EMC2104 datasheet(91/101 Pages) SMSC

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Dual RPM-Based PWM Fan Controller with Hardware Thermal Shutdown

Datasheet

SMSC EMC2104

Revision 1.74 (05-08-08)

DATASHEET

Appendix B Look Up Table Operation

The EMC2104 uses a look-up table to apply a user-programmable fan control profile based on

measured temperature to each fan driver. In this look-up table, each temperature channel is allowed

to control the fan drive output independently (or jointly) by programming up to eight pairs of

temperature and drive setting entries.

The user programs the look-up table based on the desired operation. If the RPM based Fan Speed

Control Algorithm is to be used (see Section 6.6), then the user must program an RPM target for each

temperature setting of interest. Alternately, if the RPM based Fan Speed Control Algorithm is not to be

used, then the user must program a drive setting for each temperature setting of interest.

If the measured temperature on the External Diode channel meets or exceeds any of the temperature

thresholds for any of the channels, the fan output will be automatically set to the desired setting

corresponding to the exceeded temperature. In cases where multiple temperature channel thresholds

are exceeded, the highest fan drive setting will take precedence.

When the measured temperature drops to a point below a lower threshold minus the hysteresis value,

the fan output will be set to the corresponding lower set point.

The following sections show examples of how the Look Up Table is used and configured. Each Look

Up Table Example uses the Fan 1 Look Up Table Registers configured as shown in Table B.1.

B.1

Example #1

This example does not use the RPM based Fan Speed Control Algorithm. Instead, the Look Up Table

is configured to directly set a fan drive setting based on the temperature of four of its measured inputs.

The configuration is set as shown in Table B.2.

Once configured, the Look Up Table is loaded as shown in Table B.3. Table B.3 shows three

temperature configurations using the settings in Table B.3 and the final fan drive setting that the Look

Up Table will select.

Table B.1 Look Up Table Format

STEP

TEMP 1

TEMP 2

TEMP 3

TEMP 4

LUT DRIVE

LUT Temp 1

Setting 1 (52h)

LUT Temp 2

Setting 1 (53h)

LUT Temp 3

Setting 1 (54h)

LUT Temp 4

Setting 1 (55h)

LUT Drive

Setting 1 (51h)

LUT Temp 1

Setting 2 (57h)

LUT Temp 2

Setting 2 (58h)

LUT Temp 3

Setting 2 (59h)

LUT Temp 4

Setting 2 (5Ah)

LUT Drive

Setting 2 (56h)

LUT Temp 1

Setting 3 (5Ch)

LUT Temp 2

Setting 3 (5Dh)

LUT Temp 3

Setting 3 (5Eh)

LUT Temp 4

Setting 3 (5Fh)

LUT Drive

Setting 3 (5Bh)

LUT Temp 1

Setting 4 (61h)

LUT Temp 2

Setting 4 (62h)

LUT Temp 3

Setting 4 (63h)

LUT Temp 4

Setting 4 (64h)

LUT Drive

Setting 4 (60h)

LUT Temp 1

Setting 5 (66h)

LUT Temp 2

Setting 5 (67h)

LUT Temp 3

Setting 5 (68h)

LUT Temp 4

Setting 5 (69h)

LUT Drive

Setting 5 (65h)

LUT Temp 1

Setting 6 (6Bh)

LUT Temp 2

Setting 6 (6Ch)

LUT Temp 3

Setting 6 (6Dh)

LUT Temp 4

Setting 6 (6Eh)

LUT Drive

Setting 6 (6Ah)

LUT Temp 1

Setting 7 (70h)

LUT Temp 2

Setting 7 (71h)

LUT Temp 3

Setting 7 (72h)

LUT Temp 4

Setting 7 (73h)

LUT Drive

Setting 7 (6Fh)

LUT Temp 1

Setting 8 (75h)

LUT Temp 2

Setting 8 (76h)

LUT Temp 3

Setting 8 (77h)

LUT Temp 4

Setting 8 (78h)

LUT Drive

Setting 8 (74h)

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