TEA2029 STMICROELECTRONICS [STMicroelectronics], TEA2029 Datasheet - Page 6

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

TEA2028 - TEA2029 APPLICATION NOTE
V - FUNCTIONAL DESCRIPTION
Majority of the on-chip analog functions were com-
puter simulated and results such as temperature
variation, technological characteristic dispersion
and stability, have led to the enhancement and
implementation of actually employed structures. A
parallel in-depth study of the device implemented
in form of integrated sub-sections is provided to
analyze the overall performance in a TV set.
V.1 - Internal Voltage and Current References
V.1.1 - 1.26V Voltage reference
For optimum operation of the device, an accurate
and temperature-stable voltage generator inde-
pendent from V
type generator).
The generated 1.26V is particularly used as refer-
ence setting on input comparators.
V.1.1.1 - Generator block diagram
Figure 3
In practice, maximum drift due to temperature can
be + 0.23mV/
i.e.,
6/46
with
if A = 1.26 - V
Then : V
d
dT
dV
GENERATOR
dT
BE
=
1.5% for a T of 80
K
q
=
=
I
V
= + 0.086mV/
V
O
K T
BE
BE
V
q
= 1.26V (temperature-independant)
BE
o
25’
C
= 25.7mV at + 25
CC
T
BE
1.26
A
variations is used (Band-gap
-2mV/ C
o
C
= - 2mV/
o
C.
T
+0.086mV/ C
dV
V
o
o
dt
O
C
C
O
=
= 1.26V
= 0
V
BE
T
+ A .
V.1.2 - Current reference
This is implemented using the 1.26V generator in
combination with an external resistor.
Figure 4
Thus, it follows that I
pendent of both V
A set of current generators proportional to I
current are used in various circuit blocks.
V.2 - Line Sync. Extraction
Horizontal and vertical time bases should be syn-
chronized with corresponding sync. pulses trans-
mitted inside the infra-black portion of video signal.
The duty of this stage is to extract these sync
pulses. The output signal, called composite sync,
contains the vertical sync which is transmitted by
simple inversion of line sync. pulses.
The vertical sync pulse is then extracted from this
composite signal.
The main advantage of this arrangement is its
ability to operate at video input signal levels falling
within 0.2V to 3V peak-to-peak range and at any
average value.
The operating principle is to lock the black level of
the input signal (Pin 27) onto internaly fixed voltage
(V
sync pulse by using an integrating capacitor con-
nected to Pin 26.
Finally, the composite sync signal is delivered by a
comparator the inputs of which are driven by V
and video signals.
I
Let’s I
then : I
N
REF
) and then memorize the average voltage of the
1.26V
14
V
I
REF
14
Band
Gap
BE1
= I and V
=
=
R
V
V
R
+
CC
1.26
EXT
14
EXT
CC
=
EB1
V
= 380 A
and temperature.
BE2
1.26
REF
= V
I
REF
BE2
is accurate and inde-
V
R
14
BE1
EXY
I
14
V
R
3.32k
1%
BE2
EXT
REF
50%