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LA7837, 7838 Any and all SANYO products described or contained herein do not have specifications that can handle
applications that require extremely high levels of reliability, such as life-support systems, aircrafts
control systems, or other applications whose failure can be reasonably expected to result in serious
physical and/or material damage. Consult with your SANYO representative nearest you before using
any SANYO products described or contained herein in such applications.
SANYO assumes no responsibility for equipment failures that result from using products at values that
exceed, even momentarily, rated values (such as maximum ratings, operating condition ranges,or other
parameters) listed in products specifications of any and all SANYO products described or contained
herein.
Monolithic Linear IC
Vertical Deflection Circuit
with TV/CRT Display Drive
Ordering number:ENN3313C
LA7837, 7838
SANYO Electric Co.,Ltd. Semiconductor Company
TOKYO OFFICE Tokyo Bldg., 1-10, 1 Chome, Ueno, Taito-ku, TOKYO, 110-8534 JAPAN
12501TN (KT)/71693TS/8251TS(KOTO)/2090TA, TS(AF) No.33131/9
Package Dimensions
unit:mm
3107-SIP13H
[LA7837, 7838]
SANYO : SIP13H
Overview
The LA7837, 7838 are vertical deflection output ICs de-
veloped for use in high-grade TVs and displays. The inter-
lace and crossover distortion responses, in particular, have
been greatly improved, allowing excellent picture quality
on large size televisions and high precision interlace mode
displays.
Also, pulse signals can be used for input signals due to the
on-chip sawtooth wave generating circuit and driver cir-
cuit. Further, the DC and AC feedback circuit can be formed
with these ICs alone, simplifying pattern design of sets and
ensuring stable performance. All of the functions in a color
TV signal system can be processed by connecting these
ICs with SANYOs single-chip IC LA7670 series (NTSC)
and LA7680/85 series (PAL/NTSC) (VIF/SIF, video,
chroma, deflection).
The LA7837 has a maximum deflection current of 1.8Ap-
p, making it appropriate for use in portable to mid-size tele-
visions.
The LA7838 has a miximum deflection current of 2.2Ap-
p, so it can be used for large size sets, and can drive from
33 to 37 inches.
Features
Low power dissipation due to on-chip pump-up circuit.
On-chip 50/60Hz vertical size control circuit.
On-chip sawtooth wave generating circuit.
On-chip driver circuit.
Vertical output circuit.
On-chip thermal protection circuit.
Excellent interlace response.
Excellent crossover response.
0.4
0.5
3.4
1.15
25.6
10.0
2.4
2.0
1.2
2.0
0.8
1
13
1.0min
4.5
15.4max
11.8
11.2
13.9 LA7837, 7838
No.33132/9
Operating Characteristics
at Ta = 25C, +V
CC
1=12V, +V
CC
8=24V, parenthesis ( ) indicate LA7838.
Operating Conditions
at Ta = 25C, parenthesis ( ) indicates LA7838.
Specifications
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B
d LA7837, 7838
No.33133/9
LA7837, 7838 Interface Circuit
LA7837, 7838 Pin Connection Diagram and Block Diagram LA7837, 7838
No.33134/9
Sample Application Circuits for 14 Color TV
Fig. 1 +V
CC
1, 12V
Fig. 2 +V
CC
1, 9V LA7837, 7838
No.33135/9
Sample Application Circuits for 14 Display
(Retrace Time 300
�
s)
Change VR4 to fixed constant after adjustment.
( ) : For negative polarity pulse.
Fig. 3 LA7837, 7838
No.33136/9
Precautions when using with display having short retrace time :
The vertical output ICs LA7837, 7838 are appropriate for use in monitors and displays because the interlace and
crossover distortion responses are superior to those of the LA7835, 7836.
However, since the vertical retrace time of displays is shorter than that of TV, the upper portion of the vertical
picture may stretch. This is because the start waveform of the pin 6 sawtooth wave bends, as shown in Fig.4, due to
the diode response of the clamp waveform. If there is not much time difference between T
1
ant T
R
, the upper portion
of the vertical picture will tend to stretch. The use of a circuit as shown in Fig.3 will cause pin 6 waveform start
wave to become linear, so that stretching is suppressed. The example of circuit application shown in Fig.3 does not
use the trigger input circuit (pin 2) and one-shot multivibrator (pin 3) built in the LA7837, 7838 ; the pin 6 sawtooth
wave is controlled by the LA7855, 7856 vertical output pulse.
Therefore, the discharge circuit and clamp circuit are formed by the external Zener diode and transistor TR2.
Fig. 4
Design Example
For 12V pin 1 power supply
On the LA7837, 7838, pin 3 one-shot multivibrator operates when a trigger pulse enters pin 2. During this time, the
sawtooth wave generator discharge circuit and clamp circuit inside pin 6 operate.
The clamp voltage at this time is figured according to this formula :
V
CLAMP
=5/12 � V
CC ...........................
�
For 12V,
V
CLAMP
=5 [V]
Therefore, the Zener diode used in Fig.3 must be rated more than 5V (e.g. 5.6V), otherwise the clamp circuit inside
the IC will operate.
For 9V pin 1 power supply
The same as for 12V, according to formula � :
V
CLAMP
=3.75 [V]
So, that Zener diode must be rated more than 4V (e.g. 4.5V). LA7837, 7838
No.33137/9
Fig. 6
Fig. 5
Pin 6 waveform when using the LA7837, 7838 in a display application circuit (Fig. 3)
Fig. 7 LA7837, 7838
No.33138/9
LA7837, 7838 application in a multi-sync system
The LA7837, 7838 can also be used in a vertical frequency multi-sync system.
The LA7837, 7838 do not have an on-chip vertical oscillation circuit, so they operate merely by impressing a trigger
pulse (e.g. 40 to 80Hz) on pin 2.
However, there are two problems with using the LA7837, 7838 as are in a multi-sync system.
One is vertical amplitude. When the trigger pulse changes between 40 to 80Hz, the vertical frequency will rise and
amplitude size decreases (because pin 6 cycle (T1, T2) in the diagram below becomes shorter).
Fig. 8
Countermeasure 1
In order to stabilize vertical size change, an
operational amplifier is used to change the
circuit to one which controls pin 4 vertical
size control current.
Voltage which corresponds to vertical fre-
quency changes is applied to the operational
amplifier to stabilize vertical size.
The other problem is that vertical linearity chages when used at multi-frequency (e.g. 40 to 80Hz).
The reason for this is that R5 and C1 time constants are used for linearity correction (Fig.9), so even though the value
is optimum for a certain frequency, it is not for others.
Countermeasure 2
As shown in Fig.10, good linearity can be obtained by setting frequency ranges of use for R5 and C1 time constants for
vertical linearity correction, and switching them.
For example :
40 to 60Hz Switch A
60 to 80Hz Switch B
For switch A, R5 and C1 are set so that vertical linearity response is optimum for fv 50Hz.
Next, for switch B, R5 and C1 are set for optimum value at fv 70Hz.
By dividing the vertical trigger pulse range (e.g.40 to 80Hz) and performing linearity correction in this way, linearity
distortion can be kept below