pass transistor shuts off, the output falls to ground, and

supply current drops from 2µA to 0.7µA. Connect SHDN

to IN for normal operation. If reverse-battery protection

is needed, drive SHDN through a 100k

Ω resistor.

Thermal-Overload Protection

Thermal-overload protection limits total power dissipa-

tion in the MAX1725/MAX1726. When the junction tem-

signals the shutdown logic, turning off the pass transistor

and allowing the IC to cool. The thermal sensor turns

the pass transistor on again after the IC’s junction tem-

perature cools by 15°C, resulting in a pulsed output

during continuous thermal-overload conditions.

Thermal-overload protection is designed to protect the

devices in the event of fault conditions. For continuous

operation, do not exceed the absolute maximum junction

Foldback Current Limiting

The MAX1725/MAX1726 also include a foldback current

limiter. When the output is shorted to ground, the output

PMOS drive is limited so that the output current does

not exceed 40mA (typ). The output can be shorted to

ground indefinitely without damaging the part.

Reverse-Battery Protection

The MAX1725/MAX1726 have a unique protection

scheme that limits the reverse supply current to less

cuitry monitors the polarity of the input, disconnecting

the internal circuitry and parasitic diodes when the battery

is reversed. This feature prevents the device, battery,

and load from overheating and electrical stress. For

reverse-battery protection, drive SHDN through a

100k

Ω resistor.

Applications Information

Capacitor Selection and

Regulator Stability

For general purposes, use a 1µF capacitor on the

MAX1725/MAX1726 input and output. Larger input

capacitor values and lower ESR provide better supply-

noise rejection and transient response. A higher-value

input capacitor (10µF) may be necessary if large, fast

transients are anticipated and the device is located sev-

eral inches from the power source. For stable operation

over the full temperature range, use a minimum of 1µF

on the output.

Output Voltage Selection

For fixed 1.8V, 2.5V, 3.3V, or 5V output voltages, use

the MAX1726.

The MAX1725 features an adjustable output voltage

from 1.5V to 5V, using two external resistors connected

as a voltage-divider to FB (Figure 1). The MAX1725 is

optimized for operation with R2 = 1.2M

Ω. The output

voltage is set by the following equation:

tion:

Choose R2 = 1.2M

Ω for best accuracy.

Power-Supply Rejection and Operation

from Sources Other than Batteries

The MAX1725/MAX1726 are designed to deliver low

dropout voltages and low quiescent currents in battery-

powered systems. Power-supply rejection is 60dB at low

frequencies and rolls off above 100Hz. At high frequen-

cies, the output capacitor is the major contributor to the

rejection of power-supply noise (see the Power-Supply

Rejection Ratio vs. Frequency graph in the Typical

Operating Characteristics).

When operating from sources other than batteries,

improve supply-noise rejection and transient response

by increasing the value of the input and output capaci-

tors, and by using passive filtering techniques (see the

Supply and Load Transient Response graph in the

Typical Operating Characteristics).

Linear Regulators

6

_______________________________________________________________________________________

Chip Information

TRANSISTOR COUNT: 112

GND

FB (GND)

OUT

15

SHDN

IN

MAX1725

MAX1726

SOT23-5

TOP VIEW

2

34

( ) ARE FOR MAX1726 ONLY.

Pin Configuration

VV

R

R

OUT

FB

=+









1

1

2

RR

V

V

OUT

FB

12

1

=









−