LM2596S-ADJ/NOPB vs LM2596S-5.0 Component Comparison
Quick verdict
For designs requiring a flexible output voltage, the LM2596S-ADJ/NOPB wins due to its adjustable output from 1.2 V up to 37 V, enabling custom voltage rails without redesigning the power stage. For applications fixed at 5 V output, the LM2596S-5.0 is preferable because it simplifies BOM and layout by eliminating the feedback resistor divider, offering guaranteed ±4% voltage tolerance and slightly better typical efficiency (~80% vs 73% at 5 V).
Spec comparison table
| Spec | LM2596S-ADJ/NOPB | LM2596S-5.0 | Notes |
|---|---|---|---|
| Function | Step-Down Buck Regulator | Step-Down Buck Regulator | Equal |
| Input voltage max | 40 V | 40 V | Equal |
| Input voltage min | 4.5 V | Not specified | Adjustable version specifies 4.5 V min input; fixed version input min not given |
| Output voltage min | 1.2 V | 5 V | Adjustable supports lower voltages, critical for low-voltage rails |
| Output voltage max | 37 V | Not specified | Adjustable supports higher max output voltage |
| Output current max | 3 A | 3 A | Equal |
| Number of outputs | 1 | 1 | Equal |
| Output configuration | Positive | Positive | Equal |
| Output type | Adjustable | Fixed | Adjustable allows custom voltages; fixed simplifies design and improves accuracy |
| Package case | TO-263-6, D2PAK (5 leads + tab) | TO-263-6, D2PAK (5 leads + tab) | Equal |
| Switching frequency typ | 150 kHz | 150 kHz | Equal |
| Synchronous rectifier | No | No | Equal |
| Operating temperature range | -40°C to 125°C (TJ) | -40°C to 125°C (TA) | Similar; TJ vs TA notation unclear, but both rated for typical industrial range |
| Mounting type | Surface mount | Surface mount | Equal |
| Output voltage tolerance | Not specified | ±4% max over line and load | Fixed output offers defined tolerance; adjustable depends on resistor accuracy |
| Efficiency @ 5 V output | ~73% (min) | ~80% (min) | Fixed version is typically more efficient at standard 5 V output |
| Output capacitor value min | Not specified | 22 µF/V (min) | Fixed version datasheet specifies capacitor selection guidance |
| Output capacitor value typ | Not specified | 560 µF / 16 V (typ) | Fixed version provides detailed capacitor recommendations |
| Output diode rating | Not specified | 5 A, 40 V | Fixed version datasheet specifies diode requirements |
| Input current limit | Not specified | 4.5 A | Fixed version datasheet specifies input current limit |
| Shutdown threshold voltage | Not specified | ~1.3 V (typ), max 25 V | Fixed version provides shutdown voltage specs |
| On/off pin max voltage | Not specified | 25 V max | Fixed version specifies on/off control pin limits |
| Quiescent current | Not specified | 5–10 mA typical, standby 80 µA | Fixed version provides quiescent current data; useful for power budgeting |
| Thermal resistance (typ) TO-263 | Not specified | 50°C/W (typ) | Fixed version specifies thermal resistance; likely similar for adjustable |
| Internal switch saturation voltage | Not specified | 1.16 V (min), up to 1.5 V (max) | Fixed version provides detailed switch voltage drop specs |
| Feedback bias current | Not specified | 50–100 nA typical | Fixed version has low feedback bias current, important for output voltage stability |
| Efficiency @ 3.3 V output | Not specified | 73% (min) | Fixed version datasheet includes efficiency curves for multiple voltages |
| Maximum junction temperature | Not specified | 150°C max | Fixed version specifies max junction temp |
| Storage temperature range | Not specified | -65°C to +150°C | Fixed version provides storage range |
| Startup time typical | Not specified | 2 ms or more | Fixed version specifies startup time, relevant for power sequencing |
| Inductor typical value | Not specified | 33 µH | Fixed version recommends inductor value |
| Output load current typical | 3 A typical | 3 A typical | Equal |
Design trade-offs
The primary difference between the two devices is the output voltage configurability. The LM2596S-ADJ/NOPB requires an external resistor divider to set the output voltage, allowing design flexibility from 1.2 V up to 37 V. This flexibility comes with the usual trade-offs: resistor tolerance affects output accuracy and noise sensitivity at the feedback node requires careful PCB layout to maintain stable regulation. The adjustable version typically incurs slightly lower efficiency at standard voltages like 5 V due to the resistor divider loading and the internal reference voltage (1.2 V typical).
In contrast, the LM2596S-5.0 fixed output version simplifies system design by integrating the feedback network internally, guaranteeing ±4% output voltage tolerance over line and load. This reduces component count and layout complexity, which can cut PCB assembly costs and reduce debugging time. The fixed version also provides more comprehensive datasheet guidance on external components (capacitors, diodes, inductors), which can aid design robustness and improve repeatability across production.
Both devices share the same package and switching frequency (150 kHz typical), meaning their EMI profiles, switching losses, and thermal footprints are roughly equivalent. Thermal dissipation will largely depend on output current and input-output voltage differential; however, the fixed 5 V device’s slightly higher efficiency (~80% vs. ~73% at 5 V) can translate into lower junction temperatures or smaller heatsinks in 5 V systems.
Neither device uses synchronous rectification, so conduction losses in the freewheeling diode remain a major efficiency limiter. The fixed output device specifies a 5 A, 40 V diode minimum, which should be matched in the adjustable version as well for reliability.
Quiescent current and standby currents are documented for the fixed version (5–10 mA typical, 80 µA standby), but not explicitly for the adjustable version, so power budget planning is more straightforward with the fixed device.
From a supply chain and cost perspective, the fixed device may have a slight unit cost advantage due to fewer external components and simpler testing requirements, but the adjustable version’s flexibility can justify its premium in multi-rail or configurable power supplies.
Use-case fit
Choose LM2596S-ADJ/NOPB when…
- You need a custom output voltage other than standard rails like 3.3 V or 5 V, anywhere between 1.2 V and 37 V.
- Your design requires multiple output voltages from a single regulator footprint by changing resistor values rather than swapping ICs.
- You are optimizing for minimal parts count and want to avoid multiple fixed-output regulator variants.
- You need to prototype quickly with adjustable output voltage to validate different voltage rails before finalizing fixed voltage versions.
- Your system tolerates slightly lower efficiency and you can invest effort in precise resistor selection and layout to maintain output accuracy.
Choose LM2596S-5.0 when…
- Your system voltage rail is fixed at 5 V and you want guaranteed ±4% regulation accuracy without external feedback resistors.
- You want simplified BOM and PCB layout with fewer external components.
- Efficiency at 5 V output is a priority, as it typically achieves ~80% efficiency compared to ~73% for adjustable at 5 V.
- You require detailed datasheet guidance on external component sizing to streamline design validation.
- You want documented quiescent and standby current specs for power budgeting in battery-powered or low-power applications.
Drop-in compatibility
Both devices use the TO-263-6 (D2PAK) package with 5 leads plus tab, which suggests pin compatibility. However, the LM2596S-5.0 datasheet indicates TO-263-5L package, which can imply a minor difference in lead count or pin arrangement. The adjustable version explicitly states TO-263-6 with 5 leads plus tab.
Given the same switching frequency and basic function, the pinout is likely similar but not guaranteed identical. The adjustable version requires external resistor dividers on the feedback pin, which the fixed version does not use. Substituting one for the other without adjusting the feedback network could cause incorrect output voltage or instability.
If replacing the adjustable with the fixed version, the feedback resistor divider must be removed or bypassed. Conversely, replacing fixed with adjustable requires adding the resistor divider and recalculating component values.
Because of the lack of explicit pinout cross-reference, verify the pin assignments carefully before substitution. Footprint compatibility is probable but not confirmed; always check the manufacturers’ datasheets for pinouts and mechanical drawings.
Alternatives to consider
- **LM257