5V/3.3V or Adjustable, Low-Dropout,

______________________________________________________________________________________

11

Reverse-Current Protection

The MAX882/MAX883/MAX884 have a unique protection

scheme that limits reverse currents when the input volt-

age falls below the output. It monitors the voltages on IN

and OUT and switches the IC’s substrate and power bus

to the more positive of the two. The control circuitry is

then able to remain functioning and turn the pass transis-

tor off, limiting reverse currents back through to the input

of the device. In this mode, typical current into OUT to

Reverse-current protection activates when the voltage

on IN falls 6mV (or 20mV max) below the voltage on

OUT. Before this happens, currents as high as several

milliamperes can flow back through the device.

Low-Battery-Detection Comparator

The MAX882/MAX883/MAX884 provide a low-battery com-

parator that compares the voltage on the LBI pin to the

1.20V internal reference. LBO, an open-drain output, goes

low when LBI is below 1.20V. Hysteresis of 7mV has been

added to the low-battery comparator to provide noise

immunity during switching. LBO remains functional in stand-

by mode for the MAX882, but is undefined in OFF mode for

the MAX883 and MAX884. Tie LBI to IN when not used.

Use a resistor-divider network as shown in Figure 6 to set

the low-battery trip voltage. Current into the LBI input is

±50nA (max), so R2 can be as large as 1M

Ω. Add extra

noise immunity by connecting a small capacitor from LBI

to GND. Additional hysteresis can be added by connect-

ing a high-value resistor from LBI to LBO.

Applications Information

The MAX882/MAX883/MAX884 are series linear regula-

tors designed primarily for battery-powered systems.

Figure 7 shows a typical application.

Standby Mode vs. OFF Mode

STBY is a comparator input that allows the user to set

the standby-mode threshold voltage, while OFF is a

logic-level input. When in standby mode, the output is

disconnected from the input, but the biasing circuitry

(including the low-battery comparator) is kept alive,

causing the device to draw approximately 7µA.

Standby mode is useful in applications where a low-

battery comparator function is still needed in shutdown.

A logic low at the OFF pin turns off all biasing circuitry,

including the LBI/LBO comparator, and reduces supply

current to less than 1µA. OFF mode is useful for maxi-

mizing battery life. There is little difference in the time it

takes to exit standby mode or OFF mode.

Output Capacitor Selection

and Regulator Stability

An output filter capacitor is required at the MAX882/

MAX883/MAX884 OUT pin. The minimum output

capacitance required for stability is 2.2µF.

MAX882

MAX883

MAX884

O.1

µF

2.2

µF

OUTPUT

VOLTAGE

BATTERY

LBO

LBI

OFF (STBY)

( ) ARE FOR MAX882.

IN

POWER-

FAIL

INDICATION

R3

R1 + R2

R2

OUT

GND

SET

R1

R2

MAX882

MAX883

MAX884

O.1

µF

2.2

µF

OUTPUT

VOLTAGE

INPUT

VOLTAGE

BATTERY

OFF (STBY)

ON/OFF

*

* OPTIONAL REVERSE BATTERY PROTECTION

( ) ARE FOR MAX882.

IN

OUT

GND

SET

LBI

Figure 6. Using the Low-Battery Comparator to Monitor Battery

Voltage

Figure 7. Typical 3.3V or 5V Linear Regulator Circuit