datasheetbank_Logo
Integrated circuits, Transistor, Semiconductors Search and Datasheet PDF Download Site

ADM1030ARQ-REEL View Datasheet(PDF) - ON Semiconductor

Part Name
Description
View to exact match
ADM1030ARQ-REEL Datasheet PDF : 29 Pages
First Prev 11 12 13 14 15 16 17 18 19 20 Next Last
ADM1030
It should be noted however, that changing the minimum PWM
duty cycle affects the control loop behavior.
The temperature at which the fan will run full-speed (100%
duty cycle) is given by:
Slope 1 of Figure 10 shows TMIN set to 0rC and the TRANGE
chosen is 40rC. In this case, the fan’s PWM duty cycle will vary
over the range 33% to 100%. The fan will run full-speed at
40rC. 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%.
TMAX = TMIN + ((Max DC Min DC) ¥ TRANGE/10)
where,
TMAX = Temperature at which fan runs full-speed.
TMIN = 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).
100
TRANGE = PWM Duty Cycle versus Temperature Slope.
93
Example 1
87
TMIN
= 0rC, TRANGE = 40rC
80
Min DC = 53% = 8 decimal (Table VII)
73
66
60
53
47
40
33
0
16
28
40
60
TMIN
TEMPERATURE – C
Figure 10. Effect of Changing Minimum Duty Cycle on
Control Loop with Fixed TMIN and TRANGE Values
The fan will actually reach full-speed at a much lower tempera-
ture, 28rC. Case 3 shows that when the minimum PWM duty
cycle was increased to 73%, the temperature at which the fan
ran full-speed was 16rC. So the effect of increasing the mini-
mum 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?
Calculate TMAX.
TMAX = TMIN + ((Max DC – Min DC) ¥ TRANGE/10)
TMAX = 0 + ((100% DC – 53% DC) ¥ 40/10)
TMAX = 0 + ((15 – 8) ¥ 4) = 28
TMAX = 28C (As seen on Slope 2 of Figure 10)
Example 2
TMIN
= 0rC, TRANGE = 40rC
Min DC = 73% = 11 Decimal (Table VII)
Calculate TMAX.
TMAX = TMIN + ((Max DC – Min DC) ¥ TRANGE/10)
TMAX = 0 + ((100% DC – 73% DC) ¥ 40/10)
TMAX = 0 + ((15 – 11) ¥ 4) = 16
TMAX = 16C (As seen on Slope 3 of Figure 10)
Example 3
TMIN
= 0rC, TRANGE = 40rC
In Automatic Fan Speed Control Mode, the register that
holds the minimum PWM duty cycle at TMIN, is the Fan Speed
Config Register (Register 0x22). Table VII shows the relation-
ship between the decimal values written to the Fan Speed Config
Register and PWM duty cycle obtained.
Min DC = 33% = 5 Decimal (Table VII)
Calculate TMAX.
TMAX = TMIN + ((Max DC – Min DC) ¥ TRANGE/10)
TMAX = 0 + ((100% DC – 33% DC) ¥ 40/10)
Table VII. Programming PWM Duty Cycle
Decimal Value
PWM Duty Cycle
00
01
02
03
04
05
06
07
08
09
10 (0x0A)
11 (0x0B)
12 (0x0C)
13 (0x0D)
0%
7%
14%
20%
27%
33% (Default)
40%
47%
53%
60%
67%
73%
80%
87%
TMAX = 0 + ((15 – 5) ¥ 4) = 40
TMAX = 40C (As seen on Slope 1 of Figure 10)
In this case, since the Minimum Duty Cycle is the default 33%,
the equation for TMAX reduces to:
TMAX = TMIN + ((Max DC – Min DC) ¥ TRANGE/10)
TMAX = TMIN + ((15 – 5) ¥ TRANGE/10)
TMAX
= TMIN + (10 ¥ TRANGE/10)
TMAX
= TMIN + TRANGE
14 (0x0E)
15 (0x0F)
93%
100%
Rev. 2 | Page 14 of 29 | www.onsemi.com
–14–
REV. A
 

Share Link: 

datasheetbank.com [ Privacy Policy ] [ Request Datasheet ] [ Contact Us ]