U4935B Datasheet, PDF (8/16 Pages) TEMIC Semiconductors – SECAM Decoder

U4935B
Functional Description
Bell Filter
The ACC amplifier provides a C- (chrominance) signal of
a constant peak-to-peak level for the bell filter. The bell
filter is of a gyrator-capacitor type. The resonance
frequency is
4.433619 MHz
4.286 MHz
4.33 MHz
during vertical blanking
during scanning
during burst gating.
The reference frequency should be stable during the verti-
cal blanking because it is used to calibrate the filters and
the demodulator. The capacitor C7 should be connected
as close as possible to the ground Pin of the package. If
not, this can result in a resonance frequency error.
CVBS
in
16
ACC
VBLK pulse
Bell filter
PLL
f_ref/
ident
1
Amp
Tuning
7
C₇
Gain
9611724
fo
f_ref
f
4.286 MHz 4.434 MHz
Figure 17. Block diagram of the bell filter
8 (16)
TELEFUNKEN Semiconductors
Preliminary Information
Rev. A1, 28-Jan-97