ADT7473ARQZ-REEL7 ON Semiconductor, ADT7473ARQZ-REEL7 Datasheet - Page 47

• Manufacturer Part Number: ADT7473ARQZ-REEL7
• Description: IC REMOTE THERMAL CTRLR 16QSOP
• Manufacturer: ON Semiconductor
• Series: dBCool®r

Specifications of ADT7473ARQZ-REEL7

• Function: Fan Control, Temp Monitor
• Topology: ADC, Comparator, Fan Speed Counter, Multiplexer, Register Bank
• Sensor Type: External & Internal
• Sensing Temperature: -40°C ~ 125°C, External Sensor
• Output Type: SMBus™
• Output Alarm: No
• Output Fan: Yes
• Voltage - Supply: 3 V ~ 3.6 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 16-QSOP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

at which T
of n. It also depends on how much the temperature has
increased between this monitoring cycle and the last
monitoring cycle; that is, if the temperature has increased by
1°C, then T
effect of increasing the fan speed, thus providing more
cooling to the system.
(OP − Hyst), that is, ≤0.25°C per short monitoring cycle,
then T
temperature in the desired operating zone without changing
T
temperature range (OP − Hyst) because the temperature has
not exceeded the operating temperature.
the long cycle causes T
cycle while the temperature remains above the operating
temperature. This takes place in addition to the decrease in
T
the temperature is increasing at a rate ≤0.25°C per short cycle,
no reduction in T
temperature, T
temperature starts to increase slowly, T
because the temperature increases at a rate ≤0.25°C per cycle.
Example 3: Increase T
limit, T
has the effect of running the fan slower and, therefore,
quieter. The long cycle diagram in Figure 69 shows the
conditions required for T
of those conditions and the reasons they need to be true
follows.
•
•
•
•
MIN
MIN
If the temperature slowly increases only in the range
Once the temperature exceeds the operating temperature,
Once the temperature falls below the operating
When the temperature drops below the low temperature
T
The measured temperature falls below the low temperature
limit. This means the user must choose the low limit
carefully. It should not be so low that the temperature
never falls below it because T
and the fans would run faster than necessary.
T
never allowed to increase above the high temperature
limit. As a result, the high limit should be sensibly
chosen because it determines how high T
T
should never be allowed to increase above the operating
point temperature because the fans would not switch on
until the temperature rose above the operating point.
The temperature is above T
control is turned off below T
MIN
MIN
MIN
. The long cycle makes no change to T
that occurs due to the short cycle. In Figure 71, because
MIN
MIN
can increase if:
is below the high temperature limit. T
is below the operating point temperature. T
MIN
does not decrease. This allows small changes in
MIN
can increase in the long cycle. Increasing T
decreases depends on the programmed value
is reduced by 2°C. Decreasing T
MIN
MIN
takes place during the short cycle.
stays the same. Even when the
MIN
MIN
MIN
to be reduced by 1°C every long
Cycle
to increase. A quick summary
MIN
MIN
MIN
. The dynamic T
would never increase,
.
MIN
MIN
stays the same
MIN
MIN
MIN
can go.
MIN
is
MIN
has the
http://onsemi.com
in the
MIN
47
temperature is above T
limit, and T
below the operating point. Once the temperature rises above
the low temperature limit, T
Example 4: Preventing T
for T
never switch on. As a result, T
within a specified range:
•
•
•
Figure 71. Effect of Exceeding Operating Point Minus
Figure 72 shows how T
Because T
OPERATING
The lowest possible value for T
complement mode) or −64°C (Offset 64 mode).
T
If the temperature is below T
off or runs at minimum speed and dynamic T
control is disabled.
HIGH TEMP
LOW TEMP
HYSTERESIS
Figure 72. Increasing T
MIN
OPERATING
HIGH TEMP
LOW TEMP
DECREASE HERE DUE TO
MIN
THERM
T1(n) - T1 (n - 1) = 0.55C
EVERY SHORT CYCLE
POINT
SHORT CYCLE ONLY
DECREASES BY 15C
LIMIT
LIMIT
LIMIT
THERM
OR 0.755C = > T
T
POINT
cannot exceed the high temperature limit.
MIN
LIMIT
LIMIT
LIMIT
to reach full scale (127°C) because the fan would
T
ACTUAL
MIN
TEMP
MIN
MIN
HYSTERESIS
ACTUAL
Hysteresis Temperature
TEMP
is below the high temperature limit and
is dynamically adjusted, it is undesirable
MIN
MIN
DECREASE HERE DUE TO
MIN
MIN
T1(n) - T1 (n - 1) ≤ 0.255C
AND T1(n) > OP = > T
and below the low temperature
EVERY LONG CYCLE
MIN
MIN
DECREASES BY 15C
LONG CYCLE ONLY
from Reaching Full Scale
MIN
increases when the current
MIN
for Quieter Operation
stays the same.
MIN
is allowed to vary only
, the fan is switched
DUE TO ANY CYCLE BECAUSE
NO CHANGE IN T
T1(n) - T1 (n - 1) ≤ 0.255C
AND T1(n) < OP = > T
is −127°C (twos
STAYS THE SAME
MIN
MIN
MIN
HERE
MIN