# PSSI2021SAY

**Nexperia** · Current Source / Constant Current Source · SOT-353

PSSI2021SAY from Nexperia, in a SOT-353. Pinout and pin descriptions extracted from the manufacturer datasheet by ds2sf; symbol, footprint, and 3D from KiCad-official CAD.

## Pinout

| Pin | Name | Type | Function |
|---|---|---|---|
| 1 | n.c. | unconnected | Not connected. Leave floating or tie to any convenient net; the pin has no internal bond. |
| 2 | IOUT | output | Regulated output current terminal. Sources a stabilized current (15 uA to 50 mA) into the load referenced to GND. Internal PNP collector; output voltage rating Vout = 73 V (with VS = 75 V). |
| 3 | GND | power_in | Ground / return terminal for the load current. All internal references are taken with respect to this pin. |
| 4 | REXT | passive | External resistor terminal used to program the output current. Connect a resistor Rext between REXT (pin 4) and VS (pin 5); Iout = 0.617/Rext + 15 uA. Left open, typical Iout is ~15 uA. Internal resistor value is ~48 kOhm. |
| 5 | VS | power_in | Supply voltage terminal. Absolute maximum VS = 75 V. Also serves as the reference node for the external programming resistor (Rext between pin 5 and pin 4). |

## Key specifications

| Parameter | Value |
|---|---|
| Manufacturer | Nexperia |
| Package | SOT-353 |
| Category | Power Management (PMIC) |
| Pins | 5 |

## Ordering variants

Same part, different packaging or reel option.

- `PSSI2021SAY`

## CAD (KiCad official)

- Symbol: `PSSI2021SAY`
- Footprint: `Package_TO_SOT_SMD:SOT-353_SC-70-5`
- 3D model: SOT-353 (KiCad packages3D, STEP)
- 3D model files: `pssi2021say-etched.step` / `pssi2021say-etched.glb` carry the MPN laser-etched on the die in a toggleable `Adom.LaserEtch` group (Fusion-ready); `pssi2021say.step` / `pssi2021say.glb` are the bare package body.

## Provenance

Data extracted from the manufacturer datasheet, not a distributor listing:

- **Datasheet:** [Nexperia datasheet](https://assets.nexperia.com/documents/data-sheet/PSSI2021SAY.pdf) (13 pp, sha256 `403e1e89af407de3`, retrieved 2026-08-17, tier: manufacturer)
- **Extractor:** `ds2sf` (Claude). Every pin and dimension is cited to a datasheet page; it refuses to fabricate.
- **CAD:** KiCad official libraries (CC-BY-SA 4.0).

[Datasheet PDF](docs/pssi2021say-datasheet.pdf)