YDA135 Datasheet, PDF (10/22 Pages) YAMAHA CORPORATION – STEREO 5W-20W DIGITAL AUDIO POWER AMPLIFIER CONTROLLER

YDA135
Selection of Power MOSFET
Power MOSFET can be selected on the user side within the range of the absolute maximum rating.
When selecting Power MOSFET, take note of the following matters.
・The drain side voltage may be twice the maximum power supply voltage due to the counter electromotive force
developed in the inductive load.
When VDDP=12V, use Power MOSFET of which withstand voltage VDS is 30V or higher.
・For the gate voltage, the voltage VDDP is applied. Therefore, use Power MOSFET of which withstand voltage VGS
is 20V or higher.
・Due to the limitation of allowable power consumption of this IC, use Power MOSFET of which total input charges
(VDS=10V, VGS=10V) is 9 nC or less.
To prevent destruction of Power MOSFET caused by simultaneous turn-on of PMOS and NMOS of Power MOSFET,
off time such as the following "Power MOSFET output waveform and off time" can be set for Power MOSFET
depending on the resistor (RD) and capacitor (CD) that are connected to CDIL, CDIR, CDOL and CDOR terminals.
Connect a proper resistor (RD) and capacitor (CD) according the characteristics of Power MOSFET.
As the time constant is made smaller, off time becomes shorter. Adjust the off time so that the penetration current
does not flow through the Power MOSFET, as shorter off time can cause penetration current to flow.
As the time constant is made larger, off time becomes longer. Longer off time makes the margin from the moment of
simultaneous turn on of the Power MOSFET larger, but at the same time, the distortion characteristic changes for the
worse.
Off time
Off time
HP_L (HP_R)
LP_L (LP_R)
HN_L (HN_R)
LN_L (LN_R)
Off time
Off time
Power MOSFET output waveform and off time
An indication of off time is in the range approximately from 10ns to 40ns. As an example, the relationship between
the resistance (RD) and off time is as described by the “Relationship between off time and resistance (RD)”
described below when the capacitance (CD) = 15pF.
Relationship between off time and resistance (RD) : (CD=15pF)
40.0
30.0
20.0
10.0
0.0
0
1
2
3
4
5
resistance(RD) (kΩ)
Selection of inductor for output filter
The cutoff frequency (fc) of the LC low pass filter that is connected to the output of the Power MOSFET can be
obtained by using the following formula.
To obtain an ideal frequency response, set the Q value of LCR resonance circuit to approximately 0.7.
fc(Hz) = 1/(2*π*√(Lo*Co))
Q = 1/RL*√(Lo/Co) =0.7
Typically, the one with the following value is used depending on the speaker impedance assuming that the cutoff
frequecy of 50kHz is used.
RL(Load impedance)
4Ω
8Ω
16Ω
Lo(Inductance)
10μH
22μH
39μH
Co(Capacitor)
1μF
0.47μF
0.27μF
The distortion factor and voice quality may be affected by the type of coil to be used. Select the best suited one
according to the response required.
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