Video ICs Stereo microphone amplifier for camcorders BA7781K The BA7781K allows construction of a stereo-microphone amplifier for camcorder use with a minimum number of external components. The IC has a built-in wind-noise detection circuit, and wind-noise rejection filter. The filter circuit is controlled automatically. The IC can operate off a 3.0V power supply. Applications •Camcorders •1)Features Operates off a 3.0V to 5.25V power supply. 4) Automatic switching circuit for external microphones, built-in external monaural decision circuit, and input switch mode decision circuit. 2) Automatic wind-noise rejection circuit. 3) Matrix circuit for stereo emphasis. INV IN L INV OUT L MTX IN L MTX OUT L HPF IN L OUT L 23 22 21 20 19 18 17 – + 13dB INT IN L 27 GND 16 DET OUT 15 DET IN 14 BIAS EXT + – MIX REG GND 28 15dB DET BG 26 INT WND PRE OUT L 24 EXT IN L 25 EXT NOR MODE 24 •Block diagram BIAS VCC 10dB VREG 29 13 VCC 12 LPF INV OUT RIPL 31 INT 11 LPF INV IN EXT 10 MIX OUT 13dB + – 09 MIC MONO 01 02 03 04 05 06 07 08 PRE OUT R INV IN R INV OUT R MTX IN R MTX OUT R HPF IN R OUT R 15dB MODE 1 EXT IN R 32 EXT NOR WND INT IN R 30 BIAS + – 1 Video ICs BA7781K •Absolute maximum ratings (Ta = 25°C) Parameter Symbol Limits Unit Power supply voltage VCC 7.0 V Power dissipation Pd 400∗ mW Operating temperature Topr – 10 ~ +70 °C Storage temperature Tstg – 55 ~ +125 °C ∗ Reduced by 4mW for each increase in Ta of 1°C over 25°C. •Recommended operating conditions (Ta = 25°C) Parameter Symbol Min. Typ. Max. Unit VCCS 3.0 — 5.25 V Power supply voltage •Electrical characteristics (unless otherwise noted, Ta = 25°C and V Parameter Symbol Min. Typ. CC Max. = 3.3V) Unit Conditions Current dissipation 1 I INT — 5.0 8.0 mA INT MIC IN, L / Rch No dissipation by mic Current dissipation 2 IEXT — 4.8 8.0 mA EXT MIC IN, L / Rch No dissipation by mic Preamplifier gain VGPR 12 13 14 dB 30 / 32pin→2pin GAIN 27 / 25pin→23pin GAIN Output amplifier gain VGOA 14 15 16 dB 3 / 6 / 7pin→8pin GAIN 22 / 19 / 18pin→17pin GAIN Distortion THD — 0.05 0.3 % INT / EXT, Vo = 300mVrms, L / Rch∗2 Maximum output voltage Vom 0.85 1.1 — Vrms INT / EXT MIC IN, L / Rch f = 1kHz (distortion 1%∗2 ) Output noise voltage VNO — – 90 – 80 dBV INT / EXT, L / Rch, Rg = 1kΩ When gain is 28dB∗1 Input switch separation CTI→E — – 88 – 70 dB INT→EXT MIC IN, Rg = 1kΩ, L / Rch (distortion 1%∗2 ) , when gain is 28dB∗1 — – 61 – 50 dB INT / EXT MIC, Lch→Rch, Rg = 1kΩ (distortion 1%∗2 ) , when gain is 28dB∗1 VREG 2.3 2.5 2.75 V Pin 27 output voltage for 30kΩ load VHSWH 1.6 — VCC V “H”level, 1 / 24 pin DC VHSWL 0 — 0.6 V “L” level, 1 / 24 pin DC Interchannel separation Internal microphone power supply voltage Input switch control voltage CTL← →R Input 80Hz signal to pin 15, and measure gain at switch off side.∗1 High-pass filter switching attenuation characteristic High-pass filter control voltage ∗1 JIS-A filter used. ∗2 400Hz to 30kHz filter used. 2 15pin – 29.0dBV IN (80Hz) 6 / 19pin – 25.5dBV IN (1kHz) 6→8pin / 19→17pin GAIN 15pin – 45.0dBV IN (80Hz) 7 / 18pin – 25.5dBV IN (1kHz) 7→8pin / 18→17pin GAIN VGHON — — – 30 dB VGHOFF — — – 30 dB VHON 2.5 — VCC V HPF on holding voltage (pin 16) VHOFF 0 — 0.3 V HPF off holding voltage (pin 16) Video ICs BA7781K •Pin descriptions Pin No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 Pin name MODE 1 PRE OUT R INV IN R INV OUT R MTX IN R MTX OUT R HPF IN R OUT R MIC MONO MIX OUT LPF INV IN LPF INV OUT VCC BIAS DET IN DET OUT OUT L HPF IN L MTX OUT L MTX IN L INV OUT L INV IN L PRE OUT L MODE 24 EXT IN L BG INT IN L GND VREG INT IN R RIPL EXT IN R Function Mode control 1 input Preamplifier output Inverter input Inverter output Matrix amplifier input Matrix amplifier output High-pass filter input Signal output External microphone monaural decision signal output Mix Output Low-pass filter block inverter input Low-pass filter block inverter output VCC Bias voltage Detector circuit input Detector circuit output Signal output High-pass filter input Matrix amplifier output Matrix amplifier input Inverter output Inverter input Preamplifier output Mode control 24 input External microphone input For regulator ripple filter capacitor Internal microphone input GND Regulator output Internal microphone input For bias ripple filter capacitor External microphone input Voltage (V) — 1.65 1.65 1.65 1.65 1.65 1.65 1.65 — 1.65 — — 3.3 1.65 1.65 — 1.65 1.65 1.65 1.65 1.65 1.65 1.65 — 1.65 1.25 1.65 — 2.5 1.65 1.65 1.65 Circuit 25kΩ EF (P - P) 100kΩ EF (P - P) B EF (P - P) 100kΩ C (P - P) C EF (P - P) B EF (P - P) — EF (P - P) 2kΩ 22kΩ C (P - P) 100kΩ EF (P - P) B EF (P - P) 100kΩ EF (P - P) 25kΩ 75kΩ 10kΩ 75kΩ — C 75kΩ 50kΩ 75kΩ ∗ EF: emitter follower, P-P: push pull, B: base, and C: collector. All numerical values are standardized values. 3 Video ICs BA7781K •Measurement circuit MODE 24 HPF IN SW2 1 10k 10.5k 0.1µ 2 2200p 0.1µ 0.1µ Lch 26 EXT INT 20 19 18 – + 15dB 13dB 10µ 28 GND 30k 10µ EXT IN 0.1µ + 10µ VCC 13 12 BIAS + – 200k 31 INT + – 2 200k 0.1µ INV (11) IN 10 13dB 32 EXT 1 11 EXT 3 NOR WND Rch 1M 0.1µ BIAS VCC 10dB 29 30 + 15 L OUT 14 0.1µ INT IN 16 EXT + MIX – GND 27 0.1µ REG INT IN 2.2µ + 17 DET + 21 NOR 25 22 WND 0.1µ EXT IN 23 24 5 4 6 9 15dB 8 7 0.1µ 0.1µ R OUT 2200p 0.1µ 10k 10.5k 1 2 SW1 MODE 1 HPF IN Fig. 1 4 UNITS RESISTOR: Ω CAPACITOR: F Video ICs BA7781K •Application example UNITS RESISTOR: Ω CAPACITOR: F B' A' 15k 2200p 10k 0.1µ 0.022µ 100k 10.5k 0.1µ L OUT 0.022µ 2.2µ 26 20 19 – + EXT INT 18 + 24k 17 15dB 16 1M 13dB DET L ch 21 NOR 25 + 22 WND EXT IN 23 24 0.1µ 15 10µ 28 BIAS VCC 10dB GND + – 220k 32 INT 100k 13dB 0.1µ 2 3 0.1µ 0.01µ 5 4 0.1µ 6 MIC-MONO 24k 8 7 0.01µ 9 15dB 0.022µ 10k 10.5k 0.022µ 100k A 150k 100k + – EXT 1 11 WND 10µ EXT IN VCC 2200p 10 NOR 31 EXT BIAS 30 + R ch 10µ 13 12 29 0.1µ INT IN + 14 EXT + MIX – GND 27 0.1µ REG INT IN R OUT 2200p B 15k Additional components INT / EXT monitoring INT / EXT L OPEN 100k 12 + 1µ ∗1) When using the matrix circuit connect A-A' and B-B'. ∗2) The pin 10 and 12 low-pass filter components are for fc = 150Hz, Gain = 0dB, 18dB / oct. Fig. 2 5 Video ICs BA7781K •Measurement circuit switch table (blank cells: no spesification) SW1 SW2 MODE1 MODE24 Current dissipation 1 1 1 H L Current dissipation 2 1 1 Preamplifier gain 1 1 Output amplifier gain 1 1 Distortion 1 1 Maximum output 1 1 Output noise voltage 1 1 Input switch separation (INT→ EXT) 1 1 L L INT INT 1 1 H L INT EXT 1 1 L L EXT 1 1 1 1 H Vth 1 1 Vth L INT, EXT 2 2 H L INV (11) , HPF 1 1 H L INV (11) , INT 1 1 H L INV, 16pin of Vth 2 2 H L HPF, 16pin of Vth Parameter Interchannel separation Internal microphone power supply voltage Input switch control voltage High-pass filter switching attenuation characteristic High-pass filter control voltage Signal input pin Conditions other than No. 1 INT, EXT ∗ H and L are VCC and GND levels. Measure the voltage range that maintains the mode for Vth. notes •(1)Operation Automatic wind-noise rejection circuit The MAX OUT (pin 10) signal passes through the three-stage low-pass filter connected between pins 10 and 12, and the DC level of the low-frequency signal component is detected. This DC voltage (pin 16 DC voltage) automatically controls the on / off switching of the high-pass filter. The components connected to pins 11 and 12 set the gain of a multiple-feedback-type twostage low-pass filter constructed around an inverting amplifier, and by changing the gain of the circuit you can adjust the detection sensitivity. It is also possible to switch the high-pass filter manually by applying a DC voltage to pin 16 (see Fig 2). 6 (2) Additional compornents for INT / EXT monitor use An internal circuit sets pin 12 to roughly the bias potential in INT mode, and to GND for EXT mode. This switches the external transistor on and off for INT and EXT modes respectively. This can be used to indicate whether the microphone amplifier is operating with the INT or EXT input. In the case of a camcorder, this can be used to display a massage such as “EXT MIC ON” in the EVF. Video ICs BA7781K VCC = 3.3V Input: 80Hz Ta = 25°C 16PIN DETECT OUTPUT: VDETOUT (V) OUTPUT LEVEL: VROUT (dBV) •Electrical characteristic curves 0 – 20 HPF side output 7→8pin NOR side output 6→8pin – 40 – 60 – 60 – 50 – 40 – 30 – 20 VCC = 3.3V Input: 80Hz Ta = 25°C 2.5 2.0 1.5 1.0 0.5 0 – 60 – 10 – 50 – 40 – 30 – 20 – 10 15PIN INPUT SIGNAL LEVEL: VDETIN (dBV) 15PIN INPUT SIGNAL LEVEL: VDETIN (dBV) Fig. 4 Detector voltage characteristis Fig. 3 HPF switching characteristics •External dimensions (Units: mm) 9.0 ± 0.3 7.0 ± 0.2 16 32 9 1.45 ± 0.1 1 0.05 17 25 0.8 8 0.4 7.0 ± 0.2 9.0 ± 0.3 24 0.15 ± 0.1 0.4 ± 0.1 0.15 QFP32 7