FD0251b

FD0255b

Rev1.9 Dec. 18, 2008

P.2

FEELING

TECHNOLOGY

PIN CONNECTION

Figure.2

PIN DESCRIPTIONS

Legend: I=input, O=output, I/O=input/output, P=power supply, G=ground

FUNCTIONAL DESCRIPTIONS

Refer to the block diagram (Figure.1), FD0251b/FD0255b is composed of the following building blocks:

Bias generator

The bias generator provides precise, temperature- and process-insensitive bias references for the analog blocks.

These references guarantee proper operation of the IC under all conditions specified in this specification.

Oscillator

The built-in oscillator provides the clock signal for the digital control logics

Power-on Reset

Used to detect the power-up ramp and reset the digital circuits to achieve correct operation as soon as the power is

ready.

Chopper Amplifier

To achieve a higher magnetic sensitivity the chopper amplifier structure is adopted in this design. Use of this

structure dynamically removes both the offset and flicker noise at the same time.

Digital control logics

Hall sensor part – generates controlling signals for the Hall sensor.

Coil driver part – generates controlling signals for the Coil driver.

Tachometer (FG) signal output

Name

I/O

FD0251b

FD0255b

Description

FG

O

1

1

Frequency generation

VSS

G

2

2

Ground

NO

O

3

3

Driver output

SO

O

4

4

Driver output

VDD

P

5

5

Positive power supply

PWM

I

-

6

Pulse Width Modulation speed control

b

1

2

3

4

5

b

g

b

1

2

3

4

6

a

g

5

FD0251b

FD0255b