5 V/3 .3 V o r Ad ju s t a b le , Lo w -Dro p o u t ,
Lo w I , 2 0 0 m A Lin e a r Re g u la t o rs
Q
23/MAX84
OUTPUT
VOLTAGE
OUT
IN
ON/OFF
OFF (STBY)
IN
OUTPUT
VOLTAGE
BATTERY
OFF (STBY)
R1
R2
*
R3
OUT
INPUT
VOLTAGE
MAX882
LBI
LBO
LBI
MAX882
MAX883
MAX884
GND
MAX883
MAX884
SET
POWER-
C
2.2µF
FAIL
OUT
BATTERY
C
O.1µF
IN
C
INDICATION
OUT
GND
2.2µF
C
IN
SET
O.1µF
( ) ARE FOR MAX882
R1 + R2
( ) ARE FOR MAX882
V
LBI TRIP
= V
, V = 1.20V
LBI
LBI
R2
* 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
Re ve rs e -Cu rre n t P ro t e c t io n
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
__________Ap p lic a t io n s In fo rm a t io n
The MAX882/MAX883/MAX884 are series linear regula-
tors designed primarily for battery-powered systems.
Figure 7 shows a typical application.
S t a n d b y Mo d e vs . OFF Mo d e
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.
GND is 15µA at V
= 3.3V and 50µA at V
= 5V.
OUT
OUT
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.
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.
Lo w -Ba t t e ry-De t e c t io n Co m p a ra t o r
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.
Ou t p u t Ca p a c it o r S e le c t io n
a n d Re g u la t o r S t a b ilit y
An output filter capacitor is required at the MAX882/
MAX883/MAX884 OUT p in. The minimum outp ut
capacitance required for stability is 2.2µF.
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.
______________________________________________________________________________________ 11
MAXIM [ MAXIM INTEGRATED PRODUCTS ]
