bd6709fs ROHM Co. Ltd., bd6709fs Datasheet - Page 23

• Manufacturer Part Number: bd6709fs
• Description: Dc Brushless Motor Drivers For Cooling Fans Speed Controllable Single-phase Full-wave Dc Brushless Fan Motor Drivers
• Manufacturer: ROHM Co. Ltd.

b) PWM operation by pulse input ＜BD6709FS, BD6718FV, BD6721FS＞
By pulling up VTH(4PIN) to Vcc as shown in Fig.80, the output can operate in PWM by inputting the pulse signal
directly to VMIN(6PIN). However, adjust the value of R2 to become VTH=15V at Vcc≧15V so that the voltage of the
terminal VTH should not exceed 15V.
The ratio of ON-DUTY of the output changes by the cycle of the input pulse signal as shown in Fig.81.
b-2) PWM operation by pulse input＜BD6722FS＞
Pulse signal can be input to VMIN terminal for PWM operation as shown in Fig.78.
The ratio of ON-DUTY of the output changes by the cycle of the input pulse signal as shown in Fig.79.
Set the voltage of the terminal VTH as VREF＞VTH＞COSCH.
Set the voltage input to the VMIN terminal
as shown in Fig.79.
Output is ON in H logic of external PWM signal and OFF in L logic.
Set the voltage input to the VMIN terminal
as shown in Fig.81.
Output is ON in H logic of external PWM signal and OFF in L logic.
Fig.80
PULSE INPUT
COSC
VREF
VMIN
GND
GND
OUT
VTH
External PWM signal input
Fig.79 VTH, VMIN input voltage and output PWM timing chart in pulse input mode
R1
R2
Vcc
PWM input
VTH
VMIN
COSC
Fig.78
－
+
VREF
Direct control by DUTY of external PWM
LAIN
VTH
VMIN
COSC
LAOUT
-
+
23/40
LEVEL AMP
H level : VREF＞VMIN＞VOSCH
L level : VOSCL＞VMIN
H level : Vcc-2.0V＞VMIN＞VOSCH
L level : VOSCL＞VMIN
OUTPUT
A1H or A2H
GND
COSC
VMIN
Fig.81
+
-
PWM COMP
OUTPUT Tr
Pulse input operation timing chart
ON
OUTPUT Tr
OFF
OUTPUT Tr. OFF