AME, Inc.
600mA CMOS LDO
AME8805 / 8810
n Detailed Description
n External Capacitors
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 AME8805/8810 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. Un-
fortunately, large value ceramic capacitors are compara-
tively expensive. One option is to parallel a 0.1µF ce-
ramic capacitor with a 10µF Aluminum Electrolytic. The
benefit is low ESR, high capacitance, and low overall
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
150oC, or the current exceeds 600mA. During thermal
shutdown, the output voltage remains low. Normal op-
eration is restored when the junction temperature drops
below 120oC.
A second capacitor is recommended between the in-
put and ground to stabilize Vin. The input capacitor should
be at least 0.1µF to have a beneficial effect.
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.
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.
8
AME [ ANALOG MICROELECTRONICS ]
