ADT7482ARMZ datasheet(8/20 Pages) ONSEMI

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ADT7482

http://onsemi.com

Figure 15. Input Signal Conditioning

y IN2 y I

IBIAS

VDD

VOUT+

TO ADC

VOUT–

REMOTE

SENSING

TRANSISTOR

NOTE: CAPACITOR C1 IS OPTIONAL.

D+

D–

BIAS

DIODE

LOW−PASS FILTER

fC = 65kHz

IT SHOULD ONLY BE USED IN NOISY ENVIRONMENTS.

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 1 is a list of the temperature measurement registers.

Table 1. Register Address for the Temperature Values

Temperature

Channel

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

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 2 shows the data format for the

remote temperature low byte.

Table 2. 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.

Temperature Data Format

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 3.

Switching between measurement ranges can be done 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. Ensure that

when the data format changes, the limit registers are

reprogrammed as necessary. For more information, refer to

the Limit Registers section.

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