ST1115D SITI [Silicon Touch Technology Inc.], ST1115D Datasheet - Page 6

• Manufacturer Part Number: ST1115D
• Description: PWM Speed Control Double Coil Brushless DC Motor Driver
• Manufacturer: SITI [Silicon Touch Technology Inc.]

Application Circuits and Designer’s Notes
1. Temperature-sensing fan speed control ―Refer to Figure 1.
(1) If the linear temperature control is desired, the VT terminal is connected to a
(2) Figure 2 illustrates the desired temperature-speed curve. Assume that the resistance of
thermistor-resistor divider, as shown in Fig. 1. In this way, the fan speed can vary
linearly with respect to the temperature variation; the higher temperature results in the
faster speed.
the thermistor is R
the voltage V1 applied to the VT pin will result in the fan speed rpm1, and V2 applied to
the VT pin yielding rpm2. Note that the relation between the VT voltage and the fan
speed depends on the size and the coil impedance of the fan. To obtain the desired
temperature-speed curve, the resistance values of R1 and R2 in Fig. 1 can be roughly
selected by the following equations.
SP-ST1115CD-A.005
V
T
點晶科技股份有限公司
SILICON TOUCH TECHNOLOGY INC.
Figure 1. Fan speed control by the external temperature sensor.
HALL
C
IC
F
T1
GND
VDD
V
HIN
VT
CF
DD
when the temperature is at T1, and R
75 ohm
LOCK DETECTION
and PROTECTION
PWM CONTROL
Version
POWER
BLOCK
LOGIC
D1
：
A.005
+
-
T2
at T2. Also assume that
ST1115C/ST1115D
FGR
O1
O2
Page
COM
：
5