LT1720IS8#PBF

Overview

The LT1720IS8#PBF is a dual ultrafast comparator optimized for single supply operation with a voltage range of 2.7V to 6V. It features rail-to-rail outputs compatible with TTL and CMOS logic. The device offers a propagation delay of 4.5ns at 20mV overdrive and 7ns at 5mV overdrive, with a quiescent supply current of 4mA per comparator. Input voltage ranges extend from 100mV below ground to 1.2V below the supply voltage. It includes internal hysteresis and operates within an industrial temperature range of -40°C to +85°C.

Feature Summary

• Ultrafast response time with 4.5ns propagation delay at 20mV overdrive
• Rail-to-rail outputs directly interface to TTL and CMOS logic levels
• Input voltage range extends 100mV below the negative supply rail
• Internal hysteresis ensures stable operation with slow-moving input signals

Applications

• Crystal oscillator circuits
• Window comparators
• Threshold detectors and discriminators
• High-speed sampling circuits
• Zero-crossing detectors

Procurement Notes

Verify the specific package variant (SOIC-8) and temperature grade (Industrial, -40°C to +85°C) against project requirements. Confirm that the lead-free finish matches environmental compliance standards. Ensure the ordering suffix #PBF corresponds to the desired manufacturing specifications. Cross-reference the manufacturer part number with official distributor catalogs to validate authenticity and current availability status before finalizing procurement.

Selection Notes

Select this component for applications requiring high speed and low power consumption in single-supply systems. The rail-to-rail output capability simplifies interfacing with digital logic without additional level shifting. Consider the internal hysteresis for noise immunity in threshold detection tasks. Verify that the supply voltage remains within the 2.7V to 6V range and that the input signals stay within the specified common-mode limits to ensure correct operation.

Part Context

The LT1720 is part of Analog Devices' UltraFast comparator family, designed for high-speed analog-to-digital conversion interfaces and precision timing applications. It shares architectural similarities with the quad-channel LT1721 but provides two independent comparators in an 8-pin package. The series is characterized by low dynamic current drain and optimized pinouts to minimize parasitic effects between inputs and outputs.

Replacement Considerations

LT1720CS8#PBF: Same functional device with commercial temperature range (0°C to 70°C).

FAQ

How does the internal hysteresis affect the trip points?

The internal hysteresis creates distinct positive and negative trip points, defined as VTRIP+ and VTRIP-. The offset voltage is the average of these points, while the hysteresis voltage is the difference between them.

What happens if both inputs go above the positive common mode limit?

The input stage becomes debiased, causing the output polarity to become random. However, the internal hysteresis holds the output to a valid logic level until at least one input returns to within the common mode limits.