LM2907D-8RG

The LM2907/LM2917 series are monolithic frequency-to-voltage converters with integrated high-gain op-amp/comparators, designed to drive relays, indicator lamps, or other loads when the input frequency reaches or exceeds a selected rate. The built-in tachometer uses charge pump technology to achieve frequency doubling with low ripple; the comparator features 30 mV of hysteresis, which can be used to suppress external interference. The op-amp/comparator is fully compatible with the tachometer and uses a floating transistor as the output, allowing loads to be powered to ground or up to 50 mA. The collector voltage can exceed VCC, with a maximum VCE of 28V. The general-purpose configuration provides differential tachometer inputs and unrestricted op-amp inputs; in this version, the tachometer input can float, and the op-amp is suitable for active filter conditioning of the tachometer output. This configuration can be used as an active shunt regulator connected via the supply line, where the regulator clamps the supply voltage, enabling stable frequency-to-voltage and frequency-to-current conversion using 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
• Speedometer
• Handheld tachometer
• Cruise control

Key features

• Single RC network required for frequency doubling.
• 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.
• Built-in tachometer uses charge pump technology with frequency doubling for low ripple; comparator hysteresis of 30 mV provides immunity to external interference.
• Output voltage proportional to input frequency, typical linearity of ±0.3%.
• Protection circuitry prevents damage from input signals above VCC or below ground reference.
• At zero frequency input, LM2907 output voltage is self-adjustable via external circuitry.
• Output can drive relays, indicator lights, and other loads when input frequency reaches or exceeds a given value.
• Zero frequency input determines output swing to ground.
• Easy to use: VOUT = fIN × VCC × R1 × C1.
• Single RC network provides frequency doubling.
• On-chip zener regulator enables precise and stable frequency-to-voltage or frequency-to-current conversion (LM2917).