- SS-HQ1 Application Notes -
Ver.1.0.0 January 7, 2005
218
Table 12.2-27 External Input Signal (VBS Lock (VBSLHP) Mode)
Pin Name(Pin No)
I/O signals
S0(44pin)
Connected (3.3V) power supply
S3(48pin) FSC
signal
EXVIDEOY(57pin) EXT-VIDEO-Y(1Vpp:
Analog
signal)
EXVIDEO(58pin) EXT-VIDEO(1Vpp:
Analog
signal)
The external video signal input to EXVIDEOY should be passed through the LPF to remove the subcarrier
component. The phase of the FSC signal output from S4 (pin 49) must be adjusted and the signal must be
re-input to S3 (pin 48).
Internal phase comparison
• HD phase comparison
The MCK-frequency-divided HD (MCK-HD) signal and the horizontal signal separated inside the CXD3172AR
from the external video signal (luminance signal) input through EXVIDEOY (pin 57) are phase-compared, and
the result of the 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 the external video signal and look at the PCOMP output waveform to check whether
the lock is on.
Fig 12.2-33 PCOMP output waveform (locked)
PCOMP
output
EXT-VIDEO
EXVIDEOY
input
Ch1
Ch2
Ch1:500mV / DIV
Ch2:1.00V / DIV
20.0us / DIV
[TRIGGER]