ADT7483A(2012) View Datasheet(PDF) - ON Semiconductor

Part Name

Description

Manufacturer

ADT7483A
(Rev.:2012)

Dual Channel Temperature Sensor and Over Temperature Alarm

ON Semiconductor 

ADT7483A

Table 6. REGISTER ADDRESS FOR

THE TEMPERATURE VALUES

Temperature

Channel

Register Address,

MSBs

Register Address,

LSBs

Local

Remote 1

Remote 2

0x00

0x01

0x30

N/A

0x10 (2 MSBs)

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 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

0.25C

0.50C

0.75C

0 000 0000

0 100 0000

1 000 0000

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 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

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

measurements 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 8.

Table 8. TEMPERATURE DATA FORMAT

(LOCAL AND REMOTE TEMPERATURE HIGH BYTE)

Temperature

Binary

Offset Binary

(Note 1)

−55C

0 000 0000

(Note 2)

0 000 1001

0C

0 000 0000

0 100 0000

+1C

0 000 0001

0 100 0001

+10C

0 000 1010

0 100 1010

+25C

0 001 1001

0 101 1001

+50C

0 011 0010

0 111 0010

+75C

0 100 1011

1 000 1011

+100C

0 110 0100

1 010 0100

+125C

0 111 1101

1 011 1101

+127C

0 111 1111

1 011 1111

+150C

0 111 1111

(Note 3)

1 101 0110

1. Offset binary scale temperature values are offset by +64.

2. Binary scale temperature measurement returns 0 for all

temperatures < 0C.

3. Binary scale temperature measurement returns 127 for all

temperatures > 127C.

The user may switch between measurement ranges at any

time. Switching the range also switches the data format. The

next temperature result following the switching is reported

back to the register in the new format. However, the contents

of the limit registers do not change. It is up to the user to

ensure that when the data format changes, the limit registers

are reprogrammed as necessary (for more information, see

the Limit Registers section).

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