ADT7473 Analog Devices, Inc., ADT7473 Datasheet - Page 42

• Manufacturer Part Number: ADT7473
• Description: Dbcool Remote Thermal Monitor And Fan Controller
• Manufacturer: Analog Devices, Inc.

ADT7473
T
is changed, T
same. The higher the PWM
T
temperature. Figure 55 shows how increasing PWM
the effective T
For a given T
at full speed for different PWM
calculated as follows:
where:
T
T
Max DC is the maximum duty cycle (100%) = 255 decimal.
Min DC is equal to PWM
T
Example 1: Calculate T, given that T
and PWM
Example 2: Calculate T
40°C, and PWM
RANGE
RANGE
MAX
MIN
RANGE
T
is the temperature at which the fan turns on.
T
T
T
T
T
T
T
T
is the temperature at which the fan runs full speed.
MAX
MAX
MAX
MAX
MAX
MAX
MAX
MAX
MAX
, that is, the fan rea
is the duty PWM duty cycle vs. temperature slope.
is implemented a
100%
Figure 55. Increasing PWM
= T
= T
= 30°C + (100% − 10%) × 40°C/170
= 30°C + (255 − 26) × 40°C/170
= 84°C (effective T
= T
= 30°C + (100% − 25%) × 40°C/170
= 30°C + (255 − 64) × 40°C/170
= 75°C (effective T
50%
33%
25%
10%
MIN
0%
RANGE
RANGE
MIN
MIN
MIN
= 10% duty cycle = 26 (decimal).
RA
NGE
MIN
+ (Max DC − Min DC) × T
+ (Max DC − Min DC) × T
+ (Max DC − Min DC) × T
changes, but the actual slope remains the
value, the temperature at which the fan runs
.
= 25% duty cycle = 64 (decimal).
T
MIN
MAX
s a slope, which means that as PWM
ches full speed (100%) at a lower
MIN
, given that T
MIN
.
RANGE
RANGE
30°C
value, the smaller the effective
MIN
MIN
40°C
= 54°C)
= 45°C)
45°C
Changes Effective T
values can be easily
54°C
MIN
MIN
= 30°C, T
= 30°C, T
RANGE
RANGE
RANGE
/170
/170
/170
RANGE
RANGE
MIN
RANGE
= 40°C,
changes
=
Rev. A | Page 42 of 76
MIN
Example 3: Calculate T
40°C, and PWM
Example 4: Calculate T
40°C, and PWM
Selecting a T
The T
Remote 1, local, and Remote 2. Bits [7:4] (T
Register 0x5F to Register 0x61 define the T
temperature channe
Table 14. Selecting
Bits [7:4]
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010
1011
1100
1101
1110
1111
1
Summary of T
When using the automatic fan control function, the
temperature at which the fan reaches full speed can be
calculated by
Equation 1 holds true only when PWM
PWM duty cycle.
Register 0x5F configures Remote 1 T
T
RANGE
T
T
T
T
T
T
T
T
T
; Register 0x61 configures Remote 2 T
RANGE
MAX
MAX
MAX
MAX
MAX
MAX
MAX
MAX
MAX
1
= T
= 30°C + (100% − 33%) × 40°C/170
=
= 70°C (effective T
= T
= 30°C + (100% − 50%) ×
= 30°C + (255 − 128) × 40°C/170
= 60°C (effective T
= T
value can be selected for each temperature channel:
30°C + (255 − 85) × 40°C/170
MIN
MIN
MIN
RANGE
RANGE
MIN
MIN
+ (Max DC − Min DC) × T
+ (Max DC − Min DC) × T
+ T
Slope
= 33% duty cycle = 85 (decimal).
= 50% duty cycle = 128 (decimal).
l.
a T
RANGE
Function
T
2
2.5
3.33
4
5
6.67
8
10
13.33
16
20
26.67
32 (default)
40
53.33
80
MAX
MAX
RANGE
RANGE
, given that T
, given that T
RANGE
RANGE
Value
(°C)
RANGE
= 40°C)
= 30°C)
; Register 0x60 configures local
40°C/170
RANGE
MIN
MIN
MIN
.
is equal to 33%
RA
= 30°C, T
= 30°C, T
RANGE
RANGE
RANGE
NGE
) of
value for each
/170
/170
RANGE
RANGE
=
=
(1)