4. AUX Input (pin 16)
The pin 16 is for input terminal of AUX
The total gain is 0dB by using of AUX amplifier.
Therefore, the µ-COM can directly drive the
BEEP sound or voice synthesizer signal can be
input to pin 16 directly.
When AUX function is not used, this pin must be
connected to PRE-GND (pin 13) via a capacitor.
Figure 6 AUX Input
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 4)
The speaker impedance 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 4 Ω
Operating point of protector
About 1 Ω 4 Ω
Note 4: It is appeared by biased input DC voltage
(for example, large leakage of the input capacitor, short-circuit between copper patterns of PCB.)