LT1528

Manufacturer Part NumberLT1528
Description3A Low Dropout Regulator for Microprocessor Applications
ManufacturerLinear Technology
LT1528 datasheet
 


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FEATURES
Dropout Voltage: 0.6V at I
= 3A
OUT
Fast Transient Response
Output Current: 3A
Quiescent Current: 400 A
No Protection Diodes Needed
Fixed Output Voltage: 3.3V
Controlled Quiescent Current in Dropout
Shutdown I
= 125 A
Q
Stable with 3.3 F Output Capacitor
Reverse Battery Protection
No Reverse Output Current
Thermal Limiting
U
APPLICATIONS
Microprocessor Applications
Post Regulator for Switching Supplies
5V to 3.3V Logic Regulator
U
TYPICAL
APPLICATION
Microprocessor Supply with Shutdown
5
1
IN
OUT
V
=5V
LT1528
IN
J1
4
2
SHDN
SENSE
GND
330
3
V
(PIN 4)
OUTPUT
SHORTING
V
SHDN
OUT
<0.25
OFF
J1
3.30
>2.80
ON
J2
3.45
NC
ON
J3
4.00
3A Low Dropout Regulator
for Microprocessor Applications
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 400 A. 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 3.3 F, 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 125 A 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.
V
OUT
+
4
47 F*
15
68
SOLID TANTALUM
J2
J3
*CHOOSE CAPACITORS
TO MEET PROCESSOR
REQUIREMENTS
LT1528 • TA01
LT1528
U
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

LT1528 Summary of contents

  • Page 1

    ... Intel, IBM, AMD, and Cyrix. The LT1528 has both reverse input and reverse output protection and includes a shutdown feature. Quiescent current drops to 125 A 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. ...

  • Page 2

    ... Dropout Voltage (Note RATINGS Output Short-Circuit Duration .......................... Indefinite Storage Temperature Range ................. – 150 C Operating Junction Temperature Range LT1528C ............................................... 125 C Lead Temperature (Soldering, 10 sec).................. 300 C *For applications requiring input voltage ratings greater than 15V, contact the factory ORDER PART ...

  • Page 3

    ... When operating at maximum input voltage, the output current must be limited. When operating at maximum output current, the input voltage range must be limited. Note 3: The LT1528 is tested and specified with the Sense pin connected to the Output pin. CONDITIONS I ...

  • Page 4

    ... DEVICE IS OPERATING IN DROPOUT 125 – 0.5 1.5 2.0 2.5 3.0 1.0 OUTPUT CURRENT (A) LT1528 • TPC08 Quiescent Current 2. 4. 1.50 1.25 1.00 0. OPEN SHDN 0. 0.25 SHDN 0 –50 – 100 125 TEMPERATURE ( C) LT1528 • TPC03 Ground Pin Current ...

  • Page 5

    ... OUTPUT VOLTAGE (V) LT1528 • TPC17 LT1528 Shutdown Pin Input Current SHUTDOWN PIN VOLTAGE (V) LT1528 • TPC12 Current Limit OUT INPUT VOLTAGE (V) LT1528 • TPC15 Ripple Rejection ...

  • Page 6

    ... V (NOMINAL OUT I = 1mA TO 3A LOAD –5 –50 – 100 125 TEMPERATURE ( C) LT1528 • TPC20 Transient Response 3 OUT 100 120 140 160 180 200 TIME ( s) LT1528 • TPC22 ). BE ...

  • Page 7

    ... Output pin. In the case of reversed input, the LT1528 will act as if there is a diode in series with its input. There will be no reverse current flow into the LT1528 and no reverse voltage will appear at the load. The device will protect both itself and the load ...

  • Page 8

    ... LT1528 U U APPLICATIONS INFORMATION The LT1528 is specified with the Sense pin tied to the Output pin. This sets the output voltage to 3.3V. Specifica- tions for output voltage greater than 3.3V will be propor- tional to the ratio of the desired output voltage to 3.3V (V /3.3V). For example, load regulation for an output OUT current change of 1mA to 1.5A is – ...

  • Page 9

    ... 31 81.4 C JMAX Output Capacitance and Transient Performance The LT1528 is designed to be stable with a wide range of output capacitors. The minimum recommended value is 3.3 F with an ESR less. The LT1528 output transient response will be a function of output capaci- tance ...

  • Page 10

    ... Figure 3. This can happen if the input of the LT1528 is connected to a low voltage and the output is held second regulator circuit. When the input pin is forced below the 0utput pin or the Output pin is pulled above the input pin, the input current will typically drop to less than 2 A (see Figure 4) ...

  • Page 11

    ... TYP 0.057 – 0.077 (1.447 – 0.955) (0.330 – 0.584) 0.028 – 0.038 (0.711 – 0.965) LT1528 0.045 – 0.055 (1.143 – 1.397) +0.008 0.004 –0.004 0.059 (1.499) +0.203 0.102 – ...

  • Page 12

    ... LT1528 PACKAGE DESCRIPTION 0.390 – 0.415 (9.906 – 10.541) 0.460 – 0.500 (11.684 – 12.700) 0.057 – 0.077 (1.448 – 1.956) (0.711 – 0.965) RELATED PARTS PART NUMBER DESCRIPTION ® LTC 1265 High Efficiency Step-Down Switching Regulator LTC1266 Synchronous Switching Controller ...