BA6901F_12 Datasheet, PDF (11/21 Pages) Rohm – Two-phase Full-wave DC Brushless Fan Motor Drivers

BA6901F
Datasheet
4) Variable speed control application
This is an example of the application which makes the fan motor rotating speed variable corresponding to ambient
temperature with thermistor by use of charging and discharging pulse circuit and PWM input.
VTH
-⁺
Thermistor
CR
1
FG
2
AL
3
ALB
4
PWM
5
LD
6
CNF
7
GND
8
Lock
Detect
Auto
Restart
PWM
-⁺
-⁺
-⁺
REG
A2
A1
-
+
TOUT
16
Vcc
15
A2
14
A1
13
CL
12
CS
11
H-
10
-
+
H+
HALL
9
Fig. 16 Example of temperature variable speed application
VTH
TOUT
PWM
A1
A2
Fig. 17 Temperature variable speed timing chart
When the temperature becomes the lower and the thermistor terminal voltage the higher, PWM pulse becomes the
shorter and speed is reduced as shown in Fig. 17.
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TSZ02201-0H1H0B100500-1-2
18.DEC.2012 Rev.002