
Altera Corporation
5–77
April 2011
Stratix II Device Handbook, Volume 1
DC & Switching Characteristics
Duty Cycle
Distortion
Duty cycle distortion (DCD) describes how much the falling edge of a
clock is off from its ideal position. The ideal position is when both the
clock high time (CLKH) and the clock low time (CLKL) equal half of the
clock period (T), as shown in
Figure 5–7. DCD is the deviation of the
non-ideal falling edge from the ideal falling edge, such as D1 for the
falling edge A and D2 for the falling edge B (
Figure 5–7). The maximum
DCD for a clock is the larger value of D1 and D2.
3.3-V LVTTL
OCT
50
Ω
133
152
133
152
147
152
2.5-V LVTTL
OCT
50
Ω
207
274
207
274
235
274
1.8-V LVTTL
OCT
50
Ω
151
165
151
165
153
165
3.3-V LVCMOS
OCT
50
Ω
300
316
300
316
263
316
1.5-V LVCMOS
OCT
50
Ω
157
171
157
171
174
171
SSTL-2 Class I
OCT
50
Ω
121
134
121
134
77
134
SSTL-2 Class II
OCT
25
Ω
56
101
56
101
58
101
SSTL-18 Class I
OCT
50
Ω
100
123
100
123
106
123
SSTL-18 Class II
OCT
25
Ω
61
110
-
59
110
OCT
50
Ω
95
-
95
(1)
For LVDS and HyperTransport technology output on row I/O pins, the toggle rate derating factors apply to loads
larger than 5 pF. In the derating calculation, subtract 5 pF from the intended load value in pF for the correct result.
For a load less than or equal to 5 pF, refer to
Table 5–78 for output toggle rates.
(2)
1.2-V HSTL is only supported on column I/O pins in I/O banks 4,7, and 8.
(3)
Differential HSTL and SSTL is only supported on column clock and DQS outputs.
(4)
LVPECL is only supported on column clock outputs.
Table 5–79. Maximum Output Clock Toggle Rate Derating Factors (Part 5 of 5)
I/O Standard
Drive
Strength
Maximum Output Clock Toggle Rate Derating Factors (ps/pF)
Column I/O Pins
Row I/O Pins
Dedicated Clock Outputs
-3
-4
-5
-3
-4
-5
-3
-4
-5