EMC2113 Datasheet, PDF (29/85 Pages) SMSC Corporation – RPM-Based Fan Controller with Multiple Temperature Zones & Hardware Thermal Shutdown

RPM-Based Fan Controller with Multiple Temperature Zones & Hardware Thermal Shutdown
Datasheet
6.4.1 Programming the Look Up Table
When the Look Up Table is used, it must be loaded and configured correctly based on the system
requirements. The following steps outline the procedure.
1. Determine whether the Look Up Table will drive a PWM duty cycle or a tachometer target value
and set the RPM / PWM bit in the Fan LUT Configuration Register (see Section 7.34, "Look Up
Table Configuration Register").
2. Determine which measurement channels (up to four) are to be used with the Look Up Table and
set the TEMP1_CFG, TEMP3_CFG and TEMP4_CFG bits accordingly in the Fan LUT
Configuration Register.
3. For each step to be used in the LUT, set the Fan Setting (either PWM or TACH Target as set by
the RPM / PWM bit). If a setting is not used, then set it to FFh (if a PWM) or 00h (if a TACH Target).
Load the lowest settings first in ascending order (i.e. Fan Setting 1 is the lowest setting greater
than “off”. Fan Setting 2 is the next highest setting, etc.). See Section 7.35, "Look Up Table
Registers".
4. For each step to be used in the LUT, set each of the measurement channel thresholds. These
values must be set in the same data format that the data is presented. If DTS is to be used, then
the format should be in temperature with a maximum threshold of 100°C (64h). If a measurement
channel is not used, then set the threshold at FFh.
5. Update the threshold hysteresis to be smaller than the smallest table step.
6. Configure the RPM-based Fan Speed Control Algorithm if it is to be used. See Section 7.24, "Fan
Configuration 1 Register" for more details.
7. Set the LUT_LOCK bit to enable the Look Up Table and begin fan control in the Fan LUT
Configuration Register.
6.4.2 DTS Support
The EMC2113 supports DTS (Intel’s Digital Temperature Sensor) data in the Fan Control Look Up
Table. Intel’s DTS data is a positive number that represents the processor’s relative temperature below
a fixed value called T_CONTROL which is generally equal to 100°C for Intel Mobile processors. For
example, a DTS value of 10°C means that the actual processor temperature is 10°C below T_CONTROL
or equal to 90°C.
Either or both of the Pushed Temperature Registers can be written with DTS data and used to control
the fan driver. When DTS data is entered, then the USE_DTS_Fx bit must be set in the Fan LUT
Configuration register. Once this bit is set, the DTS data entered is automatically subtracted from a
value of 100°C. This delta value is then used in the Look Up Table as standard temperature data.
APPLICATION NOTE: The device is designed with the assumption that T_CONTROL is 100°C. As such, all DTS
related conversions are done based on this value including Look Up Table comparisons. If
T_CONTROL is adjusted (i.e. T_CONTROL is shifted to 105°C), then all of the Look Up Table
thresholds should be adjusted by a value equal to T_CONTROL - 100°C.
6.5
PWM Input
The EMC2113 supports a PWM input that is used as an input to the fan speed control Look Up Table.
This is controlled by the PUSH1_CFG bit and either the TEMP1_CFG or TEMP3_CFG bits in the Look
Up Table Configuration register (see Section 7.34).
When a signal is driven into the PWM_IN pin, then the device will automatically calculate the duty cycle
of the input signal (provided that the frequency is within the specified range). This value is stored in
the PWM Input Duty Cycle register and may be used as an input to the Look Up Table.
APPLICATION NOTE: The PWM Input duty cycle value is a unit-less value that does not correspond to specific
temperature values. When used in the Fan Control LUT, It is compared against unit-less 7-
bit values that represent PWM duty cycle thresholds to control the desired fan speed.
SMSC EMC2113
29
DATASHEET
Revision 1.2 (10-08-09)