AME8818_12 Datasheet, PDF(13/25 Page) Analog Microelectronics

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AME8818_12 Datasheet, PDF (13/25 Pages) Analog Microelectronics – Low Dropout 300mA CMOS Regulator

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AME

AME8818

Low Dropout

300mA CMOS Regulator

n Detailed Description

The AME8818 is low-dropout, low quiescent-current linear

regulator designed primarily for battery-powered applications.

It is available with present output voltage ranging from 1.2V

to 4.5V, and can supply loads up to 300mA.

n Shutdown Mode

The AME8818 has enable-control-pin. Drive EN low to shut-

down OUT. Drive EN to shutdown the entire chip, reducing

supply current to 5ÂµA. Connected EN to logic-high or IN for

normal operation.

n Circuit Limit

The AME8818 contains current limiters which monitor and

control the pass transistor's Gate voltage, limiting the guar-

anteed maximum output current to 330mA minimum. The

output can be shorted to ground for an indefinite time without

damaging the part.

n Capacitor Selection and

Regulator Stability

Use a 1ÂµF capacitor on the AME8818 input and a

1ÂµF capacitor on the OUT. Larger input capacitor val-

ues and lower ESR provide better supply noise rejec-

tion and line transient response. To reduce output

noise and improve load transient voltage dips, use

larger output capacitors up to 4.7ÂµF. For stable op-

eration over the full temperature range with load cur-

rents up to 300mA, input and output capacitors should

be a minimum of 1ÂµF by X7R.

Note that some ceramic dielectrics large capacitance

and ESR variation with temperature. With dielectrics

such as Z5U and Y5V, it may be necessary to use

2.2ÂµF or more for up to 300mA load current to ensure

stability at temperatures below -10oC. With X7R or

X5R dielectrics, 1ÂµF is sufficient at all operating tem-

peratures. These regulators are optimized for ceramic

capacitors. Tantalum capacitors are not recommended.

Bypass capacitor can be in between 0.1ÂµF~0.001ÂµF.

A larger capacitor improves AC ripple rejection, but

also make the output come up slowly.

n Thermal-Overload Protection

n Adjustable Version

Thermal-overload protection limits total power dissipation

in the AME8818. When the junction temperature arrive TJ =

160oC approximately, the thermal sensor signals the shut-

down logic, turning off the pass transistor and allowing the IC

to cool.

n PSRR and Operation from

sources Other than Batteries

The AME8818 is designed to deliver low-dropout voltage

and low quiescent currents in battery-powered system.

Power-supply rejection ratio is 60dB (Typ.) at 1KHz. When

operating from sources other than betteries, PSRR and tran-

sient response can be improved by increasing input, output

and bypass capacitors(see PSRR vs Frequency Curve).

The adjustable version uses external feedback re-

sistors to generate an output voltage anywhere from

0.98V to 4.5V. VADJ is trimmed to 0.98V and VOUT is

given by the equation:

VOUT = VADJ ( 1 + R1 / R2 )

Feedback resistors R1 and R2 should be high enough

to keep quiescent current low, but increasing R1 + R2

will reduce stability. In general, R1 and R2 in the 10's

of kâ¦ will produce adequate stability, given reason-

able layout precautions. To improve stability charac-

teristics, keep parasitics on the ADJ pin to a mini-

mum, and lower R1 and R2 values.

Rev.D.06

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