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Adventurer
Adventurer
236 Views
Registered: ‎09-14-2018

Kintex-7 auxiliary power (1.8V) supply requirements

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Hello,

I am wondering if Kintex-7 has special requirements for the auxiliary power (1.8V) rail? LDO vs switching power?

Thank you.

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174 Views
Registered: ‎01-22-2015

Re: Kintex-7 auxiliary power (1.8V) supply requirements

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@arotenst 

For the Kintex-7, VCCAUX and VCCAUX_IO are typically tied together and come from the same ~1.8V supply.   As explained in page 18 of UG471(v1.10), VCCAUX_IO is sometimes separately powered at ~2.0V when “slightly-increased performance is required for the very fastest bit rates supported for the single-ended drivers”.

Data sheet, DS182(v2.18), gives Xilinx guidance for powering VCCAUX and VCCAUX_IO:

  • Table 2: recommended min/max voltage (1.71 - 1.89)
  • Table 6: quiescent current (ICCAUXQ, ICCAUX_IOQ) – varies with FPGA package
  • Table 7: power-on current (typically adds 80 – 220mA to ICCAUXQ + ICCAUX_IOQ) – varies with FPGA package
  • Table 8: voltage ramp time ( 0.2 – 50 ms)

For larger FPGAs with high power/current requirements, we typically use a switching power supply IC to the get needed current and keep size small.  However, for smaller FPGAs (like Kintex-7) that could be powered by an LDO regulator, it may surprise you to know that a switching supply is preferred for reasons (soft-start and sequencing) described in the following very nice paper from Texas Instruments.

http://www.ti.com/lit/an/slyt079/slyt079.pdf

Finally, powering the FPGA properly also requires careful circuit board design and sufficient use of PCB decoupling capacitors as described in UG483.

Mark

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175 Views
Registered: ‎01-22-2015

Re: Kintex-7 auxiliary power (1.8V) supply requirements

Jump to solution

@arotenst 

For the Kintex-7, VCCAUX and VCCAUX_IO are typically tied together and come from the same ~1.8V supply.   As explained in page 18 of UG471(v1.10), VCCAUX_IO is sometimes separately powered at ~2.0V when “slightly-increased performance is required for the very fastest bit rates supported for the single-ended drivers”.

Data sheet, DS182(v2.18), gives Xilinx guidance for powering VCCAUX and VCCAUX_IO:

  • Table 2: recommended min/max voltage (1.71 - 1.89)
  • Table 6: quiescent current (ICCAUXQ, ICCAUX_IOQ) – varies with FPGA package
  • Table 7: power-on current (typically adds 80 – 220mA to ICCAUXQ + ICCAUX_IOQ) – varies with FPGA package
  • Table 8: voltage ramp time ( 0.2 – 50 ms)

For larger FPGAs with high power/current requirements, we typically use a switching power supply IC to the get needed current and keep size small.  However, for smaller FPGAs (like Kintex-7) that could be powered by an LDO regulator, it may surprise you to know that a switching supply is preferred for reasons (soft-start and sequencing) described in the following very nice paper from Texas Instruments.

http://www.ti.com/lit/an/slyt079/slyt079.pdf

Finally, powering the FPGA properly also requires careful circuit board design and sufficient use of PCB decoupling capacitors as described in UG483.

Mark

Adventurer
Adventurer
135 Views
Registered: ‎09-14-2018

Re: Kintex-7 auxiliary power (1.8V) supply requirements

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Mark,

thank you very much.

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