ADT7461AR-REEL7 ON Semiconductor, ADT7461AR-REEL7 Datasheet - Page 10

• Manufacturer Part Number: ADT7461AR-REEL7
• Description: IC SENSOR TEMP 2-CH 8SOIC
• Manufacturer: ON Semiconductor

Specifications of ADT7461AR-REEL7

• Rohs Status: RoHS non-compliant
• Function: Temp Monitoring System (Sensor)
• Topology: ADC, Comparator, Multiplexer, Register Bank
• Sensor Type: External & Internal
• Sensing Temperature: 0°C ~ 127°C, External Sensor
• Output Type: SMBus™
• Output Alarm: Yes
• Output Fan: Yes
• Voltage - Supply: 3 V ~ 5.5 V
• Operating Temperature: -40°C ~ 120°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)

ADT7461
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 value is in Register 0x00 and has a
resolution of 1°C. The external temperature value is stored in
two registers, with the upper byte in Register 0x01 and the
lower byte in Register 0x10. Only the two MSBs in the external
temperature low byte are used. This gives the external
temperature measurement a resolution of 0.25°C. Table 5 shows
the data format for the external temperature low byte.
Table 5. Extended Temperature Resolution (Remote
Temperature Low Byte)
Extended Resolution
0.00°C
0.25°C
0.50°C
0.75°C
When reading the full external temperature value, both the high
and low byte, the two registers should be read in succession.
Reading one register does not lock the other, so both should be
read before the next conversion finishes. In practice, there is
more than enough time to read both registers, as transactions
over the SMBus are significantly faster than a conversion time.
TEMPERATURE MEASUREMENT RANGE
The temperature measurement range for both internal and
external measurements is, by default, 0°C to +127°C. However,
the ADT7461 can be operated using an extended temperature
range. It can measure the full temperature range of an external
diode, from −55°C to +150°C. The user can switch between
these two temperature ranges by setting or clearing Bit 2 in the
configuration register. A valid result is available in the next
measurement cycle after changing the temperature range.
In extended temperature mode, the upper and lower tempera-
ture that can be measured by the ADT7461 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
TRANSISTOR
SENSING
REMOTE
Remote Temperature Low Byte
0 000 0000
0 100 0000
1 000 0000
1 100 0000
*CAPACITOR C1 IS OPTIONAL. IT SHOULD ONLY BE USED IN NOISY ENVIRONMENTS.
C1*
D+
D–
I
Rev. 3 | Page 10 of 23 | www.onsemi.com
N1
Figure 16. Input Signal Conditioning
×
I
DIODE
BIAS
N2
×
I
I
BIAS
LOW-PASS FILTER
f
C
= 65kHz
range of −55°C to +150°C.
Above 150°C, they may lose their semiconductor characteristics
and approximate conductors instead. This results in a diode
short. In this case, a read of the temperature result register gives
the last good temperature measurement. The user should be
aware that the temperature measurement on the external channel
may not be accurate for temperatures that are outside the
operating range of the remote sensor.
While both local and remote temperature measurements can be
made while the part is in extended temperature mode, the
ADT7461 itself should not be exposed to temperatures greater than
those specified in the Absolute Maximum Ratings section. Also,
the device is guaranteed to operate only as specified at ambient
temperatures from −40°C to +120°C.
TEMPERATURE DATA FORMAT
The ADT7461 has two temperature data formats. When the
temperature measurement range is from 0°C to +127°C
(default), the temperature data format for both internal and
external temperature results is binary. When the measurement
range is in extended mode, an offset binary data format is used
for both internal and external results. Temperature values in the
offset binary data format are offset by 64°C. Examples of tem-
peratures in both data formats are shown in Table 6.
Table 6. Temperature Data Format (Local and Remote
Temperature High Byte)
Temperature
–55°C
0°C
+1°C
+10°C
+25°C
+50°C
+75°C
+100°C
+125°C
+127°C
+150°C
1
2
3
Offset binary scale temperature values are offset by 64°C.
Binary scale temperature measurement returns 0°C for all temperatures < 0°C.
Binary scale temperature measurement returns 127°C for all temperatures > 127°C.
V
DD
Binary
0 000 0000
0 000 0000
0 000 0001
0 000 1010
0 001 1001
0 011 0010
0 100 1011
0 110 0100
0 111 1101
0 111 1111
0 111 1111
2
3
V
TO ADC
V
OUT+
OUT–
0 100 0000
0 100 0001
0 100 1010
0 101 1001
0 111 0010
1 000 1011
1 010 0100
1 011 1101
1 011 1111
Offset Binary
0 000 1001
1 101 0110
1