TEA2029 STMICROELECTRONICS [STMicroelectronics], TEA2029 Datasheet - Page 12

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

TEA2028 - TEA2029 APPLICATION NOTE
Where :
R1 = 7 , L1 = 1.26mH, C1 = 78pF, C0 = 507pF
- Series resonance frequency :
- Parallel resonance frequency :
- Tolerance within the resonance area :
- Temperature stability : 0.3% of f
Figure 18
B - SIMPLIFIED BLOCK DIAGRAM OF VCO
Figure 19
12/46
V
f
f
503kHz
S
P
22
=
= f
22
Comparator
2
5.6V
S
i
1
10
10
10
10
+90
-90
L1 C1
1
1
0.3 %
3
0
4
2
1
Non-linear
Amplifier
A4
450
C1
C0
= 503kHz
+
= 540kHz
A2
+
500
f
S
V
A1
I
S1
3
500
A3
2mA
+
550
f
P
1.1 V
R
I
I
O
1
2
at T = 100
DC
600
18
17
19
1.5nF
220
220
C1
R1
1.8
k
150
pF
C
R
R
o
C
The overall arrangement is equivalentto a variable-
phase amplifier configured in closed loop with the
external passive filter.
The system will oscillate if the open-loop gain is
0dB and if V
In closed-loop oscillating mode, the phase variation
of V
V
This phase change will finally correspond to a
change in frequency.
Figure 20
C. - CHARACTERISTICS OF THE EXTERNAL
FILTER
The ceramic resonator behaves as a capacitor at
f < f
inductor at frequenciesfalling between its two reso-
nance frequencies.
Combined with a ”R.C” network to generate a 90
phase lag, the overall arrangement will exhibit the
following characteristics : see Figure 21
Figure 21
OUT
S
18
/V
(f
/V
S
18
V
IN
: series resonance frequency) and as an
OUT
variation but of opposite sign.
2.4k Resistor = Pin 19 Input Resistance
-150
imposed by V
-30
-90
V
OUT
/
V
IN
18
V
440
18
19
(Degrees)
leads V
480
A tt e n
Working Area
-24
(open-loop)
A mp.
503kHz
u a t i o
V
Filter
V
500
OUT
22
-135
IN
n
.
Phase Control
22
520
19
will result in same
20 log
1 8
V
OUT
Frequency
V
(kHz)
18
V
V
OUT
-20
-10
18
(dB)
V
18
o