Technical Note
7/21
BD5471MUV
www.rohm.com
2010.06 - Rev.A
© 2010 ROHM Co., Ltd. All rights reserved.
●Evaluation board Parts List
Qty. Item Description SMD Size Manufacturer/Part Number
1 C1 Capacitor, 0.01μF 1608
Murata
GRM188R71C103KA01D
1 C2 Capacitor, 2.2μF 1608
Murata
GRM188R61C225KE15D
2 C3, C4,C6,C7 Capacitor, 0.1μF 1608
Murata
GRM188R71C104KA01D
1 C5, C8 Capacitor, 10μF A (3216)
ROHM
TCFGA1A106M8R
1 U1
IC, BD5471MUV,
Stereo Class-D audio
amplifier
4.0mm X 4.0mm
VQFN Package
ROHM
BD5471MUV
1 PCB1
Printed-circuit board,
BD5471MUV EVM
― ―
●The relation in the gain setting and input impedance Ri
The gain setting terminal (G0,G1)
G0 G1 Gain[dB] Ri [Ohm]
L L 6 90k
L H 12 60k
H L 18 36k
H H 24 20k
●Description of External parts
①Power down timing capacitor (C1)
It’s the capacitor which adjusts time from BEEP signal stop to amplifier stop.
Turn off time Toff is set the following formula.
②Regulator output capacitor(C2)
Output capacitor of 3.3V regulator.
Use capacitance equal to or more than 1uF.
③Input coupling capacitor Ci (C3,C4, C6,C7)
It makes an Input coupling capacitor 0.1uF.
Input impedance Ri in each gain setting becomes the above table.
In 18dB gain setting, it is Ri=36kΩ(Typ.).
It sets cutoff frequency fc by the following formula by input coupling capacitor Ci (C3,C4, C6,C7) and input impedance Ri
In case of Ri=36kΩ, Ci=0.1uF, it becomes fc=about 44Hz.
④The power decoupling capacitor (C5,C8)
It makes a power decoupling capacitor 10uF.
When making capacitance of the power decoupling capacitor small, there is an influence in the Audio characteristic.
When making small, careful for the Audio characteristic at the actual application.
[Hz]
CiRi2π
1
fc
[ms]
5
VDDC1
Toff
μ
8.0
