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Audio ICs
Serial sound control IC
BH3854AS / BH3854AFS
The BH3854AS and BH3854AFS are signal processing ICs designed for volume and tone control in CD radio cassettes and other audio products. Their three-line serial control enables them to control volume and tone on the basis of signals from a microcomputer, etc. FApplications CD radio cassettes, mini component stereo systems, car stereos FFeatures 1) They facilitate direct serial control from a microcomputer of volume (main volume) and tone (bass, treble). DC control is also possible. 2) Volume is produced by a low-distortion, low-noise VCA. Designed to minimize step noise. 3) Input amp can be used for gain adjustment, and matrix surround yields powerful sound. 4) Stable standard voltage supply and built-in I / O buffer mean that few attachments are needed. SSOP32 package designed to save space. FAbsolute maximum ratings (Ta = 25_C) 5) Open collector has four outputs, which makes logic control possible. 6) Excellent for volume and tone control devices in CD radio cassettes, micro components, car stereos, televisions, etc. 7) Digital GND pin and analog GND pin are separated with an impedence of more than 1M.
FRecommended operating conditions (Ta = 25_C)
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Audio ICs
FBlock diagram
BH3854AS / BH3854AFS
FPin descriptions
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BH3854AS / BH3854AFS
FElectrical characteristics (unless otherwise noted, Ta = 25_C, VCC = 8V, f = 1kHz, BW = 20 X 20kHz, VOL = Max., TONE = ALL FLAT, Rg = 600, RL = 10k, INPUT AMP GAIN = 0dB)
FTiming chart constants
Note: About the output pins... SPins 1 through 4 (pins 12 through 15) are reset when the power is turned ON. SAfter the pins are reset, until the Vcc voltage setting for this IC (BH3854) is reached and the next data Sis input, the pins only operate while the CK, DATA, and LATCH lines are all maintained at LOW. SBe sure that no more than 9V is applied to any of the output pins.
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FMeasurement circuit
BH3854AS / BH3854AFS
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FOperation of measuring circuit switches
BH3854AS / BH3854AFS
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FPin descriptions
BH3854AS / BH3854AFS
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BH3854AS / BH3854AFS
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FDigital control specifications (1) Data format: total of 23 bits
BH3854AS / BH3854AFS
(2)
Timing (recommended conditions)
(1) Surround is ON when the bit data is 0, and OFF when the bit data is 1. (2) Pins 1 through 4 are set so that the output transistors will turn OFF if data is not input when the power is turned ON. They turn ON when the bit data is 1, and OFF when the bit data is 0. (3) "H" level is 4V or greater. "L" level is 1V or less. (4) Make the end of each control command LOW.
(5) The MUTE function can be controlled externally if the VC (volume control) pin is configured as shown in the diagram above. Attenuation is equal to the figure for attenuation when volume is at MIN.
FVolume data settings (reference values)
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Audio ICs
BH3854AS / BH3854AFS
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FTreble settings (reference values) Treble data
BH3854AS / BH3854AFS
Bass data
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FApplication example
BH3854AS / BH3854AFS
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FOperation notes (1) Operating power supply voltage range As long as the operating power supply voltage and ambient temperature are kept within the specified range, the basic circuits are guaranteed to function, but be sure to check the constants as well as the element settings, voltage settings, and temperature settings. Also, please take into consideration internal IC resistance dispersion (approx. "20%) and temperature fluctuation when making settings for IC internal resistance, attachment resistance, capacitor gain, or frequency. (2) Primary amp
BH3854AS / BH3854AFS
(1) The BPF is composed of a multifeedback active filter. fo can be varied according to the value of C. (theoretical equation) fO = G= 1 2 R2 1 R1R2C1C2 1) C1
*1 1 2
5k C2 (When R1 = 11.5k, R2 = 85k, C1 = C2 = C) 5.1 10 -6 fO = Q 1.36 G 8.5 C R1 R2C1C2
1 2 *1
(1) The input impedance is 47k. (2) A buffer if R and C1 are not present. (3) The gain can be set by R and the 20k. GVC = (R + 20k) / R
Note: Set C2 (input coupling) and C1 (used to set the gain) depending on the frequency band used.
Q
(C1 ) C2)
Note: Filter gain is calculated using the equation above. Total output gain is the sum of the gain for each of the internal circuits.
(3)
Bass filter
(4)
Treble filter
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Audio ICs
BH3854AS / BH3854AFS
(6) Signal level setting The following figure represents the standard setting for the BH3854A.
S Cutoff frequency (fC1) for the bypass filter can be changed using the attached C1. fC1 = 1 2 C1 2k
The fC1 for the recommended constant is approximately 8kHz. S fC2 is determined by the band of the built-in amp. fC2 is approximately 100kHz. The tone control is designed for a fluctuation of "15dB (Typ.) when the frequency that you want to boost or cut is a peak or valley of the frequency characteristics for the filter. So be sure to design the filter while taking into consideration its frequency characteristics. (5) Tone boost When volume attenuation increases, tone control width will change. Reference values are listed below, but be aware that actual values vary for different products. (Reference values) At attenuation of 0dB, tone control width is "15.0dB. At attenuation of *40dB, tone control width is "13.5dB.
As indicated above, if the front volume and rear volume input level are set so as not to exceed +6dBV (2 Vrms), the pre-amp gain setting can be used to improve the S / N ratio.
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(7) Serial control High-frequency digital signals are input into the CK, DATA, and LATCH pins. Configure the wiring for these pins in such a manner that it does not create interference for lines carrying analog signals. When measuring for step switching noise caused by interference, connect in serial format resistance of approximately 2 k right next to the microcomputer output pin (CK, DATA, LATCH) for each line. (8) Step switching noise In the circuit of the sample application, a constant is given, as an example, to each of the VC (pin 23), TC (pin 22), BC (pin 21), and SC (pin 11) pins. These constants vary depending upon signal level settings, wiring patterns in the device to which they are mounted, etc. Consider each constant carefully. The following diagram depicts an internal equivalent circuit. (It is equipped with a primary integration circuit so that changes will occur slowly.)
BH3854AS / BH3854AFS
(10) D / A separation With this IC (BH3854AS / AFS), the analog and digital systems are completely separated in the power supply and GND. Within the digital system, there is a stable builtin standard voltage supply, all of which is supplied via the VREF (pin 17, 3.8V), so this IC can be used without any worry about timing being off or digital noise interference occurring. (11) Output pins PORT 1 through 4 (pins 12 through 15) are reset when the power is turned ON, and remain reset until the next serial data is input. Note: From the time the power is turned ON until the next data is input, data in the CK, DATA, and LATCH lines are all maintained at LOW. S Be sure that no more than 9V is applied to any of the output pins. (12) Matrix surround
The structure of the matrix surround is as shown in the figure above. Use the equations shown in the figure to calculate gain. (9) Setting the volume and tone levels These specifications include, as reference values, figures for attenuation or gain for control serial data. The internal D / A converter features an R-2R structure, thus when there is no change between consecutive data, data exists. This can be used when very fine settings must be made, provided that volume is 8 bits (256 steps) or fewer, and tone is 5 bits (32 steps) or fewer.
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(13) DC control There is internal impedance of 10k at the VC (pin 23), TC (pin 22), and BC (pin 21) pins, and internal impedance of 200k at the SC pin (pin 11). For this reason, it is recommended that DC control of these pins be performed by voltage delivered directly from the voltage source. When using variable volume, take the impedance into account in determining the settings. Note: The voltage range for DC control is 0V to 3.8V. Be sure not to apply greater than 3.8V to any pin. (14) GND S Connect the GND of the attached element, which is shown in the circuit of the sample application, to the analog GND. S Connect the GND of the capacitor that is connected to pin 17 to the digital GND. S If several capacitors with good high-frequency characFElectrical characteristic curves
BH3854AS / BH3854AFS
teristics are connected in parallel to the 17th-pin capacitor, the characteristics will be improved with respect to static electricity noise. (Recommended: ceramic capacitors of 0.001F to 0.1F) If the wiring to the analog GND and digital GND is long, make sure that no potential difference arises between the two GNDs. (15) BH3854AS ! BH3854AFS: Differences S The bass filter R2 constant changes from 100 k ! 85 k. Accordingly, bass filter f0 changes from 70Hz ! 75Hz, which means bass filter Q changes from 1.47 ! 1.36. S The resistance at the treble filter's TIN pin changes from 20 k ! 2 k. Accordingly, the value for the attached capacitor changes from 470pF ! 0.01F, which means that cutoff frequency (fC1) changes from 17kHz ! 8kHz.
FExternal dimensions (Units: mm)
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