ADS8681

@@ -0,0 +1,60 @@+# ADS8681++**Texas Instruments** · SAR ADC · QFN-16++High-resolution 18-bit successive-approximation ADC that samples one input at up to 1 MSPS over SPI, with an integrated reference and reference buffer so the full-scale span is defined without external precision parts. A front-end that accepts true bipolar and wide unipolar input ranges lets it digitize signals directly from a sensor or amplifier without extra scaling, and an on-chip ALARM flags over-range. Aimed at precision data acquisition, test-and-measurement, and control.++## Pinout++| Pin | Name | Type | Function |+|---|---|---|---|+| 1 | AGND | power_in | Analog ground pin. Decouple with the AVDD pin. |+| 2 | REFIO | bidirectional | Internal 4.096 V reference output and external reference input pin. Decouple with REFGND. |+| 3 | REFGND | power_in | Reference ground pin; short to the analog ground plane. Decouple with the REFIO and REFCAP pins. |+| 4 | REFCAP | passive | ADC reference buffer decoupling capacitor pin. Decouple with the REFGND pin. |+| 5 | AIN_P | input | Analog input: positive. Constant resistive input impedance ≥1 MΩ with overvoltage protection up to ±20 V. Decouple with the AIN_GND pin. |+| 6 | AIN_GND | input | Analog input: negative. Constant resistive input impedance ≥1 MΩ with overvoltage protection up to ±20 V. Decouple with the AIN_P pin. |+| 7 | RST | input | Active low logic input to reset the device. |+| 8 | SDI | input | Dual function: data input pin (MOSI) for serial communication; chain data input during serial communication in daisy-chain mode. |+| 9 | CONVST/CS | input | Dual-function pin. Active-high logic: CONVST rising edge starts a conversion (acquisition→conversion). Active-low logic: chip-select input; device drives the data bus when CS is low, SDO-x go tri-state when CS is high. |+| 10 | SCLK | input | Serial communication clock input pin; all system-synchronous data transfer protocols are timed with respect to SCLK. |+| 11 | SDO-0 | output | Serial communication: data output 0 (MISO). |+| 12 | SDO-1 | output | Multifunction output pin: active-high ALARM flag, data output 1 for serial communication, or general-purpose output. Function selected via configuration register. |+| 13 | RVS | output | Multifunction output pin for serial interface. With CS high, RVS reflects the internal ADCST signal; with CS low, RVS status depends on the output protocol selection. |+| 14 | DVDD | power_in | Digital supply pin (1.65 V to AVDD, nominal 3.3 V). Decouple with the DGND pin. |+| 15 | DGND | power_in | Digital ground pin. Decouple with the DVDD pin. |+| 16 | AVDD | power_in | Analog supply pin (4.75 V to 5.25 V nominal 5 V). Decouple with the AGND pin. |++## Key specifications++| Parameter | Value |+|---|---|+| Type | 18-bit SAR ADC |+| Throughput | 1 MSPS |+| Input | Single-ended, bipolar/unipolar ranges |+| Interface | SPI |+| Reference | Integrated + buffer |+| Extras | ALARM over-range flag |+| Supply | AVDD 5 V, DVDD 1.65-5.5 V |+| Package | QFN-16 |++## Ordering variants++- `ADS8681RUM (QFN-16)`+- `ADS8681IPW (TSSOP-16)`++## CAD (KiCad official)++- Symbol: `Analog_ADC:ADS8681RUM (KiCad official)`+- Footprint: `Package_DFN_QFN:QFN-16-1EP_4x4mm_P0.65mm_EP2.7x2.7mm`+- 3D model: QFN-16 (KiCad packages3D, STEP)++## Provenance++Data extracted from the manufacturer datasheet, not a distributor listing:++- **Datasheet:** [Texas Instruments datasheet](https://www.ti.com/lit/ds/symlink/ads8681.pdf) (75 pp, sha256 `7352b44f82a9fefd`, 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/ads8681-datasheet.pdf)

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