ADT7463 Analog Devices, ADT7463 Datasheet - Page 10

• Manufacturer Part Number: ADT7463
• Description: Dbcool Thermal Management Controller And Voltage Monitor
• Manufacturer: Analog Devices

AN-613
Example: Calculate T
40°C, and PWM
T
T
T
T
SELECTING A T
The T
channel: Remote 1, Local, and Remote 2 Temp. Bits
<7:4> (T
value for each temperature channel.
SUMMARY OF T
When using the automatic fan control function, the tem-
perature at which the fan reaches full speed can be
calculated by
T
Equation 1 only holds true when PWM
duty cycle.
Increasing or decreasing PWM
tive T
same PWM duty cycle to temperature slope. The effec-
tive T
calculated using Equation 2.
T
where:
( Max D. C. – Min D. C. )
value .
MAX
MAX
MAX
MAX
MAX
MAX
= T
= 30° C + (100% – 50%)
= 30° C + (255 – 128)
= 60° C ( effective T
= T
= T
RANGE
RANGE
RANGE
RANGE
MIN
MIN
MIN
, although the fan control will still follow the
Bits <7:4>*
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010
1011
1100
1101
1110
1111
* Register 0x5F configures Remote 1 T
value can be selected for each temperature
+ ( Max D. C. – Min D. C. )
+ T
+ ( Max D. C. – Min D. C. )
Register 0x60 configures Local T
Register 0x61 configures Remote 2 T
Table I. Selecting a T
) of registers 0x5F to 0x61 define the T
for different PWM
RANGE
RANGE
MIN
RANGE
= 50% duty cycle = 128 decimal
SLOPE
FUNCTION
MAX
RANGE
, given T
T
40° C /170
RANGE
= 30° C )
T
2°C
2.5°C
3.33°C
4°C
5°C
6.67°C
8°C
10°C
13.33°C
16°C
20°C
26.67°C
32°C (default)
40°C
53.33°C
80°C
40° C /170
MIN
RANGE
RANGE
/170 = effective T
will change the effec-
MIN
MIN
Value
RANGE
= 30°C, T
T
T
values can be
MIN
RANGE
RANGE
RANGE
RANGE
= 33% PWM
/170
/170
RANGE
RANGE
RANGE
(1)
(2)
=
–10–
Remember that %PWM duty cycle does not correspond
to %RPM. %RPM relates to the square root of the PWM
duty cycle.
Figure 13 shows PWM duty cycle versus temperature for
each T
T
can be seen from the graph, the effect on fan speed is
nonlinear. The graphs in Figure 13 assume that the fan
starts from 0% PWM duty cycle. Clearly, the minimum
PWM duty cycle, PWM
how the loop actually performs in the system. Figure 14
shows how T
set to 20%. It can be seen that the fan will actually run at
about 45% fan speed when the temperature exceeds T
RANGE
100
100
90
80
70
60
50
40
30
20
10
90
80
70
60
50
40
30
20
10
0
0
0
0
Figure 13. T
RANGE
setting affects fan speed versus temperature. As
% fan speed
20
20
setting. The lower graph shows how each
RANGE
TEMPERATURE ABOVE T
TEMPERATURE ABOVE T
RANGE
40
40
is affected when the PWM
=
MIN
vs. Actual Fan Speed Profile
60
60
, needs to be factored in to see
PWM duty cycle 10
80
80
MIN
MIN
100
100
×
MIN
120
120
value is
REV. 0
2 C
2.5 C
3.33 C
4 C
5 C
6.67 C
8 C
10 C
13.3 C
16 C
20 C
26.6 C
32 C
40 C
53.3 C
80 C
2 C
2.5 C
3.33 C
4 C
5 C
6.67 C
8 C
10 C
13.3 C
16 C
20 C
26.6 C
32 C
40 C
53.3 C
80 C
MIN
.