ZHCSEV8D March 2016 – January 2018 ADS131A02 , ADS131A04
PRODUCTION DATA.
An optional negative charge pump is available to power AVSS with an operating voltage of –1.95 V. Enabling the negative charge pump allows for input signals below analog ground when using a unipolar analog supply (for example, AVDD = 3.3 V, AVSS = 0 V). The VNCPEN bit in the A_SYS_CFG register must be set high by the user to enable the negative charge pump. The VNCP pin outputs the nominal –1.95-V negative charge pump output and requires a capacitor to AVSS in the range of 220 pF to 470 pF. The charge pump operates at a switching frequency of 2fMOD. The minimum ADC absolute input voltage range is –1.5 V with the negative charge pump enabled. The maximum analog supply limit (AVDD – AVSS) is restricted to 3.6 V maximum. Exceeding this limit can permanently damage the device.
The negative charge pump is internally activated when the VNCPEN bit is set to 1 and the device is in wake-up mode with all ADC channels enabled (ADC_ENA = 0Fh).
Connect VNCP directly to AVSS when not using the negative charge pump.