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EVAL-ADT7483EB

Dual Channel Temperature Sensor and Over Temperature Alarm

ON Semiconductor 

ADT7483A

Table 7. Temperature Data Format (Local and Remote Temperature High Byte)

Temperature

Binary

–55°C

0 000 00002

0°C

0 000 0000

+1°C

0 000 0001

+10°C

0 000 1010

+25°C

0 001 1001

+50°C

0 011 0010

+75°C

0 100 1011

+100°C

0 110 0100

+125°C

0 111 1101

+127°C

0 111 1111

+150°C

0 111 11113

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.

Offset Binary1

0 000 1001

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

1 101 0110

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).

REGISTERS

The registers in the ADT7483A are eight bits wide. These

registers are used to store the results of remote and local

temperature measurements, and high and low temperature

limits, and to configure and control the device. A description of

these registers is provided in this section.

Address Pointer Register

The address pointer register does not have, nor does it require,

an address because the first byte of every write operation is

automatically written to this register. The data in this first byte

always contains the address of another register on the ADT7483A,

which is stored in the address pointer register. It is to this other

register address that the second byte of a write operation is

written, or to which a subsequent read operation is performed.

The power-on default value of the address pointer register is

0x00, so if a read operation is performed immediately after

power-on without first writing to the address pointer, the value

of the local temperature will be returned, since its register

address is 0x00.

Temperature Value Registers

The ADT7483A has five registers to store the results of local

and remote temperature measurements. These registers can

only be written to by the ADC and can be read by the user over

the SMBus.

• The local temperature value register is at Address 0x00.

• The Remote 1 temperature value high byte register is

at Address 0x01, with the Remote 1 low byte register at

Address 0x10.

• The Remote 2 temperature value high byte register is

at Address 0x30, with the Remote 2 low byte register

at Address 0x33.

• The Remote 2 temperature values can be read from

Address 0x01 for the high byte and Address 0x10 for

the low byte if Bit 3 of Configuration Register 1 is set to 1.

• To read the Remote 1 temperature values, Bit 3 of

Configuration Register 1 should be set to 0.

• The power-on default for all five registers is 0x00.

Rev. 1 | Page 11 of 24 | www.onsemi.com

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