ZHCSQZ8A May 2022 – December 2022 ADS1285
PRODUCTION DATA
The ADC provides a buffer option, bypassing the PGA. Bypassing the PGA reduces device power consumption. Use the buffer for ±2.5-VPP input signals when operating AVDD1 at 3.3 V. Buffer operation is enabled by setting the GAIN[2:0] bits = 111b of the CONFIG1 register.
Figure 8-7 shows the buffer voltage headroom with AVDD1 = 3.3 V, VCM = 1.65 V, and the input signal = ±2.5 VPP. The buffer has sufficient voltage headroom for ±2.5-VPP input signals when operating with AVDD1 = 3.3 V.
Regardless of PGA or buffer operation, connect two 47-nF, C0G-dielectric capacitors from each buffer output to AVSS (CAPBP and CAPBN). The voltage charge pump increases the buffer input operating headroom. Connect an external 4.7-nF capacitor between CAPC and AGND for the charge pump operation.