DESCRIPTION

· The LM2907 and LM2917 are monolithic frequency-to-voltage converters with a high gain op amp.

· Designed to operate a relay, lamp, or other load when the input frequency reaches or exceeds a selected rate.

· Uses a charge pump technique with frequency doubling for low ripple.

· Offers full-input protection and output swings to ground for zero frequency input.

· The op amp is fully compatible with the tachometer and has a floating transistor output.

· Suitable for single speed or frequency switching and fully buffered frequency-to-voltage conversion applications.

FEATURES

· Ground referenced tachometer input interfaces directly with variable reluctance magnetic pickups.

· Op amp has a 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.

· ±0.3% linearity (typical).

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

· Output swings to ground for zero frequency input.

· Easy to use; VOUT = fIN × VCC × R1 × C1.

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

APPLICATIONS

· Over- and under-speed sensing.

· Frequency-to-voltage conversion (Tachometer).

· Speedometers.

· Breaker point dwell meters.

· Hand-held tachometers.

· Speed governors.

· Cruise control.

· Automotive door lock control.

· Clutch control.

· Horn control.

· Touch or sound switches.