SD7402 Silan Microelectronics, SD7402 Datasheet - Page 5

• Manufacturer Part Number: SD7402
• Description: Three-Channel Audio Amplifier
• Manufacturer: Silan Microelectronics

www.DataSheet4U.com
2.
The proportional amplifier shown as above is adopted for microphone amplifier with setting gain of about 29dB,
and capacitor C is used for high frequency signal filtering. As described above, the gain can be also adjusted by
changing R1.
3.
4.
5.
The pin STBY_N controls system entering standby mode by turning off internal amplifier bias circuit. When this
pin is connected to Vss, system enters standby mode, and when floated, system works normally.
Note: internal voltage regulating circuit still works in standby mode and supplies working current.
HANGZHOU SILAN MICROELECTRONICS CO.,LTD
Http://www.silan.com.cn
Mute control pin (pin 4) controls 3-channel as mute by internal switches. It comes to mute mode when pin 4 is
connected to Vcc (high level) and comes to normal mode when connected to ground.
Pin 2 is used for POP noise restrain by connecting an external capacitor which can be increased appropriately
for better POP noises restrain effect. In general, POP noise restrain is realized by mute control. Mute pulse is
generated when turned on for zero output and ended after powered on for normal output; mute pulse is also
generated when power supply is threshold value below during turned off for zero output. Thus, pop noise is
restrained during power on/down.
The built-in voltage regulator for negative power supply is shown as below. An external resistor R guarantees
voltage stability near -5V on pin 15 and the chip power supply is ±5V for normal operation. Because the
negative power to provide current is decided by this resistance, if the system output is light load, this resistance
can be properly increased to reduce operate current, but the voltage of pin 15 must be maintained and can not
drop significantly.
Microphone amplifier
Mute & ON/OFF POP noise control
Power supply
System standby
REV:1.0
Page 5 of 7
2009.11.11