ADT7463 Analog Devices, ADT7463 Datasheet - Page 20

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

AN-613
EXAMPLES
The following are examples of some circumstances that
may cause T
NORMAL OPERATION—NO T
1. If measured temperature never exceeds the pro-
2. If measured temperature never drops below the low
Since neither the operating point–hysteresis tempera-
ture
exceeded, the T
at a speed determined by the fixed T
ues defined in the automatic fan speed control mode.
OPERATING POINT EXCEEDED—T
When the measured temperature is below the operating
point temperature less the hysteresis, T
the same.
Figure 25. Temperature between Operating Point and
Low Temperature Limit
grammed operating point–hysteresis temperature,
then T
setting.
temperature limit, then T
THERM LIMIT
OPERATING
HIGH TEMP
LOW TEMP
nor
POINT
LIMIT
LIMIT
T
MIN
MIN
the
MIN
is not adjusted, i.e., remains at its current
ACTUAL
to increase or decrease or stay the same.
MIN
TEMP
HYSTERESIS
low
value is not adjusted and the fan runs
temperature
Figure 26. Effect of Exceeding Operating Point – Hysteresis Temperature
MIN
OPERATING
MIN
HIGH TEMP
LOW TEMP
is not adjusted.
THERM
ADJUSTMENT
POINT
LIMIT
LIMIT
LIMIT
MIN
T
MIN
REDUCED
MIN
DECREASE HERE DUE TO
limit
T1(n) – T1 (n–1) = 0.5 C
EVERY SHORT CYCLE
SHORT CYCLE ONLY
HYSTERESIS
DECREASES BY 1 C
OR 0.75 C = > T
and T
MIN
has
RANGE
ACTUAL
TEMP
remains
been
MIN
val-
–20–
DECREASE HERE DUE TO
T1(n) – T1 (n–1)
AND T1(n) > OP = > T
EVERY LONG CYCLE
DECREASES BY 1 C
LONG CYCLE ONLY
Once the temperature exceeds the operating tempera-
ture less the hysteresis (OP – Hys), the T
decrease. This occurs during the short cycle; see Figure 23.
The rate with which T
grammed value of n. It also depends on how much the
temperature has increased between this monitoring
cycle and the last monitoring cycle, i.e., if the tempera-
ture has increased by 1°C, then T
Decreasing T
speed, thus providing more cooling to the system.
If the temperature is only slowly increasing in the range
(OP – Hys), i.e., ≤ 0.25°C per short monitoring cycle, then
T
temperature in the desired operating zone without
changing T
in the temperature range (OP – Hys) since the tempera-
ture has not exceeded the operating temperature.
Once the temperature exceeds the operating tempera-
ture, the long cycle will cause T
every long cycle while the temperature remains above
the operating temperature. This takes place in addition
to the decrease in T
cycle. In Figure 26, since the temperature is only increas-
ing at a rate less than or equal to 0.25°C per short cycle,
no reduction in T
Once the temperature has fallen below the operating
temperature, T
ture starts to increase slowly, T
the temperature increases at a rate ≤ 0.25°C per cycle.
MIN
does not decrease. This allows small changes in
NO CHANGE IN T
DUE TO ANY CYCLE SINCE
T1(n) – T1 (n–1)
AND T1(n) < OP = > T
STAYS THE SAME
0.25 C
MIN
MIN
MIN
. The long cycle makes no change to T
MIN
MIN
stays the same. Even when the tempera-
has the effect of increasing the fan
MIN
takes place during the short cycle.
MIN
MIN
0.25 C
that would occur due to the short
HERE
MIN
decreases depends on the pro-
MIN
stays the same because
MIN
MIN
is reduced by 2°C.
to reduce by 1°C
MIN
starts to
REV. 0
MIN