EP1C12F256C8N Datasheet, PDF (61/106 Pages) Altera Corporation – Section I. Cyclone FPGA Family Data Sheet

Power Sequencing and Hot Socketing
The Cyclone V_CCINT pins must always be connected to a 1.5-V power
supply. If the V_CCINT level is 1.5 V, then input pins are 1.5-V, 1.8-V, 2.5-V,
and 3.3-V tolerant. The V_CCIO 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 V_CCIO pins are connected to a 1.5-V power
supply, the output levels are compatible with 1.5-V systems). When V_CCIO
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)
V_CCIO (V)
1.5
1.8
2.5
3.3
1.5 V
v
v
—
—
Input Signal
Output Signal
1.8 V 2.5 V 3.3 V 5.0 V 1.5 V 1.8 V 2.5 V 3.3 V
v ^{v (2) v (2)} —
v
—
—
—
v v (2) v (2) — ^{v (3)} v
—
—
—
v
v
— v (5) ^{v (5)} v
—
— v (4) v v (6) v (7) v (7) v (7) v
5.0 V
—
—
—
v (8)
Notes to Table 2–14:
(1) The PCI clamping diode must be disabled to drive an input with voltages higher than V_CCIO.
(2) When V_CCIO = 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 V_CCIO = 1.8-V, a Cyclone device can drive a 1.5-V device with 1.8-V tolerant inputs.
(4) When V_CCIO = 3.3-V and a 2.5-V input signal feeds an input pin, the V_CCIO supply current will be slightly larger
than expected.
(5) When V_CCIO = 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 V_CCIO = 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 V_CCIO = 3.3-V, a Cyclone device can drive a device with 5.0-V LVTTL inputs but not 5.0-V LVCMOS inputs.
Power
Sequencing and
Hot Socketing
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 V_CCIO and V_CCINT power supplies may be
powered in any order.
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
May 2008
2–55
Preliminary