ADT7485A

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Product Description

The ADT7485A is a temperature− and voltage−monitoring

device. The ADT7485A can monitor the temperature of one

remote sensor diode, plus its own internal temperature. It can

also monitor up to five voltage channels, including its own

supply voltage.

SST Interface

SST is a one−wire serial bus and a communications

protocol between components intended for use in personal

computers, personal hand−held devices, or other industrial

sensor nets. The ADT7485A supports SST Rev 1.0.

SST is a licensable bus technology from Analog Devices,

Inc., and Intel Corporation. To inquire about obtaining a

copy of the Simple Serial Transport Specification or an SST

technology license, please email Analog Devices at

sst_licensing@analog.com or write to Analog Devices,

3550 North First Street, San Jose, CA 95134, Attention: SST

Licensing, M/S B7−24.

ADT7485A Client Address

The client address for the ADT7485A is selected using the

address pin. The address pin is connected to a float detection

circuit, which allows the ADT7485A to distinguish between

three input states: high, low (GND), and floating. The

address range for the fixed address, discoverable device is

0x48 to 0x4A.

Table 1. ADT7485A Selectable Addresses

ADD

Address Selected

Low (GND)

0x48

Float

0x49

High

0x4A

Command Summary

Table 2 summarizes the commands supported by the

ADT7485A device when directed at the target address

selected by the fixed address pin. It contains the command

name, command code (CC), write data length (WL), read

data length (RL), and a brief description.

Table 2. Command Code Summary

Command

Command

Code, CC

Write

Length, WL

Read

Length, RL

Description

Ping()

0x00

0x00

0x00

Shows a nonzero FCS over the header if present.

GetIntTemp()

0x00

0x01

0x02

Shows the temperature of the device’s internal thermal diode.

GetExtTemp()

0x01

0x01

0x02

Shows the temperature of External Thermal Diode.

GetAllTemps()

0x00

0x01

0x04

Returns a 4−byte block of data (GetIntTemp, GetExt1Temp).

GetVolt12V()

0x10

0x01

0x02

Shows the voltage attached to 12 V input.

GetVolt5V()

0x11

0x01

0x02

Shows the voltage attached to 5.0 V input.

GetVoltVCC()

0x12

0x01

0x02

GetVolt2.5V()

0x13

0x01

0x02

Shows the voltage attached to 2.5 V input.

GetVoltVCCP()

0x14

0x01

0x02

GetAllVolts()

0x10

0x01

0x10

Shows all voltage measurement values.

SetExtOffset()

0xe0

0x02

0x00

Sets the offset used to correct errors in External Diode.

GetExtOffset()

0xe0

0x01

0x01

Shows the offset that the device is using to correct errors in

External Diode.

ResetDevice()

0xf6

0x01

0x00

Functional reset. The ADT7485A also responds to this

command when directed to the Target Address 0x00.

GetDIB()

0xf7

0xf7

0x01

0x01

0x08

0x10

Shows information used by SW to identify the device’s

capabilities. Can be in 8− or 16−byte format.

Command Code Details

ADT7485A Device Identifier Block

The GetDIB() command retrieves the device identifier

block (DIB), which provides information to identify the

capabilities of the ADT7485A. The data returned can be in

8− or 16−byte format. The full 16 bytes of DIB is detailed in

Table 3. The 8−byte format involves the first eight bytes

described in this table. Byte−sized data is returned in the

respective fields as it appears in Table 3. Word−sized data,

including vendor ID, device ID, and data values use little

endian format, that is, the LSB is returned first, followed by

the MSB.