st1115j Silicon Touch Technology Inc., st1115j Datasheet - Page 6

• Manufacturer Part Number: st1115j
• Description: Flexible Speed Control Double Coil Brushless Motor Pre-driver
• Manufacturer: Silicon Touch Technology Inc.

Application Notes
1. The fan speed can be controlled by external PWM input signal. The fan speed curve can
2. The voltage setting of VZ, VM and VF determine DM, DH and RM. The input voltage of CF
3. Roughly, the VZ, VM, VF can be expressed by the following equations:
with fan motor.
To get motor precision speed curve, the voltage setting of VF, VM and VZ must be refined
be adjusted by setting appropriate voltage levels of the pins SEL, VZ, VM and VF. The
typical fan speed curve is shown in Figure.2, which indicates that the full speed is achieved
when the duty cycle of the PWM is DH (maximum PWM input duty), and RM ratio of the
full speed (say, 50%, for example) is achieved when the duty cycle is DM (minimum PWM
input duty). As for the duty cycle below DM, the fan will either stop or keep rotating at the
constant speed RM ratio of the full speed, depending on the voltage level of SEL (stop
when SEL= VDD and keep rotating at a constant speed when SEL=GND).
pin will determine the fan speed by controlling the duty of output terminals. The setting and
relation of control voltage are shown in Figure 3.
VF
=
SP-ST1115J-A.003
VDD
K
(2
點晶科技股份有限公司
SILICON TOUCH TECHNOLOGY INC.
−
D
MAX
Figure 3. The relations of the voltage of VZ, VM, VF
)
SEL Voltage
;
VM
and PWM duty ratio on output terminal.
GND
100%
VDD
=
VDD
K
Voltage of CF v.s. PWM Duty on Output
(2
Version
V
−
F
Fan Speed (under the minimum PWM duty)
D
MIN
V
)
M
：
;
A.003
VZ
V
Z
Keep Minimum speed
=
Voltage of CF (Vol.)
VM
1
−
−
D
STOP
D
MIN
V
MIN
DD
⋅
VF
,
where K is constant.
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ST1115J