LT1577CS-3.3/2.8#TRPBF

Overview

The LT1577CS-3.3/2.8#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 low dropout regulators. It provides two fixed output voltages: 3.3V and 2.8V. The device operates with an input voltage range up to 20V and features a typical quiescent current of 9mA. It utilizes high-side current sensing via IPOS and INEG pins with a 50mV threshold. The package is a 16-lead narrow body SOIC.

Feature Summary

• Dual channel architecture providing independent 3.3V and 2.8V fixed outputs
• Ultrafast transient response capability eliminates bulk tantalum or electrolytic capacitors
• Integrated multifunction shutdown pin supports latchoff, overvoltage protection, and thermal shutdown
• High-side sense current limit amplifier with programmable time-out function

Applications

• Microprocessor core supplies requiring fast load transient response
• PowerPC processor power management
• GTL termination circuits
• Low voltage logic supplies

Procurement Notes

Verify the specific suffix #TRPBF indicates tape and reel packaging when sourcing. Confirm the manufacturer is Analog Devices Inc. Ensure the part number matches the dual fixed output configuration (3.3V/2.8V) rather than adjustable variants. Check datasheet revision history for any pinout or electrical characteristic updates before finalizing design integration.

Selection Notes

Select this component when dual isolated rails are required from a single controller IC. The fixed 3.3V and 2.8V outputs simplify resistor divider networks compared to adjustable versions. Ensure the external N-channel MOSFET selected has a gate threshold voltage compatible with the GATE pin swing. Verify that the system can accommodate the high-side current sensing requirements using a shunt resistor or PCB trace.

Part Context

This part belongs to the LT1575/LT1577 series of low dropout regulator controllers. Unlike monolithic LDOs, these ICs require external N-channel MOSFETs to achieve superior bandwidth and transient performance. The LT1577 specifically offers dual channels in a 16-lead package, whereas the LT1575 is a single-channel version in an 8-lead package.

Replacement Considerations

LT1577CS-3.3/ADJ

FAQ

How does the LT1577 eliminate bulk output capacitors?

It achieves ultrafast transient response through a wide bandwidth control loop that drives external N-channel MOSFETs as source followers, allowing it to respond to load steps in nanoseconds without needing large bulk capacitance.

What is the function of the SHDN pin?

The SHDN pin is a multifunction shutdown input that provides latchoff capability during current limit time-outs, overvoltage protection, or thermal shutdown conditions.