AME8805_12 Datasheet, PDF(10/17 Page) Analog Microelectronics

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AME8805_12 Datasheet, PDF (10/17 Pages) Analog Microelectronics – 600mA CMOS LDO

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AME

AME8805 / 8813

n Detailed Description

The AME8805/8813 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 ampli-

fier compares the output voltage to a precision reference.

Over-current and Thermal shutdown circuits become ac-

tive when the junction temperature exceeds 150oC, or

the current exceeds 600mA. During thermal shutdown,

the output voltage remains low. Normal operation is re-

stored when the junction temperature drops below 120oC.

The AME8805/8813 switches from voltage mode to cur-

rent mode when the load exceeds the rated output cur-

rent. This prevents over-stress. The AME8805/8813 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.

600mA CMOS LDO

n External Capacitors

The AME8805/8813 is stable with an output capacitor

to ground of 2.2ÂµF 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 0.1ÂµF ce-

ramic capacitor with a 10ÂµF 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 0.1ÂµF 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.

Rev.R.12

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