Answer: The LM2596T-ADJ/NOPB is the 5-pin TO-220 version of TI’s adjustable 3 A, 150 kHz buck regulator. It runs from 4.5–40 V, regulates to a 1.23 V feedback reference and switches at 150 kHz. TI rates the TO-220 at 50 °C/W standing on 1 in² of copper with no heat sink, and says it “requires a heat sink under most conditions”. There are two Active TO-220 orderables with different outlines (NDH and NEB), so check the mechanical drawing. (TI SNVS124G §7.4, §9.4.3, Package Option Addendum.)
Key specifications
| Parameter | Value | Condition | Source |
|---|---|---|---|
| Input voltage | 4.5–40 V operating; 45 V abs. max | — | §7.3 and §7.1, p.5 |
| Feedback voltage | 1.193 / 1.23 / 1.267 V; 1.18–1.28 V over temperature | VIN 4.5–40 V, ILOAD 0.2–3 A | §7.8, p.6 |
| Efficiency (typ) | 73 % | VIN 12 V, VOUT 3 V, 3 A | §7.8, p.6 |
| Switch saturation voltage | 1.16 typ / 1.4 max V; 1.5 V max over temperature | IOUT = 3 A | §7.9, p.7 |
| Current limit (peak) | 3.6 / 4.5 / 6.9 A; 3.4–7.5 A over temperature | — | §7.9, p.7 |
| Oscillator frequency | 127 / 150 / 173 kHz; 110–173 kHz over temperature | — | §7.9, p.7 |
| Output leakage | 50 µA max (output 0 V); 2 typ / 30 max mA (output −1 V) | VIN = 40 V | §7.9, p.7 |
| Standby current | 80 typ / 200 max µA; 250 µA over temperature | ON/OFF = 5 V | §7.9, p.7 |
| RθJA, TO-220 | 50 °C/W | Vertical, leads soldered to ~1 in² of 1-oz copper, no heat sink | §7.4 note 4, p.5 |
| RθJC(top) | 2 °C/W | Case top, JEDEC metric | §7.4, p.5 |
| Maximum junction temperature | 150 °C abs. max; 125 °C operating | — | §7.1 and §7.3, p.5 |
| Moisture sensitivity | MSL 1 (unlimited) | LM2596T-ADJ/NOPB and /LF02 | Package Option Addendum |
Pinout (TO-220, 5 pins)
Table 6-1 (p.4): 1 VIN, 2 Output (switch), 3 Ground, 4 Feedback, 5 ON/OFF, the same order as the TO-263 version. The ON/OFF pin runs the regulator when grounded or open and accepts up to 25 V for shutdown.
Do you need a heat sink?
TI’s TO-220 figure (50 °C/W) assumes the part is standing vertically with about 1 in² of copper on the leads. Work out the dissipation, then the rise:
| Case (TI typical VSAT 1.16 V, diode 0.5 V) | Duty | IC loss (incl. 5 mA quiescent) | Rise at 50 °C/W | TJ at 40 °C ambient |
|---|---|---|---|---|
| 12 V → 5 V, 3 A | 0.485 | ≈1.75 W | ≈88 °C | ≈128 °C — over the limit |
| 12 V → 5 V, 2 A | 0.485 | ≈1.19 W | ≈60 °C | ≈100 °C |
| 24 V → 12 V, 3 A | 0.536 | ≈1.98 W | ≈99 °C | ≈139 °C — over the limit |
| 12 V → 3.3 V, 1 A | 0.335 | ≈0.45 W | ≈23 °C | ≈63 °C |
So the “under most conditions” warning in §9.4.3 (p.33) is literal for full-load designs. TI’s Figure 9-18 gives measured TO-220 rise curves at 3 A for different input and output voltages; use those, or a heat sink, rather than the free-standing figure.
When you size a sink, note that TI quotes RθJC(top) (2 °C/W), a JEDEC case-top metric. It is not a tab-to-sink figure, so do not treat it as one. Give yourself margin, or measure the tab temperature on the real board.
Design notes
- Divider. VOUT = 1.23 V × (1 + R2/R1), R1 240 Ω–1.5 kΩ (§9.2.2.2, p.28). R1 = 1 kΩ and R2 = 3.09 kΩ give 5.03 V. The LM2596-ADJ calculator does this with E-series values.
- Feed-forward capacitor. Add one across R2 above 10 V out or with a very-low-ESR output capacitor (§9.1.2, p.17).
- Diode. Schottky, rated at least 1.3 × the load current and 1.25 × the maximum input (§9.2.2.2.5, p.30).
- Through-hole layout. TI shows a double-sided through-hole layout for the adjustable version (Figure 9-17, p.32). Keep the VIN capacitor, diode and ground loop short.
Pitfalls specific to LM2596T-ADJ
- Running 3 A with no heat sink. At 12 V to 5 V the IC dissipates about 1.75 W, which takes the junction past 125 °C at 40 °C ambient on TI’s 50 °C/W figure.
- Ordering the wrong TO-220. TI lists LM2596T-ADJ/NOPB (package code NDH) and LM2596T-ADJ/LF02 (package code NEB). Both are 5-pin TO-220s, but they are drawn separately; check the mechanical drawing against your footprint and heat sink before you substitute one for the other.
- Reading 4.5 V as the input you need. 4.5 V is the chip’s minimum supply. For 5 V out at 3 A the switch drop alone (1.4 V max at 25 °C, 1.5 V over temperature, 100 % duty) puts the input at about 6.4–6.5 V before inductor and trace losses.
- Assuming the hottest part is the IC. The catch diode and inductor share the load current; at 3 A they also need copper.
Part numbers (information only)
| TI orderable | Package (TI code) | Packing | Marking |
|---|---|---|---|
| LM2596T-ADJ/NOPB | TO-220, 5 pins (NDH) | Tube of 45 | LM2596T |
| LM2596T-ADJ/LF02 | TO-220, 5 pins (NEB) | Tube of 45 | LM2596T |
Both are listed Active, MSL 1, in the Package Option Addendum of SNVS124G. Variants carrying ”.B” in the addendum are shown alongside each code.
FAQ
- Does the LM2596T-ADJ need a heat sink? For full-load designs, usually. At 12 V to 5 V and 3 A the IC dissipates about 1.75 W; at 50 °C/W that is an 88 °C rise, which exceeds 125 °C junction at 40 °C ambient.
- What is the difference between LM2596T-ADJ/NOPB and LM2596T-ADJ/LF02? Both are Active 5-pin TO-220 orderables, but TI lists them under different package outlines (NDH and NEB). Check the drawing before swapping one for the other.
- Is the TO-220 pinout the same as the TO-263? Yes: 1 VIN, 2 Output, 3 Ground, 4 Feedback, 5 ON/OFF.
- Can I use the 2 °C/W figure to size a heat sink? Not directly. It is RθJC(top), a case-top metric, not the tab-to-sink path.
- How do I set 5 V? R1 = 1 kΩ and R2 = 3.09 kΩ give 5.03 V with the 1.23 V reference.
Related (internal links)
- LM2596-ADJ calculator
- LM2596S-ADJ (TO-263)
- LM2596 alternatives
- LM2596 equivalents: TI vs onsemi vs XL2596
- onsemi LM2596TADJG
- Power calculator
- Buck converters
Sources (retrieved 2026-10-26)
- Texas Instruments, LM2596 SIMPLE SWITCHER Power Converter 150-kHz 3-A Step-Down Voltage Regulator, SNVS124G (revised March 2023), including the Package Option Addendum: https://www.ti.com/lit/ds/symlink/lm2596.pdf
Disclaimer
Values are copied from TI SNVS124G and its Package Option Addendum, read on 26 Oct 2026; heat figures are our arithmetic using typical saturation voltage and ignore diode and inductor losses. Verify against the current datasheet before production.
Reviewed by: Jasper · Updated: 2026-10-26