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ADM1029ARQZ-R7 数据表(PDF) 20 Page - ON Semiconductor

部件名 ADM1029ARQZ-R7
功能描述  Dual PWM Fan Controller and Temperature Monitor for High Availability Systems
PDF  50 Pages
Scroll/Zoom Zoom In 100%  Zoom Out
制造商  ONSEMI [ON Semiconductor]
网页  http://www.onsemi.com
标志 ONSEMI - ON Semiconductor

ADM1029ARQZ-R7 数据表(HTML) 20 Page - ON Semiconductor

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PROGRAMMING THE AUTOMATIC FAN SPEED
CONTROL LOOP
1. Program a value for TMIN.
2. Program a value for the slope TRANGE.
3. TMAX = TMIN + TRANGE.
4. Program a value for Fan Spin-up Time.
5. Program the desired Automatic Fan Speed Control Mode
Behavior, i.e., which temperature channel controls each fan.
OTHER CONTROL LOOP PARAMETERS?
Having programmed all the above loop parameters, are there
any other parameters to worry about?
TMIN was defined as being the temperature at which a fan
switched on and ran at minimum speed. This minimum speed
should be set to 33%. If the minimum PWM duty cycle is
programmed to 33%, the fan control loops will operate as previ-
ously described.
It should be noted, however, that changing the minimum PWM
duty cycle affects the control loop behavior.
100
33
40
47
53
60
66
73
80
87
93
TEMPERATURE
– C
TMIN
0
16
28
40
60
1
2
3
Figure 14. Effect of Changing Minimum Duty Cycle on
Control Loop with Fixed TMIN and TRANGE Values
Slope 1 of Figure 14 shows TMIN set to 0°C and the TRANGE
chosen is 40°C. In this case, the fan’s PWM duty cycle will vary
over the range 33% to 100%. The fan will run full speed at
40°C. If the minimum PWM duty cycle at which the fan runs at
TMIN is changed, its effect can be seen on Slopes 2 and 3. Take
Case 2, where the minimum PWM duty cycle is reprogrammed
from 33% (default) to 53%. The fan will actually reach full speed
at a much lower temperature, 28°C. Case 3 shows that when
the minimum PWM duty cycle was increased to 73%, the tem-
perature at which the fan ran full speed was 16°C. So the effect
of increasing the minimum PWM duty cycle, with a fixed TMIN
and fixed TRANGE, is that the fan will actually reach full speed
(TMAX) at a lower temperature than TMIN + TRANGE. How can
TMAX be calculated?
In Automatic Fan Speed Control Mode, the registers holding
the minimum PWM duty cycle at TMIN, are the Minimum/
Alarm Speed Registers (addresses 60h, 61h). Table VII shows
the relationship between the decimal values written to the Mini-
mum/Alarm Speed Registers and PWM duty cycle obtained.
Table VII. Programming PWM Duty Cycle
Decimal Value
PWM Duty Cycle
00
0%
01
7%
02
14%
03
20%
04
27%
05
33% Recommended
06
40%
07
47%
08
53%
09
60%
10 (0x0A)
67%
11 (0x0B)
73%
12 (0x0C)
80%
13 (0x0D)
87%
14 (0x0E)
93%
15 (0x0F)
100% (Default)
*Bits <3:0> set the Minimum PWM duty cycle for Automatic Mode. Bits <7:4>
set the Alarm Speed PWM duty cycle.
The temperature at which each fan will run full speed (100%
duty cycle) is given by:
T
MAX
= TMIN + (( Max DC–Min DC) × TRANGE/10)
where,
T
MAX
= Temperature at which fan runs full speed
T
MIN
= Temperature at which fan will turn on
Max DC
= Maximum Duty Cycle (100%) = 15 decimal
Min DC
= Duty Cycle at TMIN, programmed into Fan Speed
Config Register (default = 33% = 5 decimal)
T
RANGE
= PWM Duty Cycle versus Temperature Slope
Example 1
T
MIN
=
0°C, TRANGE = 40°C
Min DC
=
53% = 8 decimal (Table VII)
Calculate T
MAX
T
MAX
= TMIN + (( Max DC–Min DC) × TRANGE/10)
T
MAX
= 0 + ((100% DC – 53% DC) × 40/10)
T
MAX
= 0 + ((15 – 8)× 4) = 28
T
MAX
= 28 C. (As seen on Slope 2 of Figure 14)
Example 2
T
MIN
= 0°C, TRANGE = 40°C
Min DC
= 73% = 11 decimal (Table VII)
Calculate T
MAX
T
MAX
= TMIN + ((Max DC–Min DC) × TRANGE/10)
T
MAX
= 0 + ((100% DC – 73% DC) × 40/10)
T
MAX
= 0 + ((15 – 11) × 4) = 16
T
MAX
= 16 C. (As seen on Slope 3 of Figure 14)
Example 3
T
MIN
= 0°C, TRANGE = 40°C
Min DC
= 33% = 5 decimal from Table IV
Calculate T
MAX
T
MAX
= TMIN + ((Max DC–Min DC) × TRANGE/10)
T
MAX
= 0 + ((100% DC – 33% DC) × 40/10)
T
MAX
= 0 + ((15 – 5) × 4) = 40
T
MAX
= 40 C. (As seen on Slope 1 of Figure 14)
ADM1029



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