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ADM1030ARQZ-REEL7 View Datasheet(PDF) - ON Semiconductor

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ADM1030ARQZ-REEL7 Datasheet PDF : 29 Pages
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ADM1030
Table V. Fan Spin-Up Times
Bits 2:0
000
001
010
011
100
101
110
111
Spin-Up Time
(Fan Characteristics Register 1)
200 ms
400 ms
600 ms
800 ms
1 sec
2 secs (Default)
4 secs
8 secs
Once the Automatic Fan Speed Control Loop parameters have
been chosen, the ADM1030 device may be programmed. The
ADM1030 is placed into Automatic Fan Speed Control Mode
by setting Bit 7 of Configuration Register 1 (Register 0x00).
The device powers up into Automatic Fan Speed Control
Mode by default. The control mode offers further flexibility
in that the user can decide which temperature channel/chan-
nels control the fan.
one channel, may actually calculate a faster speed, than a higher
temperature on the other channel.
100
93
87
80
73
66
60
53
47
40
33
0
20
TMIN
40
60
TMAX = T MIN + T RANGE
LOCAL TEMPERATURE – C
a.
Table VI. Auto Mode Fan Behavior
100
Bits 6, 5 Control Operation (Config Register 1)
93
00
Remote Temperature Controls the Fan.
87
11
Maximum Speed Calculated by Local and Remote
80
Temperature Channels Control the Fan.
73
When Bits 5 and 6 of Config Register 1 are both set to 1, it
66
offers increased flexibility. The local and remote temperature
60
channels can have independently programmed control loops
53
with different control parameters. Whichever control loop
47
calculates the fastest fan speed based on the temperature being
measured, drives the fan.
40
= 80C
T RANGE
Figure 9 shows how the fan’s PWM duty cycle is determined by
two independent control loops. This is the type of Auto Mode
Fan Behavior seen when Bits 5 and 6 of Config Register 1 are
set to 11. Figure 9a shows the control loop for the Local Tem-
perature channel. Its TMIN value has been programmed to 20rC,
and its TRANGE value is 40rC. The local temperature’s TMAX will
thus be 60rC. Figure 9b shows the control loop for the Remote
Temperature channel. Its TMIN value has been set to 0rC, while its
TRANGE = 80rC. Therefore, the Remote Temperature’s TMAX
value will be 80rC.
33
0
20
40
70
80
TMIN
REMOTE TEMPERATURE – C
TMAX = T MIN + T RANGE
b.
Figure 9. Max Speed Calculated by Local and Remote
Temperature Control Loops Drives Fan
PROGRAMMING THE AUTOMATIC FAN SPEED
CONTROL LOOP
1. Program a value for TMIN.
Consider if both temperature channels measure 40rC. Both
control loops will calculate a PWM duty cycle of 66%. There-
fore, the fan will be driven at 66% duty cycle.
If both temperature channels measure 20rC, the local channel
will calculate 33% PWM duty cycle, while the remote channel
will calculate 50% PWM duty cycle. Thus, the fan will be
driven at 50% PWM duty cycle. Consider the local temperature
measuring 60rC while the remote temperature is measuring
70rC. The PWM duty cycle calculated by the local temperature
control loop will be 100% (since the temperature = TMAX). The
PWM duty cycle calculated by the remote temperature control
loop at 70rC will be approximately 90%. So the fan will run
full-speed (100% duty cycle). Remember, that the fan speed will
be based on the fastest speed calculated, and is not necessarily
based on the highest temperature measured. Depending on the
control loop parameters programmed, a lower temperature on
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 the fan.
6. Select Automatic Fan Speed Control Mode by setting Bit 7
of Configuration Register 1.
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 the fan switched
on and ran at minimum speed. This minimum speed is 33% duty
cycle by default. If the minimum PWM duty cycle is programmed
to 33%, the fan control loops will operate as previously described.
REV. A
Rev. 2 | Page 13 of 29 | www.onsemi.com
–13–
 

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