8.4.1.4 Start-Conversion Delay

Some applications require a delay at the start of a conversion in order to allow settling time for the PGA antialias filter or to allow time after input and configuration changes. The ADC provides a user programmable delay time that delays the start of a new conversion. The default value is 50 μs. 50 μs allows for settling of the antialiasing filter placed at the PGA output. Use additional delay time as needed to provide settling time for external components. The delay time increases the conversion latency values listed in Table 6. As an alternative to the programmable start-conversion delay, manually delay the start of conversion after input and configuration changes.

Start-conversion delay is an important consideration for operation in ac-bridge excitation mode. In this mode, the reference inputs to the bridge, and therefore, the bridge output signals are reversed for each conversion. As a result, time delay is required to allow for settling of external filter components after the bridge voltage is reversed. As a general guideline, set the start-conversion delay parameter to a minimum of 15 times the R-C time constant of the signal input and reference input filters.