AME8808LEGSZ datasheet(8/13 Pages) AME

8 / 13 page

AME

750mA CMOS LDO

AME8808

Rev.G.02

The AME8808 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 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 750mA. During thermal shutdown,

the output voltage remains low. Normal operation is re-

stored when the junction temperature drops below 120oC.

The AME8808 switches from voltage mode to current

mode when the load exceeds the rated output current.

This prevents over-stress. The AME8808 also incorpo-

rates current foldback to reduce power dissipation when

the output is short circuited. This feature becomes ac-

tive 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.

n Detailed Description

n External Capacitors

The AME8808 is stable with an output capacitor to

ground of 2.2

µF or greater. Ceramic capacitors have the

lowest ESR, and will offer the best AC performance. Con-

versely, Aluminum Electrolytic capacitors exhibit the high-

est ESR, resulting in the poorest AC response. Unfortu-

nately, large value ceramic capacitors are comparatively

expensive. One option is to parallel a 0.1

µF ceramic

capacitor with a 10

µF 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

µF 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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