iru1050 International Rectifier Corp., iru1050 Datasheet - Page 3

• Manufacturer Part Number: iru1050
• Description: 5a Low Dropout Positive Adjustable Regulator -
• Manufacturer: International Rectifier Corp.

PIN DESCRIPTIONS
PIN # PIN SYMBOL
BLOCK DIAGRAM
APPLICATION INFORMATION
Introduction
The IRU1050 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 5.5 V. 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 microprocessors that need typi-
cally 3.3V supply and are often generated from the 5V
supply. Another major requirement of these micropro-
cessors such as the Intel P54C
the load current from zero to several amps in tens of
Rev. 1.8
08/20/02
1
2
3
V
IN
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 drop out
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 IRU1050.
+
is the need to switch
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nanoseconds at the processor pins, which translates to
an approximately 300 to 500ns current step at the regu-
lator. In addition, the output voltage tolerances are also
extremely tight and they include the transient response
as part of the specification.For example Intel VRE
specification calls for a total of 100mV including initial
tolerance, load regulation and 0 to 4.6A load step.
The IRU1050 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.
OUT
pin and ground sets the output voltage.
1.25V
+
IRU1050
2 V
1 Adj
OUT
OUT
3