Panasonic KX-MB2061CXB Service Manual page 47

For the control of motor current, Vref voltage of each motor driver is controlled.
When Vref voltage is high, motor current is increased, and the voltage is low, motor current is reduced.
In order to control the Vref voltage, PWM pulse is supplied from IC300 pin D8.
PWM pulse is inverted by Q521 and integrated by R533, R534, and C509, then converted to DC voltage.
This DC voltage is supplied to Vref pin of each motor drivers.
When duty of PWM pulse is high, Vref voltage is decreased and when duty is low, Vref voltage is increased.
For FB motor, motor current is controlled approx. 0.1A-0.25A.
For ADF motor, motor current is controlled approx. 0.2A-0.35A (ADF equipped model only).
2. Circuit diagram of current control and OCP circuit
3. Timing chart
Following timing charts are the example when PWM pulse duty are approx 9% and 45%.
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KX-MB2061CXB/KX-MB2061CX2/KX-MB2062CXB