MP20044-DUAL, ULTRA LOW NOISE, HIGH PSRR, 300mA LINEAR REGULATOR

MP20044 Rev. 1.0

www.MonolithicPower.com

9

1/11/2013

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© 2013 MPS. All Rights Reserved.

APPLICATION INFORMATION

Power Dissipation

The power dissipation for any package depends

on the thermal resistance of the case and circuit

board, the temperature difference between the

junction and ambient air, and the rate of airflow.

The power dissipation across the device can be

represented by the equation:

The

allowable

power

dissipation

can

be

calculated using the following equation:

difference

between

the

junction

and

the

resistance from the junction to the ambient

environment. Connect the GND pin of MP20044

to ground using a large pad or ground plane

helps to channel heat away.

Input Capacitor Selection

Using a capacitor whose value is >0.47µF on the

MP20044 input and the amount of capacitance

can be increased without limit. Larger values will

help improve line transient response with the

drawback of increased size. Ceramic capacitors are

preferred, but tantalum capacitors may also suffice.

Output Capacitor Selection

The MP20044 is designed specifically to work

with very low ESR ceramic output capacitor in

space-saving and performance consideration. A

ceramic capacitor in the range of 0.47µF and

10µF, and with ESR lower than 1.2Ω is suitable

for the MP20044 application circuit. Output

capacitor of larger values will help to improve

load transient response and reduce noise with

the drawback of increased size.

0.1

1

10

100

0

50

100

150

200

250

300

OUTPUT CURRENT(MA)

Figure 2—Relationship between ESR and

LDO Stability

Reverse Current Path

The PMOS used in the MP20044 has an inherent

diode connected between input and output (see

this diode gets forward biased and starts to

conduct. To avoid misoperation, an external

Schottky connected in parallel with the internal

parasitic diode prevents it from being turned on

by limiting the voltage drop across it to about

0.3V (see Figure 4).

VIN

VOUT

Figure 3—Inherent Diode Connected between

Each Regulator Input and Output

Figure 4—External Schottky Diode Connected

in Parallel with the Internal Parasitic Diode