Article ID: 000084682 Content Type: Troubleshooting Last Reviewed: 10/13/2016

Are there any problems if a floating voltage exists on the VCCH_GXB supply rail before it is ramped in Cyclone IV GX devices?

Environment

  • Cyclone® IV GX FPGA
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Description

No, there are no problems if a floating voltage exists on the VCCH_GXB supply rail before it is ramped in Cyclone® IV GX devices. Leakage can occur between the VCCH_GXB and VCCL_GXB supply rails which can cause VCCH_GXB to float to approximately 0.7V before the power supply is ramped up.  

This is expected behavior and will not cause functional or reliability failures.

This can be observed if the VCCL_GXB supply is powered up before VCCH_GXB supply and the regulators were designed to leave the power supplies to float before they ramp up.

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