN - OUT voltage gets close to the dropout voltage. 

    LT3080 Dropout_5.png