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 •Circuits that require analog signal compression and expansion •1)Features Internal logarithmic 1 / 2 compression circuit and 2 × 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 = 25°C) Parameter Symbol Limits Unit VCC 13 V Power supply voltage Power dissipation BA7725S 1000∗1 Pd BA7725FS 600∗2 mW Storage temperature Tstg – 55 ~ + 125 °C Operating temperature Topr – 10 ~ + 70 °C ∗1 Reduced by 10mW for each increase in Ta of 1°C over 25°C. ∗2 Reduced by 6.0mW for each increase in Ta of 1°C over 25°C. •Recommended operating conditions Parameter Power supply voltage Symbol Limits Unit VCC 6.5 ∼ 12.0 V 1 Multimedia ICs BA7725S / BA7725FS •Block diagram BA7725S BA7725FS LINE IN 2 N.C. 3 22 MIC AMP IN 21 MIC AMP OUT + 20 N.C. LINE OUT 1 LINE IN 2 ECHO LEV CTRL 3 + EXP BF OUT 9 5 EXP DET 6 16 CMP DET CT EXP DET CT 7 15 CMP OUT EXP BF OUT 8 EXP BF IN 9 17 CMP DET 14 CMP BF IN 2 16 CMP DET 15 CMP DET CT 14 CMP OUT 13 CMP BF IN 12 CMP BF OUT BF BF EXP BF IN 10 DLY BF OUT 11 17 RIPPLE FILTER BF 8 LOOP GAIN CTRL 18 RIPPLE FILTER + COMPRESS EXP DET CT 4 BF 7 GND EXPAND EXP DET 18 VCC VR 6 19 MIC AMP OUT VR LOOP GAIN CTRL + COMPRESS 5 EXPAND GND 19 VCC VR 4 + + VR ECHO LEV CTRL 20 MIC AMP IN SW 1 SW LINE OUT 13 CMP BF OUT BF 12 DLY BF IN DLY BF OUT 10 BF 11 DLY BF IN Multimedia ICs BA7725S / BA7725FS •Pin descriptions Pin No. BA7725S BA7725FS 1 1 Pin name Function LINE OUT Line output Line input 2 2 LINE IN 3 — N.C. 4 3 ECHO LEV CTRL 5 4 GND Ground Setting the loop damping ratio. Set between 2-9V (Vcc = 9.0V). — Microphone turns off when voltage drops below 1V. Set echo signal damping ratio between 2-9V (Vcc = 9.0V). 6 5 LOOP GAIN CTRL 7 6 EXP DET Expand detection 8 7 EXP DET CT Setting expand attack / recovery time Attack (R) = 5.6kΩ, recovery (R) = 85.6kΩ 9 8 EXP BF OUT LPF BF output (expansion) 10 9 EXP BF IN LPF BF input (expansion) 11 10 DLY BF OUT Echo signal input BF output 12 11 DLY BF IN Echo signal input BF input 13 12 CMP BF OUT LPF BF output (compression) 14 13 CMP BF IN LPF BF input (compression) 15 14 CMP OUT Compression output 16 15 CMP DET CT Setting the compression attack / recovery time Attack (R) = 5.6kΩ, recovery (R) = 85.6kΩ 17 16 CMP DET Compression detection 18 17 RIPPLE FITER Attached ripple rejection capacitor 19 18 VCC VCC 20 — N.C. 21 19 MIC AMP OUT Microphone amplifier output 22 20 MIC AMP IN Microphone amplifier input — 3 Multimedia ICs BA7725S / BA7725FS •Input / output circuits Pin name Pin No. ECHO LEVEL CTRL 4 Equivalent circuit 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 = 25°C, Vcc = 9V) Parameter Supply current Symbol Min. Typ. Max. Unit ICC 4.3 5.7 7.6 mA – 8.0 – 7.0 dBV Conditions No input 〈LINE THROUGH〉 INPUT : LINE IN, OUTPUT : LINE OUT Line through output level Line through output distortion VOLL – 9.0 THDLL — 0.15 0.5 % VIN = – 26.0dBV VIN = – 26.0dBV, MIC OFF,∗1 Line through maximum output level VOML + 5.0 + 7.2 — dBV THD = 1%,∗1 Line through noise level VONL — – 92 – 77 dBV MIC OFF, Rg = 600Ω,∗2 dBV 〈MIC THROUGH〉 INPUT : MIC AMP IN, OUTPUT : LINE OUT Microphone through output level VOML – 8.5 – 6.5 THDML — 0.2 0.5 Microphone through input conversion noise VONM — – 114 – 104 dBV Input shorted Microphone through crosstalk CTML — – 91 – 75 dBV VIN = – 44dBV, MIC OFF,∗2 – 6.5 – 4.5 – 2.5 dBV VIN = – 52dBV THDMC — 0.5 2.0 Compress noise level VONC — – 55 – 45 dBV Rg = 600Ω,∗2 Compress characteristics CMP — – 11.0 — dB VIN = – 42dBV → – 62dBV Output level differential – 9.7 — dBV VIN = – 5.0dBV, V4 = 9.0V Microphone through output distortion – 10.5 % VIN = – 52dBV VIN = – 52dBV,∗1 〈COMPRESS〉 INPUT : MIC AMP IN, OUTPUT : CMP BF OUT Compress output level Compress output distortion VOMC % VIN = – 52dBV,∗1 〈EXPAND〉 INPUT : DLY BF IN, OUTPUT : LINE OUT Expand output level 1 VODL1 – 11.7 Expand output distortion THDDL — 0.25 2.0 % VIN = – 5.0dBV, V4 = 9.0V,∗1 Expand characteristic EXP — – 19.5 — dB VIN = 0dBV → – 10.0dBV Output level differential Expand output level 2 VODL2 — – 54 – 44 dB VIN = – 5.0dBV, V4 = 2.0V (VR = Min. time) Output level differential relative to VoDL1 〈Loop〉 INPUT : DLY BF IN, OUTPUT : CMP BF OUT Loop output level 1 VODC1 – 7.5 – 5.5 — dBV VIN = – 5.0dBV, V6 = 9.0V Loop output level 2 VODC2 — – 42 – 32 dBV VIN = – 5.0dBV, V6 = 2.0V (VR = Min. time) Output level differential relative to VoDC1 MIC OFF holding voltage V4OFF 0.0 — 1.0 V — MIC ON holding voltage V4ON 2.0 — 9.0 V — 〈Mode holding voltage〉 ∗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 VCC 9V R2 2.2k + MIC AMP IN C1 1µ R3 82k 22 21 C4 22µ + 19 18 20 + 17 R35 10k CMP BF OUT C10 R11 R8 + 16 C32 0.1µ C12 R9 C5 C6 0.1µ 0.47µ 15 14 COMPRESS 13 C33 12 0.1µ 10 11 DLY BF IN R34 1k BF BF VR + 1 SW 2 C30 + 2.2µ 3 + VR 4 EXPAND 5 6 7 9 R17 R33 1k LINE OUT 8 + C20 0.1µ R31 10k BF C20 C19 0.1µ 0.47µ LINE V4 IN C15 R16 C18 R13 C14 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 Open loop gain Voltage (dB) 30 20 10 0 – 10 – 20 Note: Microphone amplifier gain must be set above +15dB. – 30 1.5k 12k MIC AMP IN VIN R9 + 22 Fig.3 + BA7725S 1 SW + 2 + Fig.2 6 4 6 81 2 1M 4 6 81 10M Microphone amplifier frequency characteristics + 18dB Microphone amplifier frequency characteristic measurement circuit 2 100k 21 21 – + 4 6 81 Frequency characteristic (Hz) Vout 22 2 – 40 10k R10 LINE OUT LINE IN Fig.4 Multimedia ICs BA7725S / BA7725FS (2) LINE IN / LINE OUT gain Line amplifier gain is fixed at +18dB. R9 + MIC AMP IN R10 22 21 1 SW + + +12dB 2 + LINE OUT 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 Threshold voltage Operation MIC OFF L (1.0V Max.) Only line audio is output. MIC ON H (2.0V Min.) Line input and level-controlled microphone input are mixed and output. 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. Attenuation of primary echo signals can be controlled by changing the DC voltage impressed on pin 6 (BA7725S) or pin 5 (BA7725FS) . A TT (dB) A TT (dB) 0 0 Primary echo – 50 – 100 0 5 10 ECHO LEVEL CTRL pin voltage : (V) Line output attenuation vs. echo level control pin voltage Fig.6 Line output attenuation : A TT (dB) Line output attenuation : A TT (dB) Sound source Sound source Primary echo V4 = 9.0V Secondary echo – 50 – 100 0 5 10 LOOP GAIN CTRL pin voltage : (V) Line output attenuation vs. loop gain control pin voltage Fig.7 7 Multimedia ICs BA7725S / BA7725FS Relationship between echo gain and loop gain (dB) A B B A : Echo signal attenuation (t) B : Loop signal attenuation C : Delay time C C C Fig.8 LINE OUTPUT ATTENUATION : A TT (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." Sound source 0 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) Fig.9 BA7725S BA7725FS 8.7 ± 0.2 19.4 ± 0.3 1.778 0.5 ± 0.1 0° ~ 15° 11 1 10 0.8 0.36 ± 0.1 0.15 ± 0.1 7.8 ± 0.3 0.3 ± 0.1 1.8 ± 0.1 7.62 0.11 11 1 20 5.4 ± 0.2 12 6.5 ± 0.3 0.51Min. 3.4 ± 0.2 3.95 ± 0.3 22 0.3Min. 0.15 SDIP22 8 SSOP-A20