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mcp4921-e-sn-dac

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Important Note

This entire repo was AI created - including all of the data within. The intent was to A) help me with my personal electronics inventory; and B) see how I could use AI to make that process a bit easier. DO NOT TRUST!

MCP4921-E/SN - 12-Bit Single-Channel SPI DAC

Details

Description

The MCP4921 is a 12-bit, single-channel digital-to-analog converter (DAC) from Microchip’s MCP492X family. It communicates over SPI and operates from 2.7V to 5.5V, making it compatible with both 3.3V and 5V microcontroller systems without level-shifting concerns on the power rail. The rail-to-rail output amplifier allows the output to swing very close to both GND and VDD, maximizing usable output range.

A key feature is the selectable gain: you can configure the full-scale output to equal VREF (gain = 1x) or 2×VREF (gain = 2x) via a control bit in the write command. The MCP4921 also supports double-buffered operation using the LDAC pin, which lets you preload a new value into the input register and then latch it to the DAC output simultaneously with other MCP492X devices — useful for multi-channel coordinated updates. A software-controlled shutdown mode reduces current to about 150nA when the DAC output isn’t needed.

Compared to its sibling the MCP4922 (dual-channel), the MCP4921 is single-channel and comes in the smaller 8-SOIC footprint. If you need two channels independently controlled, look at the MCP4922 or use two MCP4921s with separate CS lines.

Specifications

Electrical Characteristics

  • Operating Voltage: 2.7V to 5.5V
  • Supply Current: ~175µA typical (active), ~150nA (shutdown)
  • Interface: SPI (modes 0,0 and 1,1)
  • Resolution: 12 bits (4096 steps)
  • Output Type: Rail-to-rail voltage output
  • Settling Time: 4.5µs typical
  • DNL: ±0.5 LSB max
  • INL: ±1 LSB max
  • Max SPI Clock: 20MHz at 5V

Physical Characteristics

  • Package: 8-SOIC (SOIC-8)
  • Dimensions: 4.9mm × 3.9mm body
  • Operating Temperature: -40°C to +125°C (E suffix = extended)
  • Mounting Type: Surface Mount

Key Features

  • 12-bit resolution (4096 output levels)
  • Single-supply, 2.7V to 5.5V operation
  • Rail-to-rail output amplifier
  • Selectable gain: 1x or 2x (via write command bit)
  • Double-buffered with LDAC pin for synchronous multi-DAC updates
  • Software shutdown mode (~150nA)
  • Fast SPI interface up to 20MHz
  • -40°C to +125°C extended temperature range

Image

No photo yet — please take a photo of the actual component and add it to binkey-data/attachments/ as mcp4921-e-sn-dac.jpg, then replace this line with ![MCP4921-E/SN DAC](../attachments/mcp4921-e-sn-dac.jpg)

Pinout Diagram

Pin Descriptions (8-SOIC Package)

PinNameFunction
1VDDSupply voltage (2.7V – 5.5V)
2CSChip Select, active low — frame the 16-bit write command
3SCKSPI clock input
4SDISPI data input (MOSI)
5LDACLatch DAC — pull low to transfer input reg → DAC reg; tie low for immediate update
6SHDNShutdown — active low; tie to VDD for normal operation, pull low to shut down output
7VSSGround
8VOUTAnalog voltage output

The device has no VREF pin — it uses VDD as the reference. Full-scale output = VDD (gain=1x) or 2×VDD/2 = VDD (gain=2x, but VREF is VDD/2 internally derived).

Applications

  • Audio signal generation and waveform synthesis
  • Setting bias voltages or threshold references in analog circuits
  • Analog control signals for VCA, VCF in synthesizer/eurorack projects
  • Calibration reference voltage generation
  • Arbitrary waveform generation (with MCU timer + DMA)
  • Driving analog panel meters from digital readings
  • Closed-loop feedback control output (PID controllers)
  • Test equipment — programmable voltage source

Circuit Examples

Basic Connection (Arduino / 5V SPI)

MCP4921      Arduino Uno
--------     -----------
VDD  (1) --- +5V
CS   (2) --- D10 (SS / any GPIO)
SCK  (3) --- D13 (SCK)
SDI  (4) --- D11 (MOSI)
LDAC (5) --- GND  (tie low = immediate latch on CS rising edge)
SHDN (6) --- +5V  (tie high = always enabled)
VSS  (7) --- GND
VOUT (8) --- [Analog output to load / next stage]

Optional: 100nF decoupling cap from VDD to GND, close to pin 1.
Optional: 10Ω series resistor on VOUT to prevent oscillation with capacitive loads.

SPI Write Command Format (16 bits, MSB first)

Bit 15:   /A1 — DAC select (always 0 for MCP4921)
Bit 14:   BUF — 0=unbuffered VREF, 1=buffered VREF (VDD reference, BUF is don't-care)
Bit 13:   /GA  — Gain: 0 = 2x, 1 = 1x
Bit 12:   /SHDN — 0 = shutdown output, 1 = active
Bits 11-0: D11–D0 — 12-bit data value (MSB first)

Technical Notes

  • Add a 100nF ceramic decoupling capacitor from VDD (pin 1) to VSS (pin 7), placed as close to the chip as possible.
  • If LDAC is tied permanently to GND, the DAC output updates immediately on the rising edge of CS — this is the simplest wiring for single-chip use.
  • If driving capacitive loads (> a few nF), add a 10–100Ω resistor in series with VOUT to prevent oscillation; the output amp is not unconditionally stable into heavy capacitance.
  • The E suffix in MCP4921**-E**/SN = extended temperature (-40°C to +125°C), suitable for non-climate-controlled enclosures.
  • SHDN pin (active low) controls the output stage only — the SPI interface remains active in shutdown, so you can preload a value before enabling the output.
  • SPI modes 0,0 (CPOL=0, CPHA=0) and 1,1 (CPOL=1, CPHA=1) are both supported.

Tags

dac spi 12-bit single-channel soic-8 microchip rail-to-rail cabinet-3 bin-37 status-available

Notes

  • Part of the MCP492X family: MCP4901 (8-bit), MCP4911 (10-bit), MCP4921 (12-bit), MCP4922 (dual 12-bit).
  • The MCP4921 and MCP4922 share the same SPI command protocol — only the channel-select bit (bit 15) differs.
  • For higher precision or external VREF support, consider the MCP4821 (12-bit, internal 2.048V reference) or DAC8552 (already in inventory at Cabinet 3, Bin 37E).
  • LCSC part number: C43499 — good for bulk SMT orders.

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