IRU1075 View Datasheet(PDF) - International Rectifier
Part Name
Description
Manufacturer
IRU1075 Datasheet PDF : 6 Pages
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IRU1075
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 10µF 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
1075blk1-1.0
1 Adj
Figure 2 - Simplified block diagram of the IRU1075
APPLICATION INFORMATION
Introduction
The IRU1075 adjustable Low Dropout (LDO) regulator
is a three-terminal device which can easily be pro-
grammed with the addition of two external resistors to
any voltages within the range of 1.25 to 5.5 V. This regu-
lator 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, only needs
1.3V differential to maintain output regulation. This is a
key requirement for today’s microprocessors that need
typically 3.3V supply and are often generated from the
5V supply. Another major requirement of these micro-
processors 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 IRU1075 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. 1.1
06/29/01
3
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