UH255

CMOS IC

UNISONICTECHNOLOGIESCO.,LTD

6 of 6

www.unisonic.com.tw

QW-R118-027.a



FUNCTIONAL DESCRIPTIONS

Refer to the block diagram above, UH255 is composed of the following blocks:

1.Bias generator

The bias generator provides bias references for the analog blocks.

2.Oscillator

The integrated oscillator provides the clock signal for the digital control logics.

3.Power-on Reset

The block of power-on reset is used to detect the power-up ramp and reset the digital circuits.

4.Chopper Amplifier

The chopper amplifier structure can achieve a higher magnetic sensitivity and dynamically removes both the offset

and flicker noise at the same time.

5.Digital control logics

Generates controlling signals for the Hall sensor and Coil driver and a tachometer signal output(FG).

6.PWM speed control

Voltage mode PWM:

Applying a DC voltage to the PWM pin and the UH255 will generate PWM pulses internally. The rotation speed will

be higher if the voltage applied to the PWM pin is higher. The relation of the applying DC voltage and the ‘ON’ duty

cycle of PWM pulse is as follows:

Pulse mode PWM:

User can also apply PWM pulses directly to the PWM pin. The UH255 will pass this pulse to the coil driver with the

original duty-cycle ratio.

2. The PWM pulse frequency should be higher than 200Hz, and the recommended frequency range is higher than

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

UTC assumes no responsibility for equipment failures that result from using products at values that

exceed, even momentarily, rated values (such as maximum ratings, operating condition ranges, or

other parameters) listed in products specifications of any and all UTC products described or contained

herein. UTC products are not designed for use in life support appliances, devices or systems where

malfunction of these products can be reasonably expected to result in personal injury. Reproduction in

whole or in part is prohibited without the prior written consent of the copyright owner. The information

presented in this document does not form part of any quotation or contract, is believed to be accurate

and reliable and may be changed without notice.