CS2000-CP_15 Datasheet, PDF (23/37 Pages) Cirrus Logic – Fractional-N Clock Synthesizer & Clock Multiplier

CS2000-CP
5.4 PLL Clock Output
The PLL clock output pin (CLK_OUT) provides a buffered version of the output of the frequency synthesizer.
The driver can be set to high-impedance with the ClkOutDis bit.
The output from the PLL automatically drives a static low condition while the PLL is un-locked (when the
clock may be unreliable). This feature can be disabled by setting the ClkOutUnl bit, however the state
CLK_OUT may then be unreliable during an unlock condition.
ClkOutUnl
PLL Locked/Unlocked
0
0
2:1 Mux
1
0
2:1 Mux
ClkOutDis
PLL Clock Output
PLLClkOut
PLL Clock Output Pin
(CLK_OUT)
PLL Output
1
Figure 19. PLL Clock Output Options
Referenced Control
Register Location
ClkOutUnl..............................“Enable PLL Clock Output on Unlock (ClkOutUnl)” on page 32
ClkOutDis ..............................“PLL Clock Output Disable (ClkOutDis)” on page 29
5.5 Auxiliary Output
The auxiliary output pin (AUX_OUT) can be mapped, as shown in Figure 20, to one of four signals: refer-
ence clock (RefClk), input clock (CLK_IN), additional PLL clock output (CLK_OUT), or a PLL lock indicator
(Lock). The mux is controlled via the AuxOutSrc[1:0] bits. If AUX_OUT is set to Lock, the AuxLockCfg bit is
then used to control the output driver type and polarity of the LOCK signal (see section 8.7.2 on page 32).
In order to indicate an unlock condition, REF_CLK must be present. If AUX_OUT is set to CLK_OUT the
phase of the PLL Clock Output signal on AUX_OUT may differ from the CLK_OUT pin. The driver for the
pin can be set to high-impedance using the AuxOutDis bit.
AuxOutSrc[1:0]
Timing Reference Clock
(RefClk)
Frequency Reference Clock
(CLK_IN)
PLL Clock Output
(PLLClkOut)
PLL Lock/Unlock Indication
(Lock)
4:1 Mux
AuxOutDis
AuxLockCfg
Auxiliary Output Pin
(AUX_OUT)
Figure 20. Auxiliary Output Selection
Referenced Control
Register Location
AuxOutSrc[1:0]......................“Auxiliary Output Source Selection (AuxOutSrc[1:0])” on page 29
AuxOutDis .............................“Auxiliary Output Disable (AuxOutDis)” on page 28
AuxLockCfg...........................“AUX PLL Lock Output Configuration (AuxLockCfg)” section on page 32
DS761F3
23