AME8841 Datasheet, PDF(5/10 Page) Analog Microelectronics

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AME8841 Datasheet, PDF (5/10 Pages) Analog Microelectronics – 600mA CMOS LDO

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Analog Microelectronics, Inc.

AME8841

600mA CMOS LDO

n Detailed Description

The AME8841 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 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 110oC.

The AME8841 switches from voltage mode to current mode

when the load exceeds the rated output current. This

prevents over-stress. The AME8841 also incorporates

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 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 1ÂµA. This pin behaves

much like an electronic switch.

n External Capacitors

The AME8841 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. Unfortunately,

large value ceramic capacitors are comparatively expen-

sive. One option is to parallel a 0.1ÂµF ceramic capacitor

with a 10ÂµF Aluminum Electrolytic. The benefit is low

ESR, high capacitance, and low overall cost.

A second capacitor is recommended between the input

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.

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