1 Features
• 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

2 Applications
• Analog input modules
• Semiconductor test
• Servo drive control module

3 Description
The ADS8681, ADS8685, and ADS8689 belong to a
family of integrated data 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-chip 4.096-V reference with
extremely low temperature drift.
The devices operate on a single 5-V analog supply,
but support true bipolar input ranges of ±12.288 V,
±6.144 V, ±10.24 V, ±5.12 V, and ±2.56 V, as well
as unipolar input ranges of 0 V to 12.288 V, 0 V to
10.24 V, 0 V to 6.144 V, and 0 V to 5.12 V. The gain
and offset errors are accurately trimmed within the
specified values for each input range to ensure high
dc precision. The input range selection is done by
software programming of the device internal registers.
The devices offer a high resistive input impedance
(≥ 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.