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9TCS1083
MOBILE ACCESS—CLOCK SYNTHESIZER, TEMPERATURE SENSOR, & PWM FAN CONTROLLER FOR PORTABLE DEVICES
IDT MOBILE ACCESS—CLOCK SYNTHESIZER, TEMPERATURE SENSOR, & PWM FAN CONTROLLER FOR PORTABLE DEVICES
30
9TCS1083
REV 0.5 100511
Fan Controller
Fan Controller Description
The fan driver for the 9TCS1083 controls a 4-wire, 12V or
5V, multiple pole DC fan. The fan controller has three
modes of operation: (1) direct drive, (2) thermal trigger, and
(3) Dynamic PWM. All modes have register
programmability for the user to set the desired fan speed
and necessary parameters. The controller is also capable
of detecting stalled fans and upon detection will set the
appropriate alerts. The 9TCS1083 also has user
configuration registers to adjust both the ramp-rate and the
spin-up routine to accommodate different fan start up
requirements.
The fan controller uses the input from the user selectable
external diode connections, DX1 or DX2, or the user can opt
to use the on chip internal diode for the temperature sensor
for the fan controller. The 9TCS1083 fan controller can be
set to run a user specified fan speed. In this mode the
tachometer signal from the fan will be ignored. In thermal
trigger mode, the user specifies the temperature thresholds,
the temperature threshold hysteresis, and the
corresponding fan speed (fan tachometer target) for the
different temperature zones defined by the thresholds. The
controller will then run the fan at the specified fixed fan
speed settings depending on the temperature from the
sensors. In dynamic PWM mode, the fan controller will
adjust the PWM duty cycle to maintain the system defined
fan speed. In this mode, the system reads a temperature
sensor and the corresponding fan speed, tachometer
reading. The system will then determine and update the
9TCS1083 directly by writing the accessible registers byte
32 and byte 33. 9TCS1083 will then adjust the PWM to
achieve the desired system fan speed.
The PWM has ten bits of duty cycle resolution with a 25kHz
frequency. The PWM frequency is selectable between 22,
25, and 27kHz.
The 9TCS1083 includes hardware programmable
temperature limits and dedicated system shutdown output
for thermal protection.
Fan Controller System Diagram (Schematic
Example)
Fan Selection Detail
The 9TCS1083 fan controller will control 5V - 12V Brushless
DC fans. The fans need to be 4-wire fans and can have one
to four poles. The number of fan poles is specified in
Register byte[24], bit[3:2]. A 2-pole fan is the default.
Modes of Operation
The 9TCS1083 fan controller has three user selectable
methods to control the fan speed. The default fan speed
control mode is Thermal Trigger mode. The modes are
selected by writing the I2C register byte[24], bit[7:6] as
follows:
The PWM frequency can be set by writing register byte[24],
bit[5:4] as follows:
Byte[24], Bit[3:2]
Fan Poles
[00] (default)
1
[01]
2
[10]
3
[11]
4
Fan Controller Modes
Byte[24], Bit[7:6]
Direct Drive
[00]
Thermal Trigger (default)
[01]
Dynamic PWM
[10]
PWM
Frequency
Duty Cycle
Resolution [# bits]
Byte[24],
Bit[5:4]
25kHz (default)
10
00
22kHz
11
01
27kHz
9
10
IDT
MobileAccess
9TCS1083/85
PWM
TACH
VCC
PWM
TACH
GND
5V/12V 4-wire FAN
5V/12V
10K
3.3V/5V
10K
4.7K