FG256 datasheet(12/108 Pages) ACTEL

12 / 108 page

SX-A Family FPGAs

1- 8

v5.3

Power-Up/Down and Hot Swapping

SX-A I/Os are configured to be hot-swappable, with the

exception of 3.3 V PCI. During power-up/down (or partial

up/down), all I/Os are tristated. VCCA and VCCI do not

have to be stable during power-up/down, and can be

powered up/down in any order. When the SX-A device is

plugged into an electrically active system, the device will

not degrade the reliability of or cause damage to the

host system. The device’s output pins are driven to a high

impedance state until normal chip operating conditions

are reached. Table 1-4 summarizes the VCCA voltage at

which the I/Os behave according to the user’s design for

an SX-A device at room temperature for various ramp-up

rates. The data reported assumes a linear ramp-up

profile to 2.5 V. For more information on power-up and

hot-swapping, refer to the application note, Actel SX-A

and RT54SX-S Devices in Hot-Swap and Cold-Sparing

Applications.

Table 1-2 • I/O Features

Function

Description

Input Buffer Threshold Selections

•

5 V: PCI, TTL

•

3.3 V: PCI, LVTTL

•

2.5 V: LVCMOS2 (commercial only)

Flexible Output Driver

•

5 V: PCI, TTL

•

3.3 V: PCI, LVTTL

•

2.5 V: LVCMOS2 (commercial only)

Output Buffer

“Hot-Swap” Capability (3.3 V PCI is not hot swappable)

•

I/O on an unpowered device does not sink current

•

Can be used for “cold-sparing”

Selectable on an individual I/O basis

Individually selectable slew rate; high slew or low slew (The default is high slew rate).

The slew is only affected on the falling edge of an output. Rising edges of outputs are

not affected.

Power-Up

Individually selectable pull-ups and pull-downs during power-up (default is to power-up

in tristate)

Enables deterministic power-up of device

VCCA and VCCI can be powered in any order

Table 1-3 • I/O Characteristics for All I/O Configurations

Hot Swappable

Slew Rate Control

Power-Up Resistor

TTL, LVTTL, LVCMOS2

Yes

Yes. Only affects falling edges of outputs

Pull-up or pull-down

3.3 V PCI

No. High slew rate only

Pull-up or pull-down

5 V PCI

Yes

No. High slew rate only

Pull-up or pull-down

Table 1-4 • Power-Up Time at which I/Os Become Active

Supply Ramp Rate

0.25 V/

μs 0.025 V/μs

5 V/ms

2.5 V/ms

0.5 V/ms

0.25 V/ms

0.1 V/ms

0.025 V/ms

Units

μs

msms

A54SX08A

0.34

0.65

2.7

5.4

12.9

50.8

A54SX16A

100

0.36

0.62

2.5

4.7

11.0

41.6

A54SX32A

100

0.46

0.74

2.8

5.2

12.1

47.2

A54SX72A

100

0.41

0.67

2.6

5.0

12.1

47.2

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