HYT TC-618, Руководство по обслуживанию

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TC-618/626 Service Manual
17
To detect VOX ON level;
To detect low voltage alarm;
To detect enabling and distinguishing of external earpiece.
3) Data Transmission and Processing:
To initiate EEPROM data;
To transmit programming data;
To process the code of Channel Selector knob.
To encode and decode signaling;
To transmit data of baseband processor (PLL).
7. Power Supply Processing Circuit
The block diagram is shown in the figure below:
SW
Q611
power management
Vin
V
S
S
Vout
-
-
-
7.2V
U606
L604
601s
SAVE
FMMT717 FMMT717
Q612
5V
UPA572T
Q610
TXC
V-TX
POWER-SAVE
Figure 9
After power-on, one flow of battery voltage is filtered by L604 and C682, and then feeds 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 processor 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 becomes conductive 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 becomes conductive and provides 5V voltage (TX_VCC) for the operating circuit
(Tx circuit).
The power supplies of the Tx and Rx circuits are protected by symmetrical voltage regulation measures.
When output voltage/current changes along with the change of load, the close-loop feedback circuit
operates, limiting the output voltage to 5V.