Hytera MD652, Service Manual

Page: 123 / 207

VHF1 (136
‐
174 MHz)
Circuit Description
15
Both the baseband control IC and the RF section can convert the supplied voltage to an appropriate one
via the voltage converter. See below:

Supply for RF: U2017, Q9021 and Q9022 supply power for the RF section by high current MOS
transistor and comparator, which can work as LDO (Low Dropout Regulator).

Supply for Frequency Generation Unit (FGU): U2008 and U2009 supply 3.3 V and 5 V power
respectively to U8001.

Supply for Baseband: The processor U1002 is supplied by 3.3 V (U2001), 1.8 V (U2004) and 1.6 V
(U2010); the memory is supplied by 3.3 V (U2001) and 1.8 V (U2004) respectively; the audio
processor IC is supplied by 3.3 V (U2001) and 1.8 V (U2004); the DAC is supplied by 5 V (U2014)
and 3.3 V (U2001).

: Q2009
。
5.2.2
Control Module
Powering On/Off
The mobile radio can be powered on/off through any of the following methods:

Power On/Off Key

Ignition Signal

Emergency Alarm
Power On/Off Key
To turn on the radio, press the Power On/Off Key, and R2058 becomes grounded and Q2013 is turned
on. Then Q2008 of PNP transistor outputs a high-level signal, causing U2006 to start working.
Afterwards, the processor U1002 will run the user programs to keep the power control signal Pwr_Hold
at a high level. In this case, the radio starts to work properly after the Power On/Off Key is released. To
turn off the radio, press the Power On/Off Key, and Q2013 is turned on and a low-level signal
Pwr_On_Det to power off the radio is detected by U1002, which then controls Pwr_Hold to output a
low-level signal. Afterwards, the radio is powered off.
Ignition Signal
When the voltage of ignition signal exceeds 7 V, Q2012 will be turned on by C2061, R2049 and R2051.
As a result, the PNP transistor of Q2008 will be further turned on to supply power for the whole system.
Meanwhile, Q5012 will also be turned on, and U1002 will identify ignition signals by detecting the signal
from Q5012; afterwards, the level Pwr_Hold is generated by the processor.