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
ApplicationOver/under speed sensing
Frequency to voltage conversion (tachometer)
Speedometers
Breaker point dwell meters
Hand-held tachometer
Speed governors
Cruise control
Automotive door lock control
Clutch control
Horn control
Touch or sound switches
Specifications
| Temperature Min |
-40 deg C |
| Temperature Max |
85 deg C |
| Function |
Frequency to Voltage |
| View Using Catalog |
DescriptionThe 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 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 tachometer 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.
Reliability Metrics
| Part Number |
Process |
EFR Reject |
EFR Sample Size |
PPM |
LTA Rejects |
LTA Device Hours |
FITS |
MTTF (Hours) |
| LM2907M |
SLM |
0 |
42786 |
0 |
0 |
3352500 |
2 |
951281028 |
| LM2907M-8 |
SLM |
0 |
42786 |
0 |
0 |
3352500 |
2 |
951281028 |
| LM2907MX |
SLM |
0 |
42786 |
0 |
0 |
3352500 |
2 |
951281028 |
| LM2907MX-8 |
SLM |
0 |
42786 |
0 |
0 |
3352500 |
2 |
951281028 |
| LM2907N |
SLM |
0 |
42786 |
0 |
0 |
3352500 |
2 |
951281028 |
| LM2907N-8 |
SLM |
0 |
42786 |
0 |
0 |
3352500 |
2 |
951281028 |
Note: The Early Failure Rates (EFR) were calculated as point estimate PPM based on rejects and sample size for EFR. The Long Term Failure Rates were calculated at 60% confidence using the Arrhenius equation at 0.7eV activation energy and derating the assumed stress temperature of 150°C to an application temperature of 55°C.For more information on Reliability Metrics, please click here.
More Application Notes
| Title |
Size in Kbytes |
Date |
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| AN-97: Application Note 97 Versatile Timer Operates from Microseconds to Hours |
457 Kbytes |
24-Feb-99 |
Download |
| AN-162: AN-162 LM2907 Tachometer/Speed Switch Building Block Applications |
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1-May-04 |
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| AN-607: Pulse Width Modulation A/D Conversion Techniques with COP800 Family Microcontrollers |
148 Kbytes |
5-Aug-95 |
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| AN-1237: Application Note 1237 RSDS™ Flat Panel Display Design Guidelines Part 2 |
141 Kbytes |
14-May-03 |
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LM2907 Data Sheet
