SC7422 2-CH AUDIO POWER AMPLIFIER 2W x 2 DESCRIPTION The SC7422 is a class AB power amplifier which designed for dual audio purpose. It can deliver 2W × 2 power output to the 4 load in the SOP-16-375-1.27 5V operation voltage. Total harmonic distortion is lower than 0.03%. The output mode can be switched between the SE and BTL mode. The volume also can be changed by a 32 steps volume controller. Moreover, the SC7422 requires a few extra components in the application. It is suitable for small or portable products. FEATURES DIP-16-300-2.54 * Operation voltage : 5V * Output power : 2W×2(RL=4 ) * Low harmonics distortion (THD=0.03%) * 32 steps volume control with 1.5dB per step from -45dB to 0dB * Two output modes (SE and BTL) switched * Low quiescent operation current * No POPO noise when turn on/off ORDERING INFORMATION Device Package SC7422 DIP-16-300-2.54 SC7422S SOP-16-375-1.27 * Standby function, Low standby current(Is<0.7 A) * Thermally protected APPLICATIONS * LCD Monitors for TV * Portable audio * Multimedia audio * Other audio applications BLOCK DIAGRAM HANGZHOU SILAN MICROELECTRONICS CO.,LTD Http: www.silan.com.cn REV:1.0 2006.11.13 Page 1 of 8 SC7422 ABSOLUTE MAXIMUM RATING Characteristics Symbol Rating Unit VCC 0 ~7 V Vin(max) -0.3 ~ VCC +0.3 V Iin(max) -10 ~+10 mA Operating Ambient Temperature Tamb -40 ~+85 °C Storage Temperature Tstg -65 ~+150 °C JA 88.8 (**) °C/W JC 26 (**) °C/W Supply Voltage Maximum Input Voltage For Any Pin Maximum Input Current For Each Input Pin (*) Thermal Resistance From Junction To Ambient Thermal Resistance From Junction To Case (*) Maximum instantaneous input current for any pin must be less than 100mA, so that the CMOS latch-up effect can be avoided. (**) Ambient Temperature: Tamb=25°C. ELECTRICAL CHARACTERISTICS (Refer to the test circuit, VCC=5V; f=22Hz~22KHz; Tamb=25°C, unless otherwise specified.) Characteristics Supply Voltage Quiescent Operation Current Symbol Test conditions VCC Is V BTL 8 10 14 mA SE 6 8 12 mA 0.2 0.7 1 µA THD=1%, RL=8Ω 1.0 1.1 1.1 THD=10%, RL=8Ω 1.2 1.4 1.6 THD=1%, RL=4Ω 1.4 1.6 1.8 THD=10%, RL=4Ω 1.8 2.0 2.1 THD=1%, RL=32Ω 80 85 90 THD=10%, RL=32Ω 100 110 120 Po=0.2W, RL=4Ω 0.03 0.05 0.07 % Po=1W, RL=4Ω 0.06 0.08 0.15 % Po=50mW, RL=32Ω 0.03 0.05 0.07 % DC Vol = 5V, F = 1kHz -1 0 +1 DC Vol = 17%Vcc -44 -45 -46 Po Volume Control Range THD BTL SE Vatt Unit 6 SE Distortion Max. 5 BTL Total Harmonic Typ. 3 Shutdown = ON Output Power Min. W mW dB Volume Control Step Vstep Vatt = 0 ~ -45dB 1.3 1.5 1.7 dB Mute Mute DC Vol = 0V -85 -88 -90 dB Rin = Rf = 20kΩ -1 0 +1 dB BTL 85 88 91 77 80 83 Channel Balance CB Channel Separate CS SE F=1kHz dB Signal-to-Noise Ratio SNR 85 90 91 dB Output Noise Voltage Vno 25 40 50 µV (To be continued) HANGZHOU SILAN MICROELECTRONICS CO.,LTD Http: www.silan.com.cn REV:1.0 2006.11.13 Page 2 of 8 SC7422 (Continued) Characteristics Symbol Output Offset Voltage Supply Voltage Voff Ripple SVRR Rejection Thermally protected TH Input Voltage For Shutdown VSD Pin Input Voltage For VSB SE/BTL Pin Test conditions Min. Typ. Max. Unit 25 50 100 mV DC Vol = 0V From +OUT to -OUT BTL 58 60 63 52 55 58 Overheat to shutdown - 120 - Return to normal operation - 80 - 20% 30% SE Shutdown = OFF Shutdown = ON BTL SE F=1kHz Vcc=3~5V Vcc=3~5V 50% °C 60% 10% 80% dB 20% 90% Vcc Vcc PIN CONFIGURATION PIN DESCRIPTION Pin No. Pin Name I/O Pin Description 1 Shutdown I Stand-by control, logic high active 2 VCC -- Supply 3 DC Vol I Volume control 4 VO1 I Buffer output of channel 1 5 VIN1 I Signal input of channel 1 6 VIN2 I Signal input of channel 2 7 VO2 I Buffer output of channel 2 8 GND -- Ground 9 +OUT2 O Non inverted loudspeaker output of channel 2 10 VCC -- Supply 11 -OUT2 O Inverted loudspeaker output of channel 2 12 SE/BTL I Output mode control. When this pin is logic high, SE mode is selected. When it is logic low, BTL mode is selected. (To be continued) HANGZHOU SILAN MICROELECTRONICS CO.,LTD Http: www.silan.com.cn REV:1.0 2006.11.13 Page 3 of 8 SC7422 (Continued) Pin No. Pin Name I/O Pin Description 13 Bypass O Half supply voltage ripple rejection 14 -OUT1 O Inverted loudspeaker output of channel 1 15 VCC -- Supply 16 +OUT1 O Non inverted loudspeaker output of channel 1 FUNCTION DESCRIPTION Gain Setting for Input Stage The gain for each audio input stage of the SC7422 is set by external resistors R1 and R2 (see typical application circuit). It is recommended that R1 = R2 = 20kΩ in the application and the gain is 0dB. If the amplitude of audio input voltage is lower, for example, the peak-peak value is less than 2Vpp, it should be improve the gain, whereas, it should be reduce the gain. However, the amplitude of audio input voltage is so high that the output wave would be distortion. Therefore, the amplitude of audio signal source should be checked at first. And the gain in the application should be set following Table 1. Table 1 Gain Setting for Input Stage Operation Voltage VCC=3V The peak- Gain Setting peak value of for Input input voltage Stage VIN <1.25Vpp +6dB VIN <2.5Vpp 0dB VIN <5Vpp -6dB Operation Voltage VCC=5V The peak- Gain Setting peak value of for input voltage Input Stage VIN <2Vpp +6dB VIN <4Vpp 0dB VIN <8Vpp -6dB Otherwise, the minimum value of input resistor R1 is 10kΩ, in order to ensure proper impedance for input. 32 Steps Volume Control The SC7422 includes a 32 steps volume controller. It changes the volume gain linearly with 1.5dB per step from -45dB to 0dB. The volume is controlled by input voltage of DC Vol pin. As the voltage was increasing, the volume is louder. Table 2 shows the relationship of them. Table 2 32 Steps Volume Setting Step Volume DC Vol DC Vol (dB) VH(%) VL(%) Step Volume DC Vol DC Vol (dB) VH(%) VL(%) 64.2 17 -24 38.1 30.4 64.4 62.8 18 -25.5 35.6 29.0 -3 63.0 61.2 19 -27 31.8 27.4 4 -4.5 61.4 59.4 20 -28.5 29.2 25.4 5 -6 59.8 57.6 21 -30 27.6 23.8 1 0 Vcc 2 -1.5 3 (To be continued) HANGZHOU SILAN MICROELECTRONICS CO.,LTD Http: www.silan.com.cn REV:1.0 2006.11.13 Page 4 of 8 SC7422 (Continued) Volume DC Vol DC Vol Volume DC Vol DC Vol (dB) VH(%) VL(%) (dB) VH(%) VL(%) 6 -7.5 57.9 56.0 22 31.5 26.2 21.8 7 -9 56.1 54.0 23 -33 24.0 20.0 8 -10.5 54.1 51.8 24 -34.5 22.5 18.0 9 -12 52.1 48.8 25 -36 20.4 14.4 10 -13.5 49.4 47.4 26 -37.5 18.0 13.0 11 -15 47.5 45.4 27 -39 15.1 11.0 12 -16.5 45.5 43.6 28 -40.5 13.1 9.0 13 -18 44.0 41.6 29 -42 10.6 7.2 14 -19.5 41.8 39.8 30 -43.5 8.8 5.4 15 -21 39.8 37.6 31 -45 6.7 3.0 16 -22.5 38.3 36.6 32 MUTE 4.3 GND Step Step Output Mode Control The output mode of the SC7422 can be switched between the SE (Single-Ended) and BTL (Bridge-Tied Load) mode. It is recommended to apply BTL mode to obtain more output power while driving the loud speaker. SE mode can be set to shutdown some parts of amplifiers while driving the stereo headphone. Therefore, the quiescent operation current is reduced. POPO Noise Suppress When an audio power amplifier with a single supply turns on, the POPO Noise can be heard. The reason is that the output voltage of amplifier would take hundreds of milliseconds to increase from 0V to 1/2 Vcc. This time is controlled by CB, the external capacitor of Bypass pin. As the CB was increasing, the time is longer, so it is much better to suppress POPO noise. However, the charging and discharging time for the input or output capacitors should be less than this time. Therefore, CB is related with the input or output capacitors. The values of these capacitors are recommended in the typical application circuit. Thermally protected There is a thermally protected protection circuit in the SC7422. If the chip temperature is over 120°C, the protection circuit will start up to shutdown the output stages of audio power amplifier. The chip will return to the normal operation, until the chip temperature falls to 80°C. Power Dissipation and Heat Sinking When the load is a resistor, the maximum of average power dissipation for the SC7422 is calculated as follows: PDISS(MAX) = 2(2Vcc)2 / (2π2RL) + PQ Where Vcc is the operation voltage, RL is the load resistor, PQ is the static power consumption. PQ=VCC×Is Where Is is the operation current. For example, if the SC7422 drives the 4 load in 5V supply, the power dissipation is 2.6W. HANGZHOU SILAN MICROELECTRONICS CO.,LTD Http: www.silan.com.cn REV:1.0 2006.11.13 Page 5 of 8 SC7422 There is the formula of heat sinking for the SC7422: JA = Where JA (TJ(max) -TA )/ PDISS is the thermal resistance from junction to ambient, TJ(max) is the junction temperature, TA is ambient temperature, PDISS is the power dissipation. If the junction temperature remains below 150°C but the ambient temperature has reached to 50°C, the total junction-to-ambient thermal resistance must be less than JA = JA calculated as follows: (150°C - 50°C) / 2.6W =38.4°C/W. Using JC=26°C /W, the heat-sink thermal resistance must be less than: JA - JC = 12.4°C/W So the SC7422 doesn’ t need heat sink in the normal operation. In application, the copper foil which connects GND on PCB can be utilized for heat sinking to maintain proper operation temperature. TYPICAL APPLICATION CIRCUIT HANGZHOU SILAN MICROELECTRONICS CO.,LTD Http: www.silan.com.cn REV:1.0 2006.11.13 Page 6 of 8 SC7422 PACKAGE OUTLINE Unit: mm SOP-16-375-1.27 Unit: mm 0.20±0.10 2.50±0.20 0.70±0.10 7.50±0.20 10.30±0.20 DIP-16-300-2.54 HANGZHOU SILAN MICROELECTRONICS CO.,LTD Http: www.silan.com.cn REV:1.0 2006.11.13 Page 7 of 8 SC7422 HANDLING MOS DEVICES: Electrostatic charges can exist in many things. All of our MOS devices are internally protected against electrostatic discharge but they can be damaged if the following precautions are not taken: • Persons at a work bench should be earthed via a wrist strap. • Equipment cases should be earthed. • All tools used during assembly, including soldering tools and solder baths, must be earthed. • MOS devices should be packed for dispatch in antistatic/conductive containers. HANGZHOU SILAN MICROELECTRONICS CO.,LTD Http: www.silan.com.cn REV:1.0 2006.11.13 Page 8 of 8