20-TSSOP SAR ADC with 400k SPS throughput
The MAX1280BCUP+ is a 12-bit successive-approximation (SAR) ADC from Analog Devices, sampling at 400k samples per second. The SAR architecture gives you a deterministic conversion time with no pipeline delay — each sample is ready one clock cycle after the start command, which matters when you're sequencing through multiple channels in a tight loop. It lives in a 20-TSSOP package (4.40 mm width), surface-mount, shipped in a tube. The 0.65 mm pitch is manageable on a two-layer board if you keep the analog and digital grounds separated under the part.
Input mux and signal routing
The front end is a MUX-S/H-ADC configuration with a 1:1 S/H-to-ADC ratio. You get either 4 pseudo-differential or 8 single-ended inputs — the mux architecture lets you switch between modes without external relays. The pseudo-differential mode gives you common-mode rejection on each channel pair, useful when your sensor signals share a noisy ground return. The reference can be internal or external. If your board already has a stable 2.5 V or 4.096 V reference, feed it externally and bypass the internal buffer for lower drift.
Supply rails and digital interface
Both the analog and digital supplies run on a single 5 V rail — no separate DVDD needed. The SPI data interface handles the conversion results and register configuration. At 400k SPS the SPI clock runs at roughly 6.4 MHz (16 clocks per sample), well within the capability of most MCU SPI peripherals. If your application sees -40°C or +85°C ambient, look at the industrial-grade variant in the same family.