MCP4821 12-Bit SPI DAC

@@ -0,0 +1,55 @@+# MCP4821++**Microchip** · Digital-to-Analog Converter · MSOP-8++The MCP4821 is a single-channel, 12-bit voltage-output DAC with an internal 2.048 V reference and an SPI interface. The on-chip reference and selectable output gain mean it needs no external reference to produce a precise analog voltage, suiting set-point generation, bias control, and programmable voltage sources.++## Pinout++| Pin | Name | Type | Function |+|---|---|---|---|+| 1 | VDD | power_in | Positive supply voltage input, 2.7 V to 5.5 V relative to VSS. Bypass with 0.1 µF ceramic to VSS close to the pin, plus a 10 µF tantalum in parallel for board-level noise attenuation. |+| 2 | CS | input | Active-low SPI chip-select input. Must be driven low to enable the serial clock and data functions; the DAC latches on the rising edge of CS. |+| 3 | SCK | input | SPI-compatible serial clock input. Supports SPI Modes 0,0 and 1,1 with clock rates up to 20 MHz. |+| 4 | SDI | input | SPI-compatible serial data input. Command/data word (16 bits) is shifted in MSb-first while CS is low. |+| 5 | LDAC | input | Active-low latch-DAC synchronization input. Transfers input register contents to the DAC output registers (VOUT) on its falling edge, allowing simultaneous update of both channels. May be tied to VSS to update on the rising edge of CS. |+| 6 | SHDN | output | Shutdown control input, active low. When held low, the DAC output goes to a high-impedance state and the device enters low-power shutdown. |+| 7 | VSS | power_in | Analog ground and return path for the device. Tie to the board's analog ground plane through a low-impedance connection. |+| 8 | VOUT | output | Buffered analog output of DAC channel A. Rail-to-rail swing from VSS to G·VREF (G = 1x or 2x); cannot exceed VDD. Uses the internal 2.048 V reference so full-scale is 2.048 V (G=1x) or 4.096 V (G=2x). |++## Key specifications++| Parameter | Value |+|---|---|+| Resolution | 12-bit, 1 channel |+| Output | Voltage output (buffered, rail-to-rail) |+| Reference | Internal 2.048 V, 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++- `MCP4821I/P`+- `MCP4821E/P`+- `MCP4821I/SN`+- `MCP4821E/SN`+- `MCP4821I/MS`+- `MCP4821E/MS`++## CAD (KiCad official)++- Symbol: `mcp4821.kicad_sym`+- Footprint: `mcp4821.kicad_mod`+- 3D model: MSOP-8 body from KiCad `Package_SO/MSOP-8_3x3mm_P0.65mm`.++## Provenance++Data extracted from the manufacturer datasheet, not a distributor listing:++- **Datasheet:** [Microchip datasheet](https://ww1.microchip.com/downloads/en/DeviceDoc/20002249B.pdf) (50 pp, sha256 `1f0b231636222ea5`, 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/mcp4821-datasheet.pdf)

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