10–4
Chapter 10: Hot-Socketing and Power-On Reset in the Cyclone III Device Family
Document Revision History
The POR circuit of the Cyclone III device monitors the VCCINT, VCCIO (banks 1, 6, 7,
and 8), and VCCA pins during power-on. The enhanced POR circuit of the Cyclone III
LS device includes monitoring VCCBAT to ensure that VCCBAT is always at the minimum
requirement voltage level.
1
The VCCBAT power supply is the new design security feature power supply introduced
for Cyclone III LS devices only. Cyclone III devices do not have VCCBAT power supply.
After Cyclone III device family enters user mode, the POR circuit continues to
monitor the VCCINT or VCCA pins so that a brown-out condition during user mode is
detected. If the VCCINT or VCCA voltage sags below the POR trip point during user
mode, the POR circuit resets the device. If the VCCIO voltage sags during user mode,
the POR circuit does not reset the device.
In some applications, it is necessary for a device to wake up very quickly to begin
operation. Cyclone III device family offers the Fast-On feature to support fast
wake-up time applications. For Cyclone III device family, the MSEL[3..0]pin settings
determine the POR time (tPOR) of the device. Fast POR ranges from 3 ms to 9 ms, while
standard POR ranges from 50 ms to 200 ms.
If you cannot meet the maximum VCC ramp time requirement, use an external
component to hold nCONFIGlow until the power supplies have reached their
minimum recommend operating levels. Otherwise, the device may not properly
configure and enter user mode.
f
f
For more information about the MSEL[3..0]pin settings, refer to the Configuration,
Design Security, and Remote System Upgrades in the Cyclone III Device Family chapter.
For more information about the VCCBAT pin connection, refer to the Cyclone III Device
Family Pin Connection Guidelines.
Document Revision History
Table 10–1 lists the revision history for this document.
Table 10–1. Document Revision History (Part 1 of 2)
Date
Version
Changes
■ Updated “POR Circuitry” on page 10–3.
December 2011
3.3
■ Updated hyperlinks.
■ Minor text edits.
December 2009
July 2009
3.2
3.1
Minor changes to the text.
Made minor correction to the part number.
■ Updated chapter part number.
■ Updated “I/O Pins Remain Tristated During Power-Up” on page 10–2.
■ Updated “Hot-Socketing Feature Implementation” on page 10–3.
■ Updated “POR Circuitry” on page 10–4.
■ Updated chapter to new template.
June 2009
3.0
1.2
October 2008
■ Added handnote to the “Cyclone III Hot-Socketing Specifications” section.
Cyclone III Device Handbook
Volume 1
December 2011 Altera Corporation
ALTERA [ ALTERA CORPORATION ]
