LM2907N-8/HG

The LM2907/LM2917 series devices are monolithic frequency-to-voltage converters with a built-in high-gain op-amp/comparator, designed to drive relays, indicator lamps, or other loads when the input frequency reaches or exceeds a selected rate. The on-chip tachometer employs charge pump technology with frequency doubling capability for low ripple output; the comparator features 30 mV of hysteresis to suppress external interference. The op-amp/comparator is fully compatible with the tachometer and uses a floating transistor as its output, capable of driving loads to ground or up to 50 mA. The collector voltage may exceed VCC, with a maximum VCE of 28 V. The general-purpose configuration provides differential tachometer inputs and unrestricted op-amp inputs; in this configuration, the tachometer input can float while the op-amp is used for active filter conditioning of the tachometer output. This configuration supports an active shunt regulator connected via the supply line, which clamps the supply to achieve stable frequency-to-voltage and frequency-to-current conversion at any supply voltage with an appropriate resistor. The LM2907/LM2917 are available in DIP-14, SOP-14, TSSOP-14, DIP-8, and SOP-8 packages.

Applications

• Speed Measurement
• Frequency-to-voltage conversion (tachometer)
• Speedometer
• Handheld tachometer
• Speed control switch
• Cruise control
• Automotive door lock control
• Clutch control
• Horn control
• Touch or sound switch

Key features

• Single RC network required for frequency multiplication.
• Ground-referenced tachometer (frequency) input connects directly to input pin.
• Op-amp/comparator with floating transistor output.
• Up to 50 mA output current drives switches, LEDs, and other loads.
• Integrated tachometer uses charge pump technology with low-ripple frequency multiplication.
• Comparator features 30 mV hysteresis for external noise suppression.
• Output voltage proportional to input frequency; typical linearity ±0.3%.
• Protection circuitry prevents damage from input signals above VCC or below ground.
• LM2907 output voltage at zero frequency input adjustable via external circuitry.
• Output drives relays, indicators, and other loads when input frequency meets or exceeds a set threshold.