HYT POWER446, Service Manual

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POWER446 Service Manual
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To transfer programming data;
To process the code of
Channel Selector
knob;
To encode and decode signaling;
To transfer data of baseband processing chip (PLL).
7. Power Supply Processing
Figure 9
After power-on, one flow of battery voltage is filtered by L604 and C682, and then goes to the RF power
amplifier and audio power amplifier for amplification. Another flow goes to the 5V regulator (U606). After
regulated, the VCC_5V voltage is output for use by MCU and baseband processing chip. As the radio
operates at half-duplex mode, the TX and RX power supplies need to be controlled alternately. In
addition, to meet requirements of battery save mode, MCU needs to output a pulse signal (SAVE control
signal) with fixed duty ratio. If the SAVE control signal is at high level, Q610 is turned on and provides the
5V voltage (V_SAVE) for the operating circuit (PLL and RX circuit). If the SAVE control signal is a pulse
signal, the radio will enter Battery Save Mode. During transmission, CPU control signal (TXC) is at high
level. Then Q611 is turned on and provides 5V voltage (TX_VCC) for the operating circuit (TX circuit).
The power supply of the TX and RX circuits are protected by symmetrical voltage regulation measures.
When output voltage and current change are subject to the change of load, the close-loop feedback
circuit operates, regulating the output voltage to 5V.