EMC2303-1-KP-TR Standard Microsystems (SMSC), EMC2303-1-KP-TR Datasheet - Page 42

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EMC2303-1-KP-TR

Manufacturer Part Number
EMC2303-1-KP-TR
Description
Manufacturer
Standard Microsystems (SMSC)
Datasheet

Specifications of EMC2303-1-KP-TR

Operating Supply Voltage (typ)
3.3V
Operating Supply Voltage (min)
3V
Operating Supply Voltage (max)
3.6V
Operating Temp Range
-40C to 125C
Operating Temperature Classification
Automotive
Mounting
Surface Mount
Pin Count
12
Lead Free Status / RoHS Status
Compliant
Revision 1.2 (03-22-10)
5.18
ADDR
ADDR
5Ch
5Dh
3Eh
3Fh
4Eh
4Fh
5Eh
5Fh
R/W
R/W
R/W
The TACH Target Registers hold the target tachometer value that is maintained by the RPM-based
Fan Speed Control Algorithm.
The value in the TACH Target Registers will always reflect the current TACH Target value.
If one of the algorithms is enabled, setting the TACH Target Register to FFh will disable the fan driver
(set the fan drive setting to 0%). Setting the TACH Target to any other value (from a setting of FFh)
will cause the algorithm to invoke the Spin Up Routine after which it will function normally.
The Tach Target is not applied until the high byte is written. Once the high byte is written, the current
value of both high and low bytes will be used as the next Tach target.
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.
TACH Reading Registers
R
R
R
R
R
R
R
shows the simplified translation of TACH Reading Register count to RPM assuming a 2-pole fan,
TACH Target
TACH Target
Fan 1 TACH
Fan 1 TACH
Fan 2 TACH
Fan 2 TACH
Fan 3 TACH
Fan 3 TACH
AN17.4 RPM to TACH Counts
3 High Byte
REGISTER
3 Low Byte
REGISTER
Low Byte
Low Byte
Low Byte
shows the detailed conversion from TACH measurement (COUNT) to RPM while
Table 5.27 TACH Target Registers (continued)
Table 5.28 TACH Reading Registers
4096
4096
4096
4096
B7
B7
16
16
16
16
2048
2048
2048
2048
B6
B6
DATASHEET
8
8
8
8
Conversion.
1024
1024
1024
1024
B5
B5
42
4
4
4
4
512
512
512
512
B4
B4
2
2
2
2
Multiple RPM-Based PWM Fan Controller for Three Fans
256
256
256
256
B3
B3
1
1
1
1
128
128
128
128
B2
B2
-
-
-
-
B1
B1
64
64
64
64
-
-
-
-
B0
B0
32
32
32
32
-
-
-
-
SMSC EMC2303
DEFAULT
DEFAULT
Datasheet
F8h
FFh
FFh
F8h
FFh
F8h
FFh
F8h
Equation

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