IRU1050 Ver la hoja de datos (PDF) - International Rectifier
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IRU1050 Datasheet PDF : 12 Pages
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IRU1050
PIN DESCRIPTIONS
PIN # PIN SYMBOL PIN DESCRIPTION
1
Adj
A resistor divider from this pin to the VOUT pin and ground sets the output voltage.
2
VOUT
The output of the regulator. A minimum of 10mF capacitor must be connected from this pin
to ground to insure stability.
3
VIN
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 VOUT
in order for the device to regulate properly.
BLOCK DIAGRAM
VIN 3
2 VOUT
+
CURRENT
LIMIT
+
1.25V
THERMAL
SHUTDOWN
Figure 2 - Simplified block diagram of the IRU1050.
1 Adj
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™ is the need to switch
the load current from zero to several amps in tens of
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.
Rev. 1.8
08/20/02
www.irf.com
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