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AME, Inc.
8
600mA CMOS LDO
AME8805 / 8810
The AME8805/8810 family of CMOS regulators con-
tain a PMOS pass transistor, voltage reference, error am-
plifier, 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 120
o
C.
The AME8805/8810 switches from voltage mode to cur-
rent mode when the load exceeds the rated output cur-
rent. This prevents over-stress. The AME8805/8810 also
incorporates current foldback to reduce power dissipa-
tion when the output is short circuited. This feature be-
comes 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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Detailed Description
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External Capacitors
The AME8805/8810 is stable with an output capacitor
to ground of 2.2
μ
F 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. Un-
fortunately, large value ceramic capacitors are compara-
tively expensive. One option is to parallel a 0.1
μ
F ce-
ramic capacitor with a 10
μ
F Aluminum Electrolytic. The
benefit is low ESR, high capacitance, and low overall
cost.
A second capacitor is recommended between the in-
put and ground to stabilize Vin. The input capacitor should
be at least 0.1
μ
F 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.