AME8801BEEVL datasheet(13/24 Pages) AME

13 / 24 page

AME

AME8801 / 8812 / 8840

300mA CMOS LDO

Rev.S.02

A third capacitor can be connected between the BY-

PASS pin and GND. This capacitor can be a low cost

Polyester Film variety between the value of 0.001 ~

0.01

µF. A larger capacitor improves the AC ripple rejec-

tion, but also makes the output come up slowly. This

"Soft" turn-on is desirable in some applications to limit

turn-on surges.

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.

The AME8801/8812/8840 is stable with an output ca-

pacitor to ground of 2.2

µF or greater. Ceramic capacitors

have the lowest ESR, and will offer the best AC perfor-

mance. Conversely, Aluminum Electrolytic capacitors

exhibit the highest ESR, resulting in the poorest AC re-

sponse. Unfortunately, large value ceramic capacitors are

comparatively expensive. One option is to parallel a 0.1

µF

ceramic capacitor with a 10

µFAluminum 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.

n Detailed Description

n External Capacitors

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 qui-

escent current is less than 1

µA. This pin behaves much

like an electronic switch.

The AME8801/8812/8840 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 300mA. During thermal shutdown,

the output voltage remains low. Normal operation is re-

stored when the junction temperature drops below 120oC.

The AME8801/8812/8840 switches from voltage mode

to current mode when the load exceeds the rated output

current. This prevents over-stress. The AME8801/8812/

8840 also incorporates current foldback to reduce power

dissipation when the output is short circuited. This fea-

ture becomes active when the output drops below 0.8volts,

and reduces the current flow by 65%. Full current is re-

stored when the voltage exceeds 0.8 volts.

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