Datenblatt-Suchmaschine für elektronische Bauteile |
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TDA2052 Datenblatt(PDF) 9 Page - STMicroelectronics |
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TDA2052 Datenblatt(HTML) 9 Page - STMicroelectronics |
9 / 14 page SHORT-CIRCUIT PROTECTION The TDA 2052 has an original circuit which pro- tects the device during accidental short-circuit be- tween output and GND / -Vs / +Vs, taking it in STAND-BY mode, so limiting also dangerous DC current flowing throught the loudspeaker. If a short-circuit or an overload dangerous for the final transistors are detected, the concerned SOA circuit sends out a signal to the latching circuit (with a 10 µs delay time that prevents fast random spikes from inadvertently shutting the amplifier off) which makes Q1 and Q2 saturate (see Block Diagram). Q1 immediately short-circuits to ground the A point turning the final stage off while Q2 short-circuits to ground the external capacitor driving the pin 3 (Mute/Stand-by) towards zero potential. Only when the pin 3 voltage becomes lower than 1V, the latching circuit is allowed to reset itself and restart the amplifier, provided that the short- circuit condition has been removed. In fact, a win- dow comparator is present at the output and it is aimed at preventing the amplifier from restarting if the output voltage is lower than 0.35 Total Supply Voltage or higher than 0.65 Total Supply Voltage. If the output voltage lies between these two thresholds, one may reasonably suppose the short-circuit has been removed and the amplifier may start operating again. The PLAY/MUTE/STAND-BY function pin (pin 3) is both ground- and positive supply-compatible and can be interfaced by means of the R5, C3 net either to a TTL or CMOS output ( µ-Processor) or to a specific application circuit. The R5, C3 net is fundamental, because connect- ing this pin directly to a low output impedance driver such as TTL gate would prevent the correct operation during a short-circuit. Actually a final stage overload turns on the protection latching circuit that makes Q2 try to drive the pin 3 voltage under 0.8 V. Since the maximum current this pin can stand is 3 mA, one must make sure the fol- lowing condition is met: R5 ≥ (VA − 0.7V) 3mA that yields: R5, min = 1.5 K Ω with VA=5V. In order to prevent pop-on and -off transients, it is advisable to calculate the C3, R5 net in such a way that the STAND-BY/MUTE and MUTE/PLAY threshold crossing slope (positive at the turn-on and vice-versa) is less than 100 V/sec. Figure 16: Thermal Protection Block Diagram THERMAL PROTECTION The thermal protection operates on the 125 µA current generator, linearly decreasing its value from 90 °C on. By doing this, the A voltage slowly decreases thus switching the amplifier first to MUTE (at 145 °C) and then to STAND-BY (155 °C). Figure 17: Maximum Allowable Power Dissipa- tion vs. Ambient Temperature. The maximum allowable power dissipation de- pends on the size of the external heatsink (ther- mal resistance case-ambient); figure 17 shows the dissipable power as a function of ambient temperature for different thermal resistance. TDA2052 9/14 |
Ähnliche Teilenummer - TDA2052 |
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Ähnliche Beschreibung - TDA2052 |
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