LT1577CS-3.3/ADJ#PBF

Overview

The LT1577CS-3.3/ADJ#PBF is a dual controller IC for low dropout regulators, packaged in a 16-lead narrow SOIC. It drives external N-channel MOSFETs to create ultrafast transient response supplies. One channel provides a fixed 3.3V output while the second channel offers adjustable voltage control. The device features high-side current sensing with a 50mV threshold and a multifunction shutdown pin for latchoff protection.

Feature Summary

• Ultrafast transient response capability eliminates the need for bulky tantalum or electrolytic output capacitors
• Dual configuration providing one fixed 3.3V regulator and one fully adjustable regulator channel
• High-side sense current limit amplifier activates fault protection timer circuits upon overload
• Multifunction shutdown pin enables latchoff, overvoltage protection, and thermal shutdown

Applications

• Microprocessor core power supplies requiring rapid load step response
• PowerPC processor power delivery systems
• GTL termination voltage regulation
• Low voltage logic supply generation

Procurement Notes

Verify the specific suffix /ADJ confirms the mixed fixed and adjustable channel configuration before procurement. Confirm package dimensions match the 16-lead narrow body SOIC footprint. Ensure external N-channel MOSFET selection aligns with the required dropout voltage specifications.

Selection Notes

Select this component when system design requires eliminating bulk output capacitance to save board space and cost. Verify that the external MOSFET gate drive requirements are met by the internal GATE pin swing. Ensure the input voltage range supports the required output differential for the chosen pass transistor.

Part Context

This part belongs to the LT1575/LT1577 family of ultrafast transient response low dropout regulators. While the LT1575 is a single-channel controller, the LT1577 integrates two independent channels in a single package. This allows designers to generate multiple distinct voltage rails from a single controller unit.

Replacement Considerations

LT1577CS-ADJ/ADJ

FAQ

How does the LT1577 achieve ultrafast transient response?

It achieves this by driving external N-channel MOSFETs as source followers, which allows for extremely wide bandwidth control loops that eliminate the need for slow-response bulk output capacitors.

What is the function of the SHDN pin?

The SHDN pin serves as a multifunction shutdown input that can trigger current limit time-out latchoff, overvoltage protection, or thermal shutdown depending on the external circuitry connected to it.