LT1577CS-ADJ/ADJ#PBF

Overview

The LT1577CS-ADJ/ADJ#PBF is a dual controller IC for ultrafast transient response, low dropout regulators. It drives external N-channel MOSFETs as source followers to eliminate bulk output capacitors. The device features a 1.21V reference with ±0.6% tolerance at room temperature and ±1% over the operating range. It includes high-side current limiting with a 50mV threshold and a multifunction shutdown pin for latchoff protection. Operating ambient temperature ranges from 0°C to 70°C.

Feature Summary

• Ultrafast transient response eliminates the need for tantalum or electrolytic output capacitors
• Dual channel architecture providing two independent regulator control loops
• High-side sense current limit amplifier with programmable time-out latchoff
• Multifunction shutdown pin supporting overvoltage and thermal protection

Applications

• Pentium processor supplies
• PowerPC supplies
• Microprocessor core voltage regulation (e.g., 5V to 3.3V)
• GTL termination circuits
• Low voltage logic supplies

Procurement Notes

Verify that the specific suffix ADJ/ADJ corresponds to the dual adjustable configuration in official Analog Devices documentation. Confirm the package type matches the 16-lead narrow body SO requirement. Ensure the component meets the specified industrial temperature range of 0°C to 70°C for the intended application environment.

Selection Notes

Select this component when designing power supplies for modern microprocessors requiring nanosecond-level transient response. It is suitable for applications where eliminating bulk capacitance reduces cost and board space. Ensure the external N-channel MOSFET selection supports the required dropout voltage and gate drive characteristics.

Part Context

This part belongs to the LT1575/LT1577 family of low dropout regulator controllers. While the LT1575 provides a single channel in an 8-pin package, the LT1577 integrates two channels in a 16-pin narrow body SO package. Both utilize the same UltraFast technology to drive external MOSFETs for high-performance voltage regulation.

Replacement Considerations

LT1575CN8/LT1575CS8: Single channel alternative; requires separate components for dual outputs.

FAQ

How does the LT1577 achieve ultrafast transient response?

It drives external N-channel MOSFETs as source followers, allowing the regulator bandwidth to reach approximately 1MHz. This high speed eliminates the need for bulky output capacitors typically required to handle load steps.

What is the function of the SHDN pin?

The SHDN pin is multifunctional. It controls the gate drive latchoff via a timer circuit during current limit events. It also serves as the input for overvoltage protection or thermal shutdown when driven by external resistor dividers.