Kenwood TH-77A Service Manual page 26

IA-//A/E
SEMICONDUCTOR DATA
DTMF Decoder LC7385M (Control Unit IC11)
@Block Diagram
Voo Vss Vrer ESt St/GT
Timer control |
i circuit
High-group Frequericy
bandpass detector = Q4
filter circuit 3
°o =
= eS]
2 2
& =
So o Q3
Anti- Dial 8 3
aliasing tone r a)
Py £ 5 8
filter filter 5 ce
2 BS Q2
= 52
aS 2 8
Low-group Frequency 2 40
ming bandpass detector Ql
pulse filter circuit Vop
generator
circuit
®Pin Functions
Pin No. Name vo Description
1 IN+ | Input amplifier non-inverting input
IN-
2 ! Input amplifier inverting input
a GS ie) Input amplifier output
Veer VDd/2 reference voltage output
Selects the output formats of Q1 to O4.
Hexadecimal when low.
Binary (two of eight code) when high.
Power-down mode when high.
Crystal oscillators producing 3.57954 and 3.579545 MHz are connected between the OSC1 and OSC2 pins to constitute
an oscillator circuit.
Power pin. Usually set to 0 V.
Controls the tristate outputs of Q1 to Q4.
Enabled when high; high impedance when low.
Tristate received data output
High when the continuation time of a valid tone pair exceeds the time set by the external CR.
Set high when a valid tone pair is detected.
17 Connected CR sets the guard time.
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