Hi, I looked at your board design. It's nice and definitely meets a need for 2350B prototyping. I do have a couple of comments on it. No criticism but you might want to consider them in a future rev.
- When using external DVDD generation, VREG_VIN should be tied to VREG_AVDD. At least this is what the RP engineers told the guys doing the buspirate. [RP folks - please add guidance for external DVDD generation. Not everyone wants to use the internal buck converter and Abracon inductor is surprisingly more expensive than similar ones.]
- Why no SWD port? Easy to add at zero cost and is extremely useful.
- I'd tie the unused end of RV to the wiper to prevent open circuit glitching - see the next point.
- Your DVDD generation scheme can allow > 1.21V which exceeds the absolute max rating. I would make it impossible for the top resistance (R82+R83+RV1) to exceed 42.6K. An RV of 10K and switching R83 to 12K would do that. I'd also do worst case resistor error calcs.
- If you want to reduce BOM cost for any kind of volume, I'd substitute a real crystal for the oscillator. Typical prices are about 1/4 the cost.
Phil
- When using external DVDD generation, VREG_VIN should be tied to VREG_AVDD. At least this is what the RP engineers told the guys doing the buspirate. [RP folks - please add guidance for external DVDD generation. Not everyone wants to use the internal buck converter and Abracon inductor is surprisingly more expensive than similar ones.]
- Why no SWD port? Easy to add at zero cost and is extremely useful.
- I'd tie the unused end of RV to the wiper to prevent open circuit glitching - see the next point.
- Your DVDD generation scheme can allow > 1.21V which exceeds the absolute max rating. I would make it impossible for the top resistance (R82+R83+RV1) to exceed 42.6K. An RV of 10K and switching R83 to 12K would do that. I'd also do worst case resistor error calcs.
- If you want to reduce BOM cost for any kind of volume, I'd substitute a real crystal for the oscillator. Typical prices are about 1/4 the cost.
Phil
Statistics: Posted by phil from seattle — Mon Mar 03, 2025 6:01 pm