bd6709fs ROHM Co. Ltd., bd6709fs Datasheet - Page 22

• 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.

〇Level amplifier ＜BD6709FS, BD6721FS＞
〇Restart from lock protecting operation＜BD6709FS, BD6718FV, BD6722FS＞
(Same as area ① in Fig.73)
(Same as area ② in Fig.73)
(Same as area ③ in Fig.73)
Level amplifier amplifies the voltage of VTH by the ratio of resistor connected to LAOUT and LAIN to be output to
LAOUT.
In the case of Fig.75, LAOUT = (10k + 20k)/10k×VTH, and the input voltage at VTH terminal is approximately tripled.
It enables a broad setting corresponding to the characteristics of thermistor resistor.
Furthermore, when VTH terminal voltage need not be amplified, LAOUT and LAIN should be shorted as shown in
Fig.76. VTH terminal voltage equals to LAOUT terminal voltage.
When restarting from lock protection operation, VMIN becomes L so that the motor restarts in full torque.
The time for reaching full torque is determined by resistor R1 and capacitor C1 connected to VMIN terminal as shown in
Fig.77.
Assuming that VTH thermistor resistor is open, when VTH terminal voltage is above VREF, full torque operation is
performed.
Area ①
Area ②
Area ③
R1=10k Ω
Fig.75
R2=20k Ω
Level amplifier application
rpm
VREF
Fig.74
Fig.77
LAOUT or VTH＜OSC L voltage＜VMIN＜OSC H voltage
Rotating speed in full torque operation (ON-DUTY = 100%)
OSCL voltage＜LAOUT or VTH＜VMIN＜OSC H voltage
Rotating speed is determined by ON-DUTY set by LAOUT terminal voltage or VTH
terminal voltage.
OSCL voltage＜VMIN＜LAOUT or VTH＜OSC H voltage
Rotating speed is determined by ON-DUTY set by VMIN terminal voltage.
The motor can be stopped by setting OSCH voltage＜VMIN (ON-DUTY = 0%).
LAOUT
LAIN
VTH
R1
R2
VREF
③
③Rotating speed determined by VMIN terminal
－
Setting of rotating speed
+
Restart from lock protection (DC input)
C1
②
②Determined by LAOUT terminal voltage or VTH
22/40
①
①Rotating speed in full torque operation
COSC
LAOUT
VMIN
－
+
Fig.76
Ta
VREF
Level amplifier application 2
LAOUT
LAIN
VTH
－
+