100% Original And New Integrated Circuits LM2907N-8/NOPB Chip In Stock

LM2907/LM2917
Frequency to Voltage Converter
General Description
The LM2907, LM2917 series are monolithic frequency to volt-
age converters with a high gain op amp/comparator designed
to operate a relay, lamp, or other load when the input fre-
quency 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 fre-
quency input.
The op amp/comparator is fully compatible with the tachome-
ter 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 V CC up to a maximum
VCE of 28V.
The two basic configurations offered include an 8-pin device
with a ground referenced tachometer input and an internal
connection between the tachometer output and the op amp
non-inverting input. This version is well suited for single speed
or frequency switching or fully buffered frequency to voltage
conversion applications.
The more versatile configurations provide differential
tachometer input and uncommitted op amp inputs. With this
version the tachometer input may be floated and the op amp
becomes suitable for active filter conditioning of the tachome-
ter output.
Both of these configurations are available with an active shunt
regulator connected across the power leads. The regulator
clamps the supply such that stable frequency to voltage and
frequency to current operations are possible with any supply
voltage and a suitable resistor.
Advantages
■ Output swings to ground for zero frequency input
■ Easy to use; VOUT = fIN × VCC × R1 × C1
■ Only one RC network provides frequency doubling
■ Zener regulator on chip allows accurate and stable
frequency to voltage or current conversion (LM2917)
Features
■ 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