iru1117 International Rectifier Corp., iru1117 Datasheet - Page 3

• Manufacturer Part Number: iru1117
• Description: 800ma Low Dropout Positive Adjustable Regulator
• Manufacturer: International Rectifier Corp.

PIN DESCRIPTIONS
PIN #
BLOCK DIAGRAM
Rev. 1.8
02/04/03
APPLICATION INFORMATION
Introduction
The IRU1117 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
only needs 1.3V differential to maintain output regula-
tion. Unlike the first generation of the three-terminal regu-
lators such as LM117 that required 3V differential be-
tween the input and the regulated output.
The IRU1117 is specifically designed to meet the fast
current transient needs as well as providing an accurate
1
2
3
V
IN
PIN SYMBOL
3
V
Adj
V
OUT
IN
SHUTDOWN
THERMAL
CURRENT
LIMIT
A resistor divider from this pin to the V
The output of the regulator. A minimum of 10mF 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
voltage during the load transient response. This pin must always be 1.3V higher than V
in order for the device to regulate properly.
PIN DESCRIPTION
Figure 2 - Simplified block diagram of the IRU1117.
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www.irf.com
initial voltage, reducing the overall system cost with the
need for fewer output capacitors. This is a key require-
ment for today’s low voltage IC applications that typi-
cally need 3.3V supply and are often generated from the
5V supply. Other applications such as high speed
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.
OUT
pin and ground sets the output voltage.
1.25V
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IRU1117
2 V
1 Adj
OUT
OUT
3