150mA, Low-Dropout Linear Regulator

with Power-OK Output

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PSRR and Operation from Sources

Other than Batteries

The MAX8885 is designed to allow low dropout voltages

and low quiescent currents in battery-powered systems.

Power-supply rejection is 60dB at low frequencies (see

the Power-Supply Rejection Ratio vs. Frequency graph

in the Typical Operating Characteristics).

Improve supply-noise rejection and transient response

by increasing the values of the input and output bypass

capacitors. The typical operating characteristics show

the MAX8885’s line- and load-transient responses.

Load-Transient Considerations

The MAX8885’s load-transient response graphs (see

Typical Operating Characteristics) show three compo-

nents of the output response. The first (and most signifi-

cant) component is the abrupt drop in output voltage

due to the capacitor’s ESR. The magnitude of the voltage

drop is directly proportional to the output capacitor's

ESR and the size of the load transient and is indepen-

dent of the regulator’s transient response. The second

component is the output voltage recovery, which is a

function of the regulator’s loop response and the capaci-

tance at the output. The third component is a DC shift in

the output voltage resulting from the regulator’s finite out-

put impedance. To improve the MAX8885’s load-tran-

sient response, increase the output capacitor’s value

and decrease its ESR. Take care to ensure that the out-

put capacitor is chosen to comply with the Region of

Dropout Voltage

A regulator’s minimum input-output voltage differential

(or dropout voltage) determines the lowest usable sup-

ply voltage. In battery-powered systems, this will deter-

mine the useful end-of-life battery voltage. Because the

MAX8885 uses a P-channel MOSFET pass transistor,

its dropout voltage is a function of drain-to-source on-

Typical Operating Characteristics).

Chip Information

TRANSISTOR COUNT: 266

Package Information