TMS320F280049C: ADC input signal conditioning/impedance matching

Shengnan,

For the TIDM-DC-DC-BUCK example, the BoosterPack (BOOSTXL-BUCKCONV) and LaunchPad (LAUNCHXL-F280049C) boards were designed in isolation from each other so the signal conditioning between the boards is not ideal, but they are close enough to work for demonstration purposes.

The RC filters on BOOSTXL-BUCKCONV were selected for the purpose of gross noise filtering based on engineering judgement. In terms of ILFB vs ILFB_Avg, the ILFB path is meant to provide inductor feedback readings with minimal latency for control schemes like PCMC, whereas the ILFB_Avg path is meant to provide a more smoothed (averaged) view of inductor current for user information. In practice, it has been noted that the ILFB_Avg path could be filtered even more heavily in order to provide a more DC-like current reading for the user.

For ideal signal conditioning for the F280049C ADC, there are some published appnotes that delve into the technical details and recommendations:

• Buffered Input Circuit Design
• Charge Sharing Input Circuit Design
• Mitigating Channel-to-Channel Cross-Talk

-Tommy