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Audio ICs
Preset equalizer sound control (P.S.C) IC
BA3842F
The BA3842F is a preset graphic equalizer IC with dynamic bass boost which is designed for audio equipment. FApplications Mini-component stereos Micro-component stereos Radio cassette recorders with CD FFeatures 1) Includes preset equalizer function with five equalizer positions and a flat mode setting. 2) Built-in dynamic bass boost with gain settings from 0 to 20dB in steps of 5dB.
3) Low distortion and low noise. 4) Built-in dynamic bass boost and interlocked ALC (Auto Level Control).
FAbsolute maximum ratings (Ta = 25_C)
FRecommended operating conditions
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FBlock diagram
BA3842F
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FPin descriptions
BA3842F
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FInput / output circuits
BA3842F
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BA3842F
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BA3842F
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BA3842F
FElectrical characteristics (unless otherwise noted, Ta = 25_C, VCC = 10V, f = 1HZ, VIN = 200mVrms, preset equalizer normal : Rg = 620, during dynamic bass boost : RL = 10k)
Operating specifications Input and output signal pins are in phase.
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FReference values for application circuit example (unless otherwise noted, Ta = 25_C, VCC = 10V, FVIN = 200mVrms, preset equalizer normal : Rg = 620, during dynamic bass boost : RL= 10k)
BA3842F
Operating specifications Input and output signal pins are in phase.
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FMeasurement circuit
BA3842F
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FCircuit operation (1) Operating power supply voltage range Within the operating power supply voltage range, circuit functioning is guaranteed as long as the operating temperature range is not exceeded. However, verify carefully that the voltage, temperature, and component values are appropriate. (2) Control pins and control voltage settings (1) The DC control range is 0 V to VCC for the preset equalizer and the dynamic bass boost control pins (pins 18 and 19). Make sure that the voltage applied to these control pins does not exceed VCC. (2) Mode switch threshold values are determined by dividing resistors between VCC and GND of both the preset equalizer and bass boost. If the control voltages are divided from the supply voltage of the IC, they will have greater tolerance with respect to VCC fluctuations. (3) During mode switching, an abrupt change in the level of the DC output may occur, causing a sound. In this case, add the capacitor and resistor indicated in the application, or only the capacitor as needed. 4) Here is an example of determining the control pin voltage setting with the input of three values.
BA3842F
OUT 0V 1.3 V 3V 5V 7V 9V
C L L L L H H
B L L H H L L
A L H L H L H
L : 0V H : VCC
(3) Input coupling capacitors Note that the polarity of the input coupling capacitors will change depending on the DC voltage to which they are connected. Set capacitors based on the frequency band to be used, taking into consideration the fact that the input impedance is 50k. (4) Load resistances If the values of the load resistors are too small, the output gain and total harmonic distortion may fluctuate slightly. Take this into consideration when connecting the subsequent stage. (5) The dynamic bass boost filter is a multi feedback active filter which forms the B.P.F. FO can be changed with the C value. fO = 1 / [2 {(R1 / / R2) R3 C1 C2}1 / 2] Q = 1 / 2 {(R3 / (R1 / / R2)}1 / 2 HO = R3 / {R1 (1)C1 / C2)1 / 2} When R1 = 2.4k, R2 = 4.3k, R3 = 91k, and C1 = C2 = 0.22F, fO 61Hz Q 3.8 HO 19
Connect OUT to the control pin. Regarding the values of the various constants, it is important to consider current dissipation and other such problems. If such a problem should occur, change the constants and redesign the diode logic. If R1 and R2 are too small, the bass boost characteristics such as boost gain and crosstalk may change. Keep this in mind when setting filter values. Furthermore, design the application so that the bass boost level increments by 5dB from 5 to 20dB when HO = 19.
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(6) Filter for preset equalizer (1) Low band The low cutoff frequency fc of each mode is given by the following equation : fc = 1 / 2CR = 1 / (2 C 15.6k) When C = 0.22F, fc 46 (Hz) The fc value can be changed to make slight changes in the boost and cutoff gain of each mode. (2) High band The high cutoff frequencies fc of each mode are given by the following equation : fc = 1 / 2CR When C = 2200pF, ROCK : R = 8.0k fc 9.0 (kHz) JAZZ : R = 10.7k fc 6.8 (kHz) CLASSIC : R = 14.9k fc 4.8 (kHz) BGM. POP : R = 17.4k fc 4.2 (kHz) The fc values can be changed to make slight changes in the boost and cutoff gain of each mode. Note: If a high or low fc value is changed, the gains of all modes will change. The gain cannot be changed for only one mode. (7) ALC The band of ALC detection can be changed with the value of C4. It must be adjusted appropriately for the dynamic bass boost fO. In the example application circuit C4 = 0.1F, thus fc = 1 / 2C4 (R5 / / R6 / / R7) 160 (Hz)
BA3842F
The detection wave is dually rectified. In the example application circuit, it is 1.3Vrms, but if the resistors R8 and R9 are connected as shown below, it will lower the ALC level. Adjust the ALC level as needed. The detection band at this time is : fc = 1 / 2C4 (R5 / / R6 / / R7 / / R8 / / / R9)
(8) Attack time and release time Adjust the attack and release times with the resistors and capacitors connected to the ALCC pin. The attack time is determined by R10 (1k) and C5, and the release time is determined by R11 and C5. If the value set for C5 is below 4.7F, the ALC level may become unstable.
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FElectrical characteristic curves (reference values)
BA3842F
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FExternal dimensions (Units: mm)
BA3842F
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