Three kinds of answer live in this family, and the repair dies when they are confused. The first is the same part in a different grade or package: LM317 and LM317T, TNY277 and TNY278, MC34063 and MC33063A — footprint-identical, and the substitution is safe. The second is a same-function part on a different footprint: the SMA-bodied M7 against the through-hole 1N4007, the SOT-23-5 ME6211 against the SOT-223 AMS1117 — a redesign, not a swap. The third is the trap that costs boards: TL494 and SG3525 share a 16-pin body and nothing else — inserting one into the other's footprint puts supply and outputs on the wrong pads. Same body is not the same part.
Table of Contents (8 points)
The substitutes, and what each one actually changes
| Original | Package | Verified substitute | Level | What changes |
|---|---|---|---|---|
| LM317 | TO-220 / SOT-223 / TO-92 / DPAK | LM317T | drop-in | Same TO-220 die; pin order ADJ / OUT / IN |
| LM317 | TO-220 / SOT-223 / TO-92 / DPAK | LM317L | function only | TO-92, 100 mA class — lead order follows the package drawing |
| LM317 | TO-220 / SOT-223 / TO-92 / DPAK | LM338 | function only | 5 A member of the same family; TO-220 pin order matches |
| LM337 | TO-220 / SOT-223 / TO-92 | LM337L | function only | The 100 mA member in TO-92 / SO-8 — the package governs orientation |
| LM337 | TO-220 / SOT-223 / TO-92 | LM333 | function only | Higher-current negative member; verify the tab against the drawing |
| LM7805 | TO-220 / TO-92 / DPAK | 78L05 | function only | TO-92, 100 mA — the middle letter is the current grade |
| LM7805 | TO-220 / TO-92 / DPAK | 78M05 | function only | 500 mA class; DPAK tab sits on the output node in some makers |
| L7905 / L7912 | TO-220 / TO-220FP / D2PAK | L7912 | drop-in | Same negative family pin order — the digits choose the voltage |
| L7905 / L7912 | TO-220 / TO-220FP / D2PAK | L79xxAC | drop-in | Insulated TO-220FP and D2PAK options across the family |
| AMS1117-3.3 | SOT-223 | CJ1117-3.3 | drop-in | Direct 1:1 on the SOT-223 footprint |
| AMS1117-3.3 | SOT-223 | ME6211C33M5G | function only | SOT-23-5; 1.1 V dropout and ~5 mA quiescent current against the AMS1117 class |
| LM2596 | TO-263 / TO-220-5 | LM2576 | pin-to-pin | Same five-pin outline; the passive network around it is what differs |
| LM2596 | TO-263 / TO-220-5 | XL2596 | drop-in | Same five-pin outline from a domestic fab |
| LM2576 | TO-220-5 / TO-263-5 | LM2596 | drop-in | 150 kHz sibling on the same outline — read the inductor and capacitor ratings |
| LM2576 | TO-220-5 / TO-263-5 | LM2576HV | drop-in | Same footprint, higher input ceiling |
| MC34063 | DIP-8 / SOIC-8 | MC33063A | drop-in | Same 8-pin body; the passives around it are the design |
| MC34063 | DIP-8 / SOIC-8 | CW34063 | drop-in | Same body — the marking documents the fab |
| UC3842 | DIP-8 / SOIC-8 | UC2842 | drop-in | Same body and pinout across the temperature grades |
| UC3842 | DIP-8 / SOIC-8 | UC3843 | pin-to-pin | Pin-identical; the start-up and UVLO thresholds are what move |
| UC3842 | DIP-8 / SOIC-8 | UC3844 | pin-to-pin | Same 8-pin body and pin assignment |
| UC3842 | DIP-8 / SOIC-8 | UC3845 | pin-to-pin | Same pinout; check the maximum duty cycle for the topology |
| TL494 | DIP-16 / SOIC-16 | KA7500B | drop-in | Pin-identical — the board cannot tell them apart |
| TL494 | DIP-16 / SOIC-16 | MB3759 | drop-in | Pin-identical second source; verify markings on old stock |
| SG3525 | DIP-16 / SOIC-16 | UC3525A | drop-in | Same DIP-16 / SOIC-16 body across the family |
| TNY277 | DIP-8C / SMD-8C | TNY276 | drop-in | Same outline across the TinySwitch-III row — pick the power rung you need |
| TNY277 | DIP-8C / SMD-8C | TNY278 | drop-in | Identical footprint, one rung up |
| TNY277 | DIP-8C / SMD-8C | TNY280 | drop-in | Identical DIP-8C / SMD-8C footprint, top of the ladder |
| OB2263 | SOT-23-6 / SOP-8 / DIP-8 | OB2262 | pin-to-pin | Shared small-form packages across the row |
| OB2263 | SOT-23-6 / SOP-8 / DIP-8 | CR6842S | function only | Small-form packages per vendor — verify the pin drawing before a layout swap |
| TPS54302 | SOT-23-THIN-6 | TPS54202 | pin-to-pin | Identical land pattern — the family was laid out as one board scaled by current |
| TPS54302 | SOT-23-THIN-6 | TPS54308 | pin-to-pin | Identical SOT-23-THIN-6 pinout |
| TPS54302 | SOT-23-THIN-6 | TPS62933 | function only | SOT-583 against SOT-23-THIN-6 — different footprint |
Where the grades hide
The 78xx and 79xx rows hide the current rating in one letter: 78L05 is 100 mA in TO-92, 78M05 is the 500 mA class, and the plain 7805 is 1 A in TO-220. Substituting downward is the error that looks like it works — the circuit runs, and then the regulator fails hot on the load that needed the bigger die. In the LM317 row the same ladder runs LM317L, LM317M, LM317, with the same consequence.
The AMS1117 deserves its own note because it is the most-copied 1 A regulator in prototype hardware, and its 1.1 V dropout and roughly 5–11 mA quiescent current are the two numbers that matter in a battery design. A low-dropout, low-Iq part such as the ME6211 is not a drop-in on the SOT-223 footprint, but it is the honest answer when the AMS1117 is running hot or draining the cell.
What we will not claim
Every mapping above was checked against the manufacturer datasheet for package, pinout and the ratings that decide a swap, and where the datasheet did not support a mapping it is not listed — including parts that are related rather than interchangeable, which is why the TL494 row here names only KA7500B and MB3759. Confirm against your own schematic before a redesign, and treat the level as the scope of the risk rather than a promise.
Parts named in this guide
CatalogEach of these is a part or part family this guide covers, linked to the catalog row we hold for it — specifications, package, lifecycle stage and the datasheet where we have localized one. Where the guide names a family, the row shown is the orderable part number we stock. A part the guide covers but that is missing from this list is one we do not currently carry; send the number and it goes out for sourcing with the rest.
| Part number | Manufacturer | Description |
|---|---|---|
| LM317BD2TR4GDatasheet | onsemi | IC REG LIN POS ADJ 1.5A D2PAK-3 |
| LM337D2TR4GDatasheet | onsemi | IC REG LIN NEG ADJ 1.5A D2PAK-3 |
| LM7805CTDatasheet | onsemi | IC REG LINEAR FIXED POS STD REG |
| LM2596S-3.3Datasheet | Texas Instruments | Texas Instruments SIMPLE SWITCHER® series, LM2596S-3.3, step-down buck regulator, fixed 3.3 V output, 3 A continuous, 150 kHz switching frequency, surface-mount TO-263-5 (DDPAK) package. |
| MC34063ADGDatasheet | onsemi | IC REG BUCK BST ADJ 1.5A 8SOIC |
| UC3842BD1R2GDatasheet | onsemi | IC REG CTRLR BST FLYBK ISO 8SOIC |
| TL494CDR2GDatasheet | onsemi | IC REG CTRLR BCK/PSH-PULL 16SOIC |
| KA7500BDatasheet | onsemi | — |
| TNY277GN-TLDatasheet | Power Integrations | IC OFFLINE SWITCH FLYBACK 8SMD |
| SG3525ADWR2GDatasheet | onsemi | IC REG CTRLR PUSH-PULL 16SOIC |
| L7905CV-DGDatasheet | STMicroelectronics | STMicroelectronics L7905CV-DG, a fixed -5V negative linear regulator in TO-220, rated for 1.5A output with 60dB PSRR at 120Hz and over-temperature / short-circuit protection. |
Put this to work on your component list
Send the part numbers or the whole BOM sheet. Each line comes back with current spot availability, original manufacturer condition, and verified cross-references — packed and shipped together in one single parcel.
How this guide is written
Written by the ICBOMS sourcing desk in Shenzhen and reviewed against the manufacturer documents and industry standards the guide cites. Statements are limited to what this desk does and how a part is judged — no indicative prices, lead times or stock counts, because those are quoted per line against a live check. Each guide carries the date it was last reviewed at the top of the page.