bd6709fs ROHM Co. Ltd., bd6709fs Datasheet - Page 31

• 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.

9) The upside output of pre-driver ＜ BD6718FV 、 BD6722FS ＞
＊ R2 is used to suppress the power consumption of IC.
High side output of pre-driver (half pre-driver) are constant current open-drain output. Decide the resistance of R1 so
that the voltage generated between G-S of external Pch transistor may exceed enough the threshold voltage of the
transistor.
Ex. At R1=100 Ω , VGSP : between G-S of the Pch transistor.
Especially BD6722FS, useless power consumption in the upside output is suppressed by appropriately setting R2,
and a permissible loss of the package can be used effectively in lower output.
At VM = 12V, The power consumption of upside output transistor M1 is
V
P
At R1 = 100 Ω , R2 = 0 Ω
At R1 = 100 Ω , R2 = 1k Ω
GSP
M1
= { VM - (R1 + R2) × IH } × IH
= 100 Ω × 10mA (typ.)
= 1V
= R1 × IH
Fig.96 Voltage setting between G-S of external Pch transistor
IH
M1
10
6
7
9
P
P
M1
M1
=110mW
=10mW
R2
31/40
R1
VM line