- SS-HQ1 Application Notes -
Ver.1.0.0 January 7, 2005
216
Internal phase comparison
The result of the phase comparison is output through PCOMP (pin 42). The PCOMP signal is applied to the
LPF (H-PLL) and fed back to the VCXO circuit on the MCK side to form the horizontal direction PLL. The
polarity of the PCOMP signal may be switched using PCMPINV (CAT7_Byte2_bit4).
An active or passive filter can be selected, to match the specifications of the external LPF. Note that we
recommend an active filter since active filters have better performance.
shows the PCOMP output waveform when the lock is on.
shows the PCOMP output
waveform when the lock is off. (These waveforms are the results of measurements made using our evaluation
board.) Apply a trigger to D SYNC and look at the PCOMP output waveform to check whether the lock is on.
Fig 12.2-30 PCOMP output waveform (locked)
Fig 12.2-31 PCOMP output waveform (unlocked)
PCOMP
output
D SYNC
S1 input
Ch1
Ch2
Ch1:2.00V / DIV
Ch2:1.00V / DIV
20.0us / DIV
[TRIGGER]
PCOMP
output
Ch1
Ch2
[TRIGGER]
PCOMP Waveforms
Instability
D SYNC
S1 input
Ch1:2.00V / DIV
Ch2:1.00V / DIV
20.0us / DIV