AM7301

Motor Driver ICs

http://www.amtek-semi.com

6

Specifications subject to change without notice

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Fig.3 CPWM control principle

Assume Rs1 and Rs2 ratio equal to 0.37Vref.

1. Turbo start mode:

Turbo start function can be apply, when adds Cs1 capacitor on VRS PIN. The time

constant is defined by Cs1, Rs1 and Rs2. When power on, The VRS voltage will be

rising from 0V to setting voltage by dividing Rs1 and Rs2 ratio.

In Turbo start area, the motor will full speed rotation at the beginning. After VRS

voltage arising to 0.1Vref, the motor will reduce the rotation speed. That is due to

chopping CPWM by VRS voltage. Finally the motor will into normal operation area.

2. Normal operation mode:

The VRS voltage will be setting by Rs1 and Rs2. Adjust the Rs1 and Rs2 ratio that

can control the rotation speed of Fan module by chopping the CPWM signal. When

VRS voltage rising to 0.37Vref (our assumption). The Motor will be fixed rotation

speed in normal operation mode.

3. LOCK operation mode:

When motor into lock mode operation, the VRS voltage will be reset to 0V by internal

circuit. And the VRS voltage will be recharged by Rs1, Rs2 and Cs1, when lock

function is released.