PAM3101AAA310 datasheet(12/26 Pages) PAM

12 / 26 page

Capacitor Selection and Regulator Stability

in the load current from 1mA to 300mA, is 20mV.

The ESR of the output capacitor is critical to the

transient spike. A larger capacitance along with

Similar to any low dropout regulator, the external

smaller ESR results in a smaller spike.

capacitors used with the PAM3101 must be

carefully selected for regulator stability and

performance.

Shutdown Input Operation

A capacitor C of more than 1µF can be employed

The PAM3101 is shut down by pulling the EN

input low, and is turned on by tying the EN input

in the input pin, while there is no upper limit for

to VIN.

the capacitance of C . Please note that the

distance between C

and the input pin of the

PAM3101 should not exceed 0.5 inch. Ceramic

Internal P-Channel Pass Transistor

c a p a c i t o r s a r e s u i t a b l e f o r t h e PA M 3 1 0 1 .

Capacitors with larger values and lower ESR

The PAM3101 features a 0.75Ω P-Channel

(equivalent series resistance) provide better

MOSFET device as a pass transistor. The P-

PSRR and line-transient response.

MOS pass transistor enables the PAM3101 to

consume only 65μA of ground current during low

The PAM3101 is designed specifically to work

dropout, light-load, or heavy-load operations.

with low ESR ceramic output capacitors in order

This feature increases the battery operation life

to save space and improve performance. Using

time.

an output ceramic capacitor whose value is

>2.2µF with ESR>5mΩ ensures stability.

Input-Output ( Dropout ) Voltage

A 10nF bypass capacitor connected to BYP pin is

A regulator's minimum input-output voltage

suggested for suppressing output noise. The

difference (or dropout voltage) determines the

capacitor, in series connection with an internal

lowest usable supply voltage. The PAM3101 has

200kΩ resistor, forms a low-pass filter for noise

a typical 300mV dropout voltage. In battery-

reduction. Increasing the capacitance will slightly

powered systems, this will determine the useful

decrease the output noise, but increase the start-

end-of-life battery voltage.

up time.

Current Limit and Short Circuit Protection

Load Transient Considerations

The PAM3101 features a current limit, which

C u r v e 1 0 o f t h e PA M 3 1 0 1 l o a d - t r a n s i e n t

monitors and controls the gate voltage of the

response on page 10 shows two components of

pass transistor. The output current can be

the output response: a DC shift from the output

limited to 400mA by regulating the gate voltage.

impedance due to the load current change and

The PAM3101 also has a built-in short circuit

transient response. The DC shift is quite small

current limit.

due to excellent load regulation of the PAM3101.

The transient spike, resulting from a step change

Application Information

Power Analog Microelectronics, Inc

www.poweranalog.com

PAM3101

300mA High PSRR Low Dropout CMOS Linear Regulator

11/2010 Rev 2.5

PAM3101AAA310 Datasheet(PDF) 12 Page - Power Analog Micoelectronics

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