Kanardia Boxi II, Manual

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Boxi II – Manual 2.4 Output Stage
Description Value
Maximum switch voltage 50 V
Maximum current 0.5 A
Switch resistance 2.5 Ohm
Table 3: PTT output characteristics.
2.4.2 Trim 1 and Trim 2
Motor output stage is used to control DC motors. It consists of MOSFET
switch driver with integrated short-circuit and over-temperature protection. It
also provides open load detection on the output stage.
Output stage can be configured either as two split push-pull outputs or one
full-bridge
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with PWM output. Full-bridge (motor) configuration is used for
bidirectional driving of DC-motors (trim actuators, etc.), while the split mode
allows controlling up to two loads (unidirectional motors, lights, relays, etc.).
Table 4 shows characteristics of MOSFET motor driver.
Description Value
Voltage 6 - 36 V
Current 1.5 A (max)
Switch resistance 250 mOhm
PWM frequency 12 kHz
Table 4: Motor driver characteristics.
In the motor mode the PWM switching also is implemented. Therefore it is
possible to configure soft-start or to limit the maximum power of the motor.
The user must configure start and finish PWM duty cycle and time to transit
from start to finish value.
PWM mode works like quick switching the output to on and off. The duty
cycle between on and off state can be changed. This way the power delivered
to the load is reduced. The switching is fast and at fixed frequency.
With change of PWM duty cycle the soft start of motor is realized in Boxi II.
On figure 1 the idea of soft start is presented. On keypress on Joyu the Trim
output starts switching with cycle period. On the first PWM cycle the
Start
PWM duty cycle is used. On consecutive cycles the duty cycle is increased until
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