ADM1032ARM - Analog Devices - Datasheet.Directory

REV. C

ADM1032

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1C Remote and Local

System Temperature Monitor

FUNCTIONAL BLOCK DIAGRAM

ON-CHIP

TEMPERATURE

SENSOR

A/D

CONVERTER

BUSY RUN/STANDBY

EXTERNAL DIODE OPEN-CIRCUIT

ADDRESS POINTER

CONVERSION RATE

REMOTE TEMPERATURE

HIGH LIMIT REGISTER

CONFIGURATION

INTERRUPT

MASKING

LIMIT

COMPARATOR

REMOTE TEMPERATURE

VALUE REGISTER

LOCAL TEMPERATURE

VALUE REGISTER

GND SDATA SCLK

THERM

ALERT

D+

D– REMOTE TEMPERATURE

LOW LIMIT REGISTER

LOCAL TEMPERATURE

HIGH LIMIT REGISTER

LOCAL TEMPERATURE

LOW LIMIT REGISTER

ANALOG

MUX

ADM1032

LOCAL THERM LIMIT

EXTERNAL THERM LIMIT

DIGITAL MUX

STATUS REGISTER

SMBUS INTERFACE

REMOTE OFFSET

FEATURES

On-Chip and Remote Temperature Sensing

Offset Registers for System Calibration

0.125C Resolution/1C Accuracy on Remote Channel

1C Resolution/3C Accuracy on Local Channel

Fast (Up to 64 Measurements per Second)

2-Wire SMBus Serial Interface

Supports SMBus Alert

Programmable Under/Overtemperature Limits

Programmable Fault Queue

Overtemperature Fail-Safe THERM Output

Programmable THERM Limits

Programmable THERM Hysteresis

170 A Operating Current

5.5 A Standby Current

3 V to 5.5 V Supply

Small 8-Lead SOIC and MSOP Packages

APPLICATIONS

Desktop and Notebook Computers

Smart Batteries

Industrial Controllers

Telecommunications Equipment

Instrumentation

Embedded Systems

*Patents 5,982,221, 6,097,239, 6,133,753, 6,169,442, 5,867,012.

PRODUCT DESCRIPTION

The ADM1032 is a dual-channel digital thermometer and

under/overtemperature alarm intended for use in personal comput-

ers and thermal management systems. The higher 1°C accuracy

offered allows systems designers to safely reduce temperature

guardbanding and increase system performance. The device

can measure the temperature of a microprocessor using a diode-

connected NPN or PNP transistor, which may be provided on-chip

or can be a low cost discrete device, such as the 2N3906. A

novel measurement technique cancels out the absolute value of

the transistor’s base emitter voltage so that no calibration is

required. The second measurement channel measures the output

of an on-chip temperature sensor to monitor the temperature

of the device and its environment.

The ADM1032 communicates over a 2-wire serial interface

compatible with System Management Bus (SMBus) standards.

Under and overtemperature limits can be programmed into the

device over the serial bus, and an ALERT output signals when the

on-chip or remote temperature measurement is out of range. This

output can be used as an interrupt or as an SMBus alert. The

THERM output is a comparator output that allows CPU clock

throttling or on/off control of a cooling fan. An ADM1032-1 is

also available. The only difference between the ADM1032 and the

ADM1032-1 is the default value of the external

THERM

limit.

REV. C

–2–

ADM1032–SPECIFICATIONS

(TA = TMIN to TMAX, VDD = VMIN to VMAX, unless otherwise noted.)

Parameter Min Typ Max Unit Test Conditions/Comments

POWER SUPPLY

Supply Voltage, V

3.0 3.30 5.5 V

Average Operating Supply Current, I

170 215 µA 0.0625 Conversions/Sec Rate

5.5 10 µA Standby Mode

Undervoltage Lockout Threshold 2.35 2.55 2.8 V V

Input, Disables ADC, Rising Edge

Power-On Reset Threshold 1 2.4 V

TEMPERATURE-TO-DIGITAL CONVERTER

Local Sensor Accuracy ±1 ±3 °C 0 ≤ T

≤ 100°C, V

= 3 V to 3.6 V

Resolution 1 °C

Remote Diode Sensor Accuracy ±1 °C 60°C ≤ T

≤ 100°C, V

= 3 V to 3.6 V

±3 °C 0°C ≤ T

≤ 120°C

Resolution 0.125 °C

Remote Sensor Source Current 230 µA High Level

13 µA Low Level

Conversion Time 35.7 142.8 ms From Stop Bit to Conversion Complete

(Both Channels) One-Shot Mode with

Averaging Switched On

5.7 22.8 ms One-Shot Mode with Averaging Off

(i.e., Conversion Rate = 32 or 64

Conversions per Second)

OPEN-DRAIN DIGITAL OUTPUTS

(THERM, ALERT)

Output Low Voltage, V

0.4 V I

OUT

= –6.0 mA

High Level Output Leakage Current, I

0.1 1 µA V

OUT

= V

DD2

SERIAL BUS TIMING

Logic Input High Voltage, V

2.1 V V

= 3 V to 5.5 V

SCLK, SDATA

Logic Input Low Voltage, V

0.8 V V

= 3 V to 5.5 V

Hysteresis 500 mV

SCLK, SDATA

SDATA Output Low Sink Current 6 mA SDATA Forced to 0.6 V

ALERT Output Low Sink Current 1 mA ALERT Forced to 0.4 V

Logic Input Current, I

, I

–1 +1 µA

Input Capacitance, SCLK, SDATA 5 pF

Clock Frequency 400 kHz

SMBus Timeout 25 64 ms Note 3

SCLK Clock Low Time, t

LOW

1.3 µs t

LOW

between 10% Points

SCLK Clock High Time, t

HIGH

0.6 µs t

HIGH

between 90% Points

Start Condition Setup Time, t

SU:STA

600 ns

Start Condition Hold Time, t

HD:STA

600 ns Time from 10% of SDATA to 90%

of SCLK

Stop Condition Setup Time, t

SU:STO

600 ns Time from 90% of SCLK to 10%

of SDATA

Data Valid to SCLK Rising Edge 100 ns Time for 10% or 90% of SDATA to

Time, t

SU:DAT

10% of SCLK

Data Hold Time, t

HD:DAT

300 ns

Bus Free Time, t

BUF

1.3 µs Between Start/Stop Condition

SCLK, SDATA Rise Time, t

300 ns

SCLK, SDATA Fall Time, t

300 ns

NOTES

See Table VI for information on other conversion rates.

Guaranteed by design, not production tested.

The SMBus timeout is a programmable feature. By default, it is not enabled. Details on how to enable it are available in the Serial Bus Interface section of this data sheet.

Specifications subject to change without notice.

REV. C –3–

ADM1032

tSU:DAT

tHIGH

tHD:DAT

tLOW

tSU:STO

SCLK

SDATA

tHD:STA

tSU:STA

tBUF

Figure 1. Diagram for Serial Bus Timing

PIN CONFIGURATION

TOP VIEW

(Not to Scale)

D+

SCLK

D–

THERM

ADM1032

VDD

GND

ALERT

SDATA

PIN FUNCTION DESCRIPTIONS

No. Mnemonic Description

Positive Supply, 3 V to 5.5 V.

2D+Positive Connection to Remote Temperature Sensor.

3D–Negative Connection to Remote Temperature Sensor.

4THERM THERM is an 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

5GND Supply Ground Connection.

6ALERT Open-Drain Logic Output Used as Interrupt or SMBus Alert.

7SDATA Logic Input/Output, SMBus Serial Data. Open-drain output. Requires pull-up resistor.

8SCLK Logic Input, SMBus Serial Clock. Requires pull-up resistor.

ABSOLUTE MAXIMUM RATINGS*

Positive Supply Voltage (V

) to GND . . . . . . –0.3 V, +5.5 V

D+ . . . . . . . . . . . . . . . . . . . . . . . . . . . . –0.3 V to V

+ 0.3 V

D– to GND . . . . . . . . . . . . . . . . . . . . . . . . . –0.3 V to +0.6 V

SCLK, SDATA, ALERT . . . . . . . . . . . . . . . . –0.3 V to +5.5 V

THERM . . . . . . . . . . . . . . . . . . . . . . . –0.3 V to V

+ 0.3 V

Input Current, SDATA, THERM . . . . . . . . –1 mA, +50 mA

Input Current, D– . . . . . . . . . . . . . . . . . . . . . . . . . . . . ±1 mA

ESD Rating, All Pins (Human Body Model) . . . . . . >1000 V

Maximum Junction Temperature (T

max) . . . . . . . . . 150°C

Storage Temperature Range . . . . . . . . . . . . –65°C to +150°C

IR Reflow Peak Temperature . . . . . . . . . . . . . . . . . . . . 220°C

Lead Temp (Soldering 10 sec) . . . . . . . . . . . . . . . . . . . 300°C

*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 CHARACTERISTICS

8-Lead SOIC Package

= 121°C/W

8-Lead MSOP Package

= 142°C/W

ORDERING GUIDE

Temperature Package Package Branding SMBus External

THERM

Model Range Description Option Information Addr Default

ADM1032AR 0°C to 120°C 8-Lead SOIC Package R-8 1032AR 4C 85⬚C

ADM1032ARM 0°C to 120°C

8-Lead MSOP Package

RM-8 T2A 4C 85⬚C

ADM1032AR-1 0°C to 120°C 8-Lead SOIC Package R-8 1032AR01 4C 108⬚C

ADM1032ARM-1

0°C to 120°C

8-Lead MSOP Package

RM-8 T1A 4C 108⬚C

REV. C

ADM1032–Typical Performance Characteristics

–4–

LEAKAGE RESISTANCE – M

TEMPERATURE ERROR – C

010100

–16

–4

–8

–12

D+ TO GND

D+ TO V

TPC 1. Temperature Error vs.

Leakage Resistance

FREQUENCY – Hz

VIN = 100mV p-p

TEMPERATURE ERROR – C

10 1M

VIN = 250mV p-p

TPC 4. Temperature Error vs. Power

Supply Noise Frequency

= 50mV p-p

FREQUENCY – Hz

TEMPERATURE ERROR – C

100k 1M 10M 100M

= 100mV p-p

= 25mV p-p

TPC 7. Temperature Error vs.

Common-Mode Noise Frequency

TEMPERATURE ERROR – C

–0.5

0.5

1.0

TEMPERATURE – C

020406080100 120

TPC 2. Temperature Error vs. Actual

Temperature Using 2N3906

161116 21 26 31

TEMPERATURE ERROR – C

CAPACITANCE – nF

TPC 5. Temperature Error vs.

Capacitance between D+ and D–

SCLK FREQUENCY – kHz

151025 50 75 100

SUPPLY CURRENT – A

250 500 750 1000

3.3V

TPC 8. Standby Supply Current vs.

Clock Frequency

FREQUENCY – Hz

–1

100k 100M1M

TEMPERATURE ERROR – C

10M

10mV p-p

40mV p-p

TPC 3. Temperature Error vs.

Differential Mode Noise Frequency

CONVERSION RATE – Hz

0.01

2.0

SUPPLY CURRENT – A

1.5

0.5

= 5V

0.1 1 10 100

1.0

= 3V

TPC 6. Operating Supply Current vs.

Conversion Rate

SUPPLY VOLTAGE – V

STANDBY SUPPLY CURRENT – A

1.5 2.50.5 1.0 3.0 5.03.5 4.0 4.52.0

TPC 9. Standby Supply Current vs.

Supply Voltage

REV. C

ADM1032

–5–

FUNCTIONAL DESCRIPTION

The ADM1032 is a local and remote temperature sensor and

overtemperature alarm. When the ADM1032 is operating

normally, the on-board A/D converter operates in a free-

running mode. The analog input multiplexer alternately selects

either the on-chip temperature sensor to measure its local tem-

perature or the remote temperature sensor. These signals are

digitized by the ADC and the results are stored in the Local

and Remote Temperature Value Registers.

The measurement results are compared with local and remote,

high, low, and THERM temperature limits stored in nine on-

chip registers. Out-of-limit comparisons generate flags that are

stored in the Status Register, and one or more out-of limit results

will cause the ALERT output to pull low. Exceeding THERM

temperature limits causes the THERM output to assert low.

The limit registers can be programmed, and the device con-

trolled and configured, via the Serial System Management Bus

(SMBus). The contents of any register can also be read back via

the SMBus.

Control and configuration functions consist of

•

Switching the device between normal operation and

standby mode.

•

Masking or enabling the ALERT output.

•

Selecting the conversion rate.

MEASUREMENT METHOD

A simple method of measuring temperature is to exploit the

negative temperature coefficient of a diode, or the base-emitter

voltage of a transistor, operated at constant current. Unfortu-

nately, this technique requires calibration to null out the effect

of the absolute value of V

, which varies from device to device.

The technique used in the ADM1032 is to measure the change

in V

when the device is operated at two different currents.

This is given by

where:

K is Boltzmann’s constant (1.38 × 10

–23

q is the charge on the electron (1.6 × 10

–19

Coulombs).

T is the absolute temperature in Kelvins.

N is the ratio of the two currents.

is the ideality factor of the thermal diode.

The ADM1032 is trimmed for an ideality factor of 1.008.

Figure 2 shows the input signal conditioning used to measure

the output of an external temperature sensor. This figure shows

the external sensor as a substrate transistor, provided for

temperature monitoring on some microprocessors, but it could

equally well be a discrete transistor. If a discrete transistor is

used, the collector will not be grounded and should be linked to the

base. To prevent ground noise 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

D– input. If the sensor is operating in a noisy environment, C1

may optionally be added as a noise filter. Its value is typically

2200 pF but should be no more than 3000 pF. See the section

on Layout Considerations for more information on C1.

To measure ∆V

, the sensor is switched between the operating

currents of I and N × I. The resulting waveform is passed

through a 65 kHz low-pass filter to remove noise, and then to

a chopper-stabilized amplifier that performs the functions of

amplification and rectification of the waveform to produce a dc

voltage proportional to ∆V

. This voltage is measured by the

ADC to give a temperature output in twos complement format.

To further reduce the effects of noise, digital filtering is performed

by averaging the results of 16 measurement cycles.

Signal conditioning and measurement of the internal temperature

sensor is performed in a similar manner.

TEMPERATURE DATA FORMAT

One LSB of the ADC corresponds to 0.125°C, so the ADC can

measure from 0°C to 127.875°C. The temperature data format

is shown in Tables I and II.

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.

Table I. Temperature Data Format (Local Temperature and

Remote Temperature High Byte)

Temperature Digital Output

0°C 0 000 0000

1°C 0 000 0001

10°C 0 000 1010

25°C 0 001 1001

50°C 0 011 0010

75°C 0 100 1011

100°C 0 110 0100

125°C 0 111 1101

127°C 0 111 1111

C1*

D+

D–

REMOTE

SENSING

TRANSISTOR

IN ⴛ I I

BIAS

OUT+

TO ADC

OUT–

BIAS

DIODE LOW-PASS FILTER

= 65kHz

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

C1 = 2.2nF TYPICAL, 3nF MAX.

Figure 2. Input Signal Conditioning

∆Vn

qIn N

BE f

()

REV. C

ADM1032

–6–

Status Register

Bit 7 of the Status Register indicates that the ADC is busy

converting when it is high. Bits 6 to 3, 1, and 0 are flags that

indicate the results of the limit comparisons. Bit 2 is set when the

remote sensor is open circuit.

If the local and/or remote temperature measurement is above the

corresponding high temperature limit, or below or equal to the

corresponding low temperature limit, one or more of these flags

will be set. These five flags (Bits 6 to 2) NOR’d together, so that

if any of them are high, the ALERT interrupt latch will be set

and the ALERT output will go low. Reading the Status Register

will clear the five flag bits, provided that the error conditions that

caused the flags to be set have gone away. While a limit compara-

tor is tripped due to a value register containing an out-of-limit

measurement, or the sensor is open circuit, the corresponding flag

bit cannot be reset. A flag bit can only be reset if the corre-

sponding value register contains an in-limit measurement or the

sensor is good.

The ALERT interrupt latch is not reset by reading the Status

serviced by the master reading the device address, provided the

error condition has gone away and the Status Register flag bits

have been reset.

When Flags 1 and 0 are set, the THERM output goes low to

indicate that the temperature measurements are outside the

programmed limits. THERM output does not need to be reset,

unlike the ALERT output. Once the measurements are within the

limits, the corresponding status register bits are reset and the

THERM output goes high.

Table IV. Status Register Bit Assignments

Bit Name Function

7BUSY 1 When ADC Converting

6LHIGH*1 When Local High Temp Limit Tripped

5LLOW*1 When Local Low Temp Limit Tripped

4RHIGH*1 When Remote High Temp Limit Tripped

3RLOW*1 When Remote Low Temp Limit Tripped

2OPEN*1 When Remote Sensor Open-Circuit

1RTHRM 1 When Remote THERM Limit Tripped

0LTHRM 1 When Local THERM Limit Tripped

*These flags stay high until the status register is read or they are reset by POR.

Configuration Register

Two bits of the Configuration Register are used. If Bit 6 is 0,

which is the power-on default, the device is in Operating Mode

with the ADC converting. If Bit 6 is set to 1, the device is in

Standby Mode and the ADC does not convert. The SMBus

does, however, remain active in Standby Mode so values can be

read from or written to the SMBus. The ALERT and THERM

O/Ps are also active in Standby Mode.

Bit 7 of the Configuration Register is used to mask the alert

output. If Bit 7 is 0, which is the power-on default, the output is

enabled. If Bit 7 is set to 1, the output is disabled.

Table II. Extended Temperature Resolution (Remote

Temperature Low Byte)

Extended Remote Temperature

Resolution Low Byte

0.000°C 0 000 0000

0.125°C 0 010 0000

0.250°C 0 100 0000

0.375°C 0 110 0000

0.500°C 1 000 0000

0.625°C 1 010 0000

0.750°C 1 100 0000

0.875°C 1 110 0000

ADM1032 REGISTERS

The ADM1032 contains registers that are used to store the

results of remote and local temperature measurements and high

and low temperature limits and to configure and control the

device. A description of these registers follows, and further

details are given in Tables III to VII.

Address Pointer Register

The Address Pointer Register itself does not have, or require, an

address, since it is the register to which the first data byte of

every write operation is written automatically. This data byte

is an address pointer that sets up one of the other registers for

the second byte of the write operation or for a subsequent

read operation.

The power-on default value of the Address Pointer Register is

00h, so if a read operation is performed immediately after power-on

without first writing to the Address Pointer, the value of the local

temperature will be returned, since its register address is 00h.

Value Registers

The ADM1032 has three registers to store the results of local

and remote temperature measurements. These registers are

written to by the ADC only and can be read over the SMBus.

Offset Register

Series resistance on the D+ and D– lines in processor packages

and clock noise can introduce offset errors into the remote

temperature measurement. To achieve the specified accuracy on

this channel, these offsets must be removed.

The offset value is stored as an 11-bit, twos complement value

in Registers 11h (high byte) and 12h (low byte, left justified).

The value of the offset is negative if the MSB of Register 11h is

1 and positive if the MSB of Register 12h is 0. The value is added

to the measured value of the remote temperature.

The offset register powers up with a default value of 0°C and

will have no effect if nothing is written to them.

Table III. Sample Offset Register Codes

Offset Value 11h 12h

–4°C 1 111 1100 0 000 0000

–1°C 1 111 1111 0 000 0000

–0.125°C 1 111 1111 1 110 0000

0°C 0 000 0000 0 000 0000

+0.125°C 0 000 0000 0 010 0000

+1°C 0 000 0001 0 000 0000

+4°C 0 000 0100 0 000 0000

REV. C

ADM1032

–7–

Consecutive ALERT Register

This value written to this register determines how many out-of-

limit measurements must occur before an ALERT is generated.

The default value is that one out-of-limit measurement generates

an ALERT. The max value that can be chosen is 4. The purpose

of this register is to allow the user to perform some filter

ing of the

output. This is particularly useful at the faster two conversion

rates where no averaging takes place.

Table VII. Consecutive ALERT Register Codes

Number of Out-of-Limit

yxxx 000x 1

yxxx 001x 2

yxxx 011x 3

yxxx 111x 4

NOTES

x = Don’t care bit.

y = SMBus timeout bit. Default = 0. See SMBus section for more

information.

SERIAL BUS INTERFACE

Control of the ADM1032 is carried out via the serial bus. The

ADM1032 is connected to this bus as a slave device, under the

control of a master device.

There is a programmable SMBus timeout. When this is enabled,

the SMBus will timeout after typically 25 ms of no activity. However,

this feature is not enabled by default. To enable it, set Bit 7

of the Consecutive Alert Register (Address = 22h).

The ADM1032 supports packet error checking (PEC) and its

use is optional. It is triggered by supplying the extra clock for the

PEC byte. The PEC byte is calculated using CRC-8. The frame

check sequence (FCS) conforms to CRC-8 by the polynomial

Cx xxx

()

=+++

821

Consult the SMBus 1.1 specification for more information.

ADDRESSING THE DEVICE

In general, every SMBus device has a 7-bit device address (except

for some devices that have extended, 10-bit addresses). When

the master device sends a device address over the bus, the slave

device with that address will respond. The ADM1032 is available

with one device address, which is Hex 4C (1001 100).

The serial bus protocol operates as follows:

1. The master initiates data transfer by establishing a START

condition, defined as a high-to-low transition on the serial

data line SDATA, while the serial clock line SCLK remains

high. This indicates that an address/data stream will follow.

All slave peripherals connected to the serial bus respond to

the START condition and shift in the next eight bits, consisting

of a 7-bit address (MSB first) plus an R/W bit, which determines

the direction of the data transfer, i.e., whether data will be

written to or read from the slave device.

The peripheral whose address corresponds to the transmitted

address responds by pulling the data line low during the low

period before the ninth clock pulse, known as the Acknowledge

Bit. All other devices on the bus now remain idle while the

selected device waits for data to be read from or written to it.

Table V. Configuration Register Bit Assignments

Power-On

Bit Name Function Default

7MASK1 0 = ALERT Enabled 0

1 = ALERT Masked

6RUN/STOP 0 = Run 0

1 = Standby

5–0 Reserved 0

Conversion Rate Register

The lowest four bits of this register are used to program the

conversion rate by dividing the internal oscillator clock by 1, 2,

4, 8, 16, 32, 64, 128, 256, 512, or 1024 to give conversion

times from 15.5 ms (Code 0Ah) to 16 seconds (Code 00h).

This register can be written to and read back over the SMBus.

The higher four bits of this register are unused and must be set

to zero. Use of slower conversion times greatly reduces the

device power consumption, as shown in Table VI.

Table VI. Conversion Rate Register Codes

Average Supply Current

Data Conversion/sec mA Typ at V

= 5.5 V

00h 0.0625 0.17

01h 0.125 0.20

02h 0.25 0.21

03h 0.5 0.24

04h 1 0.29

05h 2 0.40

06h 4 0.61

07h 8 1.1

08h 16 1.9

09h 32 0.73

0Ah 64 1.23

0B to FFh Reserved

Limit Registers

The ADM1032 has nine limit registers to store local and remote,

high, low, and THERM temperature limits. These registers can

be written to and read back over the SMBus.

The high limit registers perform a > comparison, while the low

limit registers perform a < comparison. For example, if the High

Limit Register is programmed with 80°C, then measuring 81

will result in an alarm condition. If the Low Limit Register is

programmed with 0°C, measuring 0°C or lower will result in an

alarm condition. Exceeding either the local or remote THERM

limit asserts THERM low. A default hysteresis value of 10°C is

provided, which applies to both channels. This hysteresis may

be reprogrammed to any value after power up (Reg 0x21h).

One-Shot Register

The One-Shot Register is used to initiate a single conversion

and comparison cycle when the ADM1032 is in Standby Mode,

after which the device returns to standby. This is not a data

one-shot conversion. The data written to this address is irrel-

evant and is not stored. The conversion time on a single shot is

96 ms when the conversion rate is 16 conversions per second or

less. At 32 conversions per second, the conversion time is 15.3 ms.

This is because averaging is disabled at the faster conversion rates

(32 and 64 conversions per second).

REV. C

ADM1032

–8–

If the R/W bit is a 0, the master will write to the slave device.

If the R/W bit is a 1, the master will read from the slave device.

2. Data is sent over the serial bus in sequences of nine clock

pulses, eight bits of data followed by an Acknowledge Bit

from the slave device. Transitions on the data line must

occur during the low period of the clock signal and remain

stable during the high period, since a low-to-high transition

when the clock is high may be interpreted as a STOP signal.

The number of data bytes that can be transmitted over the

serial bus in a single read or write operation is limited only by

what the master and slave devices can handle.

3. When all data bytes have been read or written, stop conditions

are established. In Write Mode, the master will pull the data

line high during the tenth clock pulse to assert a STOP

condition. In Read Mode, the master device will override the

Acknowledge Bit by pulling the data line high during the low

period before the ninth clock pulse. This is known as No

Acknowledge. The master will then take the data line low

during the low period before the tenth clock pulse, then high

during the tenth clock pulse to assert a STOP condition.

Any number of bytes of data may be transferred over the serial

bus in one operation, but it is not possible to mix read and write

in one operation because the type of operation is determined at the

beginning and cannot subsequently be changed without starting

a new operation.

In the case of the ADM1032, write operations contain either one

or two bytes, while read operations contain one byte and perform

the following functions.

To write data to one of the device data registers or read data

from it, the Address Pointer Register must first be set so that the

correct data register is addressed. The first byte of a write opera-

tion always contains a valid address that is stored in the Address

Pointer Register. If data is to be written to the device, the write

operation contains a second data byte that is written to the

This is illustrated in Figure 3a. The device address is sent over

the bus followed by R/W set to 0. This is followed by two data

bytes. The first data byte is the address of the internal data

internal data register.

When reading data from a register, there are two possibilities:

1. If the ADM1032’s Address Pointer Register value is unknown

or not the desired value, it is first necessary to set it to the

correct value before data can be read from the desired data

as before, but only the data byte containing the register read

address is sent, since data is not to be written to the register.

This is shown in Figure 3b.

A read operation is then performed consisting of the serial bus

address, R/W bit set to 1, followed by the data byte read from

the data register. This is shown in Figure 3c.

2. If the Address Pointer Register is known to be at the desired

address already, data can be read from the corresponding

data register without first writing to the Address Pointer

Table VIII. List of ADM1032 Registers

Read Address (Hex) Write Address (Hex) Name Power-On Default

Not Applicable Not Applicable Address Pointer Undefined

00 Not Applicable Local Temperature Value 0000 0000 (00h)

01 Not Applicable External Temperature Value High Byte 0000 0000 (00h)

02 Not Applicable Status Undefined

03 09 Configuration 0000 0000 (00h)

04 0A Conversion Rate 0000 1000 (08h)

05 0B Local Temperature High Limit 0101 0101 (55h) (85°C)

06 0C Local Temperature Low Limit 0000 0000 (00h) (0°C)

07 0D External Temperature High Limit High Byte 0101 0101 (55h) (85°C)

08 0E External Temperature Low Limit High Byte 0000 0000 (00h) (0°C)

Not Applicable 0F One-Shot

10 Not Applicable External Temperature Value Low Byte 0000 0000

11 11 External Temperature Offset High Byte 0000 0000

12 12 External Temperature Offset Low Byte 0000 0000

13 13 External Temperature High Limit Low Byte 0000 0000

14 14 External Temperature Low Limit Low Byte 0000 0000

19 19 External THERM Limit 0101 0101 (55h) (85°C) (ADM1032)

0110 1100 (6Ch) (108°C) (ADM1032-1

)

20 20 Local THERM Limit 0101 0101 (55h) (85°C)

21 21 THERM Hysteresis 0000 1010 (0Ah) (10°C)

22 22 Consecutive ALERT 0000 0001 (01h)

FE Not Applicable Manufacturer ID 0100 0001 (41h)

FF Not Applicable Die Revision Code Undefined

Writing to Address 0F causes the ADM1032 to perform a single measurement. It is not a data register as such and it does not matter what data is written to it.

REV. C

ADM1032

–9–

Notes

1. Although it is possible to read a data byte from a data register

without first writing to the Address Pointer Register, if the

Address Pointer Register is already at the correct value, it is

not possible to write data to a register without writing to the

Address Pointer Register because the first data byte of a write

is always written to the Address Pointer Register.

ALERT OUTPUT

The ALERT output goes low whenever an out-of-limit mea-

surement is detected, or if the remote temperature sensor is

open-circuit. It is an open drain and requires a pull-up to V

Several ALERT outputs can be wire-ORed together so that the

common line will go low if one or more of the ALERT outputs

goes low.

The ALERT output can be used as an interrupt signal to a

processor, or it may be used as an SMBALERT. Slave devices

on the SMBus can not normally signal to the master that they

want to talk, but the SMBALERT function allows them to do so.

1919

A5 A4 A3 A2 A1 A0 R/WD7 D6 D5 D4 D3 D2 D1 D0

SCLK

SDATA

START BY

MASTER

FRAME 1

SERIAL BUS ADDRESS BYTE

FRAME 2

ADDRESS POINTER REGISTER BYTE

STOP BY

MASTER

ACK. BY

ADM1032

ACK. BY

ADM1032

FRAME 3

DATA BYTE

SDATA (CONTINUED)

SCLK (CONTINUED)

ACK. BY

ADM1032

D7 D6 D5 D4 D3 D2 D1 D0

Figure 3a. Writing a Register Address to the Address Pointer Register, then Writing Data to the Selected Register

SCLK

SDATA

START BY

MASTER

1919

A6 A5 A4 A3 A2 A1 A0 R/WD7 D6 D5 D4 D3 D2 D1 D0

FRAME 1

SERIAL BUS ADDRESS BYTE

FRAME 2

ADDRESS POINTER REGISTER BYTE

STOP BY

MASTER

ACK. BY

ADM1032

ACK. BY

ADM1032

Figure 3b. Writing to the Address Pointer Register Only

SCLK

1919

SDATA A6 A5 A4 A3 A2 A1 A0 R/WD7 D6 D5 D4 D3 D2 D1 D0

START BY

MASTER

FRAME 1

SERIAL BUS ADDRESS BYTE

FRAME 2

DATA BYTE FROM ADM1032

STOP BY

MASTER

ACK. BY

ADM1032

ACK. BY

ADM1032

Figure 3c. Reading Data from a Previously Selected Register

2. Don’t forget that some of the ADM1032 registers have differ-

ent addresses for read and write operations. The write address

of a register must be written to the address pointer if data is

to be written to that register, but it is not possible to read

data from that address. The read address of a register must

be written to the address pointer before data can be read

from that register.

One or more ALERT outputs can be connected to a common

SMBALERT line connected to the master. When the

SMBALERT line is pulled low by one of the devices, the fol-

lowing procedure occurs as illustrated in Figure 4.

MASTER

RECEIVES

SMBALERT

MASTER SENDS

ARA AND READ

COMMAND DEVICE SENDS

ITS ADDRESS

ACK

START ALERT RESPONSE ADDRESS RD ACK DEVICE ADDRESS STOP

Figure 4. Use of

SMBALERT

REV. C

ADM1032

–10–

1. SMBALERT pulled low.

2. Master initiates a read operation and sends the Alert Response

Address (ARA = 0001 100). This is a general call address that

must not be used as a specific device address.

The device whose ALERT output is low responds to the Alert

Response Address and the master reads its device address.

Since the device address is seven bits, an LSB of 1

is added.

The address of the device is now known and it can

interrogated in the usual way.

4. If more than one device’s ALERT output is low, the one with

the lowest device address will have priority in accordance

with normal SMBus arbitration.

5. Once the ADM1032 has responded to the Alert Response

Address, it will reset its ALERT output, provided that the error

condition that caused the ALERT no longer exists. If the

SMBALERT line remains low, the master will send ARA again,

and so on until all devices whose ALERT outputs were low

have responded.

LOW POWER STANDBY MODE

The ADM1032 can be put into a Low Power Standby Mode by

setting Bit 6 of the Configuration Register. When Bit 6 is low, the

ADM1032 operates normally. When Bit 6 is high, the ADC is

inhibited and any conversion in progress is terminated without

writing the result to the corresponding value register.

The SMBus is still enabled. Power consumption in the Standby

Mode is reduced to less than 10 µA if there is no SMBus activity,

or 100 µA if there are clock and data signals on the bus.

When the device is in Standby Mode, it is still possible to initiate a

one-shot conversion of both channels by writing XXh to the

One-Shot Register (Address 0Fh), after which the device will return

to standby. It is also possible to write new values to the limit register

while it is in standby. If the values stored in the temperature value

registers are now outside the new limits, an ALERT is generated

even though the ADM1032 is still in standby.

THE ADM1032 INTERRUPT SYSTEM

The ADM1032 has two interrupt outputs, ALERT and THERM.

These have different functions. ALERT responds to violations of

software-programmed temperature limits and is maskable. THERM

is intended as a “fail-safe” interrupt output that cannot be masked.

If the temperature goes equal to or below the lower temperature limit,

the ALERT pin will be asserted low to indicate an out-of-limit

condition. If the temperature is within the programmed low and

high temperature limits, no interrupt will be generated.

If the temperature exceeds the high temperature limit, the ALERT pin

will be asserted low to indicate an overtemperature condition. A local

and remote THERM limit may be programmed into the device to set

the temperature limit above which the overtemperature THERM

pin will be asserted low. This temperature limit should be equal to

or greater than the high temperature limit programmed.

The behavior of the high limit and THERM limit is as follows:

1. If either temperature measured exceeds the high temperature

limit, the ALERT output will assert low.

2. If the local or remote temperature continues to increase and

either one exceeds the THERM limit, the THERM output

asserts low. This can be used to throttle the CPU clock or

switch on a fan.

A THERM hysteresis value is provided to prevent a cooling fan

cycling on and off. The power-on default value is 10°C, but this

may be reprogrammed to any value after power-up. This hyster-

esis value applies to both the local and remote channels.

Using these two limits in this way allows the user to gain maxi-

mum performance from the system by only slowing it down

should it be at a critical temperature.

The THERM signal is open drain and requires a pull-up to

. The THERM signal must always be pulled up to the same

power supply as the ADM1032, unlike the SMBus signals

(SDATA, SCLK, and ALERT) that may be pulled to a different

power rail, usually that of the SMBus controller.

100C

90C

80C

70C

60C

50C

40C

THERM

LOCAL THERM

LIMIT

LOCAL THERM LIMIT

–HYSTERESIS

TEMPERATURE

Figure 5. Operation of the

THERM

Output

Table IX. THERM Hysteresis Sample Values

THERM Hysteresis Binary Representation

0°C 0 000 0000

1°C 0 000 0001

10°C 0 000 1010

SENSOR FAULT DETECTION

At the D+ input, the ADM1032 has a fault detector that detects

if the external sensor diode is open circuit. This is a simple

voltage comparator that trips if the voltage at D+ exceeds V

–

1 V (typical). The output of this comparator is checked when a

conversion is initiated and sets Bit 2 of the Status Register if a

fault is detected.

If the remote sensor voltage falls below the normal measuring

range, for example due to the diode being short-circuited, the

ADC will output –128 (1000 0000). Since the normal operating

temperature range of the device only extends down to 0°C, this

output code should never be seen in normal operation, so it can

be interpreted as a fault condition. Since it will be outside the

power-on default low temperature limit (0°C) and any low limit

that would normally be programmed, a short-circuit sensor will

cause an SMBus alert.

In this respect, the ADM1032 differs from and improves upon

competitive devices that output zero if the external sensor goes

short-circuit. These devices can misinterpret a genuine 0°C

measurement as a fault condition.

When the D+ and D– lines are shorted together, an ALERT

will always be generated. This is because the Remote Value

ADM1032 performs a less-than or equal-to comparison with the

low limit, an ALERT is generated even when the low limit is set

to its minimum of –128°C.

REV. C

ADM1032

–11–

PPLICATIONS INFORMATION

FACTORS AFFECTING ACCURACY

Remote Sensing Diode

The ADM1032 is designed to work with substrate transistors

built into processors’ CPUs or with discrete transistors. Substrate

transistors will generally be PNP types with the collector connected

to the substrate. Discrete types can be either a PNP or an NPN

transistor connected as a diode (base shorted to collec

tor). If an

NPN transistor is used, the collector and base are

connected to

D+ and the emitter to D–. If a PNP transistor is used, the

collector and base are connected to D– and the emitter to D+.

Substrate transistors are found in a number of CPUs. To reduce

the error due to variations in these substrate and discrete

transistors, a number of factors should be taken into consideration:

1. The ideality factor, n

, of the transistor. The ideality factor is

a measure of the deviation of the thermal diode from the

ideal behavior. The ADM1032 is trimmed for an n

value of

1.008. The following equation may be used to calculate

the error introduced at a temperature T°C when using a

transistor whose n

does not equal 1.008. Consult the

processor data sheet for n

values.

∆TnKelvin T

natural

()

×+

()

–.

1 008

1 008 273 15

This value can be written to the Offset Register and is automati-

cally added to or subtracted from the temperature measurement.

2. Some CPU manufacturers specify the high and low current

levels of the substrate transistors. The high current level of

the ADM1032, I

HIGH

, is 230 ␮A and the low level current,

LOW

, is 13 ␮A. If the ADM1032 current levels do not match

the levels of the CPU manufacturers, then it may become

necessary to remove an offset. The CPU’s data sheet will

advise whether this offset needs to be removed and how to

calculate it. This offset may be programmed to the Offset

or more offsets is needed, then the algebraic sum of these

offsets must be programmed to the Offset Register.

If a discrete transistor is being used with the ADM1032, the

best accuracy will be obtained by choosing devices according to

the following criteria:

•Base-emitter voltage greater than 0.25 V at 6 mA, at the highest

operating temperature.

•Base-emitter voltage less than 0.95 V at 100 mA, at the lowest

operating temperature.

•Base resistance less than 100 Ω.

•Small variation in h

(say 50 to 150) that indicates tight

control of V

characteristics.

Transistors such as 2N3904, 2N3906, or equivalents in SOT-23

packages are suitable devices to use.

THERMAL INERTIA AND SELF-HEATING

Accuracy depends on the temperature of the remote-sensing

diode and/or the internal temperature sensor being at the same

temperature as that being measured, and a number of factors

can affect this. Ideally, the sensor should be in good thermal

contact with the part of the system being measured, for example

the processor. If it is not, the thermal inertia caused by the mass

of the sensor will cause a lag in the response of the sensor to a

temperature change. In the case of the remote sensor, this

should not be a problem, since it will either be a substrate tran

sistor

in the processor or a small package device, such as the SOT-23,

placed in close proximity to it.

The on-chip sensor, however, will often be remote from the

processor and will only be monitoring the general ambient

temperature around the package. The thermal time constant of

the SOIC-8 package in still-air is about 140 seconds, and if the

ambient air temperature quickly changed by 100 degrees, it

would take about 12 minutes (5 time constants) for the junction

temperature of the ADM1032 to settle within 1 degree of this. In

practice, the ADM1032 package will be in electrical and therefore

thermal contact with a printed circuit board and may also be in a

forced airflow. How accurately the temperature of the board

and/or the forced airflow reflect the temperature to be measured

will also affect the accuracy.

Self-heating due to the power dissipated in the ADM1032 or the

remote sensor causes the chip temperature of the device or remote

sensor to rise above ambient. However, the current forced through

the remote sensor is so small that self-heating is negligible. In

the case of the ADM1032, the worst-case condition occurs when

the device is converting at 16 conversions per second while sinking

the maximum current of 1 mA at the ALERT and THERM

output. In this case, the total power dissipation in the device is

about 11 mW. The thermal resistance, θ

, of the SOIC-8 package

is about 121°C/W.

In practice, the package will have electrical and therefore thermal

connection to the printed circuit board, so the temperature rise

due to self-heating will be negligible.

LAYOUT CONSIDERATIONS

Digital boards can be electrically noisy environments, and the

ADM1032 is measuring very small voltages from the remote

sensor, so care must be taken to minimize noise induced at the

sensor inputs. The following precautions should be taken:

Place the ADM1032 as close as possible to the remote sensing

diode. Provided that the worst noise sources, i.e., clock

gen

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

distance

can be 4 to 8 inches.

2. Route the D+ and D– tracks close together, in parallel, with

grounded guard tracks on each side. Provide a ground plane

under the tracks if possible.

3. Use wide tracks to minimize inductance and reduce noise

pickup. 10 mil track minimum width and spacing is

recommended.

10MIL

GND

D+

D–

GND

Figure 6. Arrangement of Signal Tracks

4. 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 D+ and D– path

and at the same temperature.

REV. C

–12–

C01906–0–3/03(C)

ADM1032

Thermocouple effects should not be a major problem since

1°C corresponds to about 200 ␮V and thermocouple voltages

are

about 3 ␮V/°C of temperature difference. Unless there are

two

thermocouples with a big temperature differential between

them,

thermocouple voltages should be much less than 200 ␮V.

5. Place a 0.1 µF bypass capacitor close to the V

pin. In very

noisy environments, place a 2200 pF input filter capacitor

across D+ and D– close to the ADM1032.

6. If the distance to the remote sensor is more than 8 inches, the

use of twisted pair cable is recommended. This will work up

to about 6 feet to 12 feet.

7. For really long distances (up to 100 feet), use shielded twisted

pair, such as Belden #8451 microphone cable. Connect the

twisted pair to D+ and D– and the shield to GND close to

the ADM1032. 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 may

be reduced or removed.

Cable resistance can also introduce errors. 1 Ω series resistance

introduces about 1°C error.

APPLICATION CIRCUIT

Figure 7 shows a typical application circuit for the ADM1032,

using a discrete sensor transistor connected via a shielded,

twisted pair cable. The pull-ups on SCLK, SDATA, and ALERT

are required only if they are not already provided elsewhere

n the system.

The SCLK and SDATA pins of the ADM1032 can be inter-

faced

directly to the SMBus of an I/O controller, such as the

Intel 820 chipset.

SHIELD

2N3906

CPU THERMAL

DIODE

ALERT

GND

THERM

D+

D–

ADM1032

SCLK

SDATA

3V TO 3.6V

TYP 10k⍀

0.1␮F

TYP 10k⍀

FAN

CONTROL

CIRCUIT

5V OR 12V

FAN

ENABLE

SMBUS

CONTROLLER

Figure 7. Typical Application Circuit

8-Lead Standard Small Outline Package [SOIC]

Narrow Body

(R-8)

Dimensions shown in millimeters and (inches)

0.25 (0.0098)

0.19 (0.0075)

1.27 (0.0500)

0.41 (0.0160)

0.50 (0.0196)

0.25 (0.0099) ⴛ 45ⴗ

8ⴗ

0ⴗ

1.75 (0.0688)

1.35 (0.0532)

SEATING

PLANE

0.25 (0.0098)

0.10 (0.0040)

5.00 (0.1968)

4.80 (0.1890)

4.00 (0.1574)

3.80 (0.1497)

1.27 (0.0500)

BSC

6.20 (0.2440)

5.80 (0.2284)

0.51 (0.0201)

0.33 (0.0130)

COPLANARITY

0.10

CONTROLLING DIMENSIONS ARE IN MILLIMETERS; INCH DIMENSIONS

(IN PARENTHESES) ARE ROUNDED-OFF MILLIMETER EQUIVALENTS FOR

REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN

COMPLIANT TO JEDEC STANDARDS MS-012AA

8-Lead Mini Small Outline Package [MSOP]

(RM-8)

Dimensions shown in millimeters

0.23

0.08

0.80

0.40

8ⴗ

0ⴗ

4.90

BSC

PIN 1

0.65 BSC

3.00

BSC

SEATING

PLANE

0.15

0.00

0.38

0.22

1.10 MAX

3.00

BSC

COMPLIANT TO JEDEC STANDARDS MO-187AA

COPLANARITY

0.10

OUTLINE DIMENSIONS

Revision History

Location Page

3/03—Data Sheet changed from REV. B to REV. C.

Edits to SPECIFICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2

10/02—Data Sheet changed from REV. A to REV. B.

Edits to the GENERAL DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Edits to the ORDERING GUIDE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Edits to Table VIII . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

OUTLINE DIMENSIONS updated . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12