STV2050A STMicroelectronics, STV2050A Datasheet - Page 53

• 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

10 DYNAMIC FOCUS
10.1 PARABOLA CURVE
The focus function delivers a current with 6-bit resolution, which is constant for horizontal
lines. In vertical direction, the current has the shape of a second order parabola.
The parabola is defined by three points, FV1, FV2 and FV3, whose values correspond to the
FV1[5:0], FV2[5:0] and FV3[5:0] values which are stored in the DE register.
The position of these last 3 points is a multiple of (VGD+1). See
on page
Figure 29. Focus Parabola
The focus DAC will provide a programmable constant value in the FVR[5:0] bits in the DE reg-
ister at the bottom of the screen and during vertical retrace.
The start of the retrace value is programmable using the FSB[7:0] bits in the DA register as
shown above.
The position is indicated by the VFP[8:0] bits in the D9 register.
Notes:
1. If VRES becomes active before the number of lines for the FSB have been counted, the parabola will
2. The hardware is not equipped with a safeguard device against DAC range overflow. This may occur
be terminated and replaced by the FVR retrace value.
if the FV2 bit is near the max. positive or negative value and the parabola is not symmetrical to the
FV2 centre value. Also, large values for the FSB have to be taken into account.
vertical retrace
(VRES)
53. The parabola is therefore linked to the value of the Vertical Grid Distance.
Focus DAC
63
48
32
16
0
VFP+3
FV1
0
x = 12 * (VGD + 1)
y = 11 * (VGD + 1)
field n
FV2
x/2
y
FSB
FV3
x
STV2050A - DYNAMIC FOCUS
FVR
Figure 29 "Focus Parabola"
FV1
field n+1
0
TV lines
53/83