SPICE subcircuitAMS1117-3.3ams1117_33
AMS1117-3.3 (1 A LDO regulator)
3.3 V linear regulator, 1 A, in SOT-223: dropout about 1.1 V (needs at least 4.4 V in for a full 3.3 V out), 5 mA quiescent current. Typical on Arduino and ESP boards. Needs 22 µF tantalum or a ceramic capacitor with some ESR at the output for stability.
Key data
- Category
- ICs
- Simulation model
- SPICE subcircuit
- Manufacturer part number
- AMS1117-3.3
- Reference prefix
- U
- Pins
- 3
- Land pattern
- SOT-223-3_TabPin2
Notes
The regulator holds 3.3 V as long as the input is at least about 1.1 V higher. Below that the output follows the input minus the dropout. The 5 mA quiescent current loads the input.
- Place 10 µF at the input and 22 µF at the output close to the pins.
- The dissipated power is (V_IN − 3.3 V) · I: from 12 V at 300 mA that is 2.6 W, too much for SOT-223 without copper area.
Simulation model
The part is a small SPICE netlist (below), solved by the analog engine together with the rest of the circuit. Pin ids are the node names, {braces} are parameters.
SPICE netlist
V1 IN h DC {VDO}
U1 h OUT GND h LDO VOUT={VOUT} RDO=0 IQ={IQ}Pins 3
| Pin | Name | Use |
|---|---|---|
| IN | VINSupply pin | Input 4.4–15 V: 10 µF to GND |
| OUT | VOUTSupply pin | Regulated 3.3 V output (also the tab): 22 µF to GND for stability |
| GND | GNDGround pin | Ground (the ADJ pin of the adjustable version) |
Parameters 3
Output voltage
VOUTDefault3.3 V
Dropout voltage
VDODefault1.06 V
Fixed drop of the pass transistor; plus 0.05 Ω output resistance: 1.1 V at 800 mA (datasheet typical)
Quiescent current
IQDefault5m A
PCB
Verified land pattern
SOT-223-3_TabPin2| Package | Land pattern | Status | Source |
|---|---|---|---|
| SOT-223 · AMS1117-3.3 | SOT-223-3_TabPin2 | Verified land pattern | KiCad Package_TO_SOT_SMD:SOT-223-3_TabPin2; AMS1117 datasheet pinout 1 GND, 2 VOUT, 3 VIN, tab VOUT |