YMF795 Datasheet, PDF (32/45 Pages) YAMAHA CORPORATION – APL-2 Automobile sound Player-2

YMF795
Warning for the device which makes sound through speaker
A speaker radiates heat in a voice-coil by air flow accompanying vibration of a diaphragm. When DC signal
(several Hz or less) is input, heat radiation characteristics falls rapidly.
In addition, even if it is used lower than the rated input, it may lead to voice-coil burnout, smoke, or ignition of a
speaker.
In order to avoid such situations, be sure to implement one or more preventive measures from the followings.
1. Don’t select settings (sound creation) which may generate DC signal.
(Since thoroughness of this preventive measure is generally difficult, we recommend the combined use with
the following 2, 3, and 4)
2. Add the equivalent of DC cut digital filter for cutting DC signal into a digital section.
(As long as “Built-in” is not mentioned in the manual, there is no such built-in circuit inside of a device).
3. Add a DC cut capacitor for cutting DC signal into an analog section.
(When addition is specified in the example of a recommended circuit diagram, be sure to add)
4. When a latter stage device exists in the signal path from this device to speaker, be sure to realize the DC cut is
realized in a latter stage device.
In addition, the above-mentioned measures are based on the assumption that the device itself, DC cut capacitor, and
a latter stage device will be in a normal operation. Therefore, it is also necessary to implement measures based on
the assumption of these part failures.
Warning for short circuit at speaker pins
Overcurrent breakdown, extraordinary heat, or package melting is caused if a short circuit is made between two
outputs, between output and power supply, and between output and Ground, because of high drive performance of
the speaker amplifier output.
In order to avoid such situations, be sure to implement one or more preventive measures from the followings.
1. Adoption of a power supply with overcurrent protection circuit for the speaker amplifier.
2. Provision of an overcurrent protection circuit in the speaker amplifier circuit.
(This device does not have the circuit)
3. Provision of a thermal shutdown circuit in the speaker amplifier section.
(This device does not have the circuit)
In addition, the above-mentioned measures are based on the assumption that overcurrent circuit or thermal
shutdown circuit will work normally. Therefore, it is also necessary to take measures based on the assumption of
these part failures.
Moreover, consider the followings as well.
- Design the board so that speaker amplifier output is not short-circuited easily even if foreign body or solder
bridge is present.
- Warning to customers of risk that may be caused by a short circuit of the speaker amplifier output.
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