IRU1010

3

Rev. 1.7

02/03/03

www.irf.com

APPLICATION INFORMATION

Introduction

The IRU1010 adjustable Low Dropout (LDO) regulator is

a three-terminal device which can easily be programmed

with the addition of two external resistors to any volt-

ages within the range of 1.25 to 5.5V. This regulator,

unlike the first generation of the three-terminal regula-

tors such as LM117 that required 3V differential between

the input and the regulated output, only needs 1.3V dif-

ferential to maintain output regulation. This is a key re-

quirement for today’s low voltage IC applications that

typically need 3.3V supply and are often generated from

the 5V supply. Other applications such as high speed

BLOCK DIAGRAM

Figure 2 - Simplified block diagram of the IRU1010.

PIN DESCRIPTIONS

PIN #

PIN SYMBOL

PIN DESCRIPTION

1

2

3

Adj

The output of the regulator. A minimum of 10

mF capacitor must be connected from this pin

to ground to insure stability.

The input pin of the regulator. Typically a large storage capacitor is connected from this

pin to ground to insure that the input voltage does not sag below the minimum dropout

in order for the device to regulate properly.

1

Adj

THERMAL

SHUTDOWN

CURRENT

LIMIT

1.25V

+

+

memory termination need to switch the load current from

zero to full load in tens of nanoseconds at their pins,

which translates to an approximately 300 to 500ns cur-

rent step at the regulator. In addition, the output voltage

tolerances are sometimes tight and they include the tran-

sient response as part of the specification.

The IRU1010 is specifically designed to meet the fast

current transient needs as well as providing an accurate

initial voltage, reducing the overall system cost with the

need for fewer output capacitors.