LT1721CS#TRPBF

Overview

The LT1721CS#TRPBF is a quad UltraFast comparator from Analog Devices, optimized for single-supply operation within a 2.7V to 6V range. It features rail-to-rail outputs compatible with TTL and CMOS logic. The device includes internal hysteresis to ensure stability with slow-moving signals. Key electrical specifications include a propagation delay of 4.5ns at 20mV overdrive and 7ns at 5mV overdrive. Supply current is typically 4mA per comparator at 5V. The input voltage range extends from 100mV below ground to 1.2V below the positive supply rail.

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
• Internal hysteresis simplifies usage with slow-moving input signals
• Input voltage range extends 100mV below the negative supply rail

Applications

• Crystal oscillator circuits
• High-speed differential line receivers
• Window comparators and threshold detectors
• Zero-crossing detectors
• High-speed sampling circuits

Procurement Notes

Verify the specific package variant, as the LT1721 family includes SSOP and SO packages. Confirm that the #TRPBF suffix indicates tape and reel packaging suitable for automated assembly. Ensure the C grade temperature range (0°C to 70°C) meets system requirements. Cross-reference the manufacturer part number with official distributor catalogs to confirm availability and lead times before finalizing procurement plans.

Selection Notes

Select this component when high speed and low power are critical in single-supply systems. The quad configuration allows multiple comparisons in a compact footprint. Consider the internal hysteresis for noise immunity without external components. Verify that the input signal amplitude and source impedance align with the specified propagation delay characteristics. Ensure the output load does not exceed the drive capabilities defined in the datasheet.

Part Context

The LT1721 is part of the LT1720/LT1721 family of UltraFast comparators designed by Linear Technology, now Analog Devices. While the LT1720 offers dual channels in smaller packages like DFN and MSOP, the LT1721 provides four channels in 16-pin SSOP and SO packages. This family is distinguished by its optimized pinout to minimize parasitic effects and its ability to operate efficiently on 3V and 5V supplies.

Replacement Considerations

LT1721CGN#TRPBF

FAQ

How does the internal hysteresis affect the input trip points?

The internal hysteresis creates two distinct trip points: VTRIP+ and VTRIP-. The offset voltage is defined as the average of these two points, while the hysteresis voltage is the difference between them. This ensures stable switching even with slowly moving input signals.

What is the common mode input voltage range?

The common mode input voltage range extends from 100mV below ground to 1.2V below the positive supply voltage (VCC). If one input is within this limit, the other can go outside it while maintaining valid output polarity.