Technical Note
13/15
www.rohm.com
2010.10 - Rev.
© 2010 ROHM Co., Ltd. All rights reserved.
BD3870FS,BD3871FS,BD3872FS,BD3873FS
●Notes for use
1) Numbers and data in entries are representative design values and are not guaranteed values of the items.
2) Although ROHM is confident that the example application circuit reflects the best possible recommendations, be sure to
verify circuit characteristics for your particular application. Modification of constants for other externally connected circuits
may cause variations in both static and transient characteristics for external components as well as this Rohm IC. Allow for
sufficient margins when determining circuit constants.
3) Absolute maximum ratings
Use of the IC in excess of absolute maximum ratings, such as the applied voltage or operating temperature range (Topr),
may result in IC damage. Assumptions should not be made regarding the state of the IC (short mode or open mode) when
such damage is suffered. A physical safety measure, such as a fuse, should be implemented when using the IC at times
where the absolute maximum ratings may be exceeded.
4) GND potential
Ensure a minimum GND pin potential in all operating conditions. Make sure that no pins are at a voltage below the GND at
any time, regardless of whether it is a transient signal or not.
5) Thermal design
Perform thermal design, in which there are adequate margins, by taking into account the permissible dissipation (Pd) in
actual states of use.
6) Short circuit between terminals and erroneous mounting
Pay attention to the assembly direction of the ICs. Wrong mounting direction or shorts between terminals, GND, or other
components on the circuits, can damage the IC.
7) Operation in strong electromagnetic field
Using the ICs in a strong electromagnetic field can cause operation malfunction.
8) Power-ON RESET
A built-in circuit for performing initialization inside the IC at power-ON is provided. In unstable systems it is recommended
that the data shall be sent to all the addresses during power-ON, until this operation cycle is completed. Mute should be
applied during this cycle.
Function Initial Condition
Input Selector
Input A
Input Gain
0dB
Loud Speaker Equalizer (BD3872FS only)
OFF
Volume
-dB
Surround
OFF
Treble Gain
0dB
Bass Gain
0dB
9) 2-wire serial control
For the CL and DA terminals, the patterned and other wirings should be routed as not to cause interference with the
analog-signal-related lines.
10) Switching between functions
Shock sound is absorbed when switching between the volume, bass, and treble functions.
11) Input coupling capacitor
As described in the figure below, low frequency characteristics are determined depending on the external capacitor value
for input coupling, and the input impedance value inside the IC.
Fig.23 Fig.24
f
G
0
A (f)
C
R
A(f)
=
1+(2πfCR)
2
(2πfCR)
2
