ADT7482 Datasheet, PDF (10/24 Pages) Analog Devices – Dual Channel Temperature Sensor and Overtemperature Alarm

ADT7482
V_DD
I
N1 × I N2 × I ^IBIAS
REMOTE
SENSING
TRANSISTOR
D+
C1¹
D–
BIAS
DIODE
LOW-PASS FILTER
f_C = 65kHz
V_OUT+
TO ADC
V_OUT–
1_{CAPACITOR C1 IS OPTIONAL. IT SHOULD ONLY BE USED IN NOISY ENVIRONMENTS.}
Figure 16. Input Signal Conditioning
TEMPERATURE MEASUREMENT RESULTS
The results of the local and remote temperature measurements
are stored in the local and remote temperature value registers
and are compared with limits programmed into the local and
remote high and low limit registers.
The local temperature measurement is an 8-bit measurement
with 1°C resolution. The remote temperature measurements are
10-bit measurements, with the 8 MSBs stored in one register
and the 2 LSBs stored in another register. Table 6 is a list of the
temperature measurement registers.
Table 6. Register Address for the Temperature Values
Temperature
Channel
Register Address, Register Address,
MSBs
LSBs
Local
0x00
N/A
Remote 1
0x01
0x10 (2 MSBs)
Remote 2
0x30
0x33 (2 MSBs)
Set Bit 3 of the Configuration 1 register to 1, to read the Remote
2 temperature values from the following register addresses:
• Remote 2, MSBs = 0x01
• Remote 2, LSBs = 0x10
The above is true only when Bit 3 of the Configuration 1
register is set. To read the Remote 1 temperatures, switch this
bit back to 0.
Only the two MSBs in the remote temperature low byte are
used. This gives the remote temperature measurement a
resolution of 0.25°C. Table 7 shows the data format for the
remote temperature low byte.
Table 7. Extended Temperature Resolution
(Remote Temperature Low Byte)
Extended Resolution Remote Temperature Low Byte
0.00°C
0 000 0000
0.25°C
0 100 0000
0.50°C
1 000 0000
0.75°C
1 100 0000
When reading the full remote temperature value, both the high
and low byte, the two registers should be read LSB first and then
MSB. Reading the LSB causes the MSB to be locked until it is
read. This guarantees that the two values are read as a result of
the same temperature measurement.
TEMPERATURE MEASUREMENT RANGE
The temperature measurement range for both local and remote
measurements is, by default, 0°C to +127°C. However, the
ADT7482 can be operated using an extended temperature
range. It can measure the full temperature range of a remote
thermal diode, from −55°C to +150°C. Switch between these
two temperature ranges by setting or clearing Bit 2 in the
Configuration 1 register. A valid result is available in the next
measurement cycle after changing the temperature range.
In extended temperature mode, the upper and lower
temperature measured by the ADT7482 is limited by the remote
diode selection. The temperature registers themselves can have
values from −64°C to +191°C. However, most temperature-
sensing diodes have a maximum temperature range of
−55°C to +150°C.
Note that while both local and remote temperature measurements
can be made while the part is in extended temperature mode, the
ADT7482 itself should not be exposed to temperatures greater than
those specified in the Absolute Maximum Ratings section.
Further, the device is only guaranteed to operate as specified at
ambient temperatures from −40°C to +120°C.
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