IC for Headphone Stereos MM1376 MITSUMI IC for Headphone Stereos Monolithic IC MM1376 Outline This IC was developed for use in 3V headphone stereos, and combines all the basic audio circuitry for headphone stereos on a single chip. Recently hearing impairment caused by the high volumes of headphone stereos has become a problem, and there has been strong demand for functions for limiting loud volumes in the sets themselves. This IC incorporates an ALC circuit and has functions to hold the output from the headphone to a fixed level; it also eliminates the ordinary electronic governor circuit in order to accommodate trends toward thinner sets, as seen in the adoption of BSL motors. Package 1. Configuration: Pre-and power amps, ALC circuit 2. Internal tape selector: A selector switch allows the user to select between normal and metal tapes. 3. Internal OCL circuit: No need for large-capacitance output capacitor 4. Preamp off function: Preamp alone can be turned off for connection to radio etc. 5. MM1376CF amp gain takes Dolby noise reduction into account Package SOP-22 Pin Assignment 1 COM1 12 Power output 2 Preamp non-inverted input 13 VCC 3 Preamp inverted input 14 Ripple filter 4 Metal switching output 15 Preamp off 5 Preamp output 16 Tape selector 6 Power input 17 Power input 7 Rectifier pin 18 Preamp output 8 ALC control 19 Metal switching output 9 Power output 20 Preamp inverted input 10 COM2 21 Preamp non-inverted input 11 GND1 22 GND2 22 21 20 19 18 17 16 15 14 13 12 1 2 3 4 5 6 7 8 9 10 11 SOP-22 Absolute Maximum Ratings Item Symbol Ratings Units Operating temperature TOPR -10~+65 °C Storage temperature TSTG -40~+125 °C Power supply current VCC -0.3~+7.5 V Power consumption Pd 350 mW IC for Headphone Stereos MM1376 MITSUMI Recommended Operating Conditions Item Symbol Ratings Units Operating temperature TOPR -10~65 °C Operating voltage VOPR 2.0~5.0 V Electrical Characteristics (Except where noted otherwise, Ta=25°C, VCC=3V, f=1kHz, RL1=10kΩ, RL2=16Ω) Item Measurement conditions Consumption current VIN=0V Min. Typ. Max. Units 6 14 22 mA Preamp unit 72 Open-circuit gain Closed-circuit gain I Closed-circuit gain II Normal Metal Normal Metal Vo=-10dBm, f=1kHz Vo=-10dBm, f=5kHz Maximum output voltage THD=10% Total harmonic distortion ratio VOUT=-10dBm Output noise voltage Normal Metal Rg=2.2k, BPF (400~30kHz) dB 31 33.5 36 29.5 32 34.5 28 30.5 33 23 25.5 28 0.30 0.45 dB dB Vrms 0.05 0.5 30 75 150 20 45 100 % µVrms Crosstalk between channels Rg=2.2kΩ, VOUT=-10dBm 50 70 dB Ripple rejection VCC=3V, VR=-20dBm, fR=100Hz Rg=2.2kΩ 45 55 dB Output voltage with preamp off VIN=100mVrms, Pre off -80 -60 dBm ALC (off) + power amp Voltage gain POUT=5mW CF 24 26 28 DF 30 32 34 -2 0 2 30 50 Voltage gain difference between channels Maximum output current THD=10%, RL=16Ω Total harmonic distortion ratio POUT=5mW Crosstalk between channels POUT=5mW Output noise voltage Ripple rejection Rg=0Ω, BPF (400~30kHz) 0.5 35 dB dB mW 1.5 45 % dB CF 85 200 DF 135 250 µVrms VCC=3V, VR=-20dBm CF 35 45 fR=100Hz, Rg=0Ω DF 35 40 19 24 29 kΩ -34 -30 -26 dBm Input resistance dB ALC (on) + power amp Power amp output voltage VIN=-40dBm ALC initiation input voltage CF -56 DF -62 ALC width Input width for output from start of up to +4dB ALC total harmonic distortion VIN=-40dBm Noise of preamp+power amp+ALC Rg=2.2kΩ (Pre amp), Noise of preamp+power amp 30 dBm 40 dB 0.5 1.5 CF 1.5 6 DF 2.8 6 % mVrms IC for Headphone Stereos MM1376 MITSUMI Application Circuits Characteristics Preamp Gain- Frequency 60.0 55.0 50.0 45.0 40.0 volt 35.0 dB 30.0 25.0 lin 20.0 15.0 10.0 5.0 0. 1.0 ALC + power amp (32 dB) VIN-VOUT RL=16ohm 10 ALC OFF 0 -10 VOUT (dBV) Normal Metal -20 ALC ON (ADJUST) -30 -40 ALC ON (max.) -50 -60 -80 -70 -60 -50 -40 -30 -20 -10 10.0 100.0 1.0k 10.0k 100.0k 1.0x Frequency (log) 10.0x VIN (dBV) 0