Analog Microelectronics, Inc.
AME8841
600mA CMOS LDO
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General Description
The AME8841 linear regulator features low quiescent cur-
rent (30µA typ.) with low dropout voltage, making it ideal
for battery applications. The space-saving SO-8 pack-
age is attractive for "Pocket” and "Hand Held" applica-
tions.
These rugged devices have both Thermal Shutdown,
and Current Fold-back to prevent device failure under
the "Worst" of operating conditions.
The AME8841 is stable with an output capacitance of
2.2µF or greater.
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Features
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Very Low Dropout Voltage
Guaranteed 600mA Output
Accurate to within 1.5%
30µA Quiescent Current
Over-Temperature Shutdown
Current Limiting
Short Circuit Current Fold-back
Power-Saving Shutdown Mode
Space-Saving SO-8 Package
Many fixed output voltages available
Low Temperature Coefficient
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Applications
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Pin Configuration
SO-8 Top View
OUT
IN
GND
OUT
AME
8841
NC
EN
NC
NC
Instrumentation
Portable Electronics
Wireless Devices
Cordless Phones
PC Peripherals
Battery Powered Widgets
Electronic Scales
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Functional Block Diagram
IN
Overcurrent
Shutdown
OUT
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Typical Application
IN
IN
AME8841
GND
OUT
EN
OUT
Thermal
Shutdown
EN
C1
5V
R1
AMP
C3
2.2µF
1µF
V
ref
=1.215V
R2
GND
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Analog Microelectronics, Inc.
AME8841
600mA CMOS LDO
n
Detailed Description
The AME8841 family of CMOS regulators contain a
PMOS pass transistor, voltage reference, error amplifier,
over-current protection, and thermal shutdown.
The P-channel pass transistor receives data from the
error amplifier, over-current shutdown, and thermal pro-
tection circuits. During normal operation, the error am-
plifier compares the output voltage to a precision refer-
ence. Over-current and Thermal shutdown circuits be-
come active when the junction temperature exceeds
150
o
C, or the current exceeds 600mA. During thermal
shutdown, the output voltage remains low. Normal op-
eration is restored when the junction temperature drops
below 110
o
C.
The AME8841 switches from voltage mode to current mode
when the load exceeds the rated output current. This
prevents over-stress. The AME8841 also incorporates
current foldback to reduce power dissipation when the
output is short circuited. This feature becomes active
when the output drops below 0.8 volts, and reduces the
current flow by 65%. Full current is restored when the
voltage exceeds 0.8 volts.
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Enable
The Enable pin normally floats high. When actively,
pulled low, the PMOS pass transistor shuts off, and all
internal circuits are powered down. In this state, the
quiescent current is less than 1µA. This pin behaves
much like an electronic switch.
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External Capacitors
The AME8841 is stable with an output capacitor to ground
of 2.2µF or greater. Ceramic capacitors have the lowest
ESR, and will offer the best AC performance. Conversely,
Aluminum Electrolytic capacitors exhibit the highest
ESR, resulting in the poorest AC response. Unfortunately,
large value ceramic capacitors are comparatively expen-
sive. One option is to parallel a 0.1µF ceramic capacitor
with a 10µF Aluminum Electrolytic. The benefit is low
ESR, high capacitance, and low overall cost.
A second capacitor is recommended between the input
and ground to stabilize Vin. The input capacitor should
be at least 0.1µF to have a beneficial effect.
All capacitors should be placed in close proximity to
the pins. A "Quiet" ground termination is desirable.
This can be achieved with a "Star" connection.
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