ROHM FAQ

FAQ's
  • For BD3491FS,
    Please explain the setting values for R1, C1, C2, and C.
    Are there MAX resistance, capacitance values, etc.?
    •  For the BASS setting, a larger value of R1 will result to a lower value of Boost/Cut gain. At 8dB gain setting, the value will be about 7.95dB for R1=4.7kΩ and about 6.73dB for R1=8.2kΩ.
       For the TREBLE setting, it can be calculated by using fc=1/(2*π*C*R3). At 8dB gain setting, fc=about 17kHz for C=820pF, and fc=about 9.5kHz for C=1500pF.
       There are no restrictions on the MAX resistance and capacitance values. However, for the BASS filter, if the capacitance is extremely large (e.g., 100 μF), it may take a long time for the bias voltage (operating point) to stabilize when the power supply is turned on, and it also may take time for the capacitance to discharge when the power supply is turned off. (Since R3 = 0 at power-on, the capacitance charge/discharge time will not be a problem. However, if the gain is changed immediately after power-on, the operating point will stabilize in the time determined by the values of R3 and C1, C2, and R1.)
       For the TREBLE filter, the operating point is stabilized in the time determined by 29.1 kΩ and the capacitance after the power is turned on. If the capacitance is extremely large (e.g., 100 μF), please check the time required for the operating point to stabilize.
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