LM337 Reference Tables, Pins & Specifications

Pin reference

Signal names, electrical functions and connection guidance

TO-220

Physical pin numbers3 pins

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LM337 pin functions and connections
Signal	Type	Function & connection
ADJ	Floating adjustment terminal	The regulator holds OUTPUT approximately 1.25 V below ADJ. Connection guidance Connect R1 from OUT to ADJ and R2 from ADJ to the common return. ADJ is not ground. Adjustment current flows into this terminal.
IN	Negative input and metal tab	Accepts a negative supply more negative than the required output. The TO-220 tab and SOT-223 tab 4 are also IN. Connection guidance Connect −9 V in the example; keep the live input tab isolated from grounded metal. This pin assignment differs from positive LM317/LM350 regulators.
OUT	Regulated negative output	Supplies the load at a controlled negative voltage relative to the common return. Connection guidance Connect R1, the load and the required output capacitor here. Polarized output capacitors have their positive end at the common return, not at OUT.
IN / TAB	SOT-223 input tab	The broad SOT-223 contact is internally connected to input lead 2. Connection guidance Connect to the negative input copper and provide an adequate thermal path. This is a separate physical contact on the same IN node; it is not ground.

TI LM337-N electrical column

Manufacturer-referenced values7 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

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.

Constant-junction pulse measurements

Manufacturer-referenced values8 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

Typical values are not guaranteed extremes.

Current capability depends on voltage drop

Manufacturer-referenced values6 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

A 1.5 A class regulator cannot supply full current at every differential voltage or without cooling.

Negative rails reverse the polarized capacitor orientation

Manufacturer-referenced values7 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

The common return is the more positive node in this circuit.

Manufacturer thermal metrics · mounting matters

Manufacturer-referenced values7 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

Use the correct case/interface/heatsink or board model when estimating junction temperature.

−9 V input · 110 Ω / 330 Ω divider

Manufacturer-referenced values7 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

Nominal calculations; verify the actual loaded voltage and temperatures.

LM337T/NOPB · TO-220

Manufacturer-referenced values6 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

Original package illustrations and reviewed starting footprints; verify the purchased part and assembly rules.