Datasheet

MAX8880/MAX8881
12V, Ultra-Low-I
Q
, Low-Dropout
Linear Regulators with POK
6 _______________________________________________________________________________________
Reverse Battery Protection
The MAX8880/MAX8881 have a unique protection
scheme that limits the reverse supply current to less
than 1mA when V
IN
is forced below ground. The circuit
monitors the polarity of IN, disconnecting the internal
circuitry and parasitic diodes when the battery is
reversed. This feature prevents the device from electri-
cal stress and damage when the battery is connected
backwards. If reverse battery protection is needed,
drive SHDN through a 100kΩ resistor.
Current Limiting
The MAX8880/MAX8881 include a current limiter. When
the output is shorted to ground, drive to the output
PMOS is limited. The output can be shorted to ground
without damage to the part.
Thermal Overload Protection
Thermal overload protection limits total power dissipa-
tion in the MAX8880/MAX8881. When the internal junc-
tion temperature exceeds T
J
= +160°C, the thermal
sensor signals the shutdown logic, turning off the pass
transistor and allowing the IC to cool. The thermal sen-
sor turns the pass transistor on again after the IC’s
junction temperature cools by 15°C, resulting in a
pulsed output during continuous thermal-overload con-
ditions.
Thermal-overload protection is designed to protect the
MAX8880/MAX8881 in the event of fault conditions. For
continuous operation, do not exceed the absolute maxi-
mum junction temperature rating of T
J(MAX)
= +150°C.
Operating Region and Power Dissipation
The MAX8880/MAX8881’s maximum power dissipation
depends on the thermal resistance of the case and cir-
cuit board, the temperature difference between the die
junction and ambient air, and the rate of airflow. The
power dissipation in the device is P = I
OUT
(V
IN
-
V
OUT
). The maximum power dissipation allowed is:
IN
OUT
FB
GND
C2
4.7μF
C1
1μF
SHDN
2.5V TO 12V
UP TO 200mA
R3
R4
REGULATION OK
POK
MAX8880
V
IN
V
OUT
1.25V TO 5.5V
Figure 3. Adjustable Output Using External Feedback Resistors
SHUTDOWN
LOGIC
ERROR
AMP
1.25V
REF
91%
REF
P
OUT
POK
GND
IN
SHDN
MAX8881
THERMAL
SENSOR
REVERSE
BATTERY
PROTECTION
MOS DRIVER
WITH I
LIMIT
POK
FB
Figure 2. Functional Diagram