SMSC EMC2102 User Manual download pdf (Page 36)

Fan Speed Control with the EMC2102 Device

Revision 0.2 (09-17-07)

USER MANUAL SMSC EMC2102

Note: Although users can set the number of edges (in register 52h) to either 3, 5, 7 or 9, it is strongly

recommended using the default value 5 while driving a 2-pole DC fan. This equal to one

complete fan revolution for a 2-pole fan.

ChipMan translates TACH counts to the RPM value and displays the fan speed. For applications not

using ChipMan software, the following equation can be used to convert the TACH Reading values to

the real RPM speeds.

6.2 Characterizing a DC Fan with EVB-EMC2102 and ChipMan

As a very important component in the closed-loop, the DC fan’s characteristics have a great impact

on the control system’s performance. Using the EVB-EMC2102 and ChipMan software tool, a 5V DC

fan’s characteristics can be easily tested.

In general, the following parameters need to be characterized:

 Minimum Startup Speed

 Stall Speed

 Minimum Valid TACH Speed

 Maximum Fan Speed

 Spin-up Level (i.e., rpm60 and rpm75. Refer to Section 5.3.1, "Fan Control Parameters" for more

details)

6.2.1 General Setup

 Setup the system and make sure the hardware and software are working as discussed in Section

5.1, "Experiment 1 - Manual Fan Control".

 Unplug the on-board DC fan from connector P1

 Connect the DC fan to be tested to P1 (refer to EVB-EMC2102 User Manual for the DC fan

connector pinouts)

Figure 6.3 Fan TACH Measurement With EMC2102

where:

EDGES = number of edges set by register 52h[4:3]

COUNT = TACH Reading (58h) value [1]

Poles = number of pole pairs in the DC fan

m = factor defined by LIMIT2K (52h[6])

(m = 1 for 500 rpm and m = 4 for 2000 rpm)

Fan Tach Signal

3 EDGES

5 EDGES

7 EDGES

32.768kHz

Clock

n-EDGE WINDOW

WINDOW

COUN

oles

EDGES

RPM *

983040

1−

1 2 ... 31 32 33 34 35 36 37 38

Comments to this Manuals

No comments

SMSC EMC2102 User Manual Page 36

Comments to this Manuals

Related products and manuals for Unknown SMSC EMC2102