4.2 - 18 MTM700 Mobile Radio / Detailed Service Manual THEORY OF OPERATION (800 MHz)
U5321. Diode D0303 compensates the base to emitter voltage drop of Q0305. The voltage is used
for the optional UART connected to J0570.
3V_DIG Linear Regulator U0305
Regulator U0305 gets its input voltage from the 5 volt regulator U0303. The output voltage 3V_DIG
is set to 3 volts with resistors R0320 and R0317 and is mainly used in the controller section.
1.8 V Linear Regulator U0306
Regulator U0306 gets its input voltage from the 5 volt regulator U0303. The output voltage 1.8V is
set to 1.8 volts with resistors R0319 and R0318 and is used in the controller section.
4.6V VSF Voltage
The fractional N synthesizer U5331 creates the 4.6 volts super filter voltage (VSF). This voltage is
used for the main VCO.
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