EVAL-ADT7467EBZ ON Semiconductor, EVAL-ADT7467EBZ Datasheet - Page 51

• 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

STEP 10: HIGH AND LOW LIMITS FOR
TEMPERATURE CHANNELS
If the temperature falls below the temperature channel’s low
limit, T
system to heat up. An interrupt can be generated when the
temperature drops below the low limit.
If the temperature increases above the temperature channel’s
high limit, T
down the system. An interrupt can be generated when the
temperature rises above the high limit.
Programming High and Low Limits
There are six limit registers; a high limit and a low limit are
associated with each temperature channel. These 8-bit registers
allow the high and low limit temperatures to be programmed
with 1°C resolution.
Temperature Limit Registers
Register 0x4E, Remote 1 temperature low limit = 0x01 default
Register 0x4F, Remote 1 temperature high limit = 0x7F default
Register 0x50, local temperature low limit = 0x01 default
Register 0x51, local temperature high limit = 0x7F default
Register 0x52, Remote 2 temperature low limit = 0x01 default
Register 0x53, Remote 2 temperature high limit = 0x7F default
How Dynamic T
The basic premise is as follows:
1.
2.
3.
Set the target temperature for the temperature zone, for
example, the Remote 1 thermal diode. This value is
programmed to the Remote 1 operating temperature
register.
As the temperature in that zone (Remote 1 temperature)
exceeds the operating point temperature, T
and the fan speed increases.
As the temperature drops below the operating point
temperature, T
MIN
increases. This reduces fan speed, allowing the
MIN
decreases. This increases fan speed to cool
MIN
MIN
Control Works
is increased and the fan speed is reduced.
MEASUREMENT
MEASUREMENT
TEMPERATURE
TEMPERATURE
TEMPERATURE
OPERATING
PREVIOUS
CURRENT
T1 (n – 1)
POINT
T1(n)
OP1
MIN
IS T1(n) – T1(n – 1) = 0.5 – 0.75°C
IS T1(n) – T1(n – 1) = 1.0 – 1.75°C
IS T1(n) – T1(n – 1) > 2.0°C
is reduced
Rev. 3 | Page 51 of 77 | www.onsemi.com
IS T1(n) – T1(n – 1)
MONITORING
(OP1 – HYS)
Figure 70. Short Cycle Steps
CYCLES
IS T1(n) >
≤ 0.25°C
WAIT n
YES
NO
NO
YES
However, the loop operation is not as simple as described in
these steps. A number of conditions govern the situations in
which T
Short Cycle and Long Cycle
The ADT7467 implements two loops: a short cycle and a long
cycle. The short cycle takes place every n monitoring cycles.
The long cycle takes place every 2n monitoring cycles. The
value of n is programmable for each temperature channel. The
bits are located at the following register locations:
Remote 1 = CYR1 = Bits <2:0> of Dynamic T
Register 2 (Address 0x37)
Local = CYL = Bits <5:3> of Dynamic T
(Address 0x37)
Remote 2 = CYR2 = Bits <7:6> of Dynamic T
Register 2 and Bit 0 of Dynamic T
Table 16. Cycle Bit Assignments
Code
000
001
010
011
100
101
110
111
Care should be taken when choosing the cycle time. A long cycle
time means that T
fast temperature transients, the dynamic T
If a cycle time is chosen that is too fast, the full benefit of chang-
ing T
next cycle; in effect, it is overshooting. Some calibration is
necessary to identify the most suitable response time.
Figure 70 shows the steps taken during the short cycle.
DECREASE T
DECREASE T
DECREASE T
MIN
FOR CONSTANT)
MIN
COOLING OFF
DO NOTHING
might not be realized and will need to change upon the
DO NOTHING
(SYSTEM IS
8 cycles
16 cycles
32 cycles
64 cycles
128 cycles
256 cycles
512 cycles
1024 cycles
can increase or decrease.
MIN
MIN
MIN
Short Cycle
BY 1°C
BY 2°C
BY 4°C
MIN
is updated less often. If a system has very
(1 sec)
(2 sec)
(4 sec)
(8 sec)
(16 sec)
(32 sec)
(64 sec)
(128 sec)
MIN
Control Register 1 (0x36)
16 cycles
32 cycles
64 cycles
128 cycles
256 cycles
512 cycles
1024 cycles
2048 cycles
MIN
MIN
Control Register 2
MIN
MIN
Long Cycle
control loop lags.
Control
Control
ADT7467
(2 sec)
(4 sec)
(8 sec)
(16 sec)
(32 sec)
(64 sec)
(128 sec)
(256 sec)