Power Sequencing & Hot Socketing
The Cyclone VCCINT pins must always be connected to a 1.5-V power
supply. If the VCCINT level is 1.5 V, then input pins are 1.5-V, 1.8-V, 2.5-V,
and 3.3-V tolerant. The VCCIO pins can be connected to either a 1.5-V, 1.8-V,
2.5-V, or 3.3-V power supply, depending on the output requirements. The
output levels are compatible with systems of the same voltage as the
power supply (i.e., when VCCIO pins are connected to a 1.5-V power
supply, the output levels are compatible with 1.5-V systems). When VCCIO
pins are connected to a 3.3-V power supply, the output high is 3.3-V and
is compatible with 3.3-V or 5.0-V systems. Table 2–14 summarizes
Cyclone MultiVolt I/O support.
Table 2–14. Cyclone MultiVolt I/O Support
Note (1)
Input Signal
1.5 V 1.8 V 2.5 V 3.3 V 5.0 V 1.5 V 1.8 V 2.5 V 3.3 V 5.0 V
Output Signal
VCCIO (V)
1.5
1.8
2.5
3.3
v (2)
v (2) v (2)
v (2)
v
v
v
v
v
v (3)
v (5)
v
v (5)
v
v
v
v (4)
v (6) v (7) v (7) v (7)
v (8)
v
v
Notes to Table 2–14:
(1) The PCI clamping diode must be disabled to drive an input with voltages higher than VCCIO
.
(2) When VCCIO = 1.5-V or 1.8-V and a 2.5-V or 3.3-V input signal feeds an input pin, higher pin leakage current is
expected. Turn on Allow voltage overdrive for LVTTL / LVCMOS input pins in the Assignments > Device >
Device and Pin Options > Pin Placement tab when a device has this I/O combinations.
(3) When VCCIO = 1.8-V, a Cyclone device can drive a 1.5-V device with 1.8-V tolerant inputs.
(4) When VCCIO = 3.3-V and a 2.5-V input signal feeds an input pin, the VCCIO supply current will be slightly larger
than expected.
(5) When VCCIO = 2.5-V, a Cyclone device can drive a 1.5-V or 1.8-V device with 2.5-V tolerant inputs.
(6) Cyclone devices can be 5.0-V tolerant with the use of an external resistor and the internal PCI clamp diode.
(7) When VCCIO = 3.3-V, a Cyclone device can drive a 1.5-V, 1.8-V, or 2.5-V device with 3.3-V tolerant inputs.
(8) When VCCIO = 3.3-V, a Cyclone device can drive a device with 5.0-V LVTTL inputs but not 5.0-V LVCMOS inputs.
Because Cyclone devices can be used in a mixed-voltage environment,
they have been designed specifically to tolerate any possible power-up
sequence. Therefore, the VCCIO and VCCINT power supplies may be
powered in any order.
Power
Sequencing &
Hot Socketing
Signals can be driven into Cyclone devices before and during power up
without damaging the device. In addition, Cyclone devices do not drive
out during power up. Once operating conditions are reached and the
device is configured, Cyclone devices operate as specified by the user.
Altera Corporation
January 2007
2–55
Preliminary
ALTERA [ ALTERA CORPORATION ]
