HGSEMI LM2907M-8/TR

The LM2907/LM2917 series are monolithic frequency-to-voltage converters with high-gain op-amp/comparators, designed to operate relays, lamps, or other loads when the input frequency reaches or exceeds a selected rate. The built-in tachometer employs charge pump technology with frequency multiplication for low ripple; the comparator features 30mV of hysteresis, which can be used to suppress external interference.

The op-amp/comparator is fully compatible with the tachometer and features a floating transistor as its output, allowing it to sink or source loads of up to 50mA. The collector may be raised above 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 may 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. The regulator clamps the supply voltage, enabling stable frequency-to-voltage and frequency-to-current operation across any supply voltage with an appropriate resistor.

• Frequency doubling with LM2907/LM2917 requires only a single RC network.
• Ground-referenced tachometer (frequency) input directly accessible from input pin.
• Op-amp/comparator with floating transistor output.
• Up to 50mA output current for driving switching transistors, LEDs, etc.
• Integrated tachometer uses charge pump technology with frequency doubling for low ripple.
• Comparator hysteresis of 30mV for external noise suppression.
• 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 × R × C
• Single RC network for frequency doubling.
• On-chip zener regulator enables precise and stable frequency-to-voltage or frequency-to-current conversion (LM2917).

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