HT98R068-1 Two-way Radio OTP MCU
Application Circuit
The application circuit is divided into three main parts.
Clock/PLL circuit: Y1, R7, C16 and C17 are from the PLL external clock source where
Y1 is a 32,768 KHz crystal to lock the PLL so as to the set frequency. R6, C14 and C15
are the PLL filter circuits. Refer to the component values for correct circuit designing.
MIC/AUX/DEMOD – The microphone/secondary audio/in-band input port: The MIC
section includes an internal OPA with a gain value =
1
2
R
R
. The R2 value can be altered
according to actual application requirments. If the internal AGC function is to be used,
please refer to the AGC section to select this resistance. DEMOD is the in-band signal
input port after RF demodulation. AUX: This external audio input supports external
audio applications. In principle, the input signal must be limited in: {signal * PGA
amplification ratio
≦
V
DD
*0.7(AD maximum)}.
MOD/SMOD/AUDO – In-band/sub-tone/audio output port: The MOD output can
generate in-band signals connected to the RF input port. The SMOD generates
sub-tone signals to be applied in applications requiring sub-tones. AUDO: The audio
signals after demodulation can generate tones through a LPF circuit connected to the
speaker drive circuit (ex: HT82V739). The output signals showing likes a ladder which
is applied in describing the precise relation of the adjacent channel power and tone
quality, but it must be followed with a LPF circuit.
Power circuit: The power consumption is so much ([email protected]) at the moment
turning on the audio processor. Hence, note that the V
CC
changement effection. Where,
C11 is the tantalum capacitor for compensation. Considering the mutual interference of
anolog and digtal signals, it’s recommended that seperate VCC and GND into two
parts. The power supply and ground portion then are connected respectively by BEAD.
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