Answer: AMS1117CD is AMS’s code for the adjustable AMS1117 in TO-252 (DPAK); the market name “AMS1117CD-ADJ” is not in AMS’s table. Electrically it is the same 1 A, 1.25 V-reference regulator as the SOT-223 part, but the package is rated 80 °C/W (vs 90) and AMS guarantees regulation up to 2.2 W (vs 1.2 W). The tab is the output. (AMS1117 datasheet pp.1–3.)
Key specifications
| Parameter | Value | Condition | Source |
|---|---|---|---|
| Package / AMS code | TO-252 (DPAK), “AMS1117CD” | Adjustable; −40 to 125 °C junction | p.1 Ordering Information |
| Tab connection | Output | “TAB IS OUTPUT” on the TO-252 front view | p.1 Pin Connections |
| θJA, TO-252 | 80 °C/W | Soldered | p.2 Absolute Maximum Ratings |
| θJC (all packages) | 15 °C/W | — | p.3 Electrical Characteristics |
| Regulation guaranteed up to | 2.2 W (TO-252) | Line and load regulation; SOT-223 1.2 W, SO-8 780 mW | p.3 Note 2 |
| Reference voltage | 1.232 / 1.250 / 1.268 V; 1.2125–1.2875 V full range | IOUT 10 mA; full range 1.5 V ≤ VIN − VOUT ≤ 12 V | p.2 Electrical Characteristics |
| Dropout voltage | 1.1 typ / 1.3 max V | IOUT = 0.8 A, ΔVREF = 1 % | p.3, Note 4 |
| Minimum load current | 5 typ / 10 max mA | VIN − VOUT = 1.5 V | p.3, Note 5 |
| Load regulation (ADJ) | 0.1 / 0.3 % (0.2 / 0.4 % full range) | VIN − VOUT 1.5 V, 10 mA–0.8 A | p.2 |
| Adjust pin current | 55 typ (25 °C) / 120 max µA (full range) | IOUT 10 mA | p.3 |
| Input voltage (abs. max) | 15 V | — | p.2 |
| Thermal shutdown | 165 °C | — | p.4 Application Hints |
Pinout (TO-252)
AMS’s “3 pin fixed/adjustable version” list applies: 1 = Ground/Adjust, 2 = VOUT, 3 = VIN (p.1). The TO-252 front view adds that the tab is the output, so the large pad on your footprint is VOUT, not ground.
When the DPAK is worth it
Both packages share the same silicon limits; what changes is how much heat you can shed and how much dissipation AMS still guarantees regulation at.
| SOT-223 (AMS1117) | TO-252 (AMS1117CD) | |
|---|---|---|
| θJA (datasheet) | 90 °C/W | 80 °C/W |
| Regulation guaranteed to | 1.2 W | 2.2 W |
| Power at TJ 125 °C, TA 40 °C, datasheet θJA | 0.94 W | 1.06 W |
| Thermal resistance needed for 2.2 W at TA 40 °C | — | 38.6 °C/W |
The headline 80 °C/W only buys about 12 % more power. The real advantage is the 2.2 W guarantee, but reaching it at 40 °C ambient needs a total junction-to-ambient resistance of about 39 °C/W, which means a large copper pour or a heatsink. AMS notes that junction-to-ambient can get as low as 45 °C/W with a reasonable board and one layer of spreading copper (p.5).
Design notes
- Example: 12 V → 5 V. With the 80 °C/W rating at 40 °C ambient: 1.06 W / 7 V ≈ 152 mA. If your copper gets you to 45 °C/W: (125 − 40)/45 = 1.89 W, or about 270 mA.
- Divider. Same formula and limits as the SOT-223 part: VOUT = VREF(1 + R2/R1) + IADJ × R2 (p.4), and R1 ≤ 125 Ω keeps the divider above the 10 mA minimum load.
- Remote sense. Connect R1 to the case (the tab is VOUT) and R2 to the load’s ground (p.4–5, Figure 3).
- Capacitors. 22 µF solid tantalum on the output covers all cases (p.4). For ADJ bypassing, the capacitor’s impedance at the ripple frequency must be below R1 (p.5).
Pitfalls specific to AMS1117CD
- Pouring ground copper under the tab. The tab is VOUT. Heat-spreading copper attached to the tab must be on the output net. AMS notes the spreading layer itself need not connect electrically to the tab, since heat can couple through the board material into an inner or back plane (p.5).
- Expecting 2.2 W from the bare 80 °C/W figure. 2.2 W × 80 = 176 °C rise; see the table above.
- Searching for “AMS1117CD-ADJ”. AMS’s code is AMS1117CD; the fixed DPAK versions are AMS1117CD-1.5 … AMS1117CD-5.0 (p.1).
- Swapping it onto a SOT-223 footprint. Different land pattern; only the electrical pin numbering is shared.
Part numbers (information only)
| AMS code | Package | Output |
|---|---|---|
| AMS1117CD | TO-252 | Adjustable (this page) |
| AMS1117CD-3.3 / -5.0 | TO-252 | Fixed 3.3 V / 5.0 V |
| AMS1117 | SOT-223 | Adjustable |
| AMS1117CS | SO-8 | Adjustable |
Source: p.1. All listed for −40 to 125 °C junction temperature.
FAQ
- Is AMS1117CD adjustable? Yes. In AMS’s ordering table, AMS1117CD (no voltage suffix) is the adjustable TO-252 version (p.1).
- Which pin is the tab on the AMS1117CD? The output. The TO-252 drawing says “TAB IS OUTPUT” (p.1).
- How much more power can the TO-252 handle than the SOT-223? With datasheet θJA values (80 vs 90 °C/W) only about 12 % more. With good copper or a heatsink you can use the 2.2 W regulation guarantee, versus 1.2 W for SOT-223 (Note 2, p.3).
- What is the minimum load? 10 mA worst case (p.3), so keep R1 at or below about 125 Ω if the divider must carry it.
- Does it use the same divider formula as the SOT-223 AMS1117? Yes: VOUT = 1.25 V × (1 + R2/R1) + IADJ × R2 (p.4).
Related (internal links)
- AMS1117-ADJ (SOT-223)
- AMS1117CS (SO-8)
- AMS1117-5.0
- AMS1117-ADJ resistor calculator
- AMS1117 equivalents
- SMD package sizes
- Linear voltage regulators
Sources (retrieved 2026-10-26)
- Advanced Monolithic Systems, AMS1117 1A Low Dropout Voltage Regulator (DS1117; no revision code printed): http://www.advanced-monolithic.com/pdf/ds1117.pdf (page numbers are PDF page order). Checked against a mirror copy of this PDF (sha256 189a2651…a3f0); AMS prints no revision code, so we cannot prove it is the newest issue.
Disclaimer
Values are copied from the AMS1117 datasheet listed above, read on 26 Oct 2026; power figures are our arithmetic. Your board’s thermal resistance will differ. Verify against the current datasheet and measure before production.
Reviewed by: Jasper · Updated: 2026-10-26