ON Semiconductor ADT7461 Technical data

±1°C Temperature Monitor with

FEATURES

On-chip and remote temperature sensor

0.25°C resolution/1°C accuracy on remote channel

1°C resolution/3°C accuracy on local channel

Automatically cancels up to 3 kΩ (typ) of resistance in series

with remote diode to allow noise filtering

Extended, switchable temperature measurement range

0°C to +127°C (default) or –55°C to +150°C

Pin- and register-compatible with the ADM1032

2-wire SMBus serial interface with SMBus alert support

Two SMBus address versions available:

ADT7461 SMBus address is 0x4C

ADT7461-2 SMBus address is 0x4D

Programmable over/under temperature limits

Offset registers for system calibration

Up to two over temperature fail-safe

Small 8-lead SOIC or8-lead MSOP packages

170 μA operating current, 5.5 μA standby current

APPLICATIONS

Desktop and notebook computers

Industrial controllers

Smart batteries

Embedded systems

Instrumentation

THERM

outputs

Series Resistance Cancellation

ADT7461

GENERAL DESCRIPTION

The ADT74611 is a dual-channel digital thermometer and under/over temperature alarm intended for use in PCs and thermal management systems. It is pin- and register-compatible with the ADM1032. The ADT7461 has three additional features: series resistance cancellation (where up to 3 kΩ (typical) of resistance in series with the temperature monitoring diode may be automatically cancelled from the temperature result, allowing noise filtering); configurable and an extended, switchable temperature measurement range. The ADT7461 can accurately measure the temperature of a remote thermal diode to ±1°C and the ambient temperature to ±3°C. The temperature measurement range defaults to 0°C to +127°C, compatible with the ADM1032, but can be switched to a wider measurement range of −55°C to +150°C. The ADT7461 communicates over a 2-wire serial interface compatible with system management bus (SMBus) standards. An

signals when the on-chip or remote temperature is out of range.

THERM

The

control of a cooling fan. The

as a second

output is a comparator output that allows on/off

ALERT

output can be reconfigured

THERM

output, if required.

The SMBus address of the ADT7461 is 0x4C. An ADT7461-2 is also available, which uses SMBus Address 0x4D.

Protected by U.S. Patents 5,195,827; 5,867,012; 5,982,221; 6,097,239;

6,133,753; 6,169,442; other patents pending.

ALERT

output;

output

CONVERSION RATE

ON-CHIP

TEMPERATURE

SENSOR

ANALOG

MUX

D+

SRC

BLOCK

D–

EXTERNAL DIODE OPEN CIRCUIT

ADT7461

LOCAL TEMPERATURE

VALUE REGISTER

ADC

RUN/STANDBYBUSY

REMOTE TE MPERATURE

VALUE REGISTER

REMOTE OFFSET

STATUS REGIST ER

SMBus INTERFACE

751 8

DIGITAL MUX

SCLKSDATAGNDV

LIMIT

COMPARATOR

ADDRESS POINTER

LOCAL TEMPERATURE

LOW LIMIT REGIST ER

LOCAL TEMPERATURE

HIGH LIMIT REGIST ER

REMOTE TE MPERATURE

LOW LIMIT REGIST ER

REMOTE TE MPERATURE

HIGH LIMIT REGIST ER

DIGITAL MUX

LOCAL THERM LIMIT

EXTERNAL THERM LIMIT

CONFIGURATION

THERM ALERT /

INTERRUPT

MASKING

THERM2

04110-0-012

Figure 1. Functional Block Diagram

ADT7461

TABLE OF CONTENTS

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

SMBus Timing Specifications..........................................................4

Absolute Maximum Ratings ............................................................5

Thermal Characteristics...............................................................5

ESD Caution .................................................................................. 5

Pin Configuration and Function Descriptions .............................6

Typical Performance Characteristics..............................................7

Functional Description.....................................................................9

Series Resistance Cancellation ....................................................9

Temperature Measurement Method...........................................9

Temperature Measurement Results..........................................10

Temperature Measurement Range............................................10

Temperature Data Format..........................................................10

ADT7461 Registers..................................................................... 11

Serial Bus Interface.....................................................................15

Addressing the Device................................................................15

ALERT

Output............................................................................17

Low Power Standby Mode .........................................................17

Sensor Fault Detection...............................................................17

The ADT7461 Interrupt System ...............................................17

Application Information............................................................19

Thermal Inertia and Self-Heating ............................................19

Layout Considerations ............................................................... 20

Application Circuit .....................................................................21

Outline Dimensions........................................................................22

Ordering Guide...........................................................................23

REVISION HISTORY

12/07- Rev 1: Conversion to ON Semiconductor

7/05—Rev. A to Rev. B

Changes to Features Section .............................................................1

Changes to Applications Section...................................................... 1

Changes to General Description Section ........................................ 1

Changes to Addressing the Device Section ...................................14

Updated Outline Dimensions..........................................................21

Changes to the Ordering Guide......................................................22

10/04—Rev. 0 to Rev. A

Change to SMBus Specifications.....................................................4

Changes to Figure 6 and Figure 10 .................................................7

Added Figure 9 and Figure 13 ......................................................... 7

Changes to Temperature Measurement Section .........................10

Changes to Figure 19 and Figure 25 .............................................16

Changes to Serial Bus Interface Section.......................................23

10/03—Revision 0: Initial Version

Rev. 3 | Page 2 of 23 | www.onsemi.com

ADT7461

SPECIFICATIONS

TA = −40°C to +120°C, VDD = 3 V to 5.5 V, unless otherwise noted.

Table 1.

Parameter Min Typ Max Unit Test Conditions

POWER SUPPLY

Supply Voltage, VDD 3.0 3.30 5.5 V Average Operating Supply Current, IDD 170 215 μA 0.0625 conversions/sec rate1

5.5 10 μA Standby mode, –40°C ≤ TA ≤ +85°C

5.5 20 μA Standby mode, +85°C ≤ TA ≤ +120°C Undervoltage Lockout Threshold 2.2 2.55 2.8 V VDD input, disables ADC, rising edge Power-On-Reset Threshold 1 2.5 V

TEMPERATURE-TO-DIGITAL CONVERTER

Local Sensor Accuracy ±1 ±3 °C −40°C ≤ TA ≤ +100°C, 3 V ≤ VDD ≤ 3.6 V Resolution 1 °C Remote Diode Sensor Accuracy ±1 °C +60°C ≤ TA ≤ +100°C, −55°C ≤ T ±3 °C −40°C ≤ TA ≤ +120°C, −55°C ≤ T Resolution 0.25 °C Remote Sensor Source Current 96 μA High level3 36 μA Middle level3 6 μA Low level3 Conversion Time 32.13 114.6 ms From stop bit to conversion complete (both channels),

one-shot mode with averaging switched on

3.2 12.56 ms One-shot mode with averaging off (that is, conversion rate = 16, 32, or 64 conversions per second)

Maximum Series Resistance Cancelled 3 kΩ Resistance split evenly on both the D+ and D– inputs

OPEN-DRAIN DIGITAL OUTPUTS

THERM, ALERT/THERM2

(

) Output Low Voltage, VOL 0.4 V I High Level Output Leakage Current, IOH 0.1 1 μA V ALERT

Output Low Sink Current

= −6.0 mA3

OUT

= V

OUT

1 mA

ALERT

forced to 0.4 V

SMBus INTERFACE3, 4

Logic Input High Voltage, VIH 2.1 V 3 V ≤ VDD ≤ 3.6 V

SCLK, SDATA

Logic Input Low Voltage, VIL 0.8 V 3 V ≤ VDD ≤ 3.6 V

SCLK, SDATA Hysteresis 500 mV SMBus Output Low Sink Current 6 mA SDATA forced to 0.6 V Logic Input Current, IIH, IIL −1 +1 μA SMBus Input Capacitance, SCLK, SDATA 5 pF SMBus Clock Frequency 400 kHz SMBus Timeout5 25 64 ms User programmable SCLK Falling Edge to SDATA Valid Time 1 μs Master clocking in data

See Table 8 for information on other conversion rates.

Guaranteed by characterization, but not production tested.

Guaranteed by design, but not production tested.

See the SMBUS Timing Specifications section for more information.

Disabled by default; see the Serial Bus Interface section for details on enabling it.

≤ +150°C, 3 V ≤ VDD ≤ 3.6 V

≤ +150°C, 3 V ≤ VDD ≤ 5.5 V

Rev. 3 | Page 3 of 23 | www.onsemi.com

ADT7461

SMBus TIMING SPECIFICATIONS

Table 2. SMBus Timing Specifications

Parameter Limit at T

400 kHz max

SCLK

1.3 μs min Clock low period, between 10% points

LOW

0.6 μs min Clock high period, between 90% points

HIGH

MIN

and T

tR 300 ns max Clock/data rise time tF 300 ns max Clock/data fall time t

600 ns min Start condition setup time

SU; STA

600 ns min Start condition hold time

HD; STA

100 ns min Data setup time

SU; DAT

300 ns min Data hold time

HD; DAT

600 ns min Stop condition setup time

SU; STO

1.3 μs min Bus free time between stop and start conditions

BUF

Guaranteed by design, but not production tested.

Time from 10% of SDATA to 90% of SCLK.

Time for 10% or 90% of SDATA to 10% of SCLK.

Time for 90% of SCLK to 10% of SDATA.

Unit Description

MAX

SCLK

SDATA

HD;DAT

LOW

HD;STA

BUF

STOP START STOPSTART

HIGH

SU;DAT

Figure 2. Serial Bus Timing

SU;STA

HD;STA

SU;STO

04110-0-001

Rev. 3 | Page 4 of 23 | www.onsemi.com

ADT7461

ABSOLUTE MAXIMUM RATINGS

Table 3.

Parameter Rating

Positive Supply Voltage (VDD) to GND −0.3 V, +5.5 V D+ −0.3 V to VDD + 0.3 V D− to GND −0.3 V to +0.6 V

SCLK, SDATA, THERM

Input Current, SDATA, Input Current, D− ±1 mA ESD Rating, All Pins (Human Body Model) 2000 V Maximum Junction Temperature (TJ max) 150°C Storage Temperature Range −65°C to +150°C IR Reflow Peak Temperature 220°C

Pb-Free Parts Only 260°C (±0.5°C)

Lead Temperature (Soldering 10 sec) 300°C

ALERT

THERM

−0.3 V to +5.5 V

−0.3 V to VDD + 0.3 V

−1 mA, +50 mA

THERMAL CHARACTERISTICS

8-lead SOIC package

= 121°C/W

8-lead MSOP package

= 142°C/W

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.

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.

Rev. 3 | Page 5 of 23 | www.onsemi.com

ADT7461

PIN CONFIGURATION AND FUNCTION DESCRIPTIONS

THERM

D+

D–

ADT7461

TOP VIEW

(Not to Scale)

SCLK

SDATA

ALERT/THERM2

GND

04110-0-013

Figure 3. Pin Configuration

Table 4. Pin Function Descriptions

Pin No. Mnemonic Description

1 VDD Positive Supply, 3 V to 5.5 V. 2 D+ Positive Connection to Remote Temperature Sensor. 3 D− Negative Connection to Remote Temperature Sensor.

THERM

Open-drain output that can be used to turn a fan on/off or throttle a CPU clock in the event of an overtemperature condition. Requires pull-up to V

5 GND Supply Ground Connection.

THERM2

ALERT

Open-Drain Logic Output Used as Interrupt or SMBus Alert. This may also be configured as a second

output. Requires pull-up resistor. 7 SDATA Logic Input/Output, SMBus Serial Data. Open-Drain Output. Requires pull-up resistor. 8 SCLK Logic Input, SMBus Serial Clock. Requires pull-up resistor.

THERM

Rev. 3 | Page 6 of 23 | www.onsemi.com

ADT7461

TYPICAL PERFORMANCE CHARACTERISTICS

D+ TO GND

250mV EXTERNAL

100mV INTERNAL

–20

D+ TO V

–40

TEMPERATURE ERROR (°C)

–60

–80

0 20406080

100

LEAKAGE RESISTANCE (MΩ)

Figure 4. Temperature Error vs. Leakage Resistance

–0.1

–0.2

–0.3

–0.4

–0.5

–0.6

TEMPERATURE ERROR (°C)

–0.7

–0.8

–3 –10 10 30 50 70 90 110 130 150

TEMPERATURE (°C)

Figure 5. Temperature Error vs. Actual Temperature Using 2N3906

–5

TEMPERATURE ERROR (°C)

–10

04110-0-017

–15

020

250mV INTERNAL

FREQUENCY (MHz)

100mV EXTERNAL

04110-0-015

Figure 7. Temperature Error vs. Power Supply Noise Frequency

–10

–20

–30

–40

–50

TEMPERATURE ERROR (°C)

–60

04110-0-022

–70

0 5 10 15 20

CAPACITANCE (nF)

04110-0-018

Figure 8. Temperature Error vs. Capacitance Between D+ and D−

TEMPERATURE ERROR (°C)

–1

–2

0 100 200 300

40mV NO FILTER 60mV NO FILTER 40mV WITH FILTER 60mV WITH FILTER

FREQUENCY (MHz)

400 500 600

Figure 6. Temperature Error vs. Differential Mode Noise Frequency

(With and Without R-C-R Filter of 100 Ω–2.2 nF–100 Ω)

Rev. 3 | Page 7 of 23 | www.onsemi.com

180

160

140

120

100

TEMPERATURE ERROR (°C)

04110-0-027

–20

0 100 200 300

FREQUENCY (MHz)

100mV NO FILTER

100mV WITH FILTER

400 500 600

04110-0-024

Figure 9. Temperature Error vs. 100 mV Differential Mode Noise Frequency

(With and Without R-C-R Filter of 100 Ω–2.2 nF–100 Ω)

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