TB2904 데이터 시트보기 (PDF) - Toshiba
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TB2904 Datasheet PDF : 16 Pages
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TB2904HQ(o)
5. 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 Ω or less and output
current over 4 A 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 4 V is made by the external
circuit failure.(Note 1)
↓
The speaker imepedance becomes 1 Ω or less as it is in a rare short circuit condition.
↓
The current more than 4 A flows into the speaker and the speaker is burned.
Current into a speaker
Less than 4A
Operating point of protector
About 1 Ω 4 Ω
Figure 8
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.)
6
2004-03-26
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