JAJSIB3D August 2017 – February 2021 THS4561
One common application for the THS4561 is to take a single-ended, high VPP voltage swing (from a high-voltage precision amplifier such as the OPA810 or OPA192) and deliver that swing to precision SAR ADC as a single-ended to differential conversion with output common-mode control and implement an active 2nd-order multiple feedback (MFB) filter design. Designing for a 16-VPP maximum input down to an 8-VPP differential swing requires a gain of 0.5 V/V. Targeting a 170-kHz Butterworth response with the RC elements tilted towards low noise gives the example design of Figure 10-7. The VCM control is set to half of a 4.096-V reference, which is typical for
5-V differential SAR applications. With the high voltage capabilities of the THS4561, the design can be easily adopted for 20-VPP input swing to the FDA for a full 10-VPP swing into 5-V differential SAR ADC by simply using wider power supplies for the THS4561 to allow for increased output swing headroom with minimal performance degradation.