EP1S30F780C6 Datasheet, PDF (335/864 Pages) Altera Corporation – Stratix Device Handbook, Volume 1

General-Purpose PLLs in Stratix & Stratix GX Devices
An advanced level of control is also possible for precise control of the
loop filter parameters. This level allows you to specifically select the
charge pump current, loop filter resistor value, and loop filter (high
frequency) capacitor value. These parameters are: charge_pump_current,
loop_filter_r, and loop_filter_c. Each parameter supports the specific
range of values listed in Table 1–8.
Table 1–8. Advanced Loop Filter Parameters
Parameter
Resistor values (kΩ)
High-frequency capacitance
values (pF)
Charge pump current settings
(μA)
Values
1, 2, 3, 4, 7, 8, 9, 10
5, 10, 15, 20
10, 15, 20, 24, 30, 35, 40, 45, 50, 55, 60, 65,
70, 75, 80, 85, 90, 100, 112, 135, 148, 164,
212
f
For more information on PLL software support in the Quartus II
software, see the altpll Megafunction User Guide.
f
Clock Switchover
For more information on implementing clock switchover, see
AN 313: Implementing Clock Switchover in Stratix & Stratix GX Devices.
Spread-Spectrum Clocking
Digital clocks are generally square waves with short rise times and a 50%
duty cycle. These high-speed digital clocks concentrate a significant
amount of energy in a narrow bandwidth at the target frequency and at
the higher frequency harmonics. This results in high energy peaks and
increased electromagnetic interference (EMI). The radiated noise from
the energy peaks travels in free air and, if not minimized, can lead to
corrupted data and intermittent system errors, which can jeopardize
system reliability.
Background
Traditional methods for limiting EMI include shielding, filtering, and
multi-layer printed circuit boards (PCBs). However, these methods
significantly increase the overall system cost and sometimes are not
enough to meet EMI compliance. Spread-spectrum technology provides
a simple and effective technique for reducing EMI emissions without
additional cost and the trouble of re-designing a board.
Altera Corporation
July 2005
1–25
Stratix Device Handbook, Volume 2