LT1575CS8-3.3#PBF

Overview

The LT1575CS8-3.3#PBF is a fixed-output low dropout regulator controller manufactured by Analog Devices Inc., housed in an 8-lead plastic SOIC package. It drives external N-channel MOSFETs to deliver a precise 3.3V output with ±0.6% tolerance at room temperature and ±1.0% over the operating range. The device features ultrafast transient response, eliminating the need for bulk tantalum or electrolytic capacitors. Key electrical parameters include a typical quiescent current of 12mA, a maximum input voltage of 20V, and a high-side current limit threshold of 50mV.

Feature Summary

• Ultrafast transient response capability that eliminates the requirement for bulky tantalum or electrolytic output capacitors
• Fixed 3.3V output voltage with precision trimming for tight tolerance across temperature ranges
• High-side sense current limit amplifier utilizing an external shunt resistor for active overload protection
• Multifunction shutdown pin providing latchoff, overvoltage protection, and thermal shutdown capabilities

Applications

• Microprocessor core power supplies requiring fast load step response
• Low voltage logic supplies where minimal dropout voltage is critical
• GTL termination circuits demanding stable voltage regulation
• PowerPC processor power delivery systems

Procurement Notes

Verify the specific suffix CS8 corresponds to the 8-lead plastic SOIC package variant when sourcing. Confirm RoHS compliance status through official manufacturer documentation prior to integration. Ensure the fixed 3.3V version matches the design requirements rather than the adjustable counterpart. Cross-reference the ordering part number with the latest datasheet revision to avoid obsolete component selection.

Selection Notes

Select this component when system design mandates elimination of bulk output capacitance to save board space and cost. The fixed 3.3V output simplifies design compared to adjustable versions by removing external feedback resistors. Ensure the external N-channel MOSFET selected has a gate threshold voltage compatible with the GATE pin drive levels. Verify that the application requires high-side current sensing via an external shunt resistor for optimal protection performance.

Part Context

This component belongs to the LT1575/LT1577 family of ultrafast transient response regulators designed for modern microprocessor applications. While the LT1575 provides single-channel regulation, the LT1577 offers dual channels in a 16-pin package. The CS8 designation indicates the surface-mount SOIC package option, distinct from the PDIP N8 through-hole variant.

Replacement Considerations

LT1575CN8-3.3#PBF (PDIP package equivalent)

FAQ

How does the LT1575CS8-3.3#PBF achieve ultrafast transient response?

It achieves this by driving an external N-channel MOSFET as a source follower, which allows for a wide bandwidth control loop that responds to load changes in nanoseconds, thereby eliminating the need for bulk output capacitors.

What is the function of the SHDN pin?

The SHDN pin serves multiple functions including current limit time-out with latchoff, overvoltage protection, and thermal shutdown. It can be driven by external components to activate these protection mechanisms.