LT1577CS-3.3/2.8#PBF

Overview

The LT1577CS-3.3/2.8#PBF 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 two independent regulators: one fixed at 3.3V and another fixed at 2.8V. The device operates with an input voltage range up to 20V and includes high-side current limiting, multifunction shutdown with latchoff, and thermal protection. Packaged in a 16-lead narrow body SOIC, it eliminates the need for bulky output capacitors by providing bandwidth sufficient for modern microprocessor power supplies.

Feature Summary

• Ultrafast transient response capability that eliminates the requirement for expensive tantalum or bulk electrolytic output capacitors
• Dual regulator architecture providing independent 3.3V and 2.8V fixed outputs within a single package
• High-side sense current limit amplifier with programmable time-out and latchoff functionality via the SHDN pin
• Precision-trimmed output voltage tolerance of ±1% over the full operating temperature range

Applications

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

Procurement Notes

Verify the specific ordering suffix matches the required output configuration. Confirm the package type corresponds to the 16-lead narrow body SOIC variant. Ensure compatibility with external N-channel MOSFET selection regarding gate drive requirements and RDS(ON) specifications. Check for any recent product change notices affecting electrical characteristics or pinout definitions.

Selection Notes

Select this component when designing dual-rail power systems for processors needing distinct core and I/O voltages. Evaluate the external MOSFET's VGS(th) to ensure proper gate drive compliance from the GATE pin. Consider the current limit threshold setting based on the chosen sense resistor value. Verify that the application environment stays within the specified 0°C to 70°C operating temperature range.

Part Context

This part belongs to the LT1575/LT1577 family of low dropout regulator controllers manufactured by Analog Devices Inc. (formerly Linear Technology). The LT1577 specifically offers a dual-channel configuration compared to the single-channel LT1575. These controllers are engineered to replace traditional linear regulators and switching converters in high-performance computing applications where speed and efficiency are critical.

Replacement Considerations

LT1577CS-ADJ/ADJ

FAQ

How does the LT1577 eliminate bulk output capacitors?

It achieves superior regulator bandwidth and transient load performance by responding to load changes in nanoseconds, allowing the use of only small ceramic decoupling capacitors instead of large tantalum or electrolytic types.

What is the function of the SHDN pin?

The SHDN pin provides multifunction shutdown capabilities, including current limit time-out with latchoff, overvoltage protection, and thermal shutdown when driven by external resistor networks or capacitors.