EMC2103 datasheet(28/85 Pages) MICROCHIP

28 / 85 page

RPM-Based Fan Controller with Hardware Thermal Shutdown

Datasheet

 2013 Microchip Technology Inc.

DS0005250A-page 28

5.4.1

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 6.32).

2. Determine which measurement channels (up to four) are to be used with the Look Up Table and

set the 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 6.33.

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 5.5.1 for

more details.

Figure 5.3 Fan Control Look-Up Table Example

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