Datasheet LT1575, LT1577 (Analog Devices)

LT1575/LT1577 Ultrafast Transient Response, Low Dropout Regulators Adjustable and Fixed
U FEATURES DESCRIPTION
■
UltraFastTM Transient Response Eliminates
The LT®1575/LT1577 are single/dual controller ICs that
Tantalum and Electrolytic Output Capacitors
drive low cost external N-channel MOSFETs as source ■
FET RDS(ON) Defines Dropout Voltage
followers to produce ultrafast transient response, low ■
1% Reference/Output Voltage Tolerance Over
dropout voltage regulators.
Temperature
The LT1575/LT1577 achieve unprecedented transient- ■ Typical Load Regulation: 1mV load performance by eliminating expensive tantalum or ■ High Side Sense Current Limit bulk electrolytic output capacitors in the most demanding ■ Multifunction Shutdown Pin with Latchoff
U
modern microprocessor applications. Precision-trimmed
APPLICATIONS
adjustable and fixed output voltage versions accommo- date any required microprocessor power supply voltage. ■ Pentium® Processor Supplies Selection of the N-channel MOSFET RDS(ON) allows very ■ PowerPCTM Supplies low dropout voltages to be achieved. ■ 5V to 3.XXV or 3.3V to 2.XXV Microprocessor Supplies Unique protection features include a high side current ■ GTL Termination limit amplifier that activates a fault protection timer ■ Low Voltage Logic Supplies circuit. A multifunction Shutdown pin provides either LT1575CN8/LT1575CS8 Adjustable current limit time-out with latchoff, overvoltage protec- LT1575CN8-1.5/LT1575CS8-1.5 1.5V Fixed tion, thermal shutdown or a combination of these func- LT1575CN8-2.8/LT1575CS8-2.8 2.8V Fixed tions. The LT1575 is available in 8-pin SO or PDIP and the LT1575CN8-3.3/LT1575CS8-3.3 3.3V Fixed LT1577 is available in 16-pin narrow body SO. LT1575CN8-3.5/LT1575CS8-3.5 3.5V Fixed LT1575CN8-5/LT1575CS8-5 5V Fixed , LTC and LT are registered trademarks of Linear Technology Corporation. UltraFast is a trademark of Linear Technology Corporation. LT1577CS-ADJ/ADJ Adjustable, Adjustable Pentium is a registered trademark of Intel Corporation. LT1577CS-3.3/ADJ 3.3V Fixed, Adjustable PowerPC is a trademark of IBM Corporation. LT1577CS-3.3/2.8 3.3V Fixed, 2.8V Fixed Consult factory for additional output voltage combinations available in the LT1577.
U TYPICAL APPLICATION Transient Response for Ultrafast Transient Response 5V to 3.3V Low Dropout Regulator 0.2A to 5A Output Load Step (For Schematic Including Current Limit, See Typical Applications)
12V LT1575-3.3 1 8 SHDN IPOS 5V 50mV/DIV 2 7 + *FOR T < 45°C: C2 VIN INEG C5 C6 = 24 × 1µF Y5V 1µF 3 6 220µF Q1 GND GATE CERAMIC SURFACE IRFZ24 4 5 R2 MOUNT CAPACITORS. OUT COMP 5Ω V FOR T > 45°C: OUT 3.3V C6 = 24 × 1µF X7R 5A CERAMIC SURFACE 2A/DIV R1 MOUNT CAPACITORS. C3 7.5k C6* PLACE C6 IN THE 10pF 24µF C4 MICROPROCESSOR 1000pF SOCKET CAVITY GND 1575/77 TA02 1575/77 TA01 100µs/DIV 1