BETANominal reference−1.25 V · OUT minus ADJ
Adjustable negative regulator
LM337 Specifications
Review LM337 electrical specifications, operating conditions and package details.
Package view
Key specifications
OUT sits about 1.25 V below ADJ. The divider lifts ADJ below the common return, setting a negative output. Keep the package pinout and capacitor polarity explicit.
Adjustment span−1.25 to −37 V · requires headroom
Current class1.5 A · thermal and safe-area limits
Common electrical range0–125 °C junction · see package notes
Package details
LM337T/NOPB · TO-220
| Property | Details |
|---|---|
| Manufacturer | Texas Instruments |
| Part number | LM337T/NOPB |
| Package | TO-220 |
| Connections | 3 pins |
| Mounting | Through-hole |
| Lead pitch | 2.54 mm |
| Package code | NDE |
| Thermal reference | 0–125°C operating junction; tab = IN |
Operating reference
TI LM337-N electrical column
Manufacturer specifications 7 parameters
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| Parameter | Value | Conditions / notes |
|---|---|---|
| Nominal output adjustment | −1.25 to −37 V | With adequate differential voltage, loading and cooling |
| TO-220 order range | 0–125°C junction | LM337T/NOPB |
| SOT-223 order range | −40–125°C junction | LM337IMP/NOPB; do not extend the 0–125°C electrical table implicitly |
| Reference at 25°C | −1.213 / −1.25 / −1.287 V | Manufacturer MIN / TYP / MAX signed entries |
| Reference over stated LM337-N range | −1.20 / −1.25 / −1.30 V | 0–125°C; stated differential and load conditions |
| Adjustment-pin current | 65 µA typical; 100 µA maximum | Flows into ADJ |
| Adjustment current change | 2 µA typical; 5 µA maximum | 10 mA–IMAX; 3–40 V differential; 25°C |
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Electrical test baseline: 5 V input-output differential and 0.5 A load for TO-220/SOT-223, unless specified. Observe the source power conditions.
Regulation and noise
Constant-junction pulse measurements
Manufacturer specifications 8 parameters
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| Parameter | Value | Conditions / notes |
|---|---|---|
| Line regulation at 25°C | 0.01%/V typical; 0.04%/V maximum | 3–40 V differential; 10 mA load |
| Line regulation over stated range | 0.02%/V typical; 0.07%/V maximum | 3–40 V differential |
| Load regulation at 25°C | 0.3% typical; 1% maximum | 10 mA–IMAX |
| Load regulation over stated range | 0.3% typical; 1.5% maximum | Constant-junction test conditions |
| Thermal regulation | 0.003%/W typical; 0.04%/W maximum | 10 ms pulse; 25°C |
| Ripple rejection without CADJ | 60 dB typical | −10 V output; 120 Hz |
| Ripple rejection with 10 µF CADJ | 66 dB minimum; 77 dB typical | −10 V output; 120 Hz |
| Output noise | 0.003% of output typical | RMS; 10 Hz–10 kHz; 25°C |
No specifications match. Try a parameter name or a unit.
Typical values are not guaranteed extremes.
Minimum load and current limiting
Current capability depends on voltage drop
Manufacturer specifications 6 parameters
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| Parameter | Value | Conditions / notes |
|---|---|---|
| Minimum load at ≤40 V differential | 2.5 mA typical; 10 mA maximum | Guarantee minimum current to maintain regulation |
| Minimum load at ≤10 V differential | 1.5 mA typical; 6 mA maximum | Manufacturer test condition |
| Current limit at ≤15 V differential | 1.5 / 2.2 / 3.7 A | Minimum / typical / maximum; DCY and NDE within power limits |
| Current limit at 40 V differential | 0.15 A minimum; 0.4 A typical | 25°C; safe-area limit reduces available current |
| Example divider | 1.25 / 110 ≈11.36 mA | Contributes to total output current |
| Divider lower bound | 1.20 / 111.1 ≈10.80 mA | 110 Ω at +1% and 1.20 V reference magnitude |
No specifications match. Try a parameter name or a unit.
A 1.5 A class regulator cannot supply full current at every differential voltage or without cooling.
Capacitors and polarity
Negative rails reverse the polarized capacitor orientation
Manufacturer specifications 7 parameters
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| Parameter | Value | Conditions / notes |
|---|---|---|
| Required output capacitor | 1 µF solid tantalum or 10 µF aluminum electrolytic | Required for stability; close to OUT and return |
| Input bypass | 1 µF solid tantalum | Required if more than 4 inches from the supply filter; used locally here |
| Positive capacitor terminals | Common return / GND | Negative ends connect to negative IN or OUT |
| Optional adjustment bypass | Improves ripple rejection | Evaluate discharge protection when added |
| Output discharge diode | Review when CL exceeds 20 µF | Source protection circuit diverts discharge during input short |
| Adjustment discharge diode | Review with CADJ >10 µF and output magnitude >25 V | Follow the source protection circuit |
| Example output capacitor | 1 µF solid tantalum, suitably voltage-rated | An arbitrary ceramic substitute is not assumed |
No specifications match. Try a parameter name or a unit.
The common return is the more positive node in this circuit.
Heat and the input tab
Manufacturer thermal metrics · mounting matters
Manufacturer specifications 7 parameters
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| Parameter | Value | Conditions / notes |
|---|---|---|
| TO-220 θJA reference | 22.9°C/W | SNVS778F test-board metric; not a universal bare-package value |
| SOT-223 θJA reference | 58.3°C/W | Board copper and mounting strongly affect actual results |
| TO-220 θJC(bottom) | 1°C/W | Manufacturer package metric |
| Live tab | IN in both packages | SOT-223 contact 4 is connected to pin 2 |
| Nominal pass loss | (9 − 5) × (0.100 + 0.01136) ≈0.445 W | At 100 mA load plus divider |
| Absolute differential limit | 40 V | Stress limit; use operating headroom and power constraints |
| Internal protection | Current, thermal and safe-area limiting | Not a substitute for normal thermal design |
No specifications match. Try a parameter name or a unit.
Use the correct case/interface/heatsink or board model when estimating junction temperature.
A nominal −5 V supply
−9 V input · 110 Ω / 330 Ω divider
Manufacturer specifications 7 parameters
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| Parameter | Value | Conditions / notes |
|---|---|---|
| R1 from OUT3 to ADJ1 | 110 Ω, 1% | Divider current about 11.36 mA |
| R2 from ADJ1 to GND | 330 Ω, 1% | R2/R1 = 3 |
| Ideal output | −1.25 × (1 + 330/110) = −5.00 V | Before adjustment current and tolerance |
| Typical IADJ correction | −65 µA × 330 Ω = −21.45 mV | Nominal result approximately −5.021 V |
| Load | 50 Ω, at least 1 W | Between GND and OUT; about 100 mA / 0.5 W |
| Input headroom | Approximately 4 V magnitude | −9 V input, −5 V output |
| Common return | Supply return, R2, load and capacitor positive ends | No dedicated ground pin on the IC |
No specifications match. Try a parameter name or a unit.
Nominal calculations; verify the actual loaded voltage and temperatures.
Physical package reference
LM337T/NOPB · TO-220
Manufacturer specifications 6 parameters
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| Parameter | Value | Conditions / notes |
|---|---|---|
| TO-220 front-view lead order | 1 ADJ; 2 IN; 3 OUT | Marking toward you; leads down |
| SOT-223 top-view contacts | 1 ADJ; 2 IN; 3 OUT; 4 IN tab | Three narrow leads opposite a broad input tab |
| Selected pitch | 2.54 mm | See physical pin map and footprint |
| Selected operating range | 0–125°C operating junction; tab = IN | Package-specific note |
| Output versus tab | OUT is pin 3; tab is IN | Do not use a positive-regulator tab assumption |
| Storage | −65 to +150°C | Unpowered storage |
No specifications match. Try a parameter name or a unit.
Original package illustrations and reviewed starting footprints; verify the purchased part and assembly rules.
Connections by function
Select a pin for its function, connection guidance and electrical notes.