Datasheet

nents of the output response: a DC shift from the output
impedance due to the load current change, and the
transient response. A typical transient response for a
step change in the load current from 5mA to 500mA is
18mV. Increasing the output capacitor’s value and
decreasing the ESR attenuates the overshoot.
Input-Output (Dropout) Voltage
A regulator’s minimum input-to-output voltage differen-
tial (dropout voltage) determines the lowest usable sup-
ply voltage. In battery-powered systems, this
determines the useful end-of-life battery voltage.
Because the MAX1857 uses a P-channel MOSFET pass
transistor, its dropout voltage is a function of drain-to-
source on-resistance (R
DS(ON)
) multiplied by the load
current (see Typical Operating Characteristics):
V
DROPOUT
= V
IN
- V
OUT
= R
DS(ON)
x I
OUT
The MAX1857 ground current remains below 150µA in
dropout.
MAX1857
500mA, Low-Dropout,
Ripple-Rejecting LDO in µMAX
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Chip Information
TRANSISTOR COUNT: 845