STV2050A STMicroelectronics, STV2050A Datasheet - Page 55

• Manufacturer Part Number: STV2050A
• Description: IC DGTL CONVERGENCE PROC 80-PQFP
• Manufacturer: STMicroelectronics
• Type: Videor

Specifications of STV2050A

• Applications: HDTV
• Mounting Type: Surface Mount
• Package / Case: 80-MQFP, 80-PQFP
• Case: QFP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

11 ELECTRICAL LOOP
11.1 PRINCIPLE OF OPERATION
It is possible to multiply convergence values with a digital gain value and add a digital offset
value to the convergence values during convergence signal processing (see
vergence Values Computation Path" on page
rent and gain differences of the external convergence amplifiers. However, aging and temper-
ature can cause drifting, and the correction values may have to be adjusted. In order to avoid
a manual after-sales re-alignment, the STV2050A can perform an automatic update of the
field offset canceller values, as well as for the gain correction values.
For this purpose a measuring line in the invisible part of the picture (for example, during the
frame retrace procedure) can be used to provide measurement values at convergence out-
puts. (Refer to
Offset current and gain values of the amplifiers are measured with comparators, which are
connected to the PORA, PORB, PORC port pins of the IC. The reference values are available
on the OGAH and OGAV pins.
Figure 31. Electrical Loop Block Diagram
Once the measurement is carried out, the convenient field offset canceller and gain compen-
sation corrections for the convergence values can be controlled by either an embedded
process (“internal loop”), or by an external MCU, when the internal loop is disabled.
The loop is activated using the STL bit in the E3 register.
Convergence
Processing
Measuring Line
STL
Figure 31 "Electrical Loop Block Diagram" on page
Electrical
Loop
0 = Internal Loop enabled
1 = Internal Loop disabled
DAC
45). This can be used to compensate offset cur-
OGAH,OGAV
PORA
PORB
PORC
STV2050A - ELECTRICAL LOOP
Amplifier
55.)
Figure 26 "Con-
Resistor
Yoke
Sense-
55/83