UG445 Datasheet, PDF (17/24 Pages) –

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Power, Sequencing, and Slew Rates
Power, Sequencing, and Slew Rates
The maximum voltage that you can you drive into an I/O with the device powered or
unpowered, is limited to the Vi/Vin parameter in the family data sheet.
• XC9500: You can drive into an unpowered I/O, provided Vin does not exceed the Vin
limits of the CPLD.
• XC9500XL: You can drive into an unpowered I/O, provided Vin does not exceed
V_CCINT by more than 4.0V.
• XC9500XV: You can drive into an unpowered I/O, provided Vin does not exceed the
Vin limits of the CPLD.
• CoolRunner XPLA3: You can drive into an unpowered I/O, provided Vin does not
exceed V_CCINT by more than 4.0V.
• CoolRunner-II: You can drive into an unpowered I/O, provided Vin does not exceed
the Vin limits of the CPLD.
In terms of current, the absolute maximum current that should be applied to an
unpowered part is 100mA to the whole part.
Before the device is configured and for unprogrammed devices, the status of the I/Os are
disabled and terminated with a weak pull-up.
Hot-Swappable
The following list indicates whether or not devices are hot-swappable:
• CoolRunner-II: Yes
• CoolRunner XPLA3: Yes
• XC9500XL: Yes
• XC9500XV: Yes
• XC9500: No
XC9500 has clamp diodes to V_CC (5V); the XC9500XL, XC9500XV, CoolRunner XPLA3 and
CoolRunner-II devices do not.
Powering CPLDs
Some of the CPLD families have multiple voltage rails. V_CCINT supplies power to internal
logic and to the configuration circuit. V_CCIO only supplies power to I/O buffers. V_CCAUX
supplies power to JTAG pins on the CoolRunner-II. In previous families the JTAG pins
were powered by V_CCIO.
CoolRunner-II CPLDs have three separate voltage rails: V_CCINT, V_CCIO, and V_CCAUX.
XC9500, XC9500XL, and XC9500XV have two separate voltage rails; V_CCINT and V_CCIO.
Power Sequencing
CoolRunner-II devices are guaranteed to work under all power sequences. However, the
order in which V_CCINT and V_CCIO are applied might cause the CPLD to function
differently. V_CCAUX can be powered at any time, independent of V_CCINT and V_CCIO.
V_CCINT and V_CCIO are most important because they determine whether the CPLD logic
comes alive before the I/Os, or if the I/Os are to come alive before the CPLD logic.
CPLD I/O User Guide
www.xilinx.com
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UG445 (v1.2) January 14, 2014