_______________Detailed Description

The MAX8867/MAX8868 are low-noise, low-dropout,

low-quiescent-current linear regulators designed pri-

marily for battery-powered applications. The parts are

available with preset output voltages varying from 2.5V

to 5.0V in 100mV increments. These devices can sup-

ply loads up to 150mA. As illustrated in Figure 1, the

MAX8867/MAX8868 consist of a 1.25V reference, error

amplifier, P-channel pass transistor, and internal feed-

back voltage divider.

The 1.25V bandgap reference is connected to the error

amplifier’s inverting input. The error amplifier compares

this reference with the feedback voltage and amplifies

the difference. If the feedback voltage is lower than the

reference voltage, the pass-transistor gate is pulled

lower, which allows more current to pass to the output

and increases the output voltage. If the feedback volt-

age is too high, the pass-transistor gate is pulled up,

allowing less current to pass to the output. The output

voltage is fed back through an internal resistor voltage

divider connected to the OUT pin.

Low-Noise, Low-Dropout,

150mA Linear Regulators in SOT23

6

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______________________________________________________________Pin Description

PIN

Active-Low Shutdown Input. A logic low reduces the supply current to 10nA. On the MAX8868, a logic low

also causes the output voltage to discharge to GND. Connect to IN for normal operation.

SHDN

1

FUNCTION

NAME

Ground. This pin also functions as a heatsink. Solder to a large pad or the circuit-board ground plane to

maximize power dissipation.

GND

2

Regulator Output. Sources up to 150mA. Bypass with a 1µF (<0.2

Ω typical ESR) capacitor to GND.

OUT

4

Regulator Input. Supply voltage can range from 2.5V to 6.5V. Bypass with a 1µF capacitor to GND (see

Capacitor Selection and Regulator Stability section).

IN

3

Reference-Noise Bypass. Bypass with a low-leakage, 0.01µF ceramic capacitor for reduced noise at the

output.

BP

5

SHUTDOWN

AND POWER-ON

CONTROL

ERROR

AMP

1.25V

REF

P

*

OUT

BP

* AUTO-DISCHARGE, MAX8868 ONLY

GND

IN

SHDN

MAX8867

MAX8868

MOS DRIVER

THERMAL

SENSOR

REVERSE

BATTERY

PROTECTION

N

Figure 1. Functional Diagram