EP1C3 datasheet(75/385 Pages) ETC2

75 / 385 page

Altera Corporation

2–55

May 2008

Preliminary

Power Sequencing and 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.

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 VCCIO and VCCINT 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.

Table 2–14. Cyclone MultiVolt I/O Support

Note (1)

VCCIO (V)

Input Signal

Output Signal

1.5 V1.8 V2.5 V3.3 V5.0 V1.5 V1.8 V2.5 V3.3 V5.0 V

1.5

v (2)

—

————

1.8

v (2)

—

v (3)

———

2.5

—

v (5) v (5)

——

3.3

——

v (4)

v (6) v (7) v (7) v (7)

v (8)

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.

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