Detailed Description

The MAX8530/MAX8531 are low-power, low-dropout,

low-quiescent current linear regulators with reset

designed primarily for battery-powered applications.

For preset output voltages, refer to the Output Voltage

Selector Guide. Other combinations between 1.5V and

3.3V are available in 50mV increments. This device

supplies loads up to 200mA for OUT1 and 150mA for

OUT2. The MAX8530/MAX8531 consist of a 1.25V ref-

erence, error amplifiers, P-channel pass transistors,

reset block, and internal feedback voltage-dividers.

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, allowing more current to pass to the output and

increasing the output voltage. If the feedback voltage 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.

RESET

The reset circuit is active at power-up and power-down.

RESET is held low at power-up. The reset timing starts

once the OUT1 voltage reaches 87% (typ) of its regula-

tion voltage. The RESET signal goes high 200ms (typ)

after the OUT1 voltage reaches 87% (typ) of its regulation

voltage. At power-off, RESET goes low when the OUT1

voltage is below 87% (typ) of its regulation voltage.

Dual Low-Dropout Linear Regulators

6

_______________________________________________________________________________________

P

N

ERROR

AMP

IN

SHDN

GND

OUT1

RESET*

* MAX8530 ONLY

**MAX8531 ONLY

BP**

OUT2

MOS

DRIVER

DELAY

THERMAL

SENSOR

LDO2

87%

REF

1.25V

REF

SHUTDOWN

AND

POWER-ON

CONTROL

MAX8530

MAX8531

Functional Diagram