ADT7486ARMZ-REEL7 - Analog Devices, Inc.

Digital Temperature Sensor

with SST Interface

Preliminary Technical Data ADT7484/ADT7486

Rev. PrA

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FEATURES

1 on-chip temperature sensor

1 or 2 remote temperature sensors

Simple Serial Transport™ (SST™) interface Rev 1 compliant

APPLICATIONS

Personal computers

Portable personal devices

Industrial sensor nets

GENERAL DESCRIPTION

The ADT7484/ADT7486 are simple digital temperature sensors for

use in PC applications with a Simple Serial Transport (SST)

interface. These devices can monitor their own temperature as

well as the temperature of one (ADT7484) or two (ADT7486)

remote sensor diodes. The ADT7484/ADT7486 are controlled

by a single SST bidirectional data line. The devices are fixed-

address SST clients where the target address is chosen by the

state of the two address pins, ADD0 and ADD1.

FUNCTIONAL BLOCK DIAGRAM

SST I NT ERFACE

ANALOG MUX

(ADT7486 O NLY)

OFFSET REGISTERS

ADDRESS

SELECTION

DIG ITAL MUX

LOCAL TEMPERATURE

VALUE REGISTER

REMOTE TEMPERATURE

VALUE REGISTER

A/D

CONVERTER

ON-CHIP

TEMPERATURE

SENSOR

D1+

D2–

GND RESERVED

ADT7484/

ADT7486

SST

ADD1

ADD0

D1–

D2+

05198-001

Figure 1.

ADT7484/ADT7486 Preliminary Technical Data

Rev. PrA | Page 2 of 16

TABLE OF CONTENTS

Features .............................................................................................. 1

Applications....................................................................................... 1

General Description ......................................................................... 1

Functional Block Diagram .............................................................. 1

Revision History ............................................................................... 2

Specifications..................................................................................... 3

Absolute Maximum Ratings............................................................ 4

Thermal Resistance ...................................................................... 4

ESD Caution.................................................................................. 4

Pin Configurations And Functional Descriptions ....................... 5

Typical Performance Characteristics ............................................. 6

Product Description......................................................................... 8

SST Interface ..................................................................................8

Temperature Measurement ........................................................... 11

Temperature Measurement Method........................................ 11

Reading Temperature Measurements...................................... 11

SST Temperature Sensor Data Format .................................... 12

Using Discrete Transistors ........................................................ 12

Layout Considerations............................................................... 12

Temperature Offset .................................................................... 13

Application Schematics ............................................................. 13

Outline Dimensions ....................................................................... 14

Ordering Guide .......................................................................... 14

REVISION HISTORY

4/06—Revision PrA: Preliminary Version

Preliminary Technical Data ADT7484/ADT7486

Rev. PrA | Page 3 of 16

SPECIFICATIONS

TA = TMIN to TMAX, VCC = VMIN to VMAX, unless otherwise noted.

Table 1.

Parameter Min Typ Max Unit Test Conditions/Comments

POWER SUPPLY

Supply Voltage, VCC 3.0 3.3 3.6 V

Undervoltage Lockout Threshold 2.8 V

Average Operating Supply Current, IDD 1.4 mA Continuous conversions

TEMPERATURE-TO-DIGITAL CONVERTER

Local Sensor Accuracy ±1 °C

40 ≤ TA ≤ 70°C, VCC = 3.3 V

±3 °C

−40 ≤ TA ≤ +125°C

Remote Sensor Accuracy ±1 °C −40 ≤ TD ≤ +125°C; −40 ≤ TA ≤ 70°C,

VCC = 3.3 V

±3 °C

−40 ≤ TD ≤ +125°C; −40 ≤ TA ≤ +125°C

Remote Sensor Source Current 6 μA Low level

36 μA Mid level

96 μA High level

Resolution 0.016 °C

Conversion Time (Local Temperature)1 12 ms Averaging enabled

Conversion Time (Remote Temperature)1 38 ms Averaging enabled

Total Monitoring Cycle Time1 50 ms Averaging enabled

DIGITAL INPUTS (ADD0, ADD1)

Input High Voltage, VIH 2.1 V

Input Low Voltage, VIL 0.8 V

Input High Current, IIH −1 μA VIN = VCC

Input Low Current, IIL 1 μA V

IN = 0

Pin Capacitance 5 pF

DIGITAL I/O (SST Pin)

Input High Voltage , VIH 1.1 V

Input Low Voltage, VIL 0.4 V

Hysteresis1 150 mV Between input switching levels

Output High Voltage, VOH 1.1 1.9 V ISOURCE = 6 mA (maximum)

High Impedance State Leakage, ILEAK ±1 µA

Device powered on SST bus;

VSST = 1.1 V, VCC = 3.3 V

High Impedance State Leakage, ILEAK ±10 µA

Device unpowered on SST bus;

VSST = 1.1 V, VCC = 0 V

Signal Noise Immunity, VNOISE 300 mV p-p

Noise glitches from 10 MHz to 100 MHz;

width up to 50 ns

SST TIMING

Bitwise Period, tBIT 0.495 500 µs

High Level Time for Logic 1, tH1 2 0.65 × tBIT 0.75 × tBIT 0.8 × tBIT µs tBIT defined in speed negotiation

High Level Time for Logic 0, tH0 2 0.2 × tBIT 0.25 × tBIT 0.4 × tBIT µs

Time to Assert SST High for Logic 1, tSU, HIGH 0.2 × tBIT µs

Hold Time, tHOLD3 0.5 × tBIT-M µs See SST Specification Rev 1.0

Stop Time, tSTOP 1.25 × tBIT 2 × tBIT 2 × tBIT µs Device responding to a constant low

level driven by originator

Time to Respond After a Reset, tRESET 0.4 ms

Response Time to Speed Negotiation

After Power-Up

500 µs

Time after power-up when device can

participate in speed negotiation

1 Guaranteed by design, not production tested.

2 Minimum and maximum bit times are relative to tBIT defined in the timing negotiation pulse.

3 Devices compatible with hold time specification as driven by SST originator.

ADT7484/ADT7486 Preliminary Technical Data

Rev. PrA | Page 4 of 16

ABSOLUTE MAXIMUM RATINGS

Table 2.

Parameter Rating

Supply Voltage (VCC) 3.6 V

Voltage on Any Other Pin (Including SST Pin) 3.6 V

Input Current at Any Pin ±5 mA

Package Input Current ±20 mA

Maximum Junction Temperature (TJ max) 150°C

Storage Temperature Range −65°C to +150°C

Lead Temperature, Soldering

IR Peak Reflow Temperature 260°C

Lead Temperature (10 sec) 300°C

ESD Rating 2000 V

Stresses above those listed under Absolute Maximum Ratings

may cause permanent damage to the device. This is a stress

rating only; functional operation of the device at these or any

other conditions above those indicated in the operational

section of this specification is not implied. Exposure to absolute

maximum rating conditions for extended periods may affect

device reliability.

THERMAL RESISTANCE

θJA is specified for the worst-case conditions, that is, a device

soldered in a circuit board for surface-mount packages.

Table 3. Thermal Resistance

Package Type θJA θ

JC Unit

8-Lead MSOP (ADT7484) 206 44 °C/W

10-Lead MSOP (ADT7486) 206 44 °C/W

ESD CAUTION

ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on

the human body and test equipment and can discharge without detection. Although this product features

proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy

electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance

degradation or loss of functionality.

Preliminary Technical Data ADT7484/ADT7486

Rev. PrA | Page 5 of 16

PIN CONFIGURATIONS AND FUNCTIONAL DESCRIPTIONS

CC 1

GND

D1+

D1–

SST

ADD0

RESERVED

ADD1

ADT7484

TOP VIEW

(Not to Scale)

5198-002

VCC 1

GND 2

D1+ 3

D1– 4

D2+ 5

SST10

ADD0

RESERVED8

ADD17

D2–6

ADT7486

TOP VIEW

(Not to Scale)

05198-003

Figure 2. ADT7484 8-Lead MSOP Figure 3. ADT7486 10-Lead MSOP

Table 4. ADT7484 Pin Function Descriptions

Pin No. Mnemonic Type Description

1 VCC Power supply 3.3 V ± 10%.

2 GND Ground Ground Pin.

3 D1+ Analog input Positive Connection to Remote Temperature Sensor.

4 D1− Analog input Negative Connection to Remote Temperature Sensor.

5 ADD1 Digital input SST Address Select.

6 RESERVED Reserved Connect to Ground.

7 ADD0 Digital input SST Address Select.

10 SST Digital input/output SST Bidirectional Data Line.

Table 5. ADT7486 Pin Function Descriptions

Pin No. Mnemonic Type Description

1 VCC Power supply 3.3 V ± 10%.

2 GND Ground Ground Pin.

3 D1+ Analog input Positive Connection to Remote 1 Temperature Sensor.

4 D1− Analog input Negative Connection to Remote 1 Temperature Sensor.

5 D2+ Analog input Positive Connection to Remote 2 Temperature Sensor.

6 D2− Analog input Negative Connection to Remote 2 Temperature Sensor.

7 ADD1 Analog input SST Address Select.

8 RESERVED Analog input Connect to Ground.

9 ADD0 Digital input SST Address Select.

10 SST Digital input/output SST Bidirectional Data Line.

ADT7484/ADT7486 Preliminary Technical Data

Rev. PrA | Page 6 of 16

TYPICAL PERFORMANCE CHARACTERISTICS

Figure 4. SST O/P Level vs. Supply Voltage

Figure 5. Supply Current vs. Temperature

Figure 6. Local Temperature Error

Figure 7. SST O/P Level vs. Pull Down(?)

Figure 8. Supply Current vs. Voltage

Figure 9. Remote Temperature Error

Preliminary Technical Data ADT7484/ADT7486

Rev. PrA | Page 7 of 16

Figure 10. Remote Temperature Error vs. PCB Resistance

Figure 11. Temperature Error vs. Common-Mode Noise Frequency

Figure 12. Temperature Error vs. Power Supply Noise

Figure 13. Remote Temperature Error vs. Capacitance Between D1+ and D1−

Figure 14. Temperature Error vs. Differential Mode Noise Frequency

ADT7484/ADT7486 Preliminary Technical Data

Rev. PrA | Page 8 of 16

PRODUCT DESCRIPTION

The ADT7484 is a single remote temperature sensor, and the

ADT7486 is a dual temperature sensor for use in PC applications.

The ADT7484/ADT7486 accurately measure local and remote

temperature and communicate over a one-wire Simple Serial

Transport (SST) bus interface.

SST INTERFACE

Simple Serial Transport (SST) is a one-wire serial bus and a

communications protocol between components intended for

use in personal computers, personal handheld devices, or other

industrial sensor nets. The ADT7484/ADT7486 support SST

specification Rev 1.

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, Inc., at sst_licensing@analog.com

or write to Analog Devices, Inc., 3550 North First Street, San

Jose, CA 95134, Attention: SST Licensing, M/S B7-24.

ADT7486 Client Address

The client address for the ADT7484/ADT7486 is selected using

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

detection circuit, which allows the ADT7484/ADT7486 to

distinguish between three input states: high, low (GND), and

floating. The address range for fixed address, discoverable

devices is 0x48 to 0x50.

Table 6. ADT7484/ADT7486 Selectable Addresses

ADD1 ADD0 Address Selected

Low (GND) Low (GND) 0x48

Low (GND) Float 0x49

Low (GND) High 0x4A

Float Low (GND) 0x4B

Float Float 0x4C

Float High 0x4D

High Low (GND) 0x4E

High Float 0x4F

High High 0x50

Preliminary Technical Data ADT7484/ADT7486

Rev. PrA | Page 9 of 16

Command Summary

Table 7 summarizes the commands supported by the ADT7484/ADT7486 devices when directed at the target address selected by the fixed

address pins. It contains the command name, command code (CC), write data length (WL), read data length (RL), and a brief description.

Table 7. 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.

GetExt1Temp() 0x01 0x01 0x02 Shows the temperature of External Thermal Diode 1.

GetExt2Temp() 0x02 0x01 0x02 Shows the temperature of External Thermal Diode 2

(ADT7486 only).

GetAllTemps() 0x00 0x01 0x04 (ADT7484)

0x06 (ADT7486)

Shows a 4- or 6-byte block of data (ADT7484: GetIntTemp,

GetExt1Temp; ADT7486: GetIntTemp, GetExt1Temp,

GetExt2Temp).

SetExt1Offset() 0xe0 0x03 0x00 Sets the offset used to correct errors in External Diode 1.

GetExt1Offset() 0xe0 0x01 0x02 Shows the offset that the device is using to correct

errors in External Diode 1.

SetExt2Offset() 0xe1 0x03 0x00 Sets the offset used to correct errors in External Diode 2

(ADT7486 only).

GetExt2Offset() 0xe1 0x01 0x02 Shows the offset that the device is using to correct

errors in External Diode 2 (ADT7486 only).

ResetDevice() 0xf6 0x01 0x00 Functional reset. The ADT7484/ADT7486 also respond to

this command when directed to the Target Address 0x00.

GetDIB() 0xf7

0xf7

0x01

0x08

0x10

Shows information used by SW to identify the device’s

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

ADT7484/ADT7486 Preliminary Technical Data

Rev. PrA | Page 10 of 16

Command Code Details

ADT7484/ADT7486 Device Identifier Block

The GetDIB() command retrieves the device identifier block

(DIB), which provides information to identify the capabilities of

the ADT7484/ADT7486. The data returned can be in 8- or 16-

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

Table 8. DIB Byte Details

Name Value Description

Device Capabilities 0xc0 Fixed address device.

Version/Revision 0x10

Meets Version 1 of the SST

specification

Vendor ID 00x11d4 Contains company ID

number in little endian

format

Device ID 0x7484

0x7486

Contains device ID number

in little endian format

Device Interface 0x01 SST device

Function Interface 0x00 Reserved

Reserved 0x00 Reserved

Vendor Specific ID 0x00 Reserved

Client Device Address 0x48 to

0x50

Dependent on the state of

the address pins.

Ping()

The Ping() command verifies if a device is responding at a

particular address. The ADT7484/ADT7486 show a valid

nonzero FCS in response to the Ping() command when

correctly addressed.

Table 9. Ping() Command

Target Address Write Length Read Length FCS

Device Address 0x00 0x00

ResetDevice()

This command resets the register map and conversion

controller. The reset command can be global or directed at the

client address of the ADT7484/ADT7486.

Table 10. ResetDevice() Command

Target Address

Write

Length

Read

Length

Reset

command FCS

Device Address 0x01 0x00 0xf6

GetIntTemp()

The ADT7484/ADT7486 show the local temperature of the

device in response to the GetIntTemp() command. The data has

a little endian, 16-bit, twos compliment format.

GetExtTemp()

Prompted by the GetExtTemp() command, the

ADT7484/ADT7486 show the temperature of the remote diode

in little endian, 16-bit, twos compliment format. The

ADT7484/ADT7486 show 0x8000 in response to this command

if the external diode is an open or short circuit.

GetAllTemps()

The ADT7484 shows the local and remote temperatures in a 4-byte

block of data (internal temperature first, followed by External

Temperature 1) in response to a GetAllTemps() command. The

ADT7486 shows the local and remote temperatures in a 6-byte

block of data (internal temperature first, followed by External

Temperature 1 and External Temperature 2) in response to this

command.

SetExtOffset()

This command sets the offset that the ADT7484/ADT7486 will

use to correct errors in the external diode. The offset is set in

little endian, 16-bit, twos compliment format. The maximum

offset is ±128°C with +0.25°C resolution.

GetExtOffset()

This command causes the ADT7484/ADT7486 to show the

offset that they are using to correct errors in the external diode.

The offset value is returned in little endian format, that is, LSB

before MSB.

ADT7484/ADT7486 Response to Unsupported Commands

A full list of command codes supported by the ADT7484/

ADT7486 is given in Table 7. The offset registers (Command

Codes 0xe0 and 0xe1) are the only registers that the user can

write to. The other defined registers are read only. Writing to

action is taken by the ADT7484/ADT7486. The

ADT7484/ADT7486 show an invalid FSC if the user attempts to

write to the devices between Command Codes 0xe2 to 0xee and

no data is written to the device. These registers are reserved for

the manufacturer’s use only, and no data can be written to the

device via these addresses.

Preliminary Technical Data ADT7484/ADT7486

Rev. PrA | Page 11 of 16

TEMPERATURE MEASUREMENT

The ADT7484/ADT7486 each have two dedicated temperature

measurement channels: one for measuring the temperature of an

on-chip band gap temperature sensor, and one for measuring the

temperature of a remote diode, usually located in the CPU or GPU.

The ADT7484 monitors one local and one remote temperature

channel, whereas the ADT7486 monitors one local and two

remote temperature channels. Monitoring of each of the

channels is done in a round-robin sequence. The monitoring

sequence is in the order shown in Table 11.

Table 11. Temperature Monitoring Sequence

Channel

Number Measurement Conversion Time (ms)

0 Local temperature 52

1 Remote Temperature 1 52

2 Remote Temperature 2

(ADT7486 only)

TEMPERATURE MEASUREMENT METHOD

A simple method for measuring temperature is to exploit the

negative temperature coefficient of a diode by measuring the

base-emitter voltage (VBE) of a transistor operated at constant

current. Unfortunately, this technique requires calibration to

null the effect of the absolute value of VBE, which varies from

device to device.

The technique used in the ADT7484/ADT7486 measures the

change in VBE when the device is operated at three different

currents.

Figure 15 shows the input signal conditioning used to measure

the output of a remote temperature sensor. This figure shows

the remote sensor as a substrate transistor, which is provided for

temperature monitoring on some microprocessors, but it could

also be a discrete transistor. If a discrete transistor is used, the

collector is not grounded and should be linked to the base. To

prevent ground noise from interfering with the measurement,

the more negative terminal of the sensor is not referenced to

ground, but is biased above ground by an internal diode at the

D1− input. If the sensor is operating in an extremely noisy

environment, C1 can be added as a noise filter. Its value should

not exceed 1000 pF.

To measure ΔVBE, the operating current through the sensor is

switched between three related currents. Figure 15 shows N1 × I

and N2 × I as different multiples of the current I. The currents

through the temperature diode are switched between I and

N1 × I, giving ΔVBE1, and then between I and N2 × I, giving

ΔVBE2. The temperature can then be calculated using the two

ΔVBE measurements. This method can also cancel the effect of

series resistance on the temperature measurement. The

resulting ΔVBE waveforms are passed through a 65 kHz low-pass

filter to remove noise and then through a chopper-stabilized

amplifier to amplify and rectify the waveform, producing a dc

voltage proportional to ΔVBE. The ADC digitizes this voltage,

and a temperature measurement is produced. To reduce the

effects of noise, digital filtering is performed by averaging the

results of 16 measurement cycles for low conversion rates.

Signal conditioning and measurement of the internal

temperature sensor is performed in the same manner.

C1*

D+

BIAS

DIODE

*CAPACITOR C1 IS OP TI O NAL. I T S HOUL D ONLY BE USED IN NOISY ENVIRO NMENT S.

TO ADC

OUT+

OUT–

REMOTE

SENSING

TRANSISTOR D–

IN1 × I N2 × I I

BIAS

LOW-PASS FILTER

=65kHz

05198-004

Figure 15. Signal Conditioning for Remote Diode Temperature Sensors

READING TEMPERATURE MEASUREMENTS

The temperature measurement command codes are detailed in

Table 10. The temperature data returned is two bytes in little

endian format, that is, LSB before MSB. All temperatures can be

read together by using Command Code 0x00 with a read length

of 0x04. The command codes and returned data are described

in Table 12.

Table 12. Temperature Channel Command Codes

Temp Channel Command Code Returned data

Internal 0x00 LSB, MSB

External 1 0x01 LSB, MSB

External 2 0x02 LSB, MSB

All Temps 0x00 Internal LSB, Internal MSB;

External 1 LSB, External 1

MSB; External 2 LSB,

External 2 MSB

ADT7484/ADT7486 Preliminary Technical Data

Rev. PrA | Page 12 of 16

SST TEMPERATURE SENSOR DATA FORMAT

The data for temperature is structured to allow values in the

range of ±512°C to be reported. Thus, the temperature sensor

format uses a twos complement, 16-bit binary value to represent

values in this range. This format allows temperatures to be

represented with approximately a 0.016°C resolution.

Table 13. SST Temperature Data Format

Twos Compliment

Temperature (°C) MSB LSB

−125 1110 0000 1100 0000

−80 1110 1100 0000 0000

−40 1111 0110 0000 0000

−20 1111 1011 0011 1110

−5 1111 1110 1100 0000

−1 1111 1111 1100 0000

0 0000 0000 0000 0000

+1 0000 0000 0100 0000

+5 0000 0001 0100 0000

+20 0000 0100 1100 0010

+40 0000 1010 0000 0000

+80 0001 0100 0000 0000

+125 0001 1111 0100 0000

USING DISCRETE TRANSISTORS

If a discrete transistor is used, the collector is not grounded and

should be linked to the base. If a PNP transistor is used, the

base is connected to the D1− input and the emitter is connected

to the D1+ input. If an NPN transistor is used, the emitter is

connected to the D1− input and the base is connected to the

D1+ input. Figure 15 shows how to connect the

ADT7484/ADT7486 to an NPN or PNP transistor for

temperature measurement. To prevent ground noise from

interfering with the measurement, the more negative terminal

of the sensor is not referenced to ground, but is biased above

ground by an internal diode at the D1− input.

D+

D–

ADT7484/

ADT7486

2N3904

NPN D+

D–

ADT7484/

ADT7486

2N3906

PNP

05198-005

Figure 16. Connections for NPN and PNP Transistors

The ADT7484/ADT7486 show an external temperature value of

0x8000 if the external diode is an open or short circuit.

LAYOUT CONSIDERATIONS

Digital boards can be electrically noisy environments. Take the

following precautions to protect the analog inputs from noise,

particularly when measuring the very small voltages from a

remote diode sensor:

• Place the device as close as possible to the remote sensing

diode. Provided that the worst noise sources, such as clock

generators, data/address buses, and CRTs, are avoided, this

distance can be four to eight inches.

• Route the D1+ and D1− tracks close together in parallel

with grounded guard tracks on each side. Provide a ground

plane under the tracks if possible.

• Use wide tracks to minimize inductance and reduce noise

pickup. A 5 mil track minimum width and spacing is

recommended.

5MIL

GND

D+

GND

D–

5198-006

Figure 17. Arrangements of Signal Tracks

• Try to minimize the number of copper/solder joints, which

can cause thermocouple effects. Where copper/solder

joints are used, make sure that they are in both the D1+

and D1− paths and are at the same temperature.

• Thermocouple effects should not be a major problem because

1°C corresponds to about 240 µV, and thermocouple voltages

are about 3 µV/°C of the temperature difference. Unless there

are two thermocouples with a big temperature differential

between them, thermocouple voltages should be much less

than 200 mV.

• Place a 0.1 µF bypass capacitor close to the device.

• If the distance to the remote sensor is more than eight

inches, the use of a twisted-pair cable is recommended.

This works for distances of about six to 12 feet.

• For very long distances (up to 100 feet), use shielded twisted-

pair cables, such as Belden #8451 microphone cables.

Connect the twisted-pair cable to D1+ and D1− and the

shield to GND, close to the device. Leave the remote end of

the shield unconnected to avoid ground loops.

Because the measurement technique uses switched current

sources, excessive cable and/or filter capacitance can affect the

measurement. When using long cables, the filter capacitor can

be reduced or removed. Cable resistance can also introduce

errors. A 1 Ω series resistance introduces about 0.5°C error.

Preliminary Technical Data ADT7484/ADT7486

Rev. PrA | Page 13 of 16

TEMPERATURE OFFSET

As CPUs run faster, it is more difficult to avoid high frequency

clocks when routing the D1+ and D1− tracks around a system

board. Even when the recommended layout guidelines are

followed, there may still be temperature errors, attributed to

noise being coupled on to the D1+ and D1− lines. High

frequency noise generally has the effect of producing

temperature measurements that are consistently too high by a

specific amount. The ADT7484/ADT7486 have a temperature

offset command code of 0xe0 through which a desired offset

can be set. By doing a one-time calibration of the system, the

offset caused by system board noise can be calculated and

nulled by specifying it in the ADT7484/ADT7486. The offset is

automatically added to every temperature measurement. The

maximum offset is ±128°C with 0.25°C resolution. The offset

format is the same as the temperature data format—16-bit, twos

compliment notation, as shown in Table 13. The offset should

be programmed in little endian format, that is, LSB before MSB.

The offset value is also returned in little endian format when read.

APPLICATION SCHEMATICS

GND

D1+

D1–

SST

ADD0

RESERVED

ADD1

ADT7484

2N3904 OR CPU

THERMAL DIODE

05198-007

SST

Figure 18. ADT7484 Typical Application Schematic

GND

D1+

D1–

D2+

SST

ADD0

RESERVED

ADD1

D2–

ADT7486

CPU

THERMAL

DIODE

N3904

NPN

SST

05198-008

Figure 19. ADT7486 Typical Application Schematic

ADT7484/ADT7486 Preliminary Technical Data

Rev. PrA | Page 14 of 16

OUTLINE DIMENSIONS

Figure 20. 8-Lead Mini Small Outline Package [MSOP]

(RM-8)

Dimensions shown in millimeters

COMPLIANT TO JEDEC STANDARDS MO-187-BA

0.23

0.08

0.80

0.60

0.40

8°

0°

0.15

0.05 0.33

0.17

0.95

0.85

0.75

SEATING

PLANE

1.10 MAX

10 6

0.50 BSC

PIN 1

COPLANARITY

0.10

3.10

3.00

2.90

3.10

3.00

2.90

5.15

4.90

4.65

Figure 21. 10-Lead Mini Small Outline Package [MSOP]

(RM-10)

Dimensions shown in millimeters

ORDERING GUIDE

Model Temperature Range Package Description Package Option

ADT7484ARMZ1 –40°C to +125°C 8-Lead MSOP RM-8

ADT7484ARMZ-REEL1 –40°C to +125°C 8-Lead MSOP RM-8

ADT7484ARMZ-REEL71 –40°C to +125°C 8-Lead MSOP RM-8

ADT7486ARMZ1 –40°C to +125°C 10-Lead MSOP RM-10

ADT7486ARMZ-REEL1 –40°C to +125°C 10-Lead MSOP RM-10

ADT7486ARMZ-REEL71 –40°C to +125°C 10-Lead MSOP RM-10

1 Z = Pb-free part.

Preliminary Technical Data ADT7484/ADT7486

Rev. PrA | Page 15 of 16

NOTES

ADT7484/ADT7486 Preliminary Technical Data

Rev. PrA | Page 16 of 16

NOTES

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PR05198-0-4/06(PrA)