LM2917N Datasheet PDF - TI

●General Description

●The LM2907, LM2917 series are monolithic frequency to voltage converters with a high gain op amp/comparator designed to operate a relay, lamp, or other load when the input frequency reaches or exceeds a selected rate. The tachometer uses a charge pump technique and offers frequency doubling for low ripple, full input protection in two versions (LM2907-8, LM2917-8) and its output swings to ground for a zero frequency input.

●The op amp/comparator is fully compatible with the tachometer and has a floating transistor as its output. This feature allows either a ground or supply referred load of up to 50 mA. The collector may be taken above VCC up to a maximum VCE of 28V.

●Advantages

●Output swings to ground for zero frequency input

●Easy to use; VOUT = fIN x VCC x R1 x C1

●Only one RC network provides frequency doubling

●Zener regulator on chip allows accurate and stable frequency to voltage or current conversion (LM2917)

●Features

●Ground referenced tachometer input interfaces directly with variable reluctance magnetic pickups

●Op amp/comparator has floating transistor output

●50 mA sink or source to operate relays, solenoids, meters, or LEDs

●Frequency doubling for low ripple

●Tachometer has built-in hysteresis with either differential input or ground referenced input

●Built-in zener on LM2917

●±0.3% linearity typical

●Ground referenced tachometer is fully protected from damage due to swings above VCC and below ground

●Applications

●Over/under speed sensing

●Frequency to voltage conversion (tachometer)

●Speedometers

●Breaker point dwell meters

●Hand-held tachometer

●Speed governors

●Cruise control

●Automotive door lock control

●Clutch control

●Horn control

●Touch or sound switches