TPS544B25EVM-681: Unable to Set >1.2V in TPS544B25EVM-581

Nishant,

This is has the potential to go down the rabbit hole. When you first posted, you stated you just wanted 1.8 V output, and that resistor suggestion was for a fixed 1.8 V output and the preset VOUT_SCALE_LOOP. That would get you the basic 1.8 V output without using any PMBus commands. For adjusting the output voltage using the AVS function from 0.8 V to 3.3 V using TPS544B25 requires crossing over two different VOUT_SCALE_LOOP settings. While that can be spoofed to work for basic Vout setting, you will have issues with the telemetry over voltage detection. The VOUT_COMMAND setting to get a specific voltage would be different than what is in the command table. You would get your desired output voltage, but TPS544B25 "thinks" it is programmed to a different voltage because you did not change the required resistor divider ratio as defined in TABLE 1. You would have to change both the VOUT_SCALE_LOOP setting AND the lower resistor divider (according to Table 1) to get accurate telemetry and fault detection since the 0.8 to 3.3 V range spans all three of the VOUT_SCALE_LOOP settings. I have some documentation I can share on that. Bottom line is that if you want a single hardware solution for 0.8 V to 3.3 V AVS adjust with consistent and accurate telemetry, you need to stay within a single VOUT_SCALE_LOOP range. Switching to TPS546C23 slves this issue as the 0.5 setting spans the range of 0.7 to 3.3 V which includes your whole range. So you can have a single hardware configuration. If you can either change the lower resistor (via digital potentiometer or FET switching) OR live with inaccurate telemetry, we can talk about the TPS544B25 approach. Let me know how you want to proceed. We should probably move this off line. I can be reached at j(dash)tucker(at)ti(dot)com. I will be off line until tomorrow after about 10 minutes tonight.