TEA2029 STMICROELECTRONICS [STMicroelectronics], TEA2029 Datasheet - Page 11

• Manufacturer Part Number: TEA2029
• Description: APPLICATION NOTE
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

Figure 13
V.3.3.2 - Low-pass filter (see Figure 14)
Its main function is to reject the 2f
quency component delivered by the phase compa-
rator.
It also defines the characteristics of the loop in
transient mode.
The filter is built around two sub-sections which
determine the stability and the response time of the
loop in the following modes of transmission :
Normal or VCR modes. See section V.3.6 ”Dy-
namic study of 1”.
Figure 14
R is the dynamic input resistance of the VCO.
The filter transfer function may be defined as fol-
lows :
- f(p) =
-
The second order terms of the denominator can be
converted to first order products as a function of
2.2 F
4.7k
Z(p) = R
C1
R1
v
i
+1
LS
-1
I+
I-
0
1
0
I
i
10nF
V
i
1
C
= Z(p)
OUT
p R C
t
V
S
22
e
i
5.6V
R1
Comparator
1
C1
VCO
Stage
1
R1 C1
R C1
p
C1
i
R1
R
H
R1
(31kHz) fre-
C
C
C1 p
R
t
t
t
VCO
V
2
frequency as follow :
with R1 = 4.7k , R = 500k , C1 = 2.2 F, C = 10nF
we obtain :
- f1 =
- f2 =
- f3 = 3.43kHz
Figure 15
V.3.3.3 - VCO (Voltage Controlled Oscillator)
Its function is to generate a frequency proportional
to a control voltage issued externally, by the low-
pass filter in our case.
The period of the output signal is used as timing
reference for various functions such as, horizontal
and vertical time bases. The frequency range must
be short and accurate :
- It must be short since the power dissipated within
- The accuracy is required if the adjustment is to
The basic arrangement is to employ a ceramic
resonator (or ceramic filter) which has quite stable
characteristics as a function of frequency.
A filter whose resonating frequency is a multiple of
line frequency (15625Hz) is to be selected. An
example is 32 15625 = 500kHz.
A. 503kHz CERAMIC FILTER
Figure 16
TEA2028 - TEA2029 APPLICATION NOTE
the horizontal scanning block is inversely propor-
tional to the line frequency.
be omitted.
20 log |f|
20 log R
Arg (z)
Symbol
2 R1 C1
2
2
0
0
R
f(jf) = R
1
f
2
0.14Hz
C1
= 15.4Hz
Figure 17
R C
1
f
1
1
15.4Hz 3.43kHz
j
R1 C1
f2
1
f
Equivalent Circuit
R1
j
f1
1
f
= 0.14Hz
C0
f
3
L1
j
f3
f
(log scale)
C1
11/46
f
f