RPM-Based Fan Controller with Multiple Temperature Zones & Hardware Thermal Shutdown
Datasheet
where:
poles = number of poles of the fan
(typically 2)
1
(n – 1)
-------------------- ---------------------------------
RPM =
×
× 1,966,080
[4]
[5]
(poles)
1
----
COUNT ×
m
n = number of edges measured
(typically 5)
m = the multiplier defined by the
RANGE bits
3,932,160 × m
--------------------------------------
RPM =
COUNT
COUNT = TACH Reading Register
value (in decimal)
7.34
Look Up Table Configuration Register
Table 7.51 Look Up Table Configuration Register
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
50h
7Dh
LUT
Configuration
USE_
DTS_P1
USE_
DTS_P2
LUT
LOCK
RPM /
PWM
PUSH1_
CFG
TEMP1_ TEMP3_ TEMP4_
CFG CFG CFG
R/W
00h
The Look Up Table Configuration Register controls the setup information for the temperature to fan
drive look up table.
APPLICATION NOTE: This register is duplicated at 50h as well as 7Dh for ease of programming using block write
mode. Example: Set register 50h to unlock the table and register 7Dh to lock the table.
The External Diode 2 channel is always used as the Temperature 2 input to the Fan Control Look Up
Table.
Bit 7 - USE_DTS_P1 - This bit determines whether the Pushed Temperature 1 Register is using DTS
data.
‘0’ (default) - The Pushed Temperature 1 Register is not using DTS data. The contents of the
Pushed Temperature 1 registers are standard temperature data.
‘1’ - The Pushed Temperature 1 Register is loaded with DTS data. The contents of this register are
automatically subtracted from a fixed value of 100°C before being compared to the Look Up Table
threshold levels.
Bit 6 - USE_DTS_P2 - This bit determines whether the Pushed Temperature 2 Register is using DTS
data.
‘0’ (default) - The Pushed Temperature 2 Register is not using DTS data. The contents of this
register are standard 2’s complement temperature data.
‘1’ - The Pushed Temperature 2 Register is loaded with DTS data. The contents of this register are
automatically subtracted from a fixed value of 100°C before being compared to the Look Up Table
threshold levels.
Bit 5 - LUT_LOCK - This bit locks updating the Look Up Table entries and determines whether the look
up table is being used.
‘0’ (default) - The Look Up Table entries can be updated normally. The Look Up Table will not be
used while the Look Up Table entries are unlocked. During this condition, the PWM output will not
change states regardless of temperature or tachometer variation.
SMSC EMC2113
Revision 1.2 (10-08-09)
DATA6S7HEET
SMSC [ SMSC CORPORATION ]
