UPGRADE YOUR BROWSER

We have detected your current browser version is not the latest one. Xilinx.com uses the latest web technologies to bring you the best online experience possible. Please upgrade to a Xilinx.com supported browser:Chrome, Firefox, Internet Explorer 11, Safari. Thank you!

AR# 19965

Spartan-II/-IIE/-3/-3E - What happens when VCCO, VCCINT, or VCCAUX is lost during device operation?

Description

What happens when VCCO, VCCINT, or VCCAUX is lost during device operation?

Solution

The following describes what happens when VCCO, VCCINT, or VCCAUX is lost during device operation. The loss of power will not damage the device.

VCCINT is Lost in a Spartan-II/-IIE/-3/-3E Device

If the VCCINT (core voltage) is lost at any time, the device configuration data is also lost because the POR circuit recognizes loss of VCCINT, and the device loses configuration. Consequently, when power is restored to VCCINT, reconfiguration is necessary. The output pins are put into a 3-state condition for as long as the VCCINT power is down. When power is restored, they revert to the configuration dictated by the mode-pins (either pulled High or in 3-state). In this case, power is considered lost when VCCINT is removed and goes to 0V.

In a brown-out condition, when VCCINT drops below its respective data retention voltage (VDRINT) as defined by the data sheet, the internal RAM content can no longer be guaranteed. In this case, either VCCINT or VCCAUX (Spartan-3/-3E only) must be dropped below its respective minimum POR threshold to guarantee that the device's configuration memory is cleared. Subsequently, both voltages must exceed the maximum POR voltage once again, in order for the device to be programmed with the new configuration.

When VCCAUX is Lost in the Spartan-3/-3E Device

If VCCAUX is lost, the behavior is similar to when VCCINT is lost. The POR circuit recognizes loss of VCCAUX, and the device loses configuration (all memory is cleared, all I/Os are 3-stated, and it then waits for power to return to normal). Once power returns to normal, the device needs to be reconfigured, just as if power had been applied for the first time. In this case, power is considered lost when VCCAUX is removed and goes to 0V.

In a brown-out condition, when VCCAUX drops below its respective data retention voltage (VDRAUX) as defined by the data sheet, the internal RAM content can no longer be guaranteed. In this case, either VCCINT or VCCAUX must be dropped below its respective minimum POR threshold to guarantee that the device's configuration memory is cleared. Subsequently, both voltages must exceed the maximum POR voltage once again, in order for the device to be programmed with the new configuration.

When VCCO is Lost in a Spartan-II/-IIE Device

If VCCO is lost during configuration, the output-High signals are put into a 3-state condition. However, because output-Low signals are not VCCO-dependent, they are still operational.

Note: VCCO for the configuration bank is monitored by the internal power on reset (POR) circuitry on initial power-up. VCCO must reach its respective POR threshold voltage to guarantee a successful power-on. However, if the VCCO for the configuration bank is lost, the device resets and configuration data is lost. The outputs revert to the preconfiguration state.

When VCCO is Lost in Spartan-3/-3E Devices

If VCCO is lost, the output data is lost. If VIN on an input pad is greater than VCCO+0.5V, the internal upper clamp diodes are forward-biased, and conduct a reverse current into the VCCO rail. This reverse current must be limited to 10 mA to protect the I/O. If you are considering hot-swapping a Spartan-3 device, refer to (Xilinx XAPP251): "Hot_Swapping Virtex-II Devices" for more information, as this Application Note also applies to Spartan-3/-3E. Also, see (Xilinx Answer 19777).

Note: VCCO for the configuration bank is monitored by the internal power on reset (POR) circuitry on initial power-up. VCCO must reach its respective POR threshold voltage to guarantee a successful power-on. Losing VCCO during device operation does not trigger POR as the POR circuitry no longer monitors VCCO after initial power-on.

The configuration bank for a Spartan-II/-IIE device is Bank 2.

The configuration banks for a Spartan-3 device are Bank 4 and Bank 5 (POR is connected only to VCCO in Bank 4 and monitors this bank only during the initial power-on).

The configuration banks for a Spartan-3E device are Banks 1 and 2 (POR is connected to VCCO in Bank 2 only and monitors this bank only during the initial power-on).

Additional References

- For more information on the state of I/O under special circumstances, refer to the Xilinx TechXclusive titled "What are Virtex and Spartan-II I/O Pins Doing?":

http://www.support.xilinx.com/xlnx/xweb/xil_tx_display.jsp?sTechX_ID=alpa_pins_doing

AR# 19965
Date Created 09/03/2007
Last Updated 12/15/2012
Status Active
Type General Article
Devices
  • Spartan-II
  • Spartan-IIE
  • Spartan-IIE XA
  • More
  • Spartan-3
  • Spartan-3E
  • Less