FD0251b

FD0255b

Rev1.9 Dec. 18, 2008

P.3

FEELING

TECHNOLOGY

PWM control

PWM(pulse-width modulation) is used for the speed control for FD0255b. 2 types of PWM input signals can be

used :

1.

Voltage mode PWM :

Applying a constant(DC) voltage to the PWM pin and the FD0255b will generate PWM pulses internally with

the “ON” duty cycle ratio according to the diagram below(Figure.3), which can be utilized by the user to control

the speed of the motor. The rotation speed will be higher if the voltage applied to the PWM pin is higher.

Figure.3

2.

Pulse mode PWM :

User can also apply PWM pulses directly to the PWM pin. The FD0255b will pass this pulse to the coil driver

with the original duty-cycle ratio.

Note:

(1) This function is only available for FD0255b

(2) While using pulse mode PWM, the “High” Value of the input pulse should be higher than 0.5*VDD and the

“Low” value should be lower than 0.14*VDD

(3) The lower-limit for the PWM pulse frequency is 200Hz, and the recommended frequency range is higher

than 30KHz where the PWM input pulses will not generate acoustic noise.

Note. The “PWM” pin contains an internal pull-up resistor so the FD0255b will rotate at full-speed(100% ON)

when this pin is left un-connected(floating).

"ON" ratio

0%

100%