Cirrus Logic CS2300-OTP - Manual (Page 12)

CS2300-OTP
12 DS844F2
to as wander. In others it may be preferable to remove only higher frequency jitter, allowing the input wan-
der to pass through the PLL without attenuation.
Typically, applications in which the PLL_OUT signal creates a new clock domain from which all other sys-
tem clocks and associated data are derived will benefit from the maximum jitter and wander rejection of
the lowest PLL bandwidth setting. See
Figure 8 .
Systems in which some clocks and data are derived from the PLL_OUT signal while other clocks and data
are derived from the CLK_IN signal will often require phase alignment of all the clocks and data in the
system. See
Figure 9 . If there is substantial wander on the CLK_IN signal in these applications, it may be
necessary to increase the minimum loop bandwidth allowing this wander to pass through to the CLK_OUT
signal in order to maintain phase alignment. For these applications, it is advised to experiment with the
loop bandwidth settings and choose the lowest bandwidth setting that does not produce system timing
errors due to wandering between the clocks and data synchronous to the CLK_IN domain and those syn-
chronous to the PLL_OUT domain.
While acquiring lock, the digital loop bandwidth is automatically set to a large value. Once lock is
achieved, the digital loop bandwidth will settle to the minimum value selected by the ClkIn_BW[2:0] pa-
rameter.
Referenced Control Parameter Definition
ClkIn_BW[2:0] ....................... “Clock Input Bandwidth (ClkIn_BW[2:0])” on page 21
Figure 8. Low bandwidth and new clock domain
LRCK
SCLK
SDATA
MCLK
MCLK Wander > 1 Hz
Wander and Jitter > 1 Hz Rejected
D0 D1
LRCK
SCLK
SDATA
Subclocks generated
from new clock domain.
or
PLL
BW = 1 Hz
CLK_IN
PLL_OUT
D0 D1
Jitter
Figure 9. High bandwidth with CLK_IN domain re-use
D0 D1
LRCK
SCLK
SDATA
MCLK
MCLK
Wander < 128 Hz
Jitter > 128 Hz Rejected
Wander < 128 Hz Passed to Output
LRCK
SCLK
SDATA
or
PLL
BW = 128 Hz
CLK_IN PLL_OUT
Subclocks and data re-used
from previous clock domain.
Jitter
D0 D1