Features and Benefits

  • Ultra Fast (5.5ns typ)
  • Complementary ECL Output
  • 50Ω Line Driving Capability
  • Low Offset Voltage
  • Output Latch Capability
  • External Hysteresis Control
  • Pin Compatible with Am685

Product Details

The LT685 is an ultrafast comparator with differential inputs and complementary outputs fully compatible with ECL logic levels. The output current capability is adequate for driving transmission lines terminated in 50Ω. The low input offset and high resolution make this comparator ideally suited for analog-to-digital signal processing applications.

A latch function is provided to allow the comparator to be used in a sample-hold mode. When the latch enable input is ECL high, the comparator functions normally. When the latch enable is driven low, the comparator outputs are locked in their existing logical states. If the latch function is not used, the latch enable must be connected to ground or ECL high.

The device is pin-compatible with the Am685. Hysteresis has been added to improve switching time with slow input signals as well as to minimize oscillation. A single resistor between the hysteresis pin and V adds input hysteresis voltage as more current is drawn. If hysteresis is not required, the pin can be left unconnected.


  • High Speed A to D Converters
  • High Speed Sampling Circuits
  • Oscillators

Product Lifecycle icon-recommended Production

At least one model within this product family is in production and available for purchase. The product is appropriate for new designs but newer alternatives may exist.

Documentation & Resources