mon2 wrote:1) ADM1085 is an open drain output. For this reason, you must apply an external pull-up resistor onto pin 4 of this component to define the weak high. Apply a 10k to +3v3 here. XMOS uses the same value in their ref designs. Without this pull-up, this output pin of the voltage supervisor will be high-z.
That's exactly what I thought about before going to bed last night. Is the output of the ADM1085 open drain without a pull-up? And yes it is. That could explain something...
2) IL717 isolators are great but more expensive than their Silabs drop in replacements. We have used both in high volumes and Silabs is a valid replacement with cost savings. Please note that we are not using in audio field so best to review the results under your test conditions.
As far as I remember if was the jitter specs that made us choose the IL-types.
4) Be sure X4 is clocking out ok @ 24 Mhz. Most clock oscillators offer pin 1 to be the EN (Enable if HIGH) function. To be sure the clock is enabled, consider to strap pin 1 to +3v3. We have seen an oscillator mfr who missed the required internal pull-up on pin 1 and the clock did not enable so best to cover yourself here.
It should have an internal pull-up, and we haven't had problems so far. The oscillators are from Fox.
mon2 wrote:1) The XMOS devices can consume some heavy amounts of current. Respectively, be sure your power rails are supporting of this requirement. Concerned about the power source feeding your circuit and also if the 500mA is ample (NCP5501DT50G) which is then fed into the Recom isolated 5 vout DC-DC module @ 200mA. It appears that this 200mA rate power supply is then feeding into the 1v0 switcher by ST. According to the XMOS datasheet, you should offer support of up to 600mA on the 1v0 rail. The 3v3 rail may be ok with the 150mA but best to check. The ST switcher is fine but limited to the max current support upstream.
So the Recom @ 200 mA (max) is being used to power the +3v3 and +1v0 rails of the XMOS CPU which may be too weak but is dependent on your XMOS IP and CPU usage.
The DC-DC module fitted is actually the 2W type with the same footprint, so I think the 400mA should be enough. I will check the 3V3 rail also.
2) Please confirm if the grounds on the left side of the NVE IL717E is the same as the right ride of these isolators.
It's not. There are two separate ground planes on the board.
3) Consider to add a few despikes and bulk caps onto each Vdd rail of the digital isolators. Recall that Silabs recommends the use at least 1uf onto each power rail.
I use the 100n caps recommended for the IL717.
I read that some time ago. I use physically large X7R caps to try to avoid that problem...
mon2 wrote:Assuming U45 is being powered ?
4) Assuming that QSPI flash U22 is being powered.
Yes, they are both powered. All pins that are declared as power pins are hidden by OrCAD... The power pins on the XMOS are declared as input pins, so they show up on the schematic.
Hope this helps.
It does! Thanks a lot!