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Application Circuit
The application circuit is divided into three main parts.
Clock/PLL circuit: Y1, R5, C13 and C14 form the PLL external clock source where Y1 is
a 32.768KHz crystal to lock the PLL to the setup frequency. R4, C11, C12 are the PLL
filter circuits. Refer to the component values for correct circuit design.
MIC/AUX/DEMOD–The microphone/secondary audio/baseband input port: The MIC
section includes an internal OPA with a gain value =
according to actual application requirements. If the internal AGC function is to be used,
then the gain needs to have a value of five (ex: R1=1K、R2=5K) before using. DEMOD
is the baseband signal input port after RF demodulation. AUX: This external audio
input supports external audio applications.
MOD/SMOD/AUDO–Baseband/sub-tone/audio output port: The MOD output can
generate baseband signals connected to the RF input port. The SMOD generates the
sub-tone signals to be used in applications requiring sub-tones. AUDO: The audio
signals after demodulation can generate tones through the LPF circuit connected to
the speaker driver circuit (ex: HT82V739.)
HT98R068 Two-way Radio MCU
R
2
. The R2 value can be altered
R
1
3
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