R
Spartan-3 FPGA Family: DC and Switching Characteristics
Table 32:
General DC Characteristics of User I/O, Dual-Purpose, and Dedicated Pins
(Continued)
Symbol
R
PD(3)
Description
Equivalent resistance of pull-down resistor
at User I/O, Dual-Purpose, and Dedicated
pins, driven from I
RPD
Test Conditions
V
IN
=V
CCO
= 3.0V to 3.465V
V
IN
=V
CCO
= 2.3V to 2.7V
V
IN
=V
CCO
= 1.7V to 1.9V
V
IN
=V
CCO
= 1.4V to 1.6V
V
IN
=V
CCO
= 1.14 to 1.26V
R
DCI
I
REF
C
IN
Notes:
Min
1.75
1.35
1.00
0.85
0.68
20
Typ
-
-
-
-
-
-
-
-
-
Max
9.35
7.30
5.15
4.35
3.465
100
Units
kΩ
kΩ
kΩ
kΩ
kΩ
Ω
μA
μA
pF
Value of external reference resistor to
support DCI I/O standards
V
REF
current per pin
Input capacitance
V
CCO
> 3.0V
V
CCO
< 3.0V
-
-
3
±
25
±
10
10
1.
2.
3.
The numbers in this table are based on the conditions set forth in
The I
L
specification applies to every I/O pin throughout power-on as long as the voltage on that pin stays between the absolute V
IN
minimum and maximum values (Table
For hot-swap applications, at the time of card connection, be sure to keep all I/O voltages
within this range before applying V
CCO
power. Consider applying V
CCO
power before connecting the signal lines, to avoid turning on
the ESD protection diodes, shown in Module 2:
When the FPGA is completely unpowered, the I/O pins are high
impedance, but there is a path through the upper and lower ESD protection diodes.
This parameter is based on characterization. The pull-up resistance R
PU
= V
CCO
/ I
RPU
. The pull-down resistance R
PD
= V
IN
/ I
RPD
.
Spartan-3 family values for both resistances are stronger than they have been for previous FPGA families.
DS099-3 (v2.4) June 25, 2008
Product Specification
59
XILINX [ XILINX, INC ]
