TDA8376 Datasheet, PDF (12/44 Pages) NXP Semiconductors – I2C-bus controlled PAL/NTSC TV processors

Philips Semiconductors
I²C-bus controlled PAL/NTSC TV processors
Objective specification
TDA8376; TDA8376A
The output signal has an amplitude of approximately 2 V
black-to-white at nominal input signals and nominal
settings of the controls.
The black current stabilization is realized by feedback from
the video output amplifiers to the RGB control circuit. The
‘black current’ of the 3 guns of the picture tube is internally
measured and stabilized. The black level control is active
during 4 lines at the end of the vertical blanking. During the
first line the leakage current is measured and the following
3 lines the 3 guns are adjusted to the required level. The
maximum acceptable leakage current is ±100 µA.
The nominal value of the ‘black current’ is 10 µA. The ratio
of the currents for the various guns automatically tracks
with the white point adjustment so that the background
colour is the same as the adjusted white point.
The input impedance of the ‘black-current’ measuring pin
is 15 kΩ. Therefore the beam current during scan will
cause the input voltage to exceed the supply voltage. The
internal protection will start conducting so that the
excessive current is bypassed.
When the TV receiver is switched on the black current
stabilization circuit is not active, the RGB outputs are
blanked and beam current limiting input pin is
short-circuited. Only during the measuring lines will the
outputs supply a voltage of 5 V to the video output stage
so that it can be detected if the picture tube is warming up.
These pulses are switched on after a waiting time of
approximately 0.5 s. This ensures that the vertical
deflection is activated so that the measuring pulses are not
visible on the screen. As soon as the current supplied to
the measuring input exceeds a value of 190 µA the
stabilization circuit is activated. After a waiting time of
approximately 0.8 s the blanking and the beam current
limiting input pin are released. The remaining switch-on
behaviour of the picture is determined by the external time
constant of the beam current limiting network.
8 I²C-BUS SPECIFICATION
handbook, halfpage
A6 A5 A4 A3 A2 A1 A0 R/W
1 0 0 0 1 0 1 1/0
MLA743
Fig.4 Slave address (8A).
Valid subaddresses: 00 to 13 (TDA8376) or 00 to 16
(TDA8376A); subaddress FE is reserved for test
purposes. Auto-increment mode is available for
subaddresses.
8.1 Start-up procedure
Read the status bytes until POR = 0 and send all
subaddress bytes. The horizontal output signal is switched
on when the oscillator is calibrated.
Each time before the data in the IC is refreshed, the status
bytes must be read. If POR = 1, the procedure previously
mentioned must be carried out to restart the IC.
When this procedure is not followed the horizontal
frequency may be incorrect after power-up or after a
power dip.
1996 Jan 26
12