LM1238AAD/NA NOPB National Semiconductor, LM1238AAD/NA NOPB Datasheet - Page 10

• Manufacturer Part Number: LM1238AAD/NA NOPB
• Manufacturer: National Semiconductor

Specifications of LM1238AAD/NA NOPB

• Operating Temperature (min): 0C
• Operating Temperature (max): 70C
• Operating Temperature Classification: Commercial
• Mounting: Through Hole
• Package Type: MDIP
• Lead Free Status / RoHS Status: Compliant

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Pin Descriptions and Application Information
No.
Pin
22
23
24
Pin Name
H Flyback
CLAMP
ABL
Schematic
10
The Automatic Beam Limiter input is biased to
the desired beam current limit by R
and normally keeps D
the current resupplying the CRT capacitance
(averaged by C
begins to turn off and the voltage at pin 22
begins to drop. The LM1238 then lowers the
gain of the three video channels until the beam
current reaches an equilibrium value.
This pin accepts either TTL or CMOS logic
levels. The internal switching threshold is
approximately one-half of V
series resistor, R
to avoid overdriving the input devices. In any
event, R
voltage at pin 23 from going higher than V
below GND.
Proper operation requires current reversal. R
should be large enough to limit the peak current
at pin 24 to about +4 ma during blanking, and
−500 µA during scan. C
logic level inputs and should be large enough to
make the time constant, R
larger than the horizontal period. R
typically 300 ohms and 330 pf when the flyback
waveform has ringing and needs filtering. C
may be needed to filter extraneous noise and
can be up to 100 pF.
(Continued)
EXT
must be large enough to prevent the
ABL
31
Description
) exceeds this limit, then D
, of about 1k is recommended
INT
17
forward biased. When
H
is usually needed for
CC
C
17
. An external
significantly
34
ABL
and C
and V
CC
8
18
H
BB
are
INT
or