MAX883CSA データシートの表示（PDF） - Maxim Integrated

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MAX883CSA

5V/3.3V or Adjustable, Low-Dropout, Low IQ, 200mA Linear Regulators

Maxim Integrated 

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

Low IQ, 200mA Linear Regulators

BATTERY

R1

CIN

O.1µF R2

IN

OFF (STBY)

LBI MAX882

MAX883

MAX884

GND SET

OUTPUT

VOLTAGE

OUT

R3

LBO

POWER-

FAIL

COUT

INDICATION 2.2µF

( ) ARE FOR MAX882

R1 + R2

VLBI TRIP = VLBI R2 , VLBI = 1.20V

ON/OFF

*

INPUT

VOLTAGE

BATTERY

CIN

O.1µF

OFF (STBY)

IN

OUT

LBI MAX882

MAX883

MAX884

SET GND

OUTPUT

VOLTAGE

COUT

2.2µF

( ) ARE FOR MAX882

* OPTIONAL REVERSE BATTERY PROTECTION

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

Voltage

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

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

GND is 15µA at VOUT = 3.3V and 50µA at VOUT = 5V.

Reverse-current protection activates when the voltage

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

on OUT. Before this happens, currents as high as sev-

eral 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 maximum, so R2 can be as large as 1MΩ. Add

extra noise immunity by connecting a small capacitor

from LBI to GND. Additional hysteresis can be added by

connecting a high-value resistor from LBI to LBO.

* Tie LBI to IN when not used.

__________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 around 7µA. Standby mode

is useful in applications where a low-battery compara-

tor 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.

______________________________________________________________________________________ 11

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