EMC2301 Standard Microsystems Corp., EMC2301 Datasheet - Page 33

• Manufacturer Part Number: EMC2301
• Description: Rpm-based Pwm Fan Controller
• Manufacturer: Standard Microsystems Corp.

RPM-Based PWM Fan Controller
Datasheet
SMSC EMC2301
2
0
0
0
0
1
1
1
1
1
0
0
1
1
DRIVE_FAIL_CNT[1:0]
Bit 7 - 6 - DRIVE_FAIL_CNT[1:0] - Determines how many update cycles are used for the Drive Fail
detection function as shown in
the desired tach target.
Bit 5 - NOKICK - Determines if the Spin Up Routine will drive the fan to 100% duty cycle for 1/4 of the
programmed spin up time before driving it at the programmed level.
Bits 4 - 2 - SPIN_LVL[2:0] - Determines the final drive level that is used by the Spin Up Routine as
shown in
Bit 1 -0 - SPINUP_TIME[1:0] - determines the maximum Spin Time that the Spin Up Routine will run
for (see
elapsed, then an interrupt will be generated. When the RPM-based Fan Speed Control Algorithm is
active, the fan driver will attempt to re-start the fan immediately after the end of the last spin up attempt.
The Spin Time is set as shown in
‘0’ (default) - The Spin Up Routine will drive the fan driver to 100% for 1/4 of the programmed spin
up time before reverting to the programmed spin level.
‘1’ - The Spin Up Routine will not drive the fan driver to 100%. It will set the drive at the
programmed spin level for the entire duration of the programmed spin up time.
Section
Table
SPIN_LVL[2:0]
5.21.
4.6). If a valid tachometer measurement is not detected before the Spin Time has
1
0
0
1
1
0
0
1
1
Table 5.20 DRIVE_FAIL_CNT[1:0] Bit Decode
0
0
1
0
1
Table
Table 5.21 Spin Level
Table
DATASHEET
5.20. This circuitry determines whether the fan can be driven to
Disabled - the Drive Fail detection circuitry is disabled (default)
16 - the Drive Fail detection circuitry will count for 16 update
periods
32 - the Drive Fail detection circuitry will count for 32 update
periods
64 - the Drive Fail detection circuitry will count for 64 update
periods
0
0
1
0
1
0
1
0
1
5.22.
33
NUMBER OF UPDATE PERIODS
SPIN UP DRIVE LEVEL
60% (default)
30%
35%
40%
45%
50%
55%
65%
Revision 1.2 (03-22-10)