LM1229YA National Semiconductor, LM1229YA Datasheet - Page 12

• Manufacturer Part Number: LM1229YA
• Description: I2C Compatible CMOS TV RGB and Deflection Processor
• Manufacturer: National Semiconductor

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Pin
No.
18
19
22
20
21
24
25
28
Application Information
Pin Name
Horizontal
FILTER2
FILTER1
Flyback
FREQ1
FREQ2
REHT1
REHT2
HEHT
(Continued)
Schematic
12
The input is a threshold detector at
approximately 2.4V. R
to limit the combined peak current during flyback
to a few milliamperes in the zener diode in
accordance with the zener power rating.
It may be desirable to add a resistor from V
GND to pin 18 to offset the switching point up or
down by a small amount. Be sure to start with
small offsets and work up from there.
These two pins select the frequency of the
horizontal PLL. They are tri-state and may be
hard wired for a single frequency design or
driven by a microcontroller for a multiple
frequency design. The 100Ω resistor is used for
ESD and arcing protection when the connections
comes from a long distance away and are
recommended even if the pins are hard wired.
The input logic states and their corresponding
scan frequencies are given in Table 1.
This pin provides horizontal phase
compensation, if needed, for beam current
loading. The polarity and magnitude are
selectable from the I
shows the compensation for R
correction is not needed then it can be disabled
by setting HEHT[3] to 1 and pin 20 can be left
open.
The R
horizontal phase compensation, HEHT. A smaller
resistor increases the compensation and a larger
resistor decreases it. If this feature is not used,
pins 21 and 24 may be left open.
These are the currently recommended filter
values for PLL 2. These components should be
kept as close to pins 25 and 26 as possible, and
high frequency signals should be routed away
from this filter to avoid affecting the loop.
These are the currently recommended filter
values for PLL 1. These components should be
kept as close to pins 28 and 29 as possible, and
high frequency signals should be routed away
from this filter to avoid affecting the loop.
EHT
resistor determines the gain of the
Description
2
C bus. See Table 4, which
H
should be large enough
EHT
= 20k. If this
CC
or