EP1AGX ALTERA [Altera Corporation], EP1AGX Datasheet - Page 219

• Manufacturer Part Number: EP1AGX
• Description: Section I. Arria GX Device Data Sheet
• Manufacturer: ALTERA [Altera Corporation]

Chapter 4: DC and Switching Characteristics
Duty Cycle Distortion
Figure 4–12. DCD Measurement Technique for DDIO (Double-Data Rate) Outputs
© December 2009 Altera Corporation
When an FPGA PLL generates the internal clock, the PLL output clocks the IOE block.
As the PLL only monitors the positive edge of the reference clock input and internally
re-creates the output clock signal, any DCD present on the reference clock is filtered
out. Therefore, the DCD for a DDIO output with PLL in the clock path is better than
the DCD for a DDIO output without PLL in the clock path.
Table 4–108
for different I/O standards on Arria GX devices. Examples are also provided that
show how to calculate DCD as a percentage.
Table 4–108. Maximum DCD for Non-DDIO Output on Row I/O Pins
Here is an example for calculating the DCD as a percentage for a non-DDIO output on
a row I/O:
If the non-DDIO output I/O standard is SSTL-2 Class II, the maximum DCD is 125 ps
(see
3.3-V LVTTTL
3.3-V LVCMOS
2.5 V
1.8 V
1.5-V LVCMOS
SSTL-2 Class I
SSTL-2 Class II
SSTL-18 Class I
1.8-V HSTL Class I
1.5-V HSTL Class I
LVDS
T = 1/ f = 1 / 267 MHz = 3.745 ns = 3,745 ps
Table
Row I/O Output Standard
4–109). If the clock frequency is 267 MHz, the clock period T is:
through
Table 4–113
show the maximum DCD in absolution derivation
Maximum DCD (ps) for Non-DDIO Output
–6 Speed Grade
275
155
135
180
195
145
125
100
115
85
80
Units
Arria GX Device Handbook, Volume 1
ps
ps
ps
ps
ps
ps
ps
ps
ps
ps
ps
4–97