FAN8420D3 View Datasheet(PDF) - Fairchild Semiconductor

Part Name

Description

Manufacturer

FAN8420D3

3-Phase BLDC Motor Driver

Fairchild Semiconductor 

FAN8420D3

4. Tsd (Thermal Shutdown)

BIAS

Gain

Controller

Q2

When the chip temperature rises above 175°C, the Q2 turns on and the output driver shuts down. When the chip temperature

falls off to about 150°C, then the Q2 turns off and the driver operates normally. TSD has the temperature hysteresis of about

25°C.

5. Rotational Direction Detection

VCC

H2+

+

H2−

−

H3+

+

H3−

−

DIR

20

D

Q

CK

D-F/F

Rotation

Forward

Reverse

20 DIR

Low

High

• The forward and the reverse rotations of the CD are detected by the D-F/F and the truth table is shown in the above.

• The rotational direction of the CD can be explained by the output waveforms of the Hall sensors. The three outputs of Hall

sensors be H1, H2 and H3 respectively.

When the spindle rotates in reverse direction, the Hall sensor output waveforms are shown in Fig.(a). The phases order are

in H1→H2→H3 with a 120°C phase difference.

H1

H2

H3

(a) Reverse rotation

On the other hand, if the spindle rotates in forward rotation, the phase relationship is H3→H2→H1 as shown in fig.(b)

10

Rev. 1.0.1

Oct.. 2000.

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