Frequency to Voltage Converter LM2907/LM2917

Friday, February 12th, 2021 - Electronic Component

General Description Frequency to Voltage Converter LM2907/LM2917

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. The differential input options (LM2907, LM2917) give the user the option of setting his own input switching level and still have the hysteresis around that level for excellent noise rejection in any application. Of course in order to allow the inputs to attain common-mode voltages above ground, input protection is removed and neither input should be taken outside the limits of the supply voltage being used. It is very important that an input not go below ground without some resistance in its lead to limit the current that will then flow in the epi-substrate diode.

Standart Aplication Of Frequency to Voltage Converter LM2907/LM2917

Schematic Circuit Frequency to Voltage Converter dengan LM2917

Features Frequency to Voltage Converter LM2907/LM2917

  • 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
  • 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)

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