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| Multimedia ICs Analog compander for KARAOKE echo systems BA7725S / BA7725FS The BA7725S and BA7725FS are analog companders designed for KARAOKE echo systems, and logarithmically compress the signal level by 1 / 2 and then logarithmically expand it by a factor of 2. These ICs can be used in combination with the BU9252S or BU9252F to create a digital echo system. These ICs have an internal line mixer amplifier for mixing line input and echo signals. The internal electronic volume control makes it possible to adjust the mixer level and loop level mixer with an external DC voltage. *Applications analog signal compression and expansion Circuits that require *Featureslogarithmic 1 / 2 compression circuit and 2 x 1) Internal expansion circuit 2) Internal 2-channel buffer amplifier used as a tertiary low pass filter 3) Internal mixer amplifier that mixes line input and microphone input 4) Internal electronic volume control allows for adjustment of the echo mixer level and loop mixer level using an external DC voltage. 5) Internal microphone amplifier and microphone input ON / OFF switch *Absolute maximum ratings (Ta = 25C) Parameter Power supply voltage Power dissipation BA7725S BA7725FS Symbol VCC Pd Tstg Topr Limits 13 10001 6002 - 55 ~ + 125 - 10 ~ + 70 Unit V mW C C Storage temperature Operating temperature 1 Reduced by 10mW for each increase in Ta of 1C over 25C. 2 Reduced by 6.0mW for each increase in Ta of 1C over 25C. *Recommended operating conditions Parameter Power supply voltage Symbol VCC Limits 6.5 12.0 Unit V 1 Multimedia ICs BA7725S / BA7725FS *Block diagram BA7725S LINE OUT LINE IN N.C. ECHO LEV CTRL GND LOOP GAIN CTRL EXP DET EXP DET CT EXP BF OUT 1 2 3 4 5 VR + SW + VR + COMPRESS BA7725FS 22 MIC AMP IN 21 MIC AMP OUT 20 N.C. 19 VCC 18 RIPPLE FILTER 17 CMP DET 16 CMP DET CT 15 CMP OUT 14 CMP BF IN BF BF LINE OUT LINE IN ECHO LEV CTRL GND LOOP GAIN CTRL EXP DET EXP DET CT EXP BF OUT EXP BF IN 1 2 3 4 5 6 7 8 BF BF 20 MIC AMP IN + SW + VR VR + COMPRESS 19 MIC AMP OUT 18 VCC 17 RIPPLE FILTER 16 CMP DET 15 CMP DET CT 14 CMP OUT 13 CMP BF IN 12 CMP BF OUT BF 6 7 8 9 EXPAND EXPAND 9 EXP BF IN 10 DLY BF OUT 11 BF 13 CMP BF OUT 12 DLY BF IN DLY BF OUT 10 11 DLY BF IN 2 Multimedia ICs BA7725S / BA7725FS *Pin descriptions Pin No. BA7725S 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 BA7725FS 1 2 -- 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 -- 19 20 Pin name LINE OUT LINE IN N.C. ECHO LEV CTRL GND LOOP GAIN CTRL EXP DET EXP DET CT EXP BF OUT EXP BF IN DLY BF OUT DLY BF IN CMP BF OUT CMP BF IN CMP OUT CMP DET CT CMP DET RIPPLE FITER VCC N.C. MIC AMP OUT MIC AMP IN Microphone amplifier output Microphone amplifier input Line output Line input -- Microphone turns off when voltage drops below 1V. Set echo signal damping ratio between 2-9V (Vcc = 9.0V). Ground Setting the loop damping ratio. Set between 2-9V (Vcc = 9.0V). Expand detection Setting expand attack / recovery time Attack (R) = 5.6k, recovery (R) = 85.6k LPF BF output (expansion) LPF BF input (expansion) Echo signal input BF output Echo signal input BF input LPF BF output (compression) LPF BF input (compression) Compression output Setting the compression attack / recovery time Attack (R) = 5.6k, recovery (R) = 85.6k Compression detection Attached ripple rejection capacitor VCC -- Function 3 Multimedia ICs BA7725S / BA7725FS *Input / output circuits Pin name Pin No. Equivalent circuit ECHO LEVEL CTRL 4 4 LOOP GAIN CTRL 6 6 Note: The BA7725FS is mounted on a 20-pin SSOP-A package with a different pin number than the BA7725S. On the BA7725FS, the ECHO LEVEL CTRL pin is pin 3, and the LOOP GAIN CTRL pin is pin 5. 4 Multimedia ICs BA7725S / BA7725FS *Electrical characteristics (unless otherwise noted, Ta = 25C, Vcc = 9V) Parameter Supply current Symbol ICC Min. 4.3 Typ. 5.7 Max. 7.6 Unit mA No input Conditions LINE THROUGH INPUT : LINE IN, OUTPUT : LINE OUT Line through output level Line through output distortion Line through maximum output level Line through noise level VOLL THDLL VOML VONL - 9.0 -- + 5.0 -- - 8.0 0.15 + 7.2 - 92 - 7.0 0.5 -- - 77 dBV % dBV dBV VIN = - 26.0dBV VIN = - 26.0dBV, MIC OFF,1 THD = 1%,1 MIC OFF, Rg = 600,2 MIC THROUGH INPUT : MIC AMP IN, OUTPUT : LINE OUT Microphone through output level Microphone through output distortion Microphone through input conversion noise Microphone through crosstalk VOML THDML VONM CTML - 10.5 -- -- -- - 8.5 0.2 - 114 - 91 - 6.5 0.5 - 104 - 75 dBV % dBV dBV VIN = - 52dBV VIN = - 52dBV,1 Input shorted VIN = - 44dBV, MIC OFF,2 COMPRESS INPUT : MIC AMP IN, OUTPUT : CMP BF OUT Compress output level Compress output distortion Compress noise level Compress characteristics VOMC THDMC VONC CMP - 6.5 -- -- -- - 4.5 0.5 - 55 - 11.0 - 2.5 2.0 - 45 -- dBV % dBV dB VIN = - 52dBV VIN = - 52dBV,1 Rg = 600,2 VIN = - 42dBV - 62dBV Output level differential EXPAND INPUT : DLY BF IN, OUTPUT : LINE OUT Expand output level 1 Expand output distortion Expand characteristic VODL1 THDDL EXP - 11.7 -- -- - 9.7 0.25 - 19.5 -- 2.0 -- dBV % dB VIN = - 5.0dBV, V4 = 9.0V VIN = - 5.0dBV, V4 = 9.0V,1 VIN = 0dBV - 10.0dBV Output level differential VIN = - 5.0dBV, V4 = 2.0V (VR = Min. time) Output level differential relative to VoDL1 Expand output level 2 VODL2 -- - 54 - 44 dB Loop INPUT : DLY BF IN, OUTPUT : CMP BF OUT Loop output level 1 Loop output level 2 VODC1 VODC2 - 7.5 -- - 5.5 - 42 -- - 32 dBV dBV VIN = - 5.0dBV, V6 = 9.0V VIN = - 5.0dBV, V6 = 2.0V (VR = Min. time) Output level differential relative to VoDC1 Mode holding voltage MIC OFF holding voltage MIC ON holding voltage V4OFF V4ON 0.0 2.0 -- -- 1.0 9.0 V V -- -- 1 2 BW = 0.4-30kHz DIN AUDIO Unless otherwise noted, V4 = 9.0V (MIC ON), V6 = 9.0V (Max. LOOP GAIN) 5 Multimedia ICs BA7725S / BA7725FS *Measurement circuit MIC AMP IN C1 1 R2 2.2k + 22 R3 82k 21 20 VCC 9V C5 C6 0.1 0.47 C4 22 + 19 18 + R8 17 + 16 15 C10 R11 14 BF R9 C32 0.1 C12 R35 10k CMP BF OUT DLY BF IN R34 1k 13 C33 12 0.1 COMPRESS VR + SW + VR EXPAND BF 1 C30 + 2.2 R31 10k 2 3 C20 0.1 R33 1k 4 5 6 7 + 8 9 10 R17 C15 R16 11 R13 C20 C19 0.1 0.47 C18 BF C14 LINE OUT LINE V4 IN V6 Fig.1 The above measurement circuit applies to a BA7725S mounted to a 22-pin SDIP package. A BA7725FS mounted to a 20pin SSOP-A package lacks N.C. pins 3 and 20; other than this difference, the above circuit diagram applies. Circuit operation (1) MIC AMP IN / LINE OUT gain Microphone amplifier gain (determined by R9 and R10) + line amplifier gain (+12dB) The audio signal is input via pin 22 (BA7725S) or pin 20 (BA7725FS) and amplified by the internal microphone amplifier, whose gain can be set with (attached) R9 and R10. * 60 50 40 30 Voltage (dB) 20 10 0 - 10 - 20 - 30 2 - 40 10k 4 6 81 2 4 6 81 2 1M 4 6 81 10M Open loop gain Note: Microphone amplifier gain must be set above +15dB. 1.5k VIN 12k Vout MIC AMP IN R9 + R10 22 21 100k Frequency characteristic (Hz) 22 - + 21 + 18dB + SW + Microphone amplifier frequency characteristics Fig.3 BA7725S + 1 LINE OUT 2 LINE IN Microphone amplifier frequency characteristic measurement circuit Fig.2 Fig.4 6 Multimedia ICs (2) LINE IN / LINE OUT gain Line amplifier gain is fixed at +18dB. MIC AMP IN R9 + R10 22 21 BA7725S / BA7725FS +12dB SW + + 1 + LINE OUT 2 LINE IN Fig.5 After being amplified by the internal microphone amplifier, the audio signal is logarithmically compressed by 1 / 2 then input to the tertiary low pass filter, which comprises an internal BF and attached capacitor and resistor. (3) Echo level control The DC voltage supplied to pin 4 (BA7725S) or pin 3 (BA7725FS) determines when the microphone switch is turned on and off and controls the echo level. Microphone switch control Mode MIC OFF MIC ON Threshold voltage L (1.0V Max.) H (2.0V Min.) Only line audio is output. Line input and level-controlled microphone input are mixed and output. Operation Echo level control Attenuation of the primary echo signals from sound source can be controlled by changing the DC voltage impressed on pin 4 (BA7725S) or pin 3 (BA7725FS) between 2V and 9V. ATT (dB) Sound source Line output attenuation : A TT (dB) Attenuation of primary echo signals can be controlled by changing the DC voltage impressed on pin 6 (BA7725S) or pin 5 (BA7725FS) . ATT (dB) 0 Line output attenuation : ATT (dB) Sound source Primary echo V4 = 9.0V 0 Primary echo Secondary echo - 50 - 50 - 100 0 5 10 ECHO LEVEL CTRL pin voltage : (V) - 100 0 5 10 LOOP GAIN CTRL pin voltage : (V) Line output attenuation vs. echo level control pin voltage Fig.6 Line output attenuation vs. loop gain control pin voltage Fig.7 7 Multimedia ICs Relationship between echo gain and loop gain (dB) BA7725S / BA7725FS A B B A : Echo signal attenuation (t) B : Loop signal attenuation C : Delay time C C C Fig.8 LINE OUTPUT ATTENUATION : ATT (dB) -- (4) Echo signal frequency characteristicis The figure below shows the attenuation of signals output from pin 1 when the audio signal is input to pin 22 (BA7725S) or pin 20 (BA7725FS). (This is the attenuation when the input signal is output without being passed through the BU9252S / F, and when the primary and secondary echo signals are passed through an attached low pass filter with the same constant shown in "Application example," and then processed by the BU9252S / F delay circuit.) Note: These are the values when using the constant shown in "Application example." 0 Sound source Primary echo signal - 10 Secondary echo signal - 20 - 30 - 40 3pin, 5pin = VCC (VR : Max.) - 50 100 1k 10k 100k SIGNAL FREQUENCY : f (Hz) Echo signal frequency characteristics *External dimensions (Units: mm) BA7725S BA7725FS 8.7 0.2 12 6.5 0.3 7.8 0.3 5.4 0.2 20 11 Fig.9 19.4 0.3 22 0.51Min. 3.4 0.2 3.95 0.3 1 0.3 0.1 10 1.8 0.1 0.11 1.778 0.5 0.1 0 ~ 15 0.8 0.36 0.1 0.3Min. 0.15 SDIP22 SSOP-A20 8 0.15 0.1 1 11 7.62 |
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