1.425V to 3.6V Input, 2A,

0.2V Dropout LDO Regulators

_______________________________________________________________________________________

7

Detailed Description

The MAX8526/MAX8527/MAX8528 are low-input, low-

dropout, PMOS regulators capable of delivering up to

2A of output current with as little as 200mV of head-

room from input to output. The PMOS output stage can

be driven from input voltages down to +1.425V without

sacrificing stability or transient performance. Since this

regulator has a PMOS output device, supply current is

not a significant function of load or input headroom.

Internal p-Channel Pass Transistor

The MAX8526/MAX8527/MAX8528 feature a 50m

Ω

(typ) p-channel MOSFET pass transistor. Unlike similar

designs using pnp pass transistors, p-channel MOSFETs

require no base drive, which reduces quiescent current.

pnp-based regulators also waste considerable current in

dropout when the pass transistor saturates, and use high

base-drive currents under large loads. The MAX8526/

MAX8527/MAX8528 do not suffer from these problems

and consume only 500µA (typ) of quiescent current

under heavy loads, as well as in dropout.

Short-Circuit/Thermal Fault Protection

The MAX8526/MAX8527/MAX8528 are fully protected

from a short circuit at the output through current-limit-

ing and thermal-overload circuitry. In the fault condition

when the output is shorted to ground, the output cur-

rent is limited to 4A. Under these conditions, the part

quickly heats up. When the junction temperature reach-

es +165°C, the thermal-overload circuitry turns off the

output, allowing the part to cool down. When the junc-

tion temperature cools to +150°C, the output turns

back on and tries to reestablish regulation. Current

limiting and thermal protection continue until the fault is

removed. For continuous operation, do not exceed the

absolute maximum junction temperature rating of

Output Voltage Selection

The

MAX8526/MAX8527/MAX8528

feature

an

adjustable output voltage from 0.5V to 3.4V, using two

external resistors connected as a voltage-divider to FB

as shown in Figure 1. The output voltage is set by the

following equation:

mize quiescent current, accuracy, and high-frequency

power-supply rejection. To simplify resistor selection:

Soft-Start

Inherent soft-start limits inrush current. Peak inrush cur-

calculated as follows:

Shutdown Mode

The MAX8526/MAX8527/MAX8528 include an enable

input. To shut down the device, pull EN to GND. For

normal operation, connect the EN to IN. During shut-

down, an internal 10k

Ω resistor pulls down the output.

Power-OK (POK, MAX8527 Only)

The MAX8527 features a power-OK output to indicate

the status of the output. POK remains high when the

regulator output is within ±10% of its nominal output

voltage. If the output voltage falls/rises outside this

range, POK transitions low. This open-drain output

requires an external pullup resistor to IN. An internal

delay circuit prevents the POK from switching for 50µs

(typ) after the trip threshold is initially reached. If the

part is in shutdown mode, POK is low.

Power-On Reset (POR, MAX8528 Only)

The MAX8528 features a power-on reset output that

transitions high 150ms (typ) after the output has risen

above 90% of its final value. This open-drain output

requires an external pullup resistor to IN. If the part is in

shutdown mode, falls below 90% of the nominal output

voltage, or experiences a short-circuit/thermal fault,

POR immediately transitions low.

II

CF

INRUSH

LOAD

OUT

=+

()

⎛

⎝

⎜

⎞

⎠

⎟

µ

66

RR

V

V

OUT

FB

12

=

⎛

⎝⎜

⎞

⎠⎟

-1

VV

R

R

OUT

FB

=+

⎛

⎝⎜

⎞

⎠⎟

1

1

2

MAX8526

MAX8527

MAX8528

2.2

µF

10

µF

ENABLE

SHUTDOWN

IN

IN

POK (MAX8527) OR

POR (MAX8528)

EN

IN

IN

OUT

OUT

GND

FB

OUT

OUT

100k

Ω*

R1

R2

ADJUSTABLE

OUTPUT

*FOR MAX8527 AND MAX8528

+1.425V TO +3.6V

Figure 1. Typical Application Circuit