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TDA8140 Datasheet(PDF) 7 Page - STMicroelectronics |
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TDA8140 Datasheet(HTML) 7 Page - STMicroelectronics |
7 / 10 page 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. & C VOLTAGE CONTROL V < 7V j OVERTEMP. PROTECTION T < 150˚C & 8 7 6 5 4 3 1 2 9 101112 13141516 Q9 V1 R2 R1 INPUT TRANSCONDUCTANCE AMPLIFIER V2 Q10 Q11 R5 D2 Q7 Q6 R4 D1 Q1 Q4 Q3 R3 Q8 R6 Q2 Q5 I 1 I 2 REF IN V V = 750mV OUTPUT I B SENSE INPUT V + CC PROTECTION AND REMOTE STANDBY INPUT CONTROL INPUT SPECIAL REMOTE STANDBY POWER GROUND SENSE GROUND C EXT C T Figure 7 : Block Diagram of the Integrated Horizontal Driver TDA8140 7/10 |
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