LT1577CS-3.3/ADJ#TRPBF

Overview

The LT1577CS-3.3/ADJ#TRPBF is a dual controller IC from the LT1575/LT1577 family, designed to drive external N-channel MOSFETs as source followers for ultrafast transient response and low dropout voltage regulation. It features one fixed 3.3V output channel and one adjustable output channel in a 16-lead narrow body SO package. The device utilizes high-side current sensing with a 50mV threshold and incorporates a multifunction shutdown pin for latchoff protection.

Feature Summary

• Ultrafast transient response capability that eliminates the need for bulky tantalum or electrolytic output capacitors
• Dual regulator architecture providing one fixed 3.3V channel and one fully adjustable channel
• High-side sense current limit amplifier with programmable time-out latchoff via the SHDN pin
• Low dropout performance determined by the external N-channel MOSFET RDS(ON)

Applications

• Pentium processor supplies
• PowerPC supplies
• Microprocessor core and I/O power supplies requiring fast load steps
• GTL termination circuits

Procurement Notes

Verify the specific suffix #TRPBF indicates tape and reel packaging when sourcing. Confirm the dual-output configuration matches the required fixed and adjustable channels. Ensure the 16-lead narrow body SO package footprint aligns with the PCB design. Check for RoHS compliance status on the latest datasheet revision.

Selection Notes

Select this part when system requirements demand extremely fast load transient response without bulk output capacitance. The dual-channel design allows simultaneous generation of a fixed logic rail and an adjustable core voltage. External N-channel MOSFETs must be chosen based on desired dropout voltage and gate drive requirements.

Part Context

This component belongs to the LT1575/LT1577 series of low dropout regulator controllers. While the LT1575 provides a single regulator channel, the LT1577 integrates two independent channels in a single package. This family is engineered specifically for modern microprocessor power applications where speed and efficiency are critical.

Replacement Considerations

LT1577CS-ADJ/ADJ

FAQ

How does the LT1577 achieve ultrafast transient response?

It drives external N-channel MOSFETs as source followers, allowing the control loop bandwidth to reach approximately 1MHz. This high speed enables the use of only ceramic decoupling capacitors instead of slow bulk electrolytic capacitors.

What is the function of the SHDN pin?

The SHDN pin serves multiple protection functions including current limit time-out latchoff, overvoltage protection, and thermal shutdown. It contains internal comparators and current sources to manage these fault states.