R
Table 27: Switching Characteristics for the DLL (Continued)
-4 Speed Grade
Min Max
Symbol
Duty Cycle(4)
Description
Units
CLKOUT_DUTY_CYCLE_DLL Duty cycle variation for the CLK0, CLK90, CLK180,
CLK270, CLK2X, CLK2X180, and CLKDV outputs,
including the BUFGMUX and clock tree duty-cycle
distortion
-
[1% of
CLKIN period
+ 400]
ps
Phase Alignment(4)
CLKIN_CLKFB_PHASE
CLKOUT_PHASE_DLL
Phase offset between the CLKIN and CLKFB inputs
-
-
200
ps
ps
Phase offset between DLL outputs
CLK0 to CLK2X
(not CLK2X180)
[1% of
CLKIN period
+ 100]
All others
-
[1% of
CLKIN period
+ 200]
ps
Lock Time
LOCK_DLL(3)
When using the DLL alone: The time 5 MHz < FCLKIN
<
-
-
5
ms
from deassertion at the DCM’s Reset
input to the rising transition at its
LOCKED output. When the DCM is
locked, the CLKIN and CLKFB
signals are in phase
15 MHz
F
CLKIN > 15 MHz
600
μs
Delay Lines
DCM_DELAY_STEP
Finest delay resolution
20
40
ps
Notes:
1. The numbers in this table are based on the operating conditions set forth in Table 6 and Table 26.
2. Indicates the maximum amount of output jitter that the DCM adds to the jitter on the CLKIN input.
3. For optimal jitter tolerance and faster lock time, use the CLKIN_PERIOD attribute.
4. Some jitter and duty-cycle specifications include 1% of input clock period or 0.01 UI. Example: The data sheet specifies a maximum
jitter of “ [1% of CLKIN period + 150]”. Assume the CLKIN frequency is 100 MHz. The equivalent CLKIN period is 10 ns and 1% of
10 ns is 0.1 ns or 100 ps. According to the data sheet, the maximum jitter is [100 ps + 150 ps] = 250ps.
Digital Frequency Synthesizer
Table 28: Recommended Operating Conditions for the DFS
-4 Speed Grade
Symbol
Description
Min
Max
Units
(2)
Input Frequency Ranges
333(4)
FCLKIN
CLKIN_FREQ_FX
Frequency for the CLKIN input
0.200
MHz
(3)
Input Clock Jitter Tolerance
CLKIN_CYC_JITT_FX_LF
CLKIN_CYC_JITT_FX_HF
Cycle-to-cycle jitter at the CLKIN
input, based on CLKFX output
frequency
F
CLKFX < 150 MHz
-
-
300
150
ps
ps
FCLKFX > 150 MHz
CLKIN_PER_JITT_FX
Period jitter at the CLKIN input
-
1
ns
Notes:
1. DFS specifications apply when either of the DFS outputs (CLKFX or CLKFX180) are used.
2. If both DFS and DLL outputs are used on the same DCM, follow the more restrictive CLKIN_FREQ_DLL specifications in Table 26.
3. CLKIN input jitter beyond these limits may cause the DCM to lose lock.
4. To support double the maximum effective FCLKIN limit, set the CLKIN_DIVIDE_BY_2 attribute to TRUE. This attribute divides the incoming
clock frequency by two as it enters the DCM.
DS635 (v2.0) September 9, 2009
www.xilinx.com
Product Specification
26
XILINX [ XILINX, INC ]
