5–8
Chapter 5: Using MAX V Devices in Multi-Voltage Systems
Power-Up Sequencing
1
For signals with a duty cycle greater than 30% on MAX V input pins, Altera
recommends using a VCCIO voltage of 3.0 V to guarantee long-term I/O reliability. For
signals with a duty cycle less than 30%, the VCCIO voltage can be 3.3 V.
Power-Up Sequencing
MAX V devices are designed to operate in multi-voltage environments where it may
be difficult to control power sequencing. Therefore, MAX V devices are designed to
tolerate any possible power-up sequence. Either VCCINT or VCCIO can initially supply
power to the device and 3.3-, 2.5-, 1.8-, 1.5-, or 1.2-V input signals can drive the
devices without special precautions before VCCINT or VCCIO is applied. MAX V devices
can operate with a VCCIO voltage level that is higher than the VCCINT level.
When VCCIO and VCCINT are supplied from different power sources to a MAX V
device, a delay between VCCIO and VCCINT may occur. Normal operation does not
occur until both power supplies are in their recommended operating range. When
VCCINT is powered-up, the IEEE Std. 1149.1 JTAG circuitry is active. If TMSand TCKare
connected to VCCIO and VCCIO is not powered-up, the JTAG signals are left floating.
Thus, any transition on TCKcan cause the state machine to transition to an unknown
JTAG state, leading to incorrect operation when VCCIO is finally powered-up. To
disable the JTAG state during the power-up sequence, pull TCKlow to ensure that an
inadvertent rising edge does not occur on TCK
.
Document Revision History
Table 5–4 lists the revision history for this chapter.
Table 5–4. Document Revision History
Date
Version
Changes
December 2010
1.0
Initial release.
MAX V Device Handbook
December 2010 Altera Corporation
ALTERA [ ALTERA CORPORATION ]
