Cyclone II Hot-Socketing Specifications
Devices Can Be Driven before Power-Up
You can drive signals into the I/O pins, dedicated input pins, and
dedicated clock pins of Cyclone II devices before or during power-up or
power-down without damaging the device. Cyclone II devices support
any power-up or power-down sequence (VCCIO and VCCINT) to simplify
system level design.
I/O Pins Remain Tri-Stated during Power-Up
A device that does not support hot socketing may interrupt system
operation or cause contention by driving out before or during power-up.
In a hot-socketing situation, the Cyclone II device’s output buffers are
turned off during system power-up or power-down. The Cyclone II
device also does not drive out until the device is configured and has
attained proper operating conditions. The I/O pins are tri-stated until the
device enters user mode with a weak pull-up resistor (R) to 3.3V. Refer to
Figure 4–1 for more information.
1
You can power up or power down the VCCIO and VCCINT pins in
any sequence. The VCCIO and VCCINT must have monotonic rise
to their steady state levels. (Refer to Figure 4–3 for more
information.) The power supply ramp rates can range from
100 µs to 100 ms for non “A” devices. Both VCC supplies must
power down within 100 ms of each other to prevent I/O pins
from driving out. During hot socketing, the I/O pin capacitance
is less than 15 pF and the clock pin capacitance is less than 20 pF.
Cyclone II devices meet the following hot-socketing
specification.
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The hot-socketing DC specification is | IIOPIN | < 300 µA.
The hot-socketing AC specification is | IIOPIN | < 8 mA for 10 ns or
less.
This specification takes into account the pin capacitance but not board
trace and external loading capacitance. You must consider additional
capacitance for trace, connector, and loading separately.
IIOPIN is the current at any user I/O pin on the device. The DC
specification applies when all VCC supplies to the device are stable in the
powered-up or powered-down conditions. For the AC specification, the
peak current duration due to power-up transients is 10 ns or less.
A possible concern for semiconductor devices in general regarding hot
socketing is the potential for latch-up. Latch-up can occur when electrical
subsystems are hot socketed into an active system. During hot socketing,
the signal pins may be connected and driven by the active system before
4–2
Cyclone II Device Handbook, Volume 1
Altera Corporation
February 2007
ALTERA [ ALTERA CORPORATION ]
