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SMSC EMC2102 6.2.8.1Spin-upLEVEL (Register 53h[2]), 6.2.8.2Minimum Fan Speed, 6.2.8.3Valid TACH Count Speed (Function of Register 56h), 6.2.8.4Maximum Fan Speed

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Fan Speed Control with the EMC2102 Device

6.2.7Determine the Spin-up Levels (rpm60 and rpm75)

Drive the fan with 60% of the maximum output (register 51h = 99h) and the rpm value in the TACH Reading register (58h) will be the fan’s rpm60

Drive the fan with 75% of the maximum output (register 51h = BFh) and the rpm value in the TACH Reading register (58h) will be the fan’s rpm75

6.2.8Using the Tested Parameters

All parameters discussed above will vary from fan to fan and with fan aging, therefore some margins have to be added when selecting the fan control settings. A minimum of 10% of full fan speed is recommended for margins.

6.2.8.1Spin-up LEVEL (Register 53h[2])

This parameter has to be set so that the corresponding fan speed is greater than Minimum Startup Speed + Margin.

6.2.8.2Minimum Fan Speed

To avoid stalling, the fan speed (a function of Fan Driver Setting [51h] or a function of TACH Target [57h]) needs to be greater than Stall Speed + Margin at all times.

6.2.8.3Valid TACH Count Speed (Function of Register 56h)

The EMC2102 will not respond to any TACH Target (57h) value that has a corresponding speed slower than Minimum Valid TACH Speed + Margin, unless the value is FFh which will stop the fan. This ensures that the RPM control algorithm will not drive too low.

6.2.8.4Maximum Fan Speed

Use the measured maximum fan speed minus margin as the Maximum Fan Speed.

Revision 0.2 (09-17-07)

USER MANUAL

SMSC EMC2102

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Contents

USER MANUAL Page Page Page Page Page Figure 4.1 EMC2102 Fan Control Evaluation System Figure 4.2 EVB-EMC2102Board 5.1.1ChipMan Installation 5.1.2Setting Up the ChipMan Figure 5.1 ChipMan Message for First Operation Note: Figure 5.2 ChipMan Device Selection Window Figure 5.3 Selecting the Device and Master Controller Type Figure 5.4 ChipMan Operation Window Notes: Figure 5.5 Changing Fan Speed 5.1.3Plotting From ChipMan Figure 5.6 Plotting from the ChipMan Figure 5.7 Plot Windows Figure 5.8 Plot Examples 5.2.1Getting Started 5.2.2Basic RPM Based Fan Control Figure 5.9 Plots for Proper Control Settings 5.2.3Effects of Loading Figure 5.10 Effects of Loading 5.2.4Register Change Summary Table 5.1 Register Change Summary for Experiment REGISTER DEFAULT 5.3.1Fan Control Parameters Figure 5.11 Fan Control Parameters 5.3.2Getting Started 5.3.3Forced Kick Function Figure 5.12 Forced Kick Function 5.3.4Spin-UpLevel Figure 5.13 60% Spin Level Setting 5.3.5Spin-UpTime Figure 5.14 Reduced Spin-upTime 5.3.6Register Change Summary Table 5.2 Register Change Summary for Experiment 5.4.1General Setup 5.4.2Controlling the Ramp Rate Figure 5.15 Default Ramp Rate Figure 5.16 Default Step Size with Different UPDATE Settings Figure 5.17 Default UPDATE with Different Step Size Settings Figure 5.18 Exceptionally Slow Rate 5.4.3Register Change Summary Table 5.3 Register Change Summary for Experiment 5.5.1General Setup 5.5.2Fan Configuration Register (52h) Figure 5.19 Update Time Modifications 5.5.3FAN Minimum Drive Register (55h) and Valid TACH Count (56h) Figure 5.20 Minimum Drive Setting Figure 5.21 Valid Tach Count Setting 5.5.4Register Change Summary Table 5.4 Register Change Summary for Experiment 5.6.1General Setup 5.6.2Fan Spin and Stall Interrupts Figure 5.22 Fan Spin and Stall 5.6.3Register Change Summary 5.7.1.1Case 1 - Spin-upLvel RPM < Valid RPM < Target RPM Figure 5.24 Theoretical Plot of Case Figure 5.25 Spin-upCase 1 Fix 5.7.1.2Case 2 - Valid RPM << Target RPM < Spin-upLevel RPM 5.7.1.3Case 3 - Valid RPM =< Target RPM << Spin-upLevel RPM Figure 5.30 Spin-upCase Figure 5.31 Spin-upRoutine Restarted During Normal Operation 5.7.1.4Case 4 - 4.Valid RPM < Spin-upLevel RPM (rpm60 or rpm75) < Target RPM 5.7.1.5Case 5 - Correct RPM Relationships with a Slow Response DC Fan Figure 6.1 A Typical 2-poleDC Fan Figure 6.2 Output Signal of a 2-poleFan Figure 6.3 Fan TACH Measurement With EMC2102 [1] 6.2.1General Setup 6.2.2Set the Correct LIMIT2K Value 6.2.3Determine the Number of Poles and the Maximum Fan Speed 6.2.4Determine the Minimum Startup Speed 6.2.5Determine the Stall Speed 6.2.6Determine the Minimum Valid TACH Speed 6.2.8.1Spin-upLEVEL (Register 53h[2]) 6.2.8.2Minimum Fan Speed 6.2.8.3Valid TACH Count Speed (Function of Register 56h) 6.2.8.4Maximum Fan Speed