LM2596S-5.0/NOPB vs LM2596T-ADJ: Technical Comparison for Hardware Designers
Quick verdict
For straightforward 5 V, 3 A buck conversion with minimal design effort, the LM2596S-5.0/NOPB fixed-output device is the better choice due to its fixed voltage and surface-mount convenience. For applications requiring adjustable output voltage from 1.2 V up to 37 V, the LM2596T-ADJ provides flexibility at the cost of through-hole mounting and more complex external resistor selection.
Spec comparison table
| Spec | LM2596S-5.0/NOPB | LM2596T-ADJ | Notes |
|---|---|---|---|
| Function | Step-Down | Step-Down | Both are buck regulators, no difference. |
| Input Voltage Max | 40 V | 40 V | Equal max input voltage rating. |
| Input Voltage Min | 4.5 V | 4.5 V | Equal min input voltage rating. |
| Mounting Type | Surface Mount | Through Hole | Surface mount (LM2596S-5.0/NOPB) better for automated assembly and smaller PCB area. |
| Number of Outputs | 1 | 1 | Both single output. |
| Operating Temperature Range | -40°C to 125°C (TJ) | -40°C to 125°C (TJ) | Equal temperature range. |
| Output Configuration | Positive | Positive | Both positive outputs. |
| Output Current Max | 3 A | 3 A | Same max output current. |
| Output Type | Fixed (5.0 V) | Adjustable (1.2 V to 37 V) | Fixed output simplifies design; adjustable offers flexibility. |
| Output Voltage Max | 5 V (fixed) | 37 V (adjustable) | Adjustable device supports wide output range; fixed device limited to 5 V. |
| Output Voltage Min | 5 V | 1.2 V | Adjustable device supports lower voltages, useful for low-voltage rails. |
| Package/Case | TO-263-6, D2PAK (5 leads + tab), TO-263BA | TO-220-5 Formed Leads | TO-263 is surface mount and lower profile; TO-220 is through hole with easier heatsinking but larger PCB footprint. |
| Supplier Device Package | TO-263 (DDPAK-5) | TO-220-5 | TO-263 preferred for compact surface mount designs; TO-220 preferred where easy heatsinking and hand soldering is needed. |
| Switching Frequency Typ | 150 kHz | 150 kHz | Identical switching frequency, so EMI and component size similar. |
| Synchronous Rectifier | No | No | Both use diode rectification, impacting efficiency and thermal performance. |
| Topology | Buck | Buck | Same topology. |
Design trade-offs
The primary distinction between these two devices is the output voltage configuration: fixed 5 V versus adjustable 1.2–37 V. The fixed 5 V LM2596S-5.0/NOPB reduces component count since no feedback resistor divider is needed, simplifying the BOM and layout. This reduces design iteration and risk, especially in high-volume production where a single output rail is required.
The LM2596T-ADJ’s adjustable output enables custom voltage rails, from 1.2 V to 37 V, allowing designers to tailor supply voltages for diverse system requirements. This flexibility comes with increased layout complexity: the feedback network must be carefully designed and routed to maintain regulation accuracy and noise immunity. The choice of feedback resistors also affects loop stability and transient response, requiring simulation or prototyping.
Thermally, both devices support up to 3 A output current and share the same maximum junction temperature rating (-40°C to 125°C TJ). However, the LM2596T-ADJ’s TO-220 package offers a larger exposed metal tab and formed leads, which typically simplify heatsink attachment and improve thermal dissipation. The LM2596S-5.0/NOPB’s TO-263 surface-mount package is more compact but requires good PCB thermal design, including large copper pours and thermal vias to spread heat effectively.
Both parts run at 150 kHz switching frequency, so input/output inductor and capacitor size will be similar. Neither uses synchronous rectification, so conduction losses in the output diode remain a limiting factor for efficiency. Designers should expect similar efficiency curves with slightly better thermal performance on the TO-220 package, assuming similar board-level thermal management.
Mounting type is a critical trade-off: LM2596S-5.0/NOPB is surface mount, favoring automated assembly and smaller PCB footprints. LM2596T-ADJ is through-hole, which can be hand-soldered or used in prototyping but occupies more PCB area and may increase assembly cost in volume.
Cost considerations depend on volume and assembly: fixed 5 V devices are often cheaper due to simpler external components and smaller package, but adjustable devices may reduce system BOM cost by replacing multiple fixed regulators.
Use-case fit
Choose LM2596S-5.0/NOPB when…
- Designing a mass-produced product requiring a stable 5 V rail with minimal design complexity.
- PCB space is limited and surface-mount assembly is preferred.
- Automated assembly lines are used, and through-hole devices are undesirable.
- Thermal dissipation must be managed via PCB copper areas rather than external heatsinks.
- The output voltage is fixed and well-known, removing the need for adjustable feedback components.
Choose LM2596T-ADJ when…
- The output voltage requirement is non-standard or varies between designs, ranging anywhere from 1.2 V to 37 V.
- Prototyping or low-volume production where through-hole parts allow easier manual soldering or heatsink attachment.
- Thermal management relies on an external heatsink mounted to the TO-220 package tab.
- System design requires fine-tuning of output voltage for different modules or supply rails.
- The design benefits from a standard regulator IC footprint with formed leads for robust mechanical mounting.
Drop-in compatibility
These devices are not pin- or footprint-compatible. The LM2596S-5.0/NOPB uses a TO-263-6 (D2PAK) surface-mount package with 5 leads plus a tab, while the LM2596T-ADJ uses a TO-220-5 through-hole package with formed leads. Substituting one for the other requires a PCB redesign due to different mechanical footprints, mounting types, and thermal management provisions.
Additionally, the fixed 5 V device eliminates the need for an adjustable feedback resistor network present on the LM2596T-ADJ, so the circuit topology differs fundamentally. Therefore, these parts are not direct replacements without board and schematic changes.
Alternatives to consider
- LM2596-5.0 (TO-220 fixed 5 V): Same family but in TO-220 package for easier heatsinking with fixed 5 V output.
- LT1767 (Analog Devices): Adjustable switching regulator with synchronous rectifier option for improved efficiency.
- TPS5430 (Texas Instruments): 3 A buck regulator with integrated synchronous rectifier and adjustable output, offering better efficiency at the cost of more complex design.