ZHCSIJ5C August 2018 – June 2019 ADS9224R , ADS9234R
PRODUCTION DATA.
The device features an internal reference source with a nominal output value of 2.5 V. The ADC internal reference voltage is brought out on the REFOUT pin. A 1-µF decoupling capacitor (CREFOUT), as shown in Figure 39, is recommended to be placed between the REFOUT pin and GND pin. The capacitor must be placed as close to the REFOUT pin as possible. The output impedance of the internal band-gap circuit creates a low-pass filter with this capacitor to band-limit the noise of the reference. The initial accuracy specification for the internal reference can be degraded if the die is exposed to any mechanical or thermal stress. Heating the device when being soldered to a printed circuit board (PCB) and any subsequent solder reflow is a primary cause for shifts in the VREF value.
All performance characteristics of the device are specified with the internal reference buffer and a specified value of CREFP_x. As shown in Figure 39, place a decoupling capacitor CREFP_x between the REFP_x and REFM_x pins as close to the device as possible.