MCP4921 12-Bit SPI DAC

@@ -0,0 +1,55 @@+# MCP4921++**Microchip** · Digital-to-Analog Converter · SOIC-8++The MCP4921 is a single-channel, 12-bit voltage-output DAC with an SPI interface. It uses an external reference input with a selectable 1x or 2x output gain and includes a shutdown mode. It suits set-point generation, bias control, and programmable voltage sources, and is the single-channel version of the dual MCP4922.++## Pinout++| Pin | Name | Type | Function |+|---|---|---|---|+| 1 | VDD | power_in | Positive supply voltage input, 2.7V to 5.5V (absolute max 6.5V). Bypass with 0.1 µF to VSS. |+| 2 | CS | input | SPI chip-select (active low). Enables the serial interface; input register writes latch on rising edge. |+| 3 | SCK | input | SPI serial clock input, up to 20 MHz. Data on SDI is sampled on the rising edge. |+| 4 | SDI | input | SPI serial data input. 16-bit command word (config bits + DAC data) shifted in MSB-first. |+| 5 | LDAC | input | Synchronous DAC latch (active low). Falling edge transfers both DAC input registers to the DAC output registers, updating VOUTA and VOUTB simultaneously. Tie low for asynchronous updates. |+| 6 | VREF | input | External voltage reference input for DAC A. Unbuffered range 0 to VDD; buffered range 0.040 V to VDD−0.040 V. Input impedance ~165 kΩ (unbuffered). |+| 7 | VSS | power_in | Ground return / negative supply. Connect to system analog ground. |+| 8 | VOUT | output | DAC channel A buffered analog output. Rail-to-rail, output swing 0.01 V to VDD−0.04 V, short-circuit current ~15 mA typ, slew rate 0.55 V/µs. |++## Key specifications++| Parameter | Value |+|---|---|+| Resolution | 12-bit, 1 channel |+| Output | Voltage output (buffered, rail-to-rail) |+| Reference | External (VREF pin), 1x or 2x gain |+| Interface | SPI (up to 20 MHz) |+| Settling time | 4.5 us typ |+| Supply voltage | 2.7 V to 5.5 V |+| Operating temperature | -40 C to 125 C |++## Ordering variants++- `MCP4921-E/P`+- `MCP4921I/P`+- `MCP4921-E/SL`+- `MCP4921I/SL`+- `MCP4921-E/ST`+- `MCP4921I/ST`++## CAD (KiCad official)++- Symbol: `mcp4921.kicad_sym`+- Footprint: `mcp4921.kicad_mod`+- 3D model: SOIC-8 body from KiCad `Package_SO/SOIC-8_3.9x4.9mm_P1.27mm`.++## Provenance++Data extracted from the manufacturer datasheet, not a distributor listing:++- **Datasheet:** [Microchip datasheet](https://ww1.microchip.com/downloads/en/DeviceDoc/22250A.pdf) (48 pp, sha256 `8c507a2bce321888`, 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/mcp4921-datasheet.pdf)

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