AME8802(2001) データシートの表示（PDF） - AME, Inc

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AME8802
(Rev.:2001)

300mA CMOS LDO

AME, Inc 

Analog Microelectronics, Inc.

AME8802

300mA CMOS LDO

n Detailed Description

The AME8802 family of CMOS regulators contain a

PMOS pass transistor, voltage reference, error ampli-

fier, over-current protection, thermal shutdown, and

power good function.

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 300mA. During thermal

shutdown, the output voltage remains low. Normal op-

eration is restored when the junction temperature drops

below 120oC.

The AME8802 switches from voltage mode to current

mode when the load exceeds the rated output current.

This prevents over-stress. The AME8802 also incor-

porates current foldback to reduce power dissipation

when the output is short circuited. This feature becomes

active when the output drops below 0.8volts, and re-

duces the current flow by 65%. Full current is restored

when the voltage exceeds 0.8 volts.

n Enable

The Enable pin normally floats high. When actively,

pulled low, the PMOS pass transistor shuts off, and all

internal circuits are powered down. In this state, the

quiescent current is less than 1µA. This pin behaves

much like an electronic switch.

n Power Good

The AME8802 includes the Power Good feature. Nor-

mally, Pin 4 is "Floating", however, when the output is

not within ±10% of the specified voltage, it pulls low.

This can occur under the following conditions:

1) Input Voltage too low.

2) During Over-Temperature.

3) During Over-Current.

4) If output is pulled up.

n External Capacitors

The AME8802 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.

Unfortunately, large value ceramic capacitors are com-

paratively expensive. One option is to parallel a 0.1µF

ceramic capacitor with a 10µF Aluminum Electrolytic.

The benefit is low ESR, high capacitance, and low over-

all cost.

A second capacitor is recommended between the input

and ground to stabilize Vin. The input capacitor should

be at least 0.1uF 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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