AME, Inc.
AME8800 / 8811
300mA CMOS LDO
n Detailed Description
n External Capacitors
The AME8800/8811 family of CMOS regulators con-
tain a PMOS pass transistor, voltage reference, error
amplifier, over-current protection, and thermal shut-
down.
The AME8800/8811 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 com-
paratively expensive. One option is to parallel a 0.1uF
ceramic capacitor with a 10uF Aluminum Electrolytic.
The benefit is low ESR, high capacitance, and low over-
all cost.
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
o
150 C, or the current exceeds 300mA. During thermal
A second capacitor is recommended between the input
shutdown, the output voltage remains low. Normal op-
eration is restored when the junction temperature drops
below 120 C.
and ground to stabilize V . The input capacitor should
be at least 0.1µF to have a beneficial effect.
IN
o
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.
The AME8800/8811 switches from voltage mode to cur-
rent mode when the load exceeds the rated output cur-
rent. This prevents over-stress. The AME8800/8811
also incorporates current foldback to reduce power dis-
sipation 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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AME [ ANALOG MICROELECTRONICS ]
