Component Comparison: LM2596S-5.0/NOPB vs. LM2596S-3.3
Quick verdict
For designs requiring a stable 5V rail at up to 3A, the LM2596S-5.0/NOPB is the straightforward choice, offering proven fixed output voltage and robust thermal handling. When a 3.3V fixed output is needed, especially for modern digital logic or microcontroller supplies, the LM2596S-3.3 fits better, delivering the same current capability and switching frequency with minimal design adjustments.
Spec comparison table
| Spec | LM2596S-5.0/NOPB | LM2596S-3.3 | Notes |
|---|---|---|---|
| Function | Step-Down Buck Regulator | Step-Down Buck Regulator | Identical function, no difference. |
| Input Voltage Max | 40 V | 40 V | Equal max input voltage rating; no advantage. |
| Input Voltage Min | 4.5 V | Not specified | 5.0V version specifies 4.5V minimum input, better defined for low input voltage designs. |
| Mounting Type | Surface Mount | Surface Mount | Same package style, no difference. |
| Number of Outputs | 1 | 1 | Both single output devices. |
| Operating Temperature | -40°C to 125°C (TJ) | -40°C to 125°C (TA) | TJ rating (junction) for 5.0V vs TA (ambient) for 3.3V; 5.0V part’s thermal spec is more conservative. |
| Output Configuration | Positive | Positive | Identical output polarity. |
| Output Current Max | 3 A | 3 A | Equal maximum current rating. |
| Output Type | Fixed 5.0 V | Fixed 3.3 V | Fixed output voltage difference defines use case. |
| Output Voltage Range | 5 V | 3.3 V | Fixed voltage; choose based on required output rail. |
| Package Case | TO-263-6, D2PAK (5 leads + Tab), TO-263BA | TO-263-6, D2PAK (5 leads + Tab), TO-263BA | Same package outline, facilitating similar thermal dissipation and mounting. |
| Supplier Device Package | TO-263 (DDPAK-5) | TO-263-5L | Slight variation in package designation; likely pin-compatible but verify pinout. |
| Switching Frequency Typ | 150 kHz | 150 kHz | Identical switching frequency, consistent design parameters. |
| Synchronous Rectifier | No | No | Both use diode rectification, impacting efficiency and thermal design similarly. |
| Topology | Buck | Buck | Same topology, no difference. |
Design trade-offs
The fundamental difference between these two devices is the fixed output voltage: 5.0 V versus 3.3 V, both designed to deliver up to 3 A with a 150 kHz switching frequency. This directly impacts the output inductor selection and output capacitor requirements due to ripple voltage and current considerations intrinsic to each voltage level.
From a thermal design perspective, both devices share the same package (TO-263-6/D2PAK) and maximum junction temperature rating (125°C). The 5.0 V device specifies junction temperature, which is more relevant for thermal management than the ambient temperature spec on the 3.3 V device. Since both lack synchronous rectification, their efficiency will be limited by the forward voltage drop of the catch diode, which typically results in higher losses than modern synchronous buck converters. This loss is more pronounced at lower output voltages, meaning the 3.3 V version may run slightly hotter at equivalent load currents due to higher duty cycles and conduction losses in the diode.
The input voltage minimum is only specified for the 5.0 V device (4.5 V), giving more confidence in low-voltage input applications. The 3.3 V device’s unspecified minimum input voltage requires consulting the datasheet or testing to confirm operation near the output voltage plus dropout margin.
Regarding layout, both devices require adequate thermal vias and copper area for the exposed tab to maintain junction temperature under high load. The identical switching frequency simplifies EMI filtering design and enables reuse of inductors and capacitors between the two output voltage variants, albeit with adjusted values to maintain ripple and transient performance.
Cost differences between the two parts may be minimal due to identical packaging and similar silicon complexity. However, sourcing from Texas Instruments (LM2596S-5.0/NOPB) versus UMW (LM2596S-3.3) may influence supply chain decisions, lead times, and quality assurance considerations.
Use-case fit
Choose LM2596S-5.0/NOPB when…
- You need a reliable, fixed 5 V supply rail capable of up to 3 A for legacy or mixed-voltage systems.
- Your input voltage ranges down to around 4.5 V, such as in battery-powered 5 V systems, where dropout margin is critical.
- Thermal management is a concern, and you prefer a device with explicitly specified junction temperature limits.
- You require a well-documented TI device with established reference designs and application notes.
- Your design demands a fixed 5 V rail without additional external feedback components or trimming.
Choose LM2596S-3.3 when…
- Your system requires a 3.3 V fixed output for powering modern low-voltage digital ICs or microcontrollers.
- Input voltage is comfortably above 3.3 V plus dropout, and you do not need a specified minimum input voltage.
- You aim to minimize board space by reusing the same 150 kHz switching frequency components but at a lower output voltage.
- You want a simpler fixed-output regulator without the need to design or calibrate adjustable output voltage.
- Cost or sourcing advantages exist with the UMW-supplied device for your volume and supply chain.
Drop-in compatibility
Both devices share the TO-263-6 package (D2PAK with 5 leads plus tab), but the LM2596S-5.0/NOPB is specified as TO-263 (DDPAK-5), and the LM2596S-3.3 as TO-263-5L. Datasheet verification is required to confirm exact pinout compatibility, but these package designations strongly suggest pin and footprint compatibility. Substituting one for the other on the same PCB layout should be feasible without mechanical modification, but the output voltage will obviously change. External components sized for 5 V operation (inductor, output capacitor ESR and ripple rating) may need adjustment for stable operation and acceptable ripple at 3.3 V.
Alternatives to consider
- LM2675 Series (TI): Lower switching frequency (52 kHz) but similar output current and fixed voltages; better for designs prioritizing reduced EMI.
- MP1584EN (Monolithic Power Systems): Synchronous buck converter with higher switching frequency (~1.5 MHz) for smaller magnetics and improved efficiency.
- TPS5430 (TI): Adjustable buck regulator with synchronous rectification, offering better efficiency and thermal performance for 3A loads.