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SMSC EMC2102 5.7.1.2Case 2 - Valid RPM << Target RPM < Spin-upLevel RPM, Figure 5.26 Spin-upCase 1 Fix, Figure 5.27 Theoretical Plot of Case

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Fan Speed Control with the EMC2102 Device

Valid Speed = 6000 rpm

Fan Drive Setting (51h)

Valid Speed = 5800 rpm

Valid Speed = 5580 rpm

Figure 5.26 Spin-up Case 1 Fix 2

5.7.1.2Case 2 - Valid RPM << Target RPM < Spin-up Level RPM

In this case, the target speed is smaller than the spin-up level speed (rpm60 or rpm75) and is much bigger than the valid speed. The theoretical plot of this situation is shown in Figure 5.27, "Theoretical Plot of Case 2".

Since the fan speed at the end of spin-up routine is always higher than the minimum valid speed, the EMC2102 will go to the normal operation after the spin-up routine.

Using the EVB-EMC2102 to test this situation with rpm75 (~5650 rpm), simply set the Valid TACH register (56h) with 4500 rpm and start the fan with TACH Target (57h) = 5500 rpm (Figure 5.28, "Spin- up Case 2").

Fan Speed

(RPM)RPM for

100% Drive

rpm60 or rpm75

Fan Speed Target Speed

Valid Speed

¼of Spin Up Time

Spin Up Time

Check TACH

Figure 5.27 Theoretical Plot of Case 2

Revision 0.2 (09-17-07)

USER MANUAL

SMSC EMC2102

30

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