
26
Lucent Technologies Inc.
Data Sheet
June 1999
ORCA Series 2 FPGAs
Programmable Input/Output Cells
(continued)
A. Simplified Diagram of OR2CxxA Programmable 
I/O Cell (PIC)
B. Simplified Diagram of OR2TxxA/OR2TxxB
Programmable I/O Cell (PIC)
Figure 24. Simplified Diagrams
Outputs
The PIC’s output drivers have programmable drive 
capability and slew rates. Three propagation delays 
(fast, slewlim, sinklim) are available on output drivers. 
The sinklim mode has the longest propagation delay 
and is used to minimize system noise and minimize 
power consumption. The fast and slewlim modes allow 
critical timing to be met. 
The drive current is 12 mA sink/6 mA source for the 
slewlim and fast output speed selections and 
6 mA sink/3 mA source for the sinklim output. Two adja-
cent outputs can be interconnected to increase the out-
put sink current to 24 mA. 
All outputs that are not speed critical should be config-
ured as sinklim to minimize power and noise. The num-
ber of outputs that switch simultaneously in the same 
direction should be limited to minimize ground bounce. 
To minimize ground bounce problems, locate heavily 
loaded output buffers near the ground pads. Ground 
bounce is generally a function of the driving circuits, 
traces on the PCB, and loads and is best determined 
with a circuit simulation. 
Outputs can be inverted, and 3-state control signals 
can be active-high or active-low. An open-drain output 
may be obtained by using the same signal for driving 
the output and 3-state signal nets so that the buffer out-
put is enabled only by a low. At powerup, the output 
drivers are in slewlim mode, and the input buffers are 
configured as TTL-level compatible with a pull-up. If an 
output is not to be driven in the selected configuration 
mode, it is 3-stated.
5 V Tolerant I/O (OR2TxxA)
The I/O on the OR2TxxA series devices allow intercon-
nection to both 3.3 V and 5 V device (selectable on a 
per-pin basis) by way of special V
DD
5 pins that have 
been added to the OR2TxxA devices. If any I/O on the 
OR2TxxA device interfaces to a 5 V input, then all of 
the V
DD
5 pins must be connected to the 5 V supply. If 
no pins on the device interface to a 5 V signal, then the 
V
DD
5 pins must be connected to the 3.3 V supply.
If the V
DD
5 pins are disconnected (i.e., they are float-
ing), the device will not be damaged; however, the 
device may not operate properly until V
DD
5 is returned 
to a proper voltage level. If the V
DD
5 pins are then 
shorted to ground, a large current flow will develop, and 
the device may be damaged.
PULL-UP
V
DD
DELAY
TTL/CMOS
PAD
SLEW RATE
POLARITY
DOUT/OUT
PULL-DOWN
dintb, dinlr
in
POLARITY
TRI
5-4591(F)
PULL-UP
V
DD
DELAY
PAD
SLEW RATE
POLARITY
DOUT/OUT
PULL-DOWN
dintb, dinlr
in
POLARITY
TRI
5-4591.T(F)