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AR# 24365

Spartan-3/3E/3A - What is the nominal VCCO value for PCI33_3 and PCI66_6?


Keywords: Spartan-3E, s3e, PCI33, PCI66, PCI, Vcco, S3A, S3, Spartan-3A, Spartan-3, PCI, Power, rail, XAPP653, XAPP457

The Spartan-3 and Spartan-3E Data Sheets state that PCI_33 and PCI_66 VCCO requirement is 3.3V with a range of -10% to +5% (3.0V to 3.45V).

Does this mean that the Spartan-3/3E can be connected directly to the PCI 3.3V power rail?

What about Spartan-3A?


The reduction in VCCO discussed in XAPP653 is no longer required for Spartan-3 Generation FPGAs based on revisions to the absolute maximum ratings specification for the VIN parameter (the voltage applied to all user I/O pins). Existing designs that use this technique continue to be valid; however, all new designs should take advantage of the enhanced absolute maximum ratings specification. Please see XAPP457 for more information on powering Vcco for Spartan-3 family devices. This application note can be found at: http://direct.xilinx.com/bvdocs/appnotes/xapp457.pdf

Summarizing XAPP457 -

Spartan-3 and Spartan-3E PCI buffer VCCO Requirement

For Spartan-3 and Spartan-3E devices, the data sheets reflect that the VCCO requirement is 3.3V with a range of -10% to +5% (3.0V to 3.45V). For existing Spartan-3 and Spartan-3E designs using a regulated VCCO to 3.0 volts, no changes are needed as this continues to be compliant. For new Spartan-3 and Spartan-3E PCI designs, it is still necessary to regulate VCCO because the PCI Specification specifies the PCI power rail to be 3.3 volts +/-10%(3.0V to 3.6V). This means a regulator is still required for Spartan-3E. However, the voltage can now be regulated to 3.3 volts instead of 3.0 volts.

Please refer to XAPP457 and the LogiCORE Initiator/Target for PCI Getting Started Guide for more information on the recommended regulator and circuit to meet these requirements.

Spartan-3A PCI buffer VCCO Requirement

No VCCO regulation is required. Spartan-3A VCCO is 3.3V, +/- 10%, which allows for VCCO to be directly connected to the PCI bus power.

AR# 24365
Date 06/26/2007
Status Active
Type General Article