AME

6

750mA CMOS LDO

AME8843

Rev. A.02

The AME8843 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-

the current exceeds 750mA. During thermal shutdown,

the output voltage remains low. Normal operation is re-

The AME8843 switches from voltage mode to current

mode when the load exceeds the rated output current.

This prevents over-stress. The AME8843 also incorpo-

rates current foldback to reduce power dissipation 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.

n Detailed Description

n External Capacitors

The AME8843 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 ca-

pacitor 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.