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ADT7483A

Dual Channel Temperature Sensor and Over Temperature Alarm

ON Semiconductor 

ADT7483A

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 eight MSBs stored in one register

and two LSBs stored in another register. Table 5 lists the

temperature measurement registers.

Table 5. Register Address for the Temperature Values

Temperature

Channel

MSB Register

Address

LSB Register

Address

Local

0x00

N/A

Remote 1

0x01

0x10 (2 MSBs)

Remote 2

0x30

0x33 (2 MSBs)

By setting Bit 3 of the Configuration 1 Register to 1, the

Remote 2 temperature values can be read 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, this bit needs

to be switched 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 6 shows the data format for the

remote temperature low byte.

Table 6. 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

the MSB. This is because reading the LSB will cause the MSB to

be locked until it is read, guaranteeing that the two values read

are 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

ADT7483A can be operated using an extended temperature

range from −64°C to +191°C. This means, the ADT7483A can

measure the full temperature range of a remote thermal diode,

from −55°C to +150°C. The user can switch between these two

temperature ranges by setting or clearing Bit 2 in the Configura-

tion 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 temperatures

that can be measured by the ADT7483A are 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 although both local and remote temperature measure-

ments can be made while the part is in extended temperature

mode, the ADT7483A should not be exposed to temperatures

greater than those specified in theAbsolute Maximum Ratings

section. Further, the device is only guaranteed to operate as

specified at ambient temperatures from −40°C to +120°C.

TEMPERATURE DATA FORMAT

The ADT7483A has two temperature data formats. When the

temperature measurement range is from 0°C to 127°C (default),

the temperature data format for both local and remote temperature

results is binary. When the measurement range is in extended

mode, an offset binary data format is used for both local and

remote results. Temperature values in the offset binary data

format are offset by +64. Examples of temperatures in both data

formats are shown in Table 7.

Rev. 1 | Page 10 of 24 | www.onsemi.com

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