EVAL-ADT7467EBZ ON Semiconductor, EVAL-ADT7467EBZ Datasheet - Page 18

• 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
The construction of a filter allows the ADT7467 and the remote
temperature sensor to operate in noisy environments. Figure 24
shows a low-pass R-C-R filter with the following values:
This filtering reduces both common-mode noise and
differential noise.
Factors Affecting Diode Accuracy
Remote Sensing Diode
The ADT7467 is designed to work with either substrate transistors
built into processors or discrete transistors. Substrate transistors
are generally PNP types with the collector connected to the
substrate. Discrete types can be either PNP or NPN transistors
connected as a diode (base-shorted to the collector). If an NPN
transistor is used, the collector and base are connected to D+
and the emitter is connected to D−. If a PNP transistor is used,
the collector and base are connected to D− and the emitter is
connected to D+.
To reduce the error due to variations in both substrate and
discrete transistors, a number of factors should be taken into
consideration:
•
•
•
R = 100 Ω, C = 1 nF
The ideality factor, n
deviation of the thermal diode from ideal behavior. The
ADT7467 is trimmed for an n
following equation to calculate the error introduced at a
temperature, T (°C), when using a transistor whose n
not equal 1.008. See the processor’s data sheet for the n
values.
ΔT = (n
To correct for this error, the user can write the ΔT value to
the offset register, and the ADT7467 automatically adds it
to or subtracts it from the temperature measurement.
Some CPU manufacturers specify the high and low current
levels of the substrate transistors. The high current level of
the ADT7467, I
is 6 μA. If the ADT7467 current levels do not match the
current levels specified by the CPU manufacturer, it may
be necessary to remove an offset. The CPU’s data sheet
should provide information relating to n
differences. An offset can be programmed to the offset
register. It is important to note that if more than one offset
must be considered, the algebraic sum of these offsets must
be programmed to the offset register.
Figure 24. Filter Between Remote Sensor and ADT7467
TEMPERATURE
f
− 1.008)/1.008 × (273.15 K + T)
REMOTE
SENSOR
HIGH
, is 96 μA, and the low level current, I
f
, of the transistor is a measure of the
f
value of 1.008. Use the
100Ω
100Ω
1nF
f
to compensate for
D+
D–
Rev. 3 | Page 18 of 77 | www.onsemi.com
f
does
f
LOW
,
If a discrete transistor is used with the ADT7467, the best
accuracy is obtained by choosing devices according to the
following criteria:
•
•
•
•
Transistors such as 2N3904, 2N3906, or equivalents in SOT-23
packages are suitable devices to use.
Table 7. Twos Complement Temperature Data Format
Temperature
−128°C
−125°C
−100°C
−75°C
−50°C
−25°C
−10°C
0°C
+10.25°C
+25.5°C
+50.75°C
+75°C
+100°C
+125°C
+127°C
1
Table 8. Offset 64 Temperature Data Format
Temperature
−64°C
−1°C
0°C
+1°C
+10°C
+25°C
+50°C
+75°C
+100°C
+125°C
+191°C
1
Bold numbers denote 2 LSBs of measurement in Extended Resolution
Bold numbers denote 2 LSBs of measurement in Extended Resolution
Register 2 (0x77) with 0.25°C resolution.
Register 2 (0x77) with 0.25°C resolution.
Base-emitter voltage is greater than 0.25 V at 6 μA with the
highest operating temperature.
Base-emitter voltage is less than 0.95 V at 100 μA with the
lowest operating temperature.
Base resistance is less than 100 Ω.
There is a small variation in h
that indicates tight control of V
Digital Output (10-Bit)
1000 0000 00
1000 0011 00
1001 1100 00
1011 0101 00
1100 1110 00
1110 0111 00
1111 0110 00
0000 0000 00
0000 1010 01
0001 1001 10
0011 0010 11
0100 1011 00
0110 0100 00
0111 1101 00
0111 1111 00
Digital Output (10-Bit)
0000 0000 00
0011 1111 00
0100 0000 00
0100 0001 00
0100 1010 00
0101 1001 00
0111 0010 00
1000 1001 00
1010 0100 00
1011 1101 00
1111 1111 00
FE
BE
(for example, 50 to 150)
characteristics.
1
1