參數(shù)資料
型號: TDA9115
廠商: STMICROELECTRONICS
元件分類: 偏轉(zhuǎn)
英文描述: HORIZ/VERT DEFLECTION IC, PDIP32
封裝: SHRINK, PLASTIC, DIP-32
文件頁數(shù): 17/45頁
文件大?。?/td> 675K
代理商: TDA9115
TDA9115
24/45
Figure 2. Horizontal sync signal
Figure 3. Extraction of V-sync signal from H/V-sync signal
9.2.2 Automatic sync. selection mode
I2C bus bit VSyncAuto is set to 1. In this mode, the
device itself controls the I2C bus bits switching the
polarity inverters and the vertical sync. signal se-
lector (VSyncSel), using the information provided
by detection circuitry. If both extracted and pure
vertical sync. signals are present, the one already
selected is maintained. No intervention of the
MCU is necessary.
9.3 HORIZONTAL SECTION
9.3.1 General
The horizontal section consists of two PLLs with
various adjustments and corrections, working on
horizontal deflection frequency, then phase shift-
ing and output driving circuitry providing H-drive
signal on HOut pin. Input signal to the horizontal
section is output of the polarity inverter on H/
HVSyn input. The device ensures automatically
that this polarity be always positive.
9.3.2 PLL1
The PLL1 block diagram is in Figure 5. It consists
of a voltage controlled oscillator (VCO), a shaper
with adjustable threshold, a charge pump with inhi-
bition circuit, a frequency and phase comparator
and timing circuitry. The goal of the PLL1 is to
make the VCO ramp signal match in frequency the
sync. signal and to lock this ramp in phase to the
sync. signal, with a possibility to adjust a perma-
nent phase offset. On the screen, this offset re-
sults in the change of horizontal position of the pic-
ture. The loop, by tuning the VCO accordingly,
gets and maintains in coincidence the rising edge
of input sync. signal with signal REF1, which is de-
rived from the VCO ramp by a comparator with
threshold adjustable through
HPOS I2C bus con-
trol. The coincidence is identified and flagged by
lock detection circuit on pin HLckVBk .
The charge pump provides positive and negative
currents charging the external loop filter on HPosF
pin. The loop is independent of the trailing edge of
sync. signal and only locks to its leading edge. By
design, the PLL1 does not suffer from any dead
band even while locked. The speed of the PLL1
depends on the current value provided by the
charge pump. While not locked, the current is very
low, to slow down the changes of VCO frequency
and thus protect the external power components
at sync. signal change. In locked state, the cur-
rents are much higher, two different values being
selectable via PLL1Pump I2C bus bit to provide a
mean to control the PLL1 speed by S/W. Lower
values make the PLL1 slower, but more stable.
Higher values make it faster and less stable. In
general, the PLL1 speed should be higher for high
deflection frequencies. The response speed and
stability (jitter level) depends on the choice of ex-
ternal components making up the loop filter. A
“CRC” filter is generally used (see Figure 4 on
page 25).
Positive
Negative
TH
tPulseHSyn
H/V-sync
Integration
Extracted
textrV
TH
tPulseHsyn
V-sync
Internal
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