EMC2305-1-AP-TR SMSC, EMC2305-1-AP-TR Datasheet - Page 47

• Manufacturer Part Number: EMC2305-1-AP-TR
• Description: Industrial Temperature Sensors Penta RPM-Based PWN Fan Speed Controller
• Manufacturer: SMSC

Specifications of EMC2305-1-AP-TR

• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

Multiple RPM-Based PWM Fan Controller for Five Fans
Datasheet
SMSC EMC2305
ADDR
4Fh
5Eh
5Fh
6Eh
6Fh
7Eh
7Fh
RPM
R/W
The TACH Reading Registers’ contents describe the current tachometer reading for each of the fans.
By default, the data represents the fan speed as the number of 32kHz clock periods that occur for a
single revolution of the fan.
Equation [2]
[3]
measuring 5 edges, with a frequency of 32.768kHz. These equations are solved and tabulated for ease
of use in
Whenever the high byte register is read, the corresponding low byte data will be loaded to internal
shadow registers so that when the low byte is read, the data will always coincide with the previously
read high byte.
R
R
R
R
R
R
R
shows the simplified translation of TACH Reading Register count to RPM assuming a 2-pole fan,
=
------------------- -
(
poles
RPM
Fan 2 TACH
Fan 3 TACH
Fan 3 TACH
Fan 4 TACH
Fan 4 TACH
Fan 5 TACH
Fan 5 TACH
AN17.4 RPM to TACH Counts
1
REGISTER
Low Byte
Low Byte
Low Byte
Low Byte
shows the detailed conversion from TACH measurement (COUNT) to RPM while
)
×
=
--------------------------------- -
COUNT
3,932,160 m
------------------------------------- -
Table 5.28 TACH Reading Registers (continued)
(
COUNT
n 1
–
4096
4096
4096
)
×
B7
16
16
16
16
---- -
m
1
×
×
f
TACH
2048
2048
2048
B6
DATASHEET
8
8
8
8
×
60
Conversion.
1024
1024
1024
B5
47
4
4
4
4
512
512
512
B4
2
2
2
2
poles = number of poles of the fan
COUNT = TACH Reading Register
measurement frequency (typically
256
256
256
m = the multiplier defined by the
B3
n = number of edges measured
1
1
1
1
(typically 5 for a 2 pole fan)
f
TACH
value (in decimal)
128
128
128
B2
-
-
-
-
RANGE bits
(typically 2)
32.768kHz)
= the tachometer
where:
B1
64
64
64
-
-
-
-
Revision 1.2 (03-22-10)
B0
32
32
32
-
-
-
-
DEFAULT
F8h
FFh
F8h
FFh
F8h
FFh
F8h
Equation
[2]
[3]