US1010 Datasheet, PDF (3/5 Pages) UNISEM – 1A LOW DROPOUT POSITIVE ADJUSTABLE REGULATOR

US1010
PIN DESCRIPTIONS
PIN #
1
2
3
PIN SYMBOL
Adj
Vout
Vin
PIN DESCRIPTION
A resistor divider from this pin to the Vout pin and ground sets the output voltage.
The output of the regulator. A minimum of 10uF 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 Vout in order for the device to regulate properly.
BLOCK DIAGRAM
Vin 3
2 Vout
+
CURRENT
LIMIT
THERMAL
SHUTDOWN
1.25V ⁺
1010blk1-1.0
1 Adj
Figure 1 - Simplified block diagram of the US1010
APPLICATION INFORMATION
Introduction
The US1010 adjustable Low Dropout (LDO) regulator is
a 3 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 3T regulators such as
LM117 that required 3V differential between the input
and the regulated output,only needs 1.3V differential to
maintain output regulation. This is a key requirement for
today’slow voltage IC applications that typically need
3.3V supply and are often generated from the 5V sup-
ply. Other applications such as high speed memory ter-
mination need to switch the load current from zero to full
load in tens of nanoseconds at the their pins ,which
translates to an approximately 300 to 500 nS current
step at the regulator . In addition, the output voltage tol-
erances are sometimes tight and they include the tran-
sient response as part of the specification.
The US1010 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. 1.3
10/30/00
2-3