MP2011A - 24V, 150mA, LOW QUIESCENT CURRENT LINEAR REGULATOR

MP2011A Rev. 1.0

www.MonolithicPower.com

11

2/19/2016

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APPLICATION INFORMATION

COMPONENT SELECTION

Setting the Output Voltage

For adjustable output version. Set the output

voltage of the MP2011A by using a resistor

divider as shown:

OUT

FB

R1

R2

GND

Choose R2=1MΩ

to

maintain

a

1.215µA

minimum load. Calculate the value for R1 using

the following equation:



















1

1.215V

V

R2

R1

OUT

(1)

The above equation is only valid on adjustable

also can be adjusted by adding external resistor

divider. Just note to take internal FB resistor

divider into consideration when choose external

divider. Choose a small resistance to mask

internal feedback resistor network. The equation

(1) still work but require the sum of R1 and R2 is

Figure 3: FB Divider of Fixed Output Version

The internal FB resistor dividers for different fixed

output versions please see below table.

Table 1: Internal FB Resistor Divider

Fixed Output Voltage

R1_IN

R2_IN

3.3V

1.72MΩ

1MΩ

Input Capacitor

For proper operation, place a ceramic capacitor

(C1) between 1µF and 10µF of dielectric type

X5R or X7R between the input pin and ground.

Larger values in this range will help to improve

line transient response.

Output Capacitor

For stable operation, use a ceramic capacitor (C2)

of type X5R or X7R between 1µF and 10µF.

Larger values in this range will help to improve

load transient response and reduce noise. Output

capacitors of other dielectric types may be used,

but are not recommended as their capacitance

can deviate greatly from their rated value over

temperature.

To improve load transient response, add a small

ceramic (X5R, X7R or Y5V dielectric) 22nF feed

forward capacitor in parallel with R1. The feed

forward capacitor is not required for stable

operation.

Output Noise

The MP2011A will exhibit noise on the output

during normal operation. This noise is negligible

for most applications. However, in applications

that include analog-to-digital converters (ADCs)

of more than 12 bits, one needs to consider the

ADC’s power supply rejection specifications. The

feed forward capacitor across R1 will significantly

reduce the output noise.

PCB layout guide

PCB layout is very important to achieve good

regulation, ripple rejection, transient response

and

thermal

performance.

It

is

highly

recommended to duplicate EVB layout for

optimum performance.

If change is necessary, please follow these

guidelines and take figure 4 for reference.

1) Input and output bypass ceramic capacitors

are suggested to be put close to the IN Pin

and OUT Pin respectively.

2) Ensure all feedback connections are short

and direct. Place the feedback resistors and

compensation components as close to the

chip as possible.