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SMSC EMC2102 5.7.1.5Case 5 - Correct RPM Relationships with a Slow Response DC Fan, Figure 5.34 Spin-upCase, Figure 5.35 Spin-upCase 5 Fix

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Fan Speed Control with the EMC2102 Device

5.7.1.5Case 5 - Correct RPM Relationships with a Slow Response DC Fan

In this case, the spin-up routine is too short to make the fan reach a speed higher than the valid speed. Since the EMC2102 cannot detect a valid TACH at the end of spin-up routine, it will try to restart the fan. Depending on the fan, it is possible that after several spin-up cycles, the fan can reach the valid speed and operate normally.

Using the EVB-EMC2102 to test this situation with rpm60 (~4500 rpm), simply set the SPINUP_TIME (53h[1:0]) = 250 ms, Valid TACH (56h) = 4400 rpm, and start the fan with TACH Target (57h) = 5500 rpm. Multiple spin-up routines will be observed (Figure 5.34, "Spin-up Case 5").

Figure 5.34 Spin-up Case 5

To fix this problem, stop the fan and set the SPINUP_TIME = 2s, and restart the fan with 5500 rpm.

Increasing Spin-up time will make a longer 100% "kick" time and provide the fan with more power to speed-up (Figure 5.35, "Spin-up Case 5 Fix").

The problem also can be fixed by changing the spin up level from 60% to 75% if not done already, as previously discussed.

Longer 100% kick provides more driving power to speed-up the fan

Figure 5.35 Spin-up Case 5 Fix

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