Answer: AMS1117CS is AMS’s code for the adjustable AMS1117 in an 8-lead SOIC. It has the same 1.25 V reference and 1.3 V dropout as the SOT-223 part, but the package is rated 160 °C/W and AMS guarantees regulation only up to 780 mW. In practice that means a few hundred milliamps, not 1 A. The pinout is not a SOT-223 swap: VOUT is on pins 2, 3, 6 and 7. (AMS1117 datasheet pp.1–3.)
Key specifications
| Parameter | Value | Condition | Source |
|---|---|---|---|
| Package / AMS code | 8-lead SOIC, “AMS1117CS” | Adjustable; −40 to 125 °C junction | p.1 Ordering Information |
| Pinout | 1 GND/ADJ; 2, 3, 6, 7 VOUT; 4 VIN; 5, 8 N/C | Top view | p.1 8L SOIC Top View |
| θJA, SO-8 | 160 °C/W | Soldered | p.2 Absolute Maximum Ratings |
| θJC (all packages) | 15 °C/W | — | p.3 Electrical Characteristics |
| Regulation guaranteed up to | 780 mW (8-lead SOIC) | Line and load regulation | 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 |
| Line regulation (ADJ) | 0.015 / 0.2 % (0.035 / 0.2 % full range) | 1.5 V ≤ VIN − VOUT ≤ 12 V | 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 |
| Lead temperature | 265 °C for 25 s | Soldering | p.2 |
Pinout (8-lead SOIC, top view)
| Pin | Function | Pin | Function |
|---|---|---|---|
| 1 | GND / ADJ | 8 | N/C |
| 2 | VOUT | 7 | VOUT |
| 3 | VOUT | 6 | VOUT |
| 4 | VIN | 5 | N/C |
Source: p.1. Connect all four VOUT pins to one wide copper area; they are the main heat path out of the package. Pins 5 and 8 are listed as no-connect.
How much current, really?
TJ = TA + (VIN − VOUT) × IOUT × θJA ≤ 125 °C (p.5), with θJA = 160 °C/W (p.2).
| Case | Allowed power | Current |
|---|---|---|
| 5 V → 3.3 V, TA 25 °C | 100/160 = 0.625 W | ≈ 368 mA |
| 5 V → 3.3 V, TA 50 °C | 75/160 = 0.469 W | ≈ 276 mA |
| 12 V → 5 V, TA 50 °C | 0.469 W | ≈ 67 mA |
| 3.3 V → 1.8 V, TA 50 °C | 0.469 W | ≈ 313 mA |
The 780 mW regulation guarantee (Note 2) is never reached with the bare 160 °C/W figure, because 0.78 × 160 = 125 °C of rise. Choose the SO-8 for board space or assembly reasons, not for power.
Design notes
- Divider. VOUT = VREF(1 + R2/R1) + IADJ × R2 (p.4). Keep R1 ≤ 125 Ω so the divider covers the 10 mA minimum load. At light loads that 10 mA is a noticeable share of a ~300 mA budget.
- Kelvin connection. Take R1 from the VOUT pins at the package, not from the far end of the output trace (p.4–5, Figure 3).
- Capacitors. 22 µF solid tantalum on the output covers all cases (p.4). An ADJ bypass capacitor must have lower impedance than R1 at the ripple frequency (p.5).
- Low-voltage rails suit it best. 3.3 V → 1.8 V or 1.5 V keeps the drop small (1.3 V maximum dropout still applies, so 3.3 V → 2.5 V is not guaranteed at 0.8 A).
Pitfalls specific to AMS1117CS
- Treating it as a SOT-223 replacement. Pin 2 is VOUT in both, but VIN moves to pin 4 and VOUT is spread over 2, 3, 6 and 7. It needs its own footprint.
- Designing for 1 A. At 160 °C/W, 1 A from 5 V to 3.3 V would mean a 272 °C rise.
- Leaving pins 3, 6 or 7 floating. Connect all four VOUT pins; they are the heat path as well as the output.
- Searching for “AMS1117CS-ADJ”. AMS’s code is plain AMS1117CS; the fixed SO-8 parts are AMS1117CS-1.5 … AMS1117CS-5.0 (p.1).
Part numbers (information only)
| AMS code | Package | Output |
|---|---|---|
| AMS1117CS | 8-lead SOIC | Adjustable (this page) |
| AMS1117CS-3.3 / -5.0 | 8-lead SOIC | Fixed 3.3 V / 5.0 V |
| AMS1117 | SOT-223 | Adjustable |
| AMS1117CD | TO-252 | Adjustable |
Source: p.1. All listed for −40 to 125 °C junction temperature.
FAQ
- Is the AMS1117CS pin-compatible with the SOT-223 AMS1117? No. It is an 8-lead SOIC with VOUT on pins 2, 3, 6, 7, VIN on pin 4 and GND/ADJ on pin 1 (p.1).
- How much current can the SO-8 AMS1117 deliver? About 276 mA from 5 V to 3.3 V at 50 °C ambient using the 160 °C/W rating; about 67 mA from 12 V to 5 V.
- What do the N/C pins connect to? AMS lists pins 5 and 8 as N/C (p.1).
- What power is regulation guaranteed to? 780 mW for the 8-lead SOIC (Note 2, p.3).
- Is AMS1117CS the adjustable version? Yes. Without a voltage suffix, AMS1117CS is the adjustable SO-8 part (p.1).
Related (internal links)
- AMS1117-ADJ (SOT-223)
- AMS1117CD (TO-252)
- AMS1117-3.3
- 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; current figures are our arithmetic using the datasheet θJA. Your board will differ. Verify against the current datasheet and measure before production.
Reviewed by: Jasper · Updated: 2026-10-26