Forum Discussion
Occasional ContributorAgilex 3 VCCLSENSE and GNDSENSE
Hello,
For Agilex 3, what is the recommendation for VCCLSENSE and GNDSENSE if our regulator for VCC does not provide remote sense inputs? Can we just leave these two device outputs as no connects?
Note that this is a very small form factor design.
Thank you
5 Replies
FvMSuper Contributor
Hello,
obviously the regulator portfolio suggested in Agilex 3 PCB Design Guidelines doesn't cover the full range of possible Agilex 3 designs. Using a multiphase VRM driver with 120 A capability for VCC is far off many smaller Agilex 3 applications. I would rather think about 5 - 20 A regulators with integrated output stage as used in many Agilex 3 development kits, including Altera originated designs. Using only one of suggested regulators is completely contradicting Agilex 3 market position as "Power and Cost-Optimized" device.
VCC precision is a different point. It can be noticed that even not all suggested regulators achieve specified 0.5 % accuracy at 0.78V, but I would basically try to follow the suggestion. If sense lines are actually required depends on expected maximal VCC load current. It should be however possible to connect at least VCCL_SENSE to regulator feedback.
Regards
Frank- Ash_R_Altera
Regular Contributor
Hi,
First thing is that whether the regulator that you choose is from a recommended list or not. Refer to
Secondly, the VCCLSENSE and GNDSENSE are recommended to be a must connected pins for VCC core. These pins compensates for the DC IR drop associated with the PCB and device package from the VCC power.
Altera strongly recommends to follow the guidelines provided for a smooth operation of the device. Any design outside the recommendations will not be supported. It will be at user risk.
Regards,
Altera support
- Ash_R_Altera
Hi,
I recommend that you choose the regulator that suites your current requirement from the vendor list that we have validated with, as it is crucial for the regulators to be SmartVID compatible with the FPGA devices.
For the SENSE, pin it is a strong recommendation to connect to the regulator pins and do not leave them unconnected.
Regards
Robert_PIN_ASAPThank you for the reply and information, but the Agilex 3 datasheet states that Vcc is a fixed voltage.
It's nice to have recommendations, but if we choose a regulator that meets the requirements stated in the datasheet, then that should be sufficient.
The Agilex 3 Pin Connection Guideline states that the sense pins are outputs. If these are truly outputs, then I would think it's OK to leave them floating if our regulator doesn't support remote sense.
In the case of our very small PCB with a power plane, I believe we can ensure that we will meet the VCC requirements without using a more expensive regulator that supports remote voltage sense.
- Ash_R_Altera
Hi,
Yes, the Agilex 3 does NOT require a SmartVID compatible regulator. You can provide a fixed voltage to VCC as mentioned in the datasheet.
However on the VCCLSENSE and GNDSENSE pins, these pins compensates for the DC IR drop associated with the PCB and device package from the VCC power. It is recommended to connect them to the regulator.
Regards
