ymf795 Yamatake Corporation, ymf795 Datasheet - Page 32

• Manufacturer Part Number: ymf795
• Description: Apl-2 Automobile Sound Player-2
• Manufacturer: Yamatake Corporation

Warning for short circuit at speaker pins
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.
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.
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.
3. Provision of a thermal shutdown circuit in the speaker amplifier section.
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
- Warning to customers of risk that may be caused by a short circuit of the speaker amplifier output.
1. Don’t select settings (sound creation) which may generate DC signal.
2. Add the equivalent of DC cut digital filter for cutting DC signal into a digital section.
3. Add a DC cut capacitor for cutting DC signal into an analog section.
4. When a latter stage device exists in the signal path from this device to speaker, be sure to realize the DC cut is
(This device does not have the circuit)
(This device does not have the circuit)
bridge is present.
(As long as “Built-in” is not mentioned in the manual, there is no such built-in circuit inside of a device).
(When addition is specified in the example of a recommended circuit diagram, be sure to add)
realized in a latter stage device.
(Since thoroughness of this preventive measure is generally difficult, we recommend the combined use with
the following 2, 3, and 4)
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YMF795