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
