BETARecommended supply4–40 V
Voltage-to-frequency converter
LM331 Specifications
Review LM331 electrical specifications, operating conditions and package details.
Key specifications
Measure an analog voltage by counting its output pulses.
Example calibrated scale1 kHz per volt
Operating ambient0–70 °C
Typical supply current3 mA at5V
Package details
LM331N/NOPB · PDIP-8
| Property | Details |
|---|---|
| Manufacturer | Texas Instruments |
| Part number | LM331N/NOPB |
| Package | PDIP-8 |
| Connections | 8 pins |
| Mounting | Through-hole |
| Lead pitch | 2.54 mm |
| Package code | PDIP-8 |
| Thermal reference | See operating and package limits |
Operating conditions
TI LM331 commercial grade
Manufacturer specifications 6 parameters
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| Parameter | Value | Conditions / notes |
|---|---|---|
| Supply | 4–40V | 15V in the example |
| Ambient | 0–70°C | LM331; LM231 grade differs |
| Comparator common-mode range | −0.2V toVS−2V | Over rated temperature |
| Supply current at5V | 3mA typical;6mA max | LM331, stated test circuit |
| Supply current at40V | 4mA typical;8mA max | Stated test circuit |
| Full-scale frequency capability | 1Hz to100kHz feature range | Requires an appropriate application circuit |
No specifications match. Try a parameter name or a unit.
The shown circuit is calibrated for10kHz full scale, not automatically for100kHz.
Accuracy and calibration
Keep the test circuit distinction
Manufacturer specifications 6 parameters
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| Parameter | Value | Conditions / notes |
|---|---|---|
| Figure16 precision circuit nonlinearity | ±0.003% typical;±0.01% max | 4.5–20V,25°C, stated calibrated conditions |
| Shown Figure14 circuit nonlinearity | ±0.024% typical;±0.14% max | 15V;10Hz to11kHz |
| Untrimmed LM331 scale factor | 0.9–1.1kHz/V | Figure16 conditions;RS14kΩ |
| Gain temperature drift | ±30ppm/°C typical;±150ppm/°C max | Non-A LM331;4.5–20V |
| Comparator offset | ±3mV typical;±10mV max | 25°C |
| Comparator bias current | −80nA typical;−300nA max | Stated conditions |
No specifications match. Try a parameter name or a unit.
The precision-circuit headline is not the guaranteed accuracy of this simpler stand-alone example.
Reference and output
25°C unless stated
Manufacturer specifications 6 parameters
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| Parameter | Value | Conditions / notes |
|---|---|---|
| IREF voltage | 1.89V typical;1.70–2.08V | LM331 |
| Switched IOUT | 136µA typical;116–156µA | RS14kΩ;IOUT at0V |
| Timer threshold | 0.667VS typical;0.63–0.70VS | RC pin5 |
| FOUT LOW | 0.15V typical;0.5V max | Sinking5mA |
| FOUT LOW overtemperature | 0.1V typical;0.4V max | Sinking3.2mA |
| FOUT OFF leakage | ±0.05µA typical;1µA max | Open collector |
No specifications match. Try a parameter name or a unit.
No load should force output or input terminals beyond their specified limits.
Stand-alone conversion network
Adapted from TI Figure14
Manufacturer specifications 8 parameters
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| Parameter | Value | Conditions / notes |
|---|---|---|
| Analog supply / output pull-up | 15V /5V | 100nF local supply bypass;FOUT through10kΩ to5V |
| RT / CT | 6.8kΩ /10nF | RT from15V toRC5;CT fromRC5 toGND |
| RIN / CIN | 100kΩ /100nF | VIN throughRIN toCOMPIN7;CIN toGND |
| RL / CL | 100kΩ /1µF in parallel | From joinedIOUT1/THRESH6 toRETURN |
| Hysteresis return | 47Ω fromRETURN toGND | Shared lower end ofRL andCL |
| RS | 12kΩ plus5kΩ rheostat | IREF2 toGND; trim gain |
| Logic output | FOUT3 tofrequency counter | Open collector with10kΩ pull-up |
| Offset adjustment | Optional manufacturer network omitted | Gain calibration retained |
No specifications match. Try a parameter name or a unit.
Use a film or other suitable low-absorption integration capacitor and stable timing components. Matching labels identify connected nodes.
Nominal conversion relationships
Ideal charge balance
Manufacturer specifications 6 parameters
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| Parameter | Value | Conditions / notes |
|---|---|---|
| Frequency | fOUT=(VIN/2.09V)×(RS/RL)×1/(RTCT) | Manufacturer application equation |
| Gain for1kHz/V | RS≈14.212kΩ | RL100kΩ,RT6.8kΩ,CT10nF; then calibrate |
| Timed current pulse | t≈1.1RTCT≈74.8µs | Nominal timing interval |
| Example input | 2.5V→2.5kHz | After calibration |
| Pulse count in100ms | 250 pulses at2.5V | Quantization step≈10mV per count |
| Response time | Filter and integration dependent | Do not treat one pulse as an instant precision reading |
No specifications match. Try a parameter name or a unit.
Values are nominal calculations; device gain, offset and component tolerance require calibration.
Package and thermal reference
LM331N/NOPB · PDIP-8
Manufacturer specifications 7 parameters
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| Parameter | Value | Conditions / notes |
|---|---|---|
| Pitch | 2.54 mm | Through-hole |
| Verified TI package | 8-pinPDIP(P) | No TI SMD option in the cited orderable table |
| Absolute supply | 40V | Same numerical upper limit as recommended; do not exceed |
| Absolute input | −0.2V toVS | Stress rating |
| Maximum junction | 150°C | Apply thermal derating |
| Junction-to-ambient | 100°C/W | Specified PDIP reference |
| Storage | −65 to+150°C | Unpowered |
No specifications match. Try a parameter name or a unit.
Verify the exact manufacturer and ordering suffix when sourcing parts.
Connections by function
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