SBOS932C January 2020 – March 2021 THP210
Many applications require to level-shift high-voltage input signals down to the lower-voltage ADC domain. Figure 9-16 shows an example of the THP210 used to attenuate a ±10-V differential signal to drive a differential SAR ADC with full-scale range of ±4.5V. The common-mode voltage is shifted to the center of the ADC input range. A multiple-feedback (MFB) configuration as described in Section 9.2.1 is used to provide a Butterworth filter response, giving a 40-dB/decade roll-off with a –3-dB frequency of 100 kHz. The THP210 is powered with a 5-V supply and a –0.232-V negative supply generated by the low-noise negative bias generator (LM7705) allowing additional headroom for output swing to GND with ultra-low distortion. Alternatively, the THP210 can be powered using a unipolar 5-V supply with good distortion performance.
The circuit is able to drive the ADS8912B 18-Bit SAR ADC at full throughput of 500-kSPS.