RPM-Based Fan Controller with HW Thermal Shutdown
Datasheet
Equation [3] shows the simplified translation of TACH Reading Register count to RPM assuming a 2-
pole fan, measuring 5 edges.
1
----------------------
1
sec
sec
min
COUNT = TACH Reading Register
value (in decimal)
⎛
⎝
⎞
⎠
⎛
⎝
⎞
⎠
--------
---------
RPM =
(revolutions) × 32768
× 60
.
[3]
COUNT
Table 6.27 Example TACH Reading for Specific Fan Speeds
TACH READING REGISTER
LIMIT2K
RPM
F6h
FFh (Note 6.2)
3Dh
0
1
0
1
0
1
0
1
500
500
2000
2000
8000
8000
16000
16000
F5h
0Fh
3Dh
07h
1Eh
Note 6.2 If the LIMIT2K bit is set, the minimum fan speed that can be measured is approximately
1950RPM. Any fan speed lower than this value will be reported as FFh.
6.20
Product ID Register
Table 6.28 Product ID Register
ADDRESS
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
FDh
Product ID
Register
(EMC2102-1)
0
0
0
1
0
1
0
0
14h
The Product ID Register contains a unique 8 bit word that identifies the product.
6.21
Revision Register
Table 6.29 Revision Register
ADDRESS
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
FFh
Revision
0
0
0
0
0
0
0
0
00h
The Revision Register contains a 8 bit word that identifies the die revision.
SMSC EMC2102
Revision 1.95 (10-19-06)
DATA4S5HEET
SMSC [ SMSC CORPORATION ]
