LT1575CN8-1.5#PBF

Overview

The LT1575CN8-1.5#PBF is a fixed-output low dropout regulator controller IC manufactured by Analog Devices Inc., housed in an 8-pin PDIP package. It provides a precise 1.5V output with ±0.6% tolerance at room temperature and ±1.0% over the operating temperature range. The device operates with an input voltage between 10V and 20V, drawing a typical quiescent current of 12.5mA. It features high-side current sensing with a 50mV threshold and includes a multifunction shutdown pin for latch-off protection.

Feature Summary

• Ultrafast transient response capability that eliminates the need for bulky tantalum or electrolytic output capacitors
• High-side sense current limit amplifier with programmable time-out latchoff via the SHDN pin
• Precision-trimmed internal reference and resistor divider network ensuring tight output voltage tolerance
• Integrated startup circuitry and error amplifier optimized for driving external N-channel MOSFETs

Applications

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

Procurement Notes

Verify the specific suffix CN8 corresponds to the 8-lead plastic PDIP package when sourcing. Confirm the -1.5 designation indicates the fixed 1.5V output variant. Ensure compatibility with the required external N-channel MOSFET gate drive characteristics. Check for RoHS compliance status as indicated on the official datasheet. Validate that the application environment remains within the specified 0°C to 70°C operating temperature range.

Selection Notes

Select this component for applications requiring extremely fast load transient response without bulk output capacitance. It is suitable for microprocessor core supplies where voltage droop must be minimized during rapid current steps. The fixed 1.5V version simplifies design by removing external feedback resistors. Ensure the external MOSFET selected has a gate threshold voltage compatible with the GATE pin swing capabilities.

Part Context

This part belongs to the LT1575/LT1577 family of ultrafast transient response low dropout regulators. While the LT1575 is a single controller, the LT1577 offers dual channels. The CN8 suffix specifically denotes the PDIP package option, distinct from the CS8 surface-mount SOIC variant. These controllers are designed to replace traditional monolithic linear regulators and switching converters in high-performance computing environments.

Replacement Considerations

LT1575CS8-1.5#PBF

FAQ

How does the LT1575 achieve ultrafast transient response?

It drives external N-channel MOSFETs as source followers, allowing the use of only small ceramic decoupling capacitors instead of large bulk electrolytic or tantalum capacitors.

What is the function of the SHDN pin?

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