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TA8751
AUTOMATIC KINE BIAS (AKB) RGB INTERFACE
TOSHIBA
TOSHIBA BIPOLAR LINEAR INTEGRATED CIRCUIT SILICON MONOLITHIC
TA8751AN
AUTOMATIC KINE BIAS (AKB)
RGB INTERFACE
TA8751AN
TA8751AN possesses functions that optimize the CRT
drive conditions in televisions, and is an IC that
automates the previously complex cutoff adjustment and
drive adjustment non-adjustment.
It has an RGB TEXT input pin, so TV signal and TEXT
signal can be switched between rapidly.
The TV's primary colors are DC coupled, so brightness
control from previous stages can be utilized.
BLOCK DIAGRAM
Outputcumff filter
blanki
Cutoff
ad ustment
ad ustment
TV/TEXT
switch
TEXT R
contrast
TEXT R
Vcc TV
Detection resistance
Drive filter
blanki
Cutoff
ad ustment
ad ustment
TV/TEXT
switch
TEXT G
contrast
TEXT G
TEXT TV TEXT
R input R input G input G input B input
blanki
Cutoff
ad ustment
ad ustment
TV ITEXT
switch
TEXT B
contrast
TEXT B
“1111111111111 1
SDIP30-P-400-1.78
Weight
formation
contrast brightness pulse
: 1.999 (Typ.)
Vertical
blanking Service
input Soft start switch
Blanking
eneration
generation
T1 T2 pulse
T1 T2 REF
insertion
TV/TEXT
switch
Reference
Blanking
separation
1 1 1 1
YS Horizontal NC Reference
blanking input pulse output
961001EBA2
O TOSHIBA is continually working to improve the quality and the reliability of its products. Nevertheless, semiconductor devices in general can
malfunction or fail due to their inherent electrical sensitivity and vulnerability to physical stress. It is the responsibility of the buyer, when utilizing
TOSHIBA products, to observe standards of safety, and to avoid situations in which a malfunction or failure of a TOSHIBA product could cause loss
of human life, bodily injury or damage to property. In developing your designs, please ensure that TOSHIBA products are used within specified
operating ranges as set forth in the most recent products specifications Also, please keep in mind the precautions and conditions set forth in the
TOSHIBA Semiconductor Reliability Handbook.
1997-06-02 1/24
TOSHIBA TA8751AN
TERMINAL FUNCTION
PIN No. NAME FUNCTION INTERFACE
VCC=12V (Standard)
1 VCC Please use voltage between 11 and -
2 TV signal input Input pin for TV primary color signals.
4 R input Used with DC direct-coupling.
6 G input Used with a standard black level of 1000
B input 3.0V (Standard).
Input pin for TEXT primary color
signals. Pntpst control
Used with AC direct-coupling. 1000 circuit
The DC voltage for the clamp interval
3 TEXT signal input of the TEXT primary color signals and ct
R input the DC voltage for the clamp interval g V
5 . . . F CC
7 G input of the TV primary color signals are
B input joggled by an input clamp circuit
inside the IC. Clamp circuit
After that the DC voltage determined
by the TEXT brightness control from
the internal matrix circuit is added.
8 GND - -
Vcc VCC
Pin that controls the amplitudes of J
9 TEXT contrast control the RGB signals input from pins 3, 5
and 7. 1000 24m
Pin that controls the DC voltage co
10 TEXT brightness control added to the RGB signals input from Matrix
pins3, 5 and 7. Clrcul
Coo", 1000
961001EBA2'
O The products described in this document are subject to foreign exchange and foreign trade control laws.
0 The information contained herein is presented only as a guide for the ap lications of our products. No responsibility is assumed by TOSHIBA
CORPORATION for any infringements of intellectual property or other rights D the third parties which may result from its use. No license is granted
by implication or otherwise under any intellectual property or other rights of TOSHIBA CORPORATION or others.
0 T e information contained herein is subject to change without notice.
1997-06-02 2/24
TOSHIBA
TA8751AN
PIN No.
FUNCTION
INTERFACE
Clamp pulse input
Input pin for the clamp pulse that
adjusts the black level of the TEXT
signal and the black level of the TV
signal.
Detection level is 2V (Standard).
Please ensure peak value is Ncc-31/)
or less.
YS input
Switches at high speed between TV
signal (Pins 2, 4 and 6) and TEXT
signal (Pins 3, 5 and 7).
At high levels TEXT signal and at low
levels TV signal can be selected.
Switch
circuit
Horizontal blanking
Input pin for horizontal blanking
pulse.
Horizontal blanking pulse and is used
in the blanking of output signal and
creation of reference pulse.
Switch
circuit
Reference pulse output
Output pin for reference pulse (T1,
This is open collector output.
Using the reference pulse output from
this pin, please set the reference pulse
interval output from the V/C/D IC in
the previous stage so it is the black
level.
2kQ IL
Service switch
Pin used to set the service mode.
Service mode fixes RGB output at T1
pulse level.
Used for adjustment.
1997-06-02 3/24
TOSHIBA TA8751AN
PIN No. NAME FUNCTION INTERFACE
When the power is off and the CRT is
not warmed up, as a beam current
does not flow to cutoff and drive
detection interval, voltage is not
obtainable from the sense pin. Vcc
Accordingly, for operation so that
current flows to the CRT for both cut
adjustment and drive adjustment, the 1000
17 Soft start . it
CRT starts from a white screen the A C;
instant it warms up. CUFO”
In order to prevent this, the soft start C,1'jttment
circuit returns the output DC voltage
and operates so that if pin 17 exceeds
a fixed value, cutoff adjustment is
fixed on the black side.
The set value is 0.9V.
Input pin for the vertical blanking
pulse that determines the timing of
the reference pulse for the cutoff
adjustment and drive adjustment.
The first 2H interval after the leading
18 Vertical blanking input edge of the vertical blanking is the
cutoff reference level, while the next
2H interval is the drive reference
level.
H timing is created by the horizontal
blanking of pin 14.
Timing generation circuit
Detection pin for the CRT beam
current. Cy-lee
The current that flows to the CRT 19
cathode as a result of the reference :3 JI.
pulse inserted for cutoff adjustment Drive
19 B sense and drive adjustment is converted to a comparator
23 G sense voltage and detected by detection VCC
27 R sense resistance. White balance can be 'll'
changed by varying detection
resistance.
The internal comparator operates in
tune with the timing of the reference
pulse.
Cutoff comparator
1997-06-02 4/24
TOSHIBA
TA8751AN
PIN No.
FUNCTION
INTERFACE
B drive filter
G drive filter
R drive filter
The comparator output over the
reference pulse interval is held for a
1V interval.
RGB gain is controlled by this voltage,
and operates so that the sense
voltages of pins 19, 23 and 27 are 5V.
Please use filter capacitance that has
as little leak current as possible.
Drive comparator
adjustment
circuit
B cutoff filter
G cutoff filter
R cutoff filter
The comparator output over the
reference pulse interval is held for a
IV interval.
The quantity of DC level shift for RGB
is controlled by this voltage, and
operates so that the sense voltages of
pins 19, 23 and 27 are 0.5V.
Please use a filter that has as little
leak current as possible.
Cutoff
co m pa rato r
Cutoff
adjustment
circuit
B output
G output
R output
Primary color signal output pin.
DC and gain determine the sense pin
voltage of the cutoff detection
interval is 0.5V and the sense pin
voltage of the drive detection interval
is 5V.
These become approximately 1V
during horizontal blanking and
vertical blanking intervals.
1997-06-02 5/24
TOSHIBA TA8751AN
MAXIMUM RATINGS (Ta = 25°C)
CHARACTERISTIC SYMBOL RATING UNIT
Power Supply Voltage VCC 15 V
Input Signal Voltage em 5 V
Primary Color Output Current 'OUT 3.5 mA
TV/TEXT Switching Voltage V12 -0.5--7.0 V
Blanking Pulse Input Voltage V18 r-lo V
Adjustment Pin Voltage VCONT tr-Vcc V
Dissipating Power PD (Note) 1.6 W
Operating Temperature Topr - 20--65 °C
Storage Temperature Tstg - 55--150 ''C
(Note) When used at temperatures of 25°C or above, please reduce the power by 12.8mW
for each 1°C over 25°C.
ELECTRICAL CHARACTERISTICS
AC CHARACTERISTICS (When not specified otherwise, VCC= 12V, Ta =25°C)
CHARACTERISTIC SYMBOL TCEET TEST CONDITION MIN. TYP. MAX. UNIT
Power Supply Current ICC - Vcc-- 12V 50 65 85 mA
TV Input Dynamic Range VTV - (Note 1) 5.0 7.0 - Vp-p
Maximum Gain Gm - (Note 2) 1.0 3.0 5.0 dB
Gain Variable Width Gr - (Note 3) 10 12 13 dB
Cutoff Control Variable Range AVCUT - (Note 4) 1.5 2.0 - V
Cutoff Control Control Sensitivity M: - (Note 5) -0.4 -0.7 -1.0
TV Frequency Characteristics fTV - (Note 6) 10 15 - MHz
Crosstalk Between Channels CpTV - (Note 7) - -50 -40 dB
Horizontal Blanking Detection Level VHBLK - (Note 8) 1.5 1.7 1.9 V
Vertical Blanking Detection Level VVBLK - (Note 9) 4.0 5.0 6.0 V
Output Blanking Level VOL - (Note 10) - 1.0 1.5 V
Black Detection Voltage VB 0.4 0.55 0.7
. . - (Note 11) V
White Detection Voltage vw 4.0 5.0 6.0
Bléck Detection Level Temperature AVB/AT - 0 i1
Drift 0
White Detection Level Temperature AV/AT - (Note 12) - 0 i2 mV/ C
Difference In Black Detection Voltage AVB - 0 AIO
Between Channels
Difference in White Detection Voltage AV - (Note 13) - 0 + 100 mV
Between Channels W -
Output Voltage Vertical Interval Sag vos - 0 i 100
Difference in Vertical Interval Sa - (Note 14) mV
between Channels g AVOS - 0 i50
1997-06-02 6/24
TOSHIBA TA8751AN
CHARACTERISTIC SYMBOL CIR- TEST CONDITION MIN. TYP. MAX. UNIT
T1, T2 Pulse Output Voltage VTO - (Note 15) - 0 0.3 V
guggut Voltage when Service Switch VSV - (Note 16) 2.6 3.1 3.6
Soft Start Detection Voltage I/SS - (Note 17) 0.8 0.9 1.0 V
TV-imc Crosstalk CPTVTX - (Note 18) - - 50 -40 dB
Output DC Voltage VOUT - (Note 19) 2.5 3.0 3.5 V
Dependence of Black Detection Level VBVcc - 0 10 mV
on VCC (Note 20)
Dependence of White Detection Level V 0 0.1 V
on VCC WVcc .
. . . Atv1 - 0 200
- Note 21
Vertical Blanking Delay Time Atvz ( ) - 0 200 ns
. . . AtH1 - 0 200
- Note 22
Horizontal Blanking Delay Time MHZ ( ) - 0 200 ns
TEXT Maximum Gain GTXM - (Note 23) 7.0 9.0 10.0 dB
TEXT Contrast Variable Width GRTX - (Note 24) 8.0 9.5 11.0 dB
TEXT Bright Voltage VTXB - (Note 25) 5.4 6.4 7.4 V
TEXT Contrast Voltage VTXC - (Note 26) 5.4 6.0 6.6 V
TEXT Frequency Characteristics fTX - (Note 27) 10 15 - MHz
Gate Input Detection Level VGT - (Note 28) 1.1 1.4 1.7 V
TEXT Crosstalk Between Channels CpTX - (Note 29) - -50 -40 dB
TEXT-YTV Crosstalk CPTXTV - (Note 30) - - 50 -40 dB
TEXT Bright Variable Width AVTXB - (Note 31) - 3.0 - V
TEXT, TC Differential Voltage Change AVde-f - (Note 32) -50 0 50 mV
TEXT RGB Relative Gain Differential AGV - (Note 33) - 1.0 0 1.0 dB
TV/TEXT Switching Level VYS - (Note 34) 0.4 0.7 1.0 V
TV-9TEXT Switching Delay Time tpTD - 20 100
TV-imc Switching Delay Time 3-
Color Differential AtpTD (N t 35) 0 '25
TEXT-YTV Switching Delay Time tpDT - o e - 20 100 ns
TEXT-m/ Switching Delay Time 3-
Color Differential AtpDT 0 LF25
1997-06-02 7/24
1997-06-02 8/24
TEST CONDITIONS
NOTE CHARACTERISTIC
TEST CONDITIONS Vcc=12V, Ta = 25 i1°C
SW 8: VR MODE
Sin Sss
TEST METHOD
1 TV Input Dynamic
ON OFF
Cutoff filter voltage Vc: 6.5V,
Drive filter voltage VD=6.0V
Measure RGB output voltage when TV input voltage is varied
from 0V to Vcc.
RGB output
VTV‘; VTvz Vin
With the maximum change in RGB output voltage is 100%,
VTV1 is when the change is 10% and VTvz is when the change
is 90%.
VTV=VTV2 —VTv1 (V)
2 Maximum Gain
ON OFF
VD=12V, vc= 6.5V, Vin: 6V
Input 0.5Vp.p, SOOkHz signal from TV input.
Measure RGB output signal amplitude Vout-
Gm = 20609 10 — (dB)
0-5Vp—p
3 Gain Variable
ON OFF
Vc=6.5V, Vin: 5v
Input 0.5Vp.p, 500kHz signal from TV input.
Vmin is defined as the RGB output signal amplitude when
VD=OV, and Vmax is defined as the RGB output signal
amplitude when VD = 12V.
Gr = 20609 10 -— (d8)
TA8751AN — 8
TOSHIBA
TA8751AN
1997-06-02 9/24
CHARACTERISTIC
TEST CONDITIONS Vcc = 12V, Ta : 25 i1°C
SW 8: VR MODE
Sn Sss
TEST METHOD
Cutoff Control
Variable Range
ON OFF
Vin = 6V, VD = 6V
Vomax is defined as the output DC voltage when VC=0V
Vomin is defined as the output DC voltage when Vc=12V
AVCUT = Vomax — Vomin (V)
Cutoff Control
Control Gain
ON OFF
wn=6v,vo=6v
V1 is defined as the output DC voltage when Vc: 5.5V
V2 is defined as the output DC voltage when Vc=6.5V
TV Frequency
Characteristics
ON OFF
Vc: 6.5V, VD=6V, Vin= 6V
The output level when a 1.0Vp.p, SOOkHz signal is input from
TV input is OdB.
Measure the 3dB band.
Crosstalk Between
Channels
ON OFF
VC 2 6.5V, V0 2 6V, Vin = 6V
The R output level when a 1.0Vp.p, SOOkHz signal is input from
TV’s R input is OdB.
Measure crosstalk to G and B channels.
Horizontal
Blanking
Detection Level
ON OFF
Vc=65V,VD=6V,Wn=3V
Vary the peak value of the horizontal blanking pulse and
measure the levels at which V1, V2 pulses are generated in the
output. ‘
TA8751AN - 9
TOSHIBA
TA8751AN
CHARACTERISTIC
TEST CONDITlONS Vcc:12V, Ta: 25 i 1°C
SW 8: VR MODE
55 Ssv SHBL SVBL
TEST METHOD
Vertical Blanking
Detection Level
OFF OFF ON ON
(1) Vc=6.5V, VD=6V, vin=3v
(2) Vary the peak value of the vertical blanking pulse and measure
the levels at which V1, V2 pulses are generated in the output.
Output Blanking
OFF OFF ON ON
(1) vc= 6.5V, VD=6V, Vin = 3v
(2) Measure the level of blanking pulse that appears in output.
Black Detection
Voltage
White Detection
Voltage
ON OFF ON ON
(1) Vin: 3.0V
(2) Measure T1, T2 pulse level at sense pins.
Black Detection
Voltage
Temperature Drift
White Detection
Voltage
Temperature Drift
0N OFF ON ON
(1) Vin=3.0V
(2) Measure temperature drift in black detection voltage level and
white detection voltage level when Ta is varied from —
20~70°C.
TA8751AN — 10
TOSHIBA
TA8751AN
CHARACTERISTIC
TEST CONDlTIONS VCC: 12V, Ta = 25 i1°C
SW & VR MODE
55 Ssv SHBL SVBL
TEST METHOD
Difference in
Black Detection
Voltage Between
Channels
Difference in
White Detection
Voltage Between
Channels
ON OFF ON ON
(1) Vin = 3.0V
(2) Measure voltage differential between RGB channels of T1, T2
pulse levels at sense pins.
Output Voltage
Vertical Interval
Differentia! in
Vertical Interval
Sag Between
Channels
ON OFF ON ON
(1) Vin = 3.0V
(2) Observe measurement pin TRO waveform using an oscilloscope.
(3) Measure vertical interval sag V05 of output waveform.
(4) Observe T60 and T30 in the same way.
(5) Observe waveforms of TRO, T60 and T30 simultaneously using
an oscilloscope, and observe the difference in vertical sag
between channels.
T1, T2 Pulse
Output Voltage
ON OFF ON ON
(1) Observe measurement pin TTO waveform using an oscilloscope.
(2) Measure the low level voltage of T1, T2 pulse that appears in
1 H H H
Output Voltage
when Service
Switch is on
OFF ON OFF OFF
(1) Vin=3.0V, Vc=6.5V, VD=6.0V
(2) Measure TRo voltage.
(3) Measure TGO, TRO voltage in the same way.
TA8751AN - 11
TOSHIBA
TA8751AN
CHARACTERISTIC
TEST CONDITIONS Vcc= 12V, Ta = 25 i1°C
SW & VR MODE
55 Ssv SHBL SVBL
TEST METHOD
Soft Start
Detection Voltage
ON OFF ON ON
(1) Vin=3.0V
(2) Observe T1, T2 pulse that appears in RGB output, and while
increasing V5 from 0V, observe V5 when the T1, T2 pulse
fluctuates.
TV—>TEXT
Crosstal k
OFF OFF OFF
Vin = 6.0V, VD = 6.0V, Vc = 6.5V
Input a 1.0Vp_p, SOOkHz signal from the TV input.
The output signal level when SYS is a is defined as OdB.
Measure the output signal levei when Sys is b.
Output DC
Voltage
OFF OFF OFF
Vin = 3.0V, VD = 6.0V, Vc= 6.5V
Measure DC voltage of R68 output pin.
Dependence of
Black Detection
Level on Vcc
Dependence of
White Detection
Level on Vcc
ON OFF ON ON
Vin = 3.0V
Measure fluctuations in the T1, T2 pulse level that occur in the
measurement pin TRs when Vcc is varied from 11~13V.
Make measurements for T65 and T55 in the same way.
Vertical Blanking
Delay Time
OFF ON ON
Vin = 3.0V, VD = 6.0V, V: = 6.5V
Measure the input waveform of pin 18’s vertical blanking.
Measure the vertical blanking pulse that appears in TRO.
(4) Make measurements for T60 and T30 in the same way.
_ Pin 18
Atw Atvz
TA8751AN - 12
TOSHIBA
TA8751AN
CHARACTERISTIC
TEST CONDITIONS Vcc: 12V, Ta :25 11°C
SW & VR MODE
TEST METHOD
Horizontal
Blanking Delay
(1) vin=3.ov, VD=6_0V, Vc=6.5V
(2) Measure horizontal blanking input waveform of pin 13.
(3) Measure the horizontal blanking pulse that appears in TRo.
(4) Make measurements for T60 and T30 in the same way.
Arm I LAtHz
TEXT Maximum
(1) Vin = 3.0V, VBR = 64V
VC = 6.5V, VD : 6V0V, VCONT : 12V
(2) Input a SOOkHz, 0.5Vp_p signal at TEXT input.
(3) Input clamp pulse at pin 11.
(4) Measure signal pulse width V0 of RGB output.
(5) GTXM = 20609 V—o (dB)
TA875‘IAN - 13
TOSHIBA
TA8751AN
NOTE CHARACTERISTIC
TEST CONDITIONS VCC = 12V, Ta = 25 i1°C
SW & VR MODE
TEST METHOD
24 TEXT Contrast
Variable Width
Vin = 3.0V, VBR : 5.4V
Vc= 6.5V, VD = 6.0V
Input a SOOkHz, 0.5Vp.p signal at TEXT input.
Input clamp pulse at pin11.
V01 is defined as the output signal amplitude when
VCQNT=OV V02 is defined as the output signal amplitude
when VCONT=1ZV.
02 20609 Ema)
0.5V 0.5V
G RTX = 20609
25 TEXT Bright
Voltage
Vin = 3.0V, VCONT = OPEN
VC : 5.5V, VD = 5.0V
Input clamp pulse at pin11.
Measure the VBR where the black level voltage for TV mode
and TEXT mode is the same when switching between TV/TEXT.
26 TEXT Contrast
Voltage
Measure voltage when pin9 is open.
27 TEXT Frequency
Characteristics
Vin = 3.0V, VBR = 6.4V
vc = 6.5V, VD = 6.0V, VCQNT = OPEN
Input a 500kHz, 0.5Vp_p signal at TEXT input
Input clamp pulse at pin11_
The output signal level is OdB at this time.
Increase signal frequency and measure the input signal
frequency at — 3dB.
TA8751AN — 14
TOSHIBA
TA8751AN
CHARACTERISTIC
TEST CONDITIONS Vcc: 12V, Ta: 25 i1°C
SW & VR MODE
TEST METHOD
Gate Input
Detection Level
Vin = 3.0V, VCONT = OPEN
VBR=6AV,VC=65V,VD=60v
Observe DC voltage at TEXT input pin.
Increase input voltage V11 at pin 11 from 0V and measure the
V11 when DC voltage at the TEXT input pin changes from low
to high.
Crosstalk Between
TEXT Channels
Vin=3.0V, VCQNT=OPEN
VBR=GAV,VC=65V,VD=60V
Input clamp pulse at pin 11.
Input a SOOkHz, 0.5Vp.p signal at R input.
Measure G and B output levels when signal level at R output is
TEXT—)TV
Crosstalk
Vin = 3.0V, VCONT = OPEN
VBR = 6.4V, VC = 6.5V, VD = 6.0V
Input clamp pulse at pin11.
Input a SOOkHz, 0.5Vp_p signal at TEXT R input.
Signal level of R output is OdB.
Measure signal level of R output when Sys is a.
TEXT Bflght
Variable Width
Vin = 3.0V, VCONT = OPEN
VBR = 6.4V, Vc = 6.5V, VD: 6.0V
Input clamp pulse at pin 11.
Input a SOOkHz, 0.5Vp.p signal at TEXT R input.
Measure change in output DC voltage when VBR is changed
from 0V to 12V.
TA8751AN — 1 5
TOSHIBA
TA8751AN
CHARACTERISTIC
TEST CONDITIONS VCC = 12V, Ta = 25 i 1°C
SW & VR MODE
55 55v SHBL SVBL
TEST METHOD
Change in TEXT,
TV Differential
Voltage
OFF OFF ON ON
Vin = 3.0V, VD = 6.0V
VC = 675V
Input clamp pulse at pin11.
Adjust VBR and black level of TV/TEXT.
Measure the change in the black level of the TEXT Signal when
VCONT is changed from 0~12V.
TEXT RGB Relative
Gain Differential
OFF OFF ON ON
Vin = 3.0V, VCONT = OPEN
VBR = 6.4V, Vc: 6.0V, VD = 6.5V
Input clamp pulse at pin11.
Input a SOOkHz, 0.5Vp.p signal at TEXT input.
no gain. Measure RGB 3-coIor differential.
TV / TEXT
Switching Level
OFF OFF ON ON
Vin = 3.0V, VCONT : OPEN
V3R= 6.4V, vc= 6.0V, VD: 6.5V
Input clamp pulse at pin11.
Input a SOOkHz, 05pr signal at TEXT input.
Change V12 from O~2V, and measure V12 when the output
signal changes from TV—)TEXT.
TA8751AN - 16
TOSHIBA
TA8751AN
CHARACTERISTIC
TEST CONDITIONS Vcc: 12V, Ta : 25 t1°C
SW & VR MODE
55 55v SHBL SVBL
TEST METHOD
Sin Sss 5Y5
TV—)TEXT
Switching Delay
TV—>TEXT
Switching Delay
Time 3-Color
Differential
TEXT-)TV
Switching Delay
TEXT—)TV
Switching Delay
Time 3-Color
Differential
OFF OFF ON ON
ON OFF — (1) Vin:3.0V, VCQNT=OPEN , VBR=6.4V
(2) Input the signal shown below at pin 11.
5n; 40/45 5ns
2V 50%
thTD tpm
(3) Observe RGB output and measure tpTD. tpm'.
TA8751AN — 17
TOSHIBA
TA8751AN
Horizontal
blanking
TEXT R
TEXT G
TEXT 8
Contrast
Brightness
Clamp pulse
Y5 input
Horizontal
blanking input
Reference
pulse output
R output
R cutoff
filter
R drive
filter
R sense
G output
G Cutoff
filter
G drive
filter
6 sense
B output
8 cutoff
8 drive
filter
3 sense
Vertical
blanking
Soft start
Service
switch
(ith a 68
00/0 m l/O n,
a 63 (Q cn
0.01M:
blanking
Vertical
TEST CIRCUIT
TOSHIBA
TA8751AN
TOSHIBA TA8751AN
CRT DRIVE DESIGN METHOD
1. Initialization
AKB (AUTOMATIC KINE BIAS) Circuits take the previously complex adjustment of CRT drive
circuits and automates by absorbing the 3-color dispersion of the CRT. It is therefore
necessary to design the CRT drive circuit in an AKB centered state to allow efficient
absorption of the CRT's dispersion.
The primary color input on the TV side takes the form of DC coupling, so please set input
levels so that the contrast control and brightness control in previous stages are under the
following conditions in the center.
_-------- 3.0V
----------- 1.5V
Cutoff control and drive control characteristics are shown in Fig.1 and Fig.2 respectively.
Please forcibly center the AKB cutoff filter voltage and drive filter voltage using the external
power supply. The I/O characteristics for TA8751AN when the various filter pins are centered
(CUTOFF : 4.5V, DRIVE : 5.5V) are shown in Fig.3.
Please leave the AKB sense pins OPEN at this time.
2. Design of CRT drive circuit
The basic structure of the CRT drive circuit is shown in Fig.4.
Drive circuit gain : G is defined by the formula :
G-- .........
(R1//R2)
R2 mainly determines gain, while R1 mainly determines the operating voltage of the load
side. Taking the signal amplitude required at the CRT cathode vc Np-p), RGB output signal
amplitude vo is determined by initialization, so the gain necessary for the CRT drive circuit is
determined by itself.
G = V_c
And so
vc - Rd
W - (R1//R2)
G is defined by the set.
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TOSHIBA TA8751AN
Next the black level is set. Turn the AKB's service switch on. T1 pulse level is output from the
AKB. Taking that voltage as vo and the cathode voltage set as Vd,
V -V V -2V -V
Vd=+B_Rdx< O f + O f " ......... (2)
In order that the black level is not crushed by bright control, a value for vo that satisfies the
following equation should be chosen.
VO>VX+2Vf
Note : When the service switch is on, please supply the cutoff filter with a center voltage
from the external power supply.
The unknowns in equations (1) and (2) are Rd, R1 and R2. When Rd is selected using
frequency characteristics, R1 and R2 are determined by the above equations.
G=24, V0=3.2V, Vx=0.5V, Vd = 140V
when Rd =15kQ, + B = 180V, Vf=0.7V
R1=2k0 and R2=9100
3. Setting sensing resistance
Sensing resistance RS is set for the CRT drive circuit set in 2.
Fig.5 shows CRT drive amplifier characteristics and CRT characteristics.
When there is a T1 pulse in the AKB circuit, current lk1 that flows to the CRT results in
feedback so that the voltage generated in Rs is 0.5V. Therefore,
RS-- ......... (3)
In the same way, when there is a T2 pulse in the AKB circuit, current K2 that flows to the
CRT results in feedback so that the voltage generated in RS is 0.5V, so
lk1 and lkz are determined when setting the CRT drive circuit in 2, so a value for Rs is
selected that satisfies equations (3) and (4).
Note : Please make selection giving priority to equation (4).
4. Soft start circuit
When power is turned on with the CRT in a cooled state, current does not flow to the
sensing resistance until the CRT warms up, so the AKB tries to start at DC level shift Max and
the screen starts from the white side.
The soft start circuit reduces this, and when the soft start pin has a T1 pulse interval of 0.9V
or more, works to control the DC level shift circuit to the Min side.
The T1 pulse level l/SS at the RGB output pin that turns soft start on is
0.9V - VSS-2Vf-Vx + Vcc-uf-Vx
RSS R2 Rx
0.9V V -V -V
"s/ss-ic-rl/CC-lf-l/x f X)R2+2Vf+VX
RSS Rx
Please set RX and RSS to satisfy the conditions above.
1997-06-02 20/24
TOSHIBA
OUTPUT VOLTAGE (V)
OUTPUT V0 LTAGE
Fig.1 Cutoff control characteristics
DRIVE FILTER VOLTAGE = 5.5V
INPUT VOLTAGE = 3.0V
Vcc= 12V
2 4 6 8 10 12
CUTOFF FILTER VOLTAGE (V)
Fig.3 l/O characteristics
CUTOFF FILTER VOLTAGE = 4.5V
DRIVE FILTER VOLTAGE = 5.5V
Vcc=12V
2 4 6 8 IO 12
INPUT VOLTAGE (V)
TA8751AN
Fig.2 Drive control characteristics
CUTOFF FILTER VOLTAGE
INPUT VOLTAGE = 2-0Vp-p
(10kHz, 5V CENTER)
Vcc=12V
2 4 6 8 10 12
DRIVE FILTER VOLTAGE (V)
1997-06-02 21/24
TOSHIBA
TA8751AN
TA8751AN RGB output
Soft start
Fig.4 Basic st
CRT drive amplifier characteristics
ructure of CRT drive circuit
CRT characteristics
i VT1 i VT2
i Vertical interval
V IKl R2 R
RGB output signal
Fig.5 CRT drive amplifier characteristics and CRT characteristics
1997-06-02 22/24
ICC = 68mA
Vcc-- 12V
CRT drive
O+B180v
1997-06-02 23/24
blanking
To V/C/DIC
0) Q) Q3) O.) (5) 96) C.)
TEXT R
TEXT G
TEXT B
Contrast
Brightn ess
Clam p pulse
Y5 input
Horizontal
blanking input
Reference
pulse output
R output
R cutoff
filter
R drive
filter
R sense
G output
6 cutoff
filter
G drive
filter
G sense
8 output
8 cutoff
8 drive
filter
B sense
Vertical
blanking
Soft start
Service
switch
CRT drive
CRT drive
CRT drive
Vertical blanking
APPLICATION CIRCUIT
TOSHIBA
TA8751AN
Tt9SFlliBA TA8751AN
OUTLINE DRAWING
SDlP30-P-400-1.78 Unit : mm
F-lr-lf-lr-ll-Irrelevant'""-)'-'!.""]?-]
L-lt-lt-ll-lt-ll-lt-lt-lt-lt-lt-ll-lL-lt-lL-d
0.4 5°
Nubian
27.4M.2
th.', 3.--
n , mu. m
'3. 4.
a' co.
m if:-,',
ll 'C'; ei
1.254TYP l I 1.0:K.1 I , 0.46t0.1 SEaiti4
l .778
Weight : 1.99g (Typ.)
1997-06-02 24124
www.ic-phoenix.com
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