57
8Bit Single Chip Microcontroller
DMC73C168
5.7.4. Programmable Divider
Programmable divider is composed of two modules prescaler, 4bit swallow counter and 12 bit
binary programmable counter.
In pulse swallow dividing type, 1/16, 1/17 - modules prescaler is active in case of FM BAND and
1/2 divider is added to the front stage of prescaler.
LATCH
AMP
VCOH
VCOL
1/2
1/16, 1/17
SWALLOW COUNTER
4BIT
AMP
4BIT REG.
12BIT REG.
12 BIT
PROGRAMMABLE
COUNTER
TO PHASE
DETECTOR
Figure 5-7-7. Circuit Diagram of Programmable Divider
In direct dividing type, input frequency (VCOL) is transfered to programmable counter directly.
Both VCOH and VCOL ports have built-in AC AMP, INPUT signal must be cut by coupling
capacitor.
5.7.5. Phase Detector
Phase detector detects the difference of phased between the reference frequency(Fref) and
programmable counter output (VCO/N).
The output of this circuit puts out its error compoment to the EO1 and EO2 pins. Output from
EO1, EO2 can be feedback to VCO through low pass filter.
VDD
Reference
frequency
Fref
BUFFER
BUFFER
PHASE
DETECTOR
EO1
EO2
Programmable
counter output
VCO/N
VDD
Figure 5-7-8. Phase Detector Circuit Diagram
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