DP405 Service Manual
3.4. Power Section
The radio applies 7.4V lithium-ion battery for power supply. RF power amplification and audio power
amplification are directly powered by battery; the battery outputs 3.6V to supply power to PMU in
RDA1846S and LT1901 through DC-DC switch; 3M, 3C and USB3.3V output from PMU separately
supply power to other baseband circuits; the battery outputs 5V voltage through LDO and then outputs
separate 5T and 5R after control by Q100 and Q102.
RF PA： RF Power Amplifier Circuit Q500（RD07MUS2B）, Q501（RD01MUS2）
Audio PA: Audio Power Amplifier Circuit U3（TDA8547TS）
3M： EEPROM IC200（AT24C512C）, encrypted IC U2（LTJMIC）
3C： Transistor X500（12.8M TCXO）
5T： RF Pre-drive Amplifer Circuit Q502 （2SC5108）、 Q503（2SC3356）
5R： Low Noise High Frequency Amplifier Circuit Q507（3SK318）
DC-DC： PMU IC1（LT1901）、 U500（RDA1846S）
3.5. IC Description
RDA1846S Feature:
Fully-integrated CMOS RF Front-end
High Linearity Low Noise Amplifer and Mixer
Low IF Receiver Path
Auomatic DC offset Calibration Circuit
High Performance analogue/digital converter and digital/analogue converter
Fully-integrated Receiver Filter
Digital AGC
Modulation and demodulation technique based on digital signal processing technique
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