LT1528 Datasheet, PDF (1/12 Pages) Linear Technology – 3A Low Dropout Regulator for Microprocessor Applications

LT1528
3A Low Dropout Regulator
for Microprocessor Applications
FEATURES
s _{Dropout Voltage: 0.6V at IOUT = 3A}
s _{Fast Transient Response}
s _{Output Current: 3A}
s _{Quiescent Current: 400µA}
s _{No Protection Diodes Needed}
s _{Fixed Output Voltage: 3.3V}
s _{Controlled Quiescent Current in Dropout}
s _{Shutdown IQ = 125µA}
s _{Stable with 3.3µF Output Capacitor}
s _{Reverse Battery Protection}
s _{No Reverse Output Current}
s _{Thermal Limiting}
U
APPLICATIONS
s _{Microprocessor Applications}
s _{Post Regulator for Switching Supplies}
s _{5V to 3.3V Logic Regulator}
DESCRIPTION
The LT ^®1528 is a 3A low dropout regulator optimized to
handle the large load current transients associated with
the current generation of microprocessors. This device
has the fastest transient response of currently available
PNP regulators and is very tolerant of variations in capaci-
tor ESR. Dropout voltage is 75mV at 10mA, rising to
300mV at 1A and 600mV at 3A. The device has a quiescent
current of 400µA. Quiescent current is well controlled; it
does not increase significantly as the device enters drop-
out. The regulator can operate with output capacitors as
small as 3.3µF, although larger capacitors will be needed
to achieve the performance required in most microproces-
sor applications. The LT1528 is available with a fixed
output voltage of 3.3V. An external Sense pin allows
adjustment to output voltages greater than 3.3V, using a
simple resistive divider. This allows the device to be
adjusted over a wide range of output voltages, including
the 3.3V to 4.2V range required by a variety of processors
from Intel, IBM, AMD, and Cyrix.
The LT1528 has both reverse input and reverse output
protection and includes a shutdown feature. Quiescent
current drops to 125µA in shutdown. The LT1528 is
available in 5-lead TO-220 and 5-lead DD packages.
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATION
Microprocessor Supply with Shutdown
5 _IN
OUT ¹
V_IN =5V
LT1528
4 _SHDN
SENSE ²
GND
3
V_OUT
15Ω 68Ω ⁺ 4 × 47µF*
SOLID TANTALUM
J1 J2
J3
330Ω
V_SHDN (PIN 4)
<0.25
>2.80
NC
OUTPUT
OFF
ON
ON
SHORTING
J1
J2
J3
V _OUT
3.30
3.45
4.00
*CHOOSE CAPACITORS
TO MEET PROCESSOR
REQUIREMENTS
LT1528 • TA01
Dropout Voltage
0.6
0.5
0.4
0.3
0.2
0.1
0
0 0.5 1.0 1.5 2.0 2.5 3.0
OUTPUT CURRENT (mA)
LT1528 • TA02
1