Answer: The AMS1117-5.0 needs about 6.3 V at its input to guarantee 5 V at 0.8 A (1.3 V maximum dropout), so it cannot make 5 V from a 5 V USB rail. From higher inputs, heat is the limit: in SOT-223 at 40 °C ambient, expect roughly 235 mA from 9 V and 135 mA from 12 V. (AMS1117 datasheet pp.1–5.)
Key specifications
| Parameter | Value | Condition | Source |
|---|---|---|---|
| Output voltage | 4.925 / 5.000 / 5.075 V | VIN = 6.5 V, IOUT = 0 mA, TJ = 25 °C | p.2 Electrical Characteristics |
| Output voltage, full range | 4.850 – 5.150 V | VIN = 6.5 V, full operating temperature range (bold row) | p.2 Electrical Characteristics |
| Line regulation | 0.5 typ / 10 max mV (1.0 / 10 mV full range) | 1.5 V ≤ VIN − VOUT ≤ 12 V | p.2 Electrical Characteristics |
| Load regulation | 5 typ / 20 max mV (10 / 35 mV full range) | VIN = 6.5 V, 0 ≤ IOUT ≤ 0.8 A | p.3 Electrical Characteristics |
| Dropout voltage | 1.1 typ / 1.3 max V | IOUT = 0.8 A, ΔVOUT = 1 % | p.3 Electrical Characteristics, Note 4 |
| Current limit | 900 min / 1100 typ / 1500 max mA | VIN − VOUT = 1.5 V | p.3 Electrical Characteristics |
| Quiescent current | 5 typ / 11 max mA | VIN − VOUT = 1.5 V | p.3 Electrical Characteristics |
| Ripple rejection | 60 min / 68 typ dB | 120 Hz, COUT 22 µF tantalum, IOUT 1 A, VIN 6.5 V | p.3 Electrical Characteristics |
| Input voltage (abs. max) | 15 V | — | p.2 Absolute Maximum Ratings |
| Regulation guaranteed up to | 1.2 W (SOT-223) | Line and load regulation | p.3 Note 2 |
| θJA, SOT-223 | 90 °C/W | Soldered; 46 °C/W to > 90 °C/W depending on copper | p.2 Absolute Maximum Ratings (footnote) |
| Junction temperature range | −40 to 125 °C | — | p.1 Ordering Information |
Pinout (SOT-223)
Pin 1 is ground, pin 2 is VOUT and pin 3 is VIN (p.1 Pin Connections), the same order as the 3.3 V and adjustable versions.
Input range that actually works
- Lower bound. 5.0 V + 1.3 V maximum dropout = 6.3 V at 0.8 A (p.3). Below 0.8 A the typical dropout is lower, but AMS gives no maximum for lighter loads, so 6.3 V is the safe design figure.
- Upper bound. 15 V is the absolute maximum (p.2).
- Where it is tested. AMS characterises the output, load regulation and ripple rejection at VIN = 6.5 V (pp.2–3), which is a good minimum design point.
Current you can draw from common inputs (SOT-223)
PD = (VIN − 5 V) × IOUT, and the junction must stay ≤ 125 °C (p.5). At 40 °C ambient, the 90 °C/W rating allows (125 − 40)/90 = 0.94 W. The 1.2 W regulation guarantee in Note 2 is a second, looser ceiling.
| Input | Headroom | Current at 0.94 W (90 °C/W, 40 °C) | Current at 1.2 W (Note 2 limit) |
|---|---|---|---|
| 7 V | 2 V | about 470 mA | 600 mA |
| 9 V | 4 V | about 235 mA | 300 mA |
| 12 V | 7 V | about 135 mA | 171 mA |
The Note 2 column is never usable at 90 °C/W, because 1.2 W × 90 °C/W = 108 °C of rise. You would only get there with the low-θJA copper layouts in AMS’s p.5 table (55 °C/W and up) or with the TO-252 version (AMS1117CD in its adjustable form, 80 °C/W, 2.2 W).
Design notes
- Ripple. 68 dB typical at 120 Hz (p.3): 1 Vpp of input ripple becomes about 0.4 mVpp. That is 4 dB below the 3.3 V version’s 72 dB typical; both have a 60 dB minimum.
- Load regulation. 20 mV max at 25 °C and 35 mV over temperature for 0–0.8 A (p.3), which is the largest of the AMS fixed versions.
- Capacitors. 22 µF solid tantalum on the output covers all cases (p.4).
- Diode. An output-to-input diode is recommended only with an input crowbar and 1000–5000 µF on the output (p.4).
Pitfalls specific to AMS1117-5.0
- Using it to “clean up” USB 5 V. With 5 V in, there is 0 V of headroom: the output is the input minus about a volt. Use the AMS1117-3.3 or a low-dropout CMOS part instead.
- Running it from a 2S Li-ion pack. A 2S pack near empty sits around 6 V, which is below the 6.3 V needed at full load.
- 12 V → 5 V at hundreds of milliamps. At 300 mA the part would dissipate 2.1 W. That exceeds the SOT-223 1.2 W guarantee and would mean a 189 °C rise at 90 °C/W. Use a buck converter such as the LM2596.
- Assuming the datasheet’s 1 A rating holds at all inputs. The current limit is tested at only 1.5 V of headroom (p.3); the thermal limit takes over long before that at higher inputs.
Part numbers (information only)
AMS lists AMS1117-5.0 (SOT-223), AMS1117CD-5.0 (TO-252) and AMS1117CS-5.0 (SO-8), all for −40 to 125 °C (p.1).
FAQ
- Can the AMS1117-5.0 output 5 V from a 5 V USB supply? No. It needs about 6.3 V at the input at 0.8 A (5 V + 1.3 V maximum dropout, p.3).
- What input voltage should I design for? At least 6.5 V, the voltage AMS uses for its 5 V characterisation (pp.2–3), and no more than you need, because every extra volt becomes heat.
- How much current from 12 V? About 135 mA in SOT-223 at 40 °C ambient with the 90 °C/W rating (7 V × 0.135 A ≈ 0.94 W).
- Why is ripple rejection lower than on the 3.3 V version? AMS specifies 68 dB typical for the 5.0 V part versus 72 dB for 3.3 V (p.3). Both have the same 60 dB minimum.
- What output capacitor does it need? AMS says 22 µF solid tantalum covers all cases (p.4).
Related (internal links)
- AMS1117-3.3
- AMS1117-ADJ (SOT-223)
- AMS1117CD (TO-252)
- LM2596S-ADJ buck regulator
- Power calculator
- 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. The input and current tables are our arithmetic on those values; your board’s thermal resistance will differ. Verify against the current datasheet and measure your design before production.
Reviewed by: Jasper · Updated: 2026-10-26