ADS8685 - 16-Bit 500kSPS Single-Supply SAR ADC Data Acquisition System With Programmable Bipolar Input Ranges

The ADS8681, ADS8685, and ADS8689 belong to a family of integrateddata acquisition system based on a successive approximation (SAR) analog-to-digital converter(ADC). The devices feature a high-speed, high-precision SAR ADC, integrated analog front-end (AFE)input driver circuit, overvoltage protection circuit up to ±20 V, and an on-chip4.096-V reference with extremely low temperature drift.

The devices operate on a single 5-V analog supply, but support true bipolar input rangesof ±12.288 V, ±6.144 V, ±10.24 V,±5.12 V, and ±2.56 V, as well as unipolar input ranges of0 V to 12.288 V, 0 V to10.24 V, 0 V to 6.144 V, and 0 Vto 5.12 V. The gain and offset errors are accurately trimmed within the specifiedvalues for each input range to ensure high dc precision. The input range selection is done bysoftware programming of the device internal registers. The devices offer a high resistive inputimpedance (≥ 1 MΩ) irrespective of the selected input range.

The multiSPI digital interface is backward-compatible to the traditional SPI protocol.Additionally, configurable features simplify interface to a wide range of host controllers.

• 16-Bit ADC With Integrated Analog Front-End
• High Speed:
  • ADS8681: 1 MSPS
  • ADS8685: 500 kSPS
  • ADS8689: 100 kSPS
• Software Programmable Input Ranges:
  • Bipolar Ranges: ±12.288 V, ±10.24 V, ±6.144 V, ±5.12 V, and ±2.56 V
  • Unipolar Ranges: 0 V–12.288 V, 0 V–10.24 V, 0 V–6.144 V, and 0 V–5.12 V
• 5-V Analog Supply: 1.65-V to 5-V I/O Supply
• Constant Resistive Input Impedance ≥ 1 MΩ
• Input Overvoltage Protection: Up to ±20 V
• On-Chip, 4.096-V Reference With Low Drift
• Excellent Performance:
  • DNL: ±0.4 LSB; INL: ±0.5 LSB
  • SNR: 92 dB; THD: –107 dB
• ALARM → High, Low Threshold
• multiSPI™ Interface With Daisy-Chain
• Extended Industrial Temperature Range:
  –40°C to +125°C

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