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Explorer
Explorer
4,730 Views
Registered: ‎07-10-2013

V7 Power Sequencing

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In a design involving the XC7VX330T-2FFG1157C, it is desired to power I/O banks 14..19 and 34..36 at 1.5V, with banks 0 and 37..39 powered at 1.8V.  It is proprosed to provide the 1.5V banks with Vccaux_io at 2.0V, and to provide banks 37..39 with Vccaux_io at 1.8V.

In order to attempt to accomplish the recommended power-up sequencing, it is further proposed to: first power Vccint and Vccbram together at 1.0V; then power Vccaux, Vccaux_io and Vcco (for banks 37..39) on together at 1.8V.  Vccaux_io and Vcco for banks 14..19 and 34..36 would remain unpowered intially and throughout Configuration.

Once the FPGA was configured, its then-functioning logic would first cause Vccaux_io for banks 14..19 and 34..36 to be turned on (at 2.0V), and would then cause Vcco for those banks to be turned on (at 1.5V).

Such an approach appears to follow the recommended power-up sequencing, as long as it is acceptable to leave some Vccaux_io and Vcco connections unpowered initially.

Will such an approach likely work as expected?

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Explorer
Explorer
6,601 Views
Registered: ‎07-10-2013

Re: V7 Power Sequencing

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All,

The power-up sequence as recommended requires that all Vccaux_io voltages be present before enabling any I/O bank Vcco voltages.  The use of 2V Vccaux_io then forces the need for two sources of 1.8V, the first used to power Vccaux and Vccaux_io at 1.8V, and the second to power Vcco for those I/O banks using 1.8V.

It is reasonable that Vcco should not be enabled before the corresponding Vccaux_io voltage for that I/O bank is present.  Is would also seem to be reasonable that such an enabling should be able to be unrelated and independent of the enabling of other Vcco voltages for other banks using different Vccaux_io voltages.

So, what about the following alternative approach: First power Vccint and Vccbram together at 1.0V; then power Vccaux, Vccaux_io and Vcco for banks 37..39 on together at 1.8V; then power Vccaux_io for banks 14..19 on at 2.0V; then power Vcco for banks 14..19 on at 1.5V; then do  Configuration.  This approach avoids any need to implement redundant and separately-controlled sources of 1.8V, and honors the requirement that Vccaux_io be present for a given I/O bank before Vcco is enabled for that bank.

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Xilinx Employee
Xilinx Employee
4,706 Views
Registered: ‎08-10-2008

Re: V7 Power Sequencing

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The power sequence matters less in a HP bank so the approach likely work. Anyhow, i doubt we have many testings against leaving some of Vccaux_io and Vcco unpowered.
It's always recommended to follow the power on sequence.
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Xilinx Employee
Xilinx Employee
4,700 Views
Registered: ‎07-31-2012

Re: V7 Power Sequencing

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Hi,

 

Ideally all the power on sequencing should be complete before the configuration starts. Hence it is recommended to begin your configuration only after all the power requirements have been met.

Thanks,
Anirudh

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Xilinx Employee
Xilinx Employee
4,679 Views
Registered: ‎07-23-2012

Re: V7 Power Sequencing

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Following the power-on sequence would ensure minimum current draw and also would keep the I/Os in tri-state during power-on.

Not following this sequence may not result in successful configuration at times.

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Explorer
Explorer
6,602 Views
Registered: ‎07-10-2013

Re: V7 Power Sequencing

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All,

The power-up sequence as recommended requires that all Vccaux_io voltages be present before enabling any I/O bank Vcco voltages.  The use of 2V Vccaux_io then forces the need for two sources of 1.8V, the first used to power Vccaux and Vccaux_io at 1.8V, and the second to power Vcco for those I/O banks using 1.8V.

It is reasonable that Vcco should not be enabled before the corresponding Vccaux_io voltage for that I/O bank is present.  Is would also seem to be reasonable that such an enabling should be able to be unrelated and independent of the enabling of other Vcco voltages for other banks using different Vccaux_io voltages.

So, what about the following alternative approach: First power Vccint and Vccbram together at 1.0V; then power Vccaux, Vccaux_io and Vcco for banks 37..39 on together at 1.8V; then power Vccaux_io for banks 14..19 on at 2.0V; then power Vcco for banks 14..19 on at 1.5V; then do  Configuration.  This approach avoids any need to implement redundant and separately-controlled sources of 1.8V, and honors the requirement that Vccaux_io be present for a given I/O bank before Vcco is enabled for that bank.

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