TDA8140 Datasheet, PDF (7/10 Pages) STMicroelectronics – HORIZONTAL DEFLECTION POWER DRIVER

TDA8140
CIRCUIT DESCRIPTION
Figure 7 shows the block diagram of the TDA8140,
the circuit consists of an input transconductance
amplifier composed by Q1, Q2, Q3 and Q4.
The symmetrical output current is fed into the load
resistor R1 and R2 ; the two amplifiers V1 and V2
realize a floating voltage to current converter which
can drive 1.2A sink current and 2A source current
for a wide common output range.
So, the overall transconductance results into :
gm
=
R1 + R2
R3
⋅
1
R5
A current source I1 generates a drop of 70mV
across the resistor R4 which provides an output
bias current of 140mA ; the control input determines
the turn ON/OFF function.
In the ON phase, Q5 shorts the external capacitor
Ct. Within the input voltage range 0 < Vin < 750mV
the element realizes the transconductance func-
tion ; lower voltages are clamped by the D1/Q6
configuration.
For input voltages higher than 750mV, Q7 limits the
maximum output current at 1.5A peak.
In the turn-OFF mode, Ct will be charged by the
controlled source I2 which is proportional to the
input voltage, by this way, the output current de-
creases quasi linearly and the system stability is
reached.
During the flyback phase, the IC is disabled via the
sync. detector input ; this function with the limited
sink and source current together with the undervol-
tage turn-OFF and a chip temperature sensor en-
sure a complete protection of the IC.
In Figure 8 is shown the application diagram of the
TDA 8140, the few external component and the
automatic handling possibility ensures a lower ap-
plication cost versus the conventional approach
shown in Figure 4.
In Figure 9 is shown the currents and voltages
waveforms of the driver circuit of Figure 8, as to be
seen, the driving charge Ib ⋅ ton has been reduced
at minimum.
Figure 7 : Block Diagram of the Integrated Horizontal Driver
PROTECTION
AND REMOTE ⁸
STANDBY INPUT
VOLTAGE
CONTROL
VC < 7V
&
OVERTEMP.
PROTECTION
Tj < 150˚C
Q9
V1
V2
INPUT
TRANSCONDUCTANCE
R1
R2
AMPLIFIER
Q10
R5
Q11
2
V_C
+
C
CONTROL ₇
INPUT
SPECIAL
REMOTE ⁶
STANDBY
I₂
&
Q5
Q3
Q4
R3
I_{1 Q6}
D1
Q2
Q1
Q7
D2
R4
R6
V_REF = 750mV
V_IN
Q8
I_B
1
OUTPUT
3 ^SENSE
INPUT
5
C _{EX T}
C_T
9 10 11 12 13 14 15 16
POWER GROUND
4
SENSE
GROUND
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