EVAL-ADT7467EBZ ON Semiconductor, EVAL-ADT7467EBZ Datasheet - Page 52

• Manufacturer Part Number: EVAL-ADT7467EBZ
• Description: BOARD EVALUATION FOR ADT7467
• Manufacturer: ON Semiconductor
• Series: dBCool®r

Specifications of EVAL-ADT7467EBZ

• Sensor Type: Temperature
• Sensing Range: -40°C ~ 120°C
• Interface: SMBus (2-Wire/I²C)
• Sensitivity: ±1.5°C
• Voltage - Supply: 3 V ~ 5.5 V
• Embedded: No
• Utilized Ic / Part: ADT7467
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

ADT7467
Figure 71 shows the steps taken during the long cycle.
The following examples illustrate circumstances that may cause
T
Normal Operation—No T
•
•
Because neither the operating point minus the hysteresis
temperature nor the low temperature limit has been exceeded,
the T
determined by the fixed T
automatic fan speed control mode in the Enhancing System
Acoustics section.
Operating Point Exceeded—T
When the measured temperature is below the operating point
temperature minus the hysteresis, T
Once the temperature exceeds the operating temperature minus
the hysteresis (OP1 − Hyst), T
cycle (see Figure 70) at a rate determined by the programmed
value of n. This rate also depends on the amount that the
Figure 72. Temperature Between Operating Point and Low Temperature Limit
MIN
MEASUREMENT
TEMPERATURE
TEMPERATURE
THERM LIMIT
OPERATING
OPERATING
HIGH TEMP
LOW TEMP
CURRENT
If measured temperature never exceeds the programmed
operating point minus the hysteresis temperature, T
not adjusted, that is, it remains at its current setting.
If measured temperature never drops below the low
temperature limit, T
to increase, decrease, or stay the same.
MIN
POINT
T1(n)
OP1
POINT
LIMIT
LIMIT
value is not adjusted and the fan runs at a speed
T
MIN
IS T1(n) < LOW TEMP LIMIT
ACTUAL
T
TEMP
HYSTERESIS
MIN
< HIGH TEMP LIMIT
Figure 71. Long Cycle Steps
IS T1(n) > OP1
MONITORING
T1(n) > T
T
WAIT 2n
CYCLES
MIN
AND
AND
AND
MIN
< OP1
MIN
NO
NO
MIN
MIN
is not adjusted.
and T
MIN
Adjustment
MIN
decreases during the short
YES
RANGE
MIN
Reduced
YES
remains the same.
values, defined in the
DECREASE T
T
INCREASE
MIN
CHANGE
DO NOT
BY 1°C
BY 1°C
Rev. 3 | Page 52 of 77 | www.onsemi.com
MIN
MIN
is
temperature has increased between this monitoring cycle and
the last monitoring cycle. For example, if the temperature has
increased by 1°C, then T
has the effect of increasing the fan speed, thus providing more
cooling to the system.
If the temperature slowly increases only in the range (OP1 − Hyst),
that is, the change in temperature is ≤0.25°C per short monitor-
ing cycle, T
temperature in the desired operating zone without changing
T
range (OP − Hyst), because the temperature has not exceeded
the operating temperature.
Once the temperature exceeds the operating temperature, T
reduces by 1°C per long cycle as long as the temperature
remains above the operating temperature. This takes place in
addition to the decrease in T
cycle. In Figure 73, because the temperature is increasing at a
rate of ≤0.25°C per short cycle, no reduction in T
during the short cycle.
Once the temperature falls below the operating temperature,
T
increase slowly, because the temperature only increases at a rate
of ≤0.25°C per cycle.
Increasing the T
When the temperature drops below the low temperature limit,
T
effect of running the fan more slowly and, therefore, more
quietly. The long cycle diagram in Figure 71 shows the
conditions necessary for T
T
•
•
•
•
MIN
MIN
MIN
MIN
. The long cycle makes no change to T
The measured temperature falls below the low temperature
limit. This means that the user must choose the low limit
carefully. It should not be so low that the temperature never
falls below it, because T
fans would run faster than necessary.
T
allowed to exceed the high temperature limit. As a result,
the high limit should be chosen carefully because it deter-
mines the high limit of T
T
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
is turned off below T
remains fixed, even when the temperature starts to
can increase during the long cycle. Increasing T
can increase if
MIN
MIN
is below the high temperature limit. T
is below the operating point temperature. T
MIN
does not decrease. This allows small changes in
MIN
Cycle
MIN
MIN
MIN
is reduced by 2°C. Decreasing T
MIN
.
MIN
MIN
to increase.
would never increase and the
that occurs during the short
MIN
.
. The dynamic T
MIN
in the temperature
MIN
MIN
is never
MIN
MIN
takes place
MIN
control
has the
should
MIN
MIN