ADT7482ARMZ datasheet(10/24 Pages) AD

10 / 24 page

ADT7482

Rev. 0 | Page 10 of 24

× IN2 × I

IBIAS

VDD

VOUT+

TO ADC

VOUT–

REMOTE

SENSING

TRANSISTOR

1 CAPACITOR C1 IS OPTIONAL. IT SHOULD ONLY BE USED IN NOISY ENVIRONMENTS.

D+

D–

C11

BIAS

DIODE

LOW-PASS FILTER

fC = 65kHz

Figure 16. Input Signal Conditioning

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 6 is a list of the

temperature measurement registers.

Table 6. 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

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 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

0 000 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.

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