Altera Stratix - Standard Current Drive Strength

4–26 Altera Corporation
Stratix Device Handbook, Volume 2 June 2006
Drive Strength
Drive Strength
Each I/O standard supported by Stratix and Stratix GX devices drives out
a minimum drive strength. When an I/O is configured as LVTTL or
LVCMOS I/O standards, you can specify the current drive strength, as
summarized in Table 4–7.
Standard Current Drive Strength
Each I/O standard supported by Stratix and Stratix GX devices drives out
a minimum drive strength. Table 4–6 summarizes the minimum drive
strength of each I/O standard.
When the SSTL-2 Class I and II I/O standards are implemented on top or
bottom I/O pins, the drive strength is designed to be higher than the
drive strength of the buffer when implemented on side I/O pins. This
allows the top or bottom I/O pins to support 200-MHz operation with the
standard 35-pF load. At the same time, the current consumption when
using top or bottom I/O pins is higher than the side I/O pins. The high
current strength may not be necessary for certain applications where the
value of the load is less than the standard test load (e.g., DDR interface).
The Quartus II software allows you to reduce the drive strength when the
I/O pins are used for the SSTL-2 Class I or Class II I/O standard and
being implemented on the top or bottom I/O through the Current
Strength setting. Select the minimum strength for lower drive strength.
Table 4–6. Minimum Current Drive Strength of Each I/O Standard
I/O Standard
Current Strength, I
OL
/I
OH
(mA)
GTL 40 (1)
GTL+ 34 (1)
SSTL-3 Class I 8
SSTL-3 Class II 16
SSTL-2 Class I 8.1
SSTL-2 Class II 16.4
SSTL-18 Class I 6.7
SSTL-18 Class II 13.4
1.5-V HSTL Class I 8
1.5-V HSTL Class II 16
CTT 8
AGP 1
×
I
OL
= 1.5, I
OH
= –0.5
Note to Ta b le 4 – 6 :
(1) Because this I/O standard uses an open drain buffer, this value refers to I
OL
.