# XC121S021

**Si Change** · Analog To Digital Converters (ADC) · SOT-23-6

XC121S021 from Si Change, in a SOT-23-6. Pinout and pin descriptions extracted from the manufacturer datasheet (extract_pins, cross-checked by a second model); symbol, footprint, and 3D from KiCad-official CAD.

## Pinout

| Pin | Name | Type | Function |
|---|---|---|---|
| 1 | VA | power_in | Power supply input (3.3 V to 5.25 V single supply), which also serves as the ADC reference voltage. |
| 2 | GND | power_in | Analog input signal ground; all analog and digital signals are referenced to this pin. |
| 3 | VIN | power_in | Analog signal input with a range of 0 V to VA; VA should be set at or above the maximum VIN to avoid saturating the maximum conversion code. |
| 4 | SCLK | input | Serial clock input that directly controls the conversion and readout process; the 16th falling edge ends the conversion cycle. |
| 5 | SDATA | output | Serial data output carrying MSB-first conversion data after three leading zeros, and entering three-state at the 16th falling SCLK edge. |
| 6 | CS | input | Active-low chip select; a falling edge with SCLK starts a conversion, and CS must be taken high after 16 SCLK cycles before the next conversion. |

## Key specifications

| Parameter | Value |
|---|---|
| Manufacturer | Si Change |
| Package | SOT-23-6 |
| Category | Data Acquisition |
| Pins | 6 |

## Electrical characteristics

Limits as printed in the datasheet (page.json `metadata.characteristics` carries them as data).

| Parameter | Symbol | Min | Typ | Max | Unit | Conditions | Page |
|---|---|---|---|---|---|---|---|
| Supply voltage range (single supply) | VA | 3.3 |  | 5.25 | V |  | 1 |
| Operating temperature range |  | -40 |  | 85 | ℃ |  | 1 |
| Sampling rate |  | 50 |  | 200 | KSPS |  | 2 |
| Integral nonlinearity (INL) |  | -1 |  | 1 | LSB |  | 1 |
| Differential nonlinearity (DNL) |  | -1 |  | 1 | LSB |  | 1 |
| Signal-to-noise ratio (SNR) |  |  | 72.5 |  | dB | @100 KHz | 2 |
| Total harmonic distortion (THD) |  |  | -83.5 |  | dB | @100 KHz | 2 |
| Typical power consumption at 5 V, 200 KSPS |  |  | 2.35 |  | mW | 5V, 200 KSPS | 1 |
| Typical power consumption at 3.3 V, 200 KSPS |  |  | 1.2 |  | mW | 3.3V, 200 KSPS | 1 |

## CAD (KiCad official)

- Symbol: `XC121S021`
- Footprint: `Package_TO_SOT_SMD:SOT-23-6`
- 3D model: SOT-23-6 (KiCad packages3D, STEP)
- 3D model files: `xc121s021-etched.step` / `xc121s021-etched.glb` carry the MPN laser-etched on the die in a toggleable `Adom.LaserEtch` group (Fusion-ready); `xc121s021.step` / `xc121s021.glb` are the bare package body.

## Provenance

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

- **Datasheet:** [Si Change datasheet](https://jlcpcb.com/api/file/downloadByFileSystemAccessId/8603387332946894848) (4 pp, sha256 `3d1e5cfbdc22022f`, retrieved 2026-10-18, tier: lcsc)
- **Datasheet language:** Chinese. Pin names, descriptions, and specs on this page were extracted and translated to English by ds2sf; the linked PDF is the manufacturer original.
- **Extractor:** parts-factory `2.0.0` / `extract_pins 0.3`, primary `claude-haiku-5-5` (text), consensus `claude-sonnet-5-5` (agreed), guards: pin_guards 0.1: passed. Pins are checked against the footprint pad set and their cited datasheet pages before publish.
- **CAD:** KiCad official libraries (CC-BY-SA 4.0).

[Datasheet PDF](docs/xc121s021-datasheet.pdf)