Device Architecture
2-146
Revision 4
Electrostatic Discharge (ESD) Protection
Fusion devices are tested per JEDEC Standard JESD22-A114-B.
Fusion devices contain clamp diodes at every I/O, global, and power pad. Clamp diodes protect all
device pads against damage from ESD as well as from excessive voltage transients.
Each I/O has two clamp diodes. One diode has its positive (P) side connected to the pad and its negative
(N) side connected to VCCI. The second diode has its P side connected to GND and its N side
connected to the pad. During operation, these diodes are normally biased in the Off state, except when
transient voltage is significantly above VCCI or below GND levels.
By selecting the appropriate I/O configuration, the diode is turned on or off. Refer to
Table 2-75 and
The second diode is always connected to the pad, regardless of the I/O configuration selected.
Table 2-75 Fusion Standard and Advanced I/O – Hot-Swap and 5 V Input Tolerance Capabilities
I/O Assignment
Clamp Diode
Hot Insertion
5 V Input Tolerance 1
Input
Buffer
Output
Buffer
Standard
I/O
Advanced
I/O
Standard
I/O
Advanced
I/O
Standard
I/O
Advanced
I/O
3.3 V LVTTL/LVCMOS
No
Yes
No
Yes1
Enabled/Disabled
3.3 V PCI, 3.3 V PCI-X
N/A
Yes
N/A
No
N/A
Yes1
Enabled/Disabled
LVCMOS 2.5 V
No
Yes
No
Enabled/Disabled
LVCMOS 2.5 V / 5.0 V
N/A
Yes
N/A
No
N/A
Yes2
Enabled/Disabled
LVCMOS 1.8 V
No
Yes
No
Enabled/Disabled
LVCMOS 1.5 V
No
Yes
No
Enabled/Disabled
Differential,
LVDS/BLVDS/M-
LVDS/ LVPECL 3
N/A
Yes
N/A
No
N/A
No
Enabled/Disabled
Notes:
1. Can be implemented with an external IDT bus switch, resistor divider, or Zener with resistor.
2. Can be implemented with an external resistor and an internal clamp diode.
3. Bidirectional LVPECL buffers are not supported. I/Os can be configured as either input buffers or output buffers.
Table 2-76 Fusion Pro I/O – Hot-Swap and 5 V Input Tolerance Capabilities
I/O Assignment
Clamp
Diode
Hot
Insertion
5 V Input
Tolerance
Input Buffer
Output Buffer
3.3 V LVTTL/LVCMOS
No
Yes
Yes1
Enabled/Disabled
3.3 V PCI, 3.3 V PCI-X
Yes
No
Yes1
Enabled/Disabled
LVCMOS 2.5 V 3
No
Yes
No
Enabled/Disabled
LVCMOS 2.5 V / 5.0 V 3
Yes
No
Yes2
Enabled/Disabled
LVCMOS 1.8 V
No
Yes
No
Enabled/Disabled
LVCMOS 1.5 V
No
Yes
No
Enabled/Disabled
Voltage-Referenced Input Buffer
No
Yes
No
Enabled/Disabled
Differential, LVDS/BLVDS/M-LVDS/LVPECL4
No
Yes
No
Enabled/Disabled
Notes:
1. Can be implemented with an external IDT bus switch, resistor divider, or Zener with resistor.
2. Can be implemented with an external resistor and an internal clamp diode.
LVCMOS5 macro for the LVCMOS 2.5 V / 5.0 V I/O standard or the LVCMOS25 macro for the LVCMOS 2.5 V I/O
standard.
4. Bidirectional LVPECL buffers are not supported. I/Os can be configured as either input buffers or output buffers.