TA8275 Просмотр технического описания (PDF) - Toshiba
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TA8275 Datasheet PDF : 13 Pages
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TA8275H
5.3 Prevention of speaker burning accident (In Case of Rare Short Circuit of Speaker)
When the direct current resistance between OUT+ and OUT- terminal
becomes 1 ohm or less and output current over 4A flows, this IC makes a protection circuit operate
and suppresses the current into a speaker.
This system makes the burning accident of the speaker prevent as below mechanism.
<The guess mechanism of a burning accident of the speaker>
Abnormal output offset voltage (voltage between OUT+ and OUT-) over 4V is made by the external
circuit failure.(Note1)
¯
The speaker impedance becomes 1 ohm or less as it is in a rare short circuit condition.
¯
The current more than 4A flows into the speaker and the speaker is burned.
Current into a speaker
Less than 4 W
Operating point of protector
About 1 W 4 W
Figure 9
Speaker impedance
Note 1: it is appeared by biased input DC voltage
(for example, large leakage of the input capacitor, short-circuit between copper patterns of PCB.)
5.4 Application
When output terminals short-circuit to Vcc or GND, the voltage of 25pin is fixed to “L”.
And when shorting OUT+ to OUT-, “L” and “H” are switched according to an input signal.
Therefore, it is possible to judge how the power IC condition is if a micro-controller detects the
25pin voltage that is smoothed out with LPF.
It is recommend that the threshold voltage(Vth) is set up as higher as possible because output level
of LPF is changed according to an input signal.
(for example, Vth is set up to 4V if 25pin is pulled up to 5V line.)
Output voltage of L.P.F.
Operating point of protector
5V
Figure 10
6
Output power
2002-02-13
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