ANALOG DEVICES ADM1028 Service Manual

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Remote Thermal Diode

a

FEATURES
On-Chip Temperature Sensor
External Temperature Measurement with Remote Diode
Interrupt and Over-Temperature Outputs
Fault-Tolerant Fan Control with Auto Hardware Trip Point
Remote Reset and Power-Down Functions
LDCM Support
System Management Bus (SMBus) Communications
Standby Mode to Minimize Power Consumption
Limit Comparison of all Monitored Values
DAC Output for Linear Fan Speed Control
Ramp Rate Register for Control of Rate of Change of

Fan Speed, Reduction of Fan Acoustics

APPLICATIONS
Network Servers and Personal Computers
Microprocessor-Based Office Equipment
Test Equipment and Measuring Instruments

Monitor with Linear Fan Control

ADM1028

GENERAL DESCRIPTION

The ADM1028 is a low-cost temperature monitor and fan
controller for microprocessor-based systems. The temperature
of a remote sensor diode may be measured, allowing monitoring
of processor temperature in single processor systems. An on-chip
temperature sensor monitors ambient system temperature.

Measured values can be read out via the System Management
Bus, and values for limit comparisons can be programmed in
over the same serial bus.

The ADM1028 also contains a DAC for fan speed control. An
automatic hardware temperature trip point is provided and the fan
will be driven to full speed if it is exceeded. A Ramp Rate Register
is provided to control the rate with which fan speed is increased or
decreased. This is to eliminate sudden changes in fan speed,
thereby reducing fan acoustics and prolonging the fan’s life.

Finally, the chip has remote reset and power-down functionality,
allowing it to be remotely shut down via the SMBus.

The ADM1028’s 3.0 V to 5.5 V supply voltage range, low
supply current, and SMBus make it ideal for a wide range of
applications. These include hardware monitoring applications
in PCs, electronic test equipment, and office electronics.

R_OFF

R_RST

AUXRST

RST

THERMA/NTEST_OUT

THERMB

FUNCTIONAL BLOCK DIAGRAM

V

CC3AUX

V

CC3AUX

10k⍀

RESET

FAN_SPD SHUTOFF
AND R_OFF RESET

D+

D–

V

CC3AUX

10k⍀

ADM1028

ANALOG

SIGNAL

CONDITIONING

POWER-ON
RESET

REMOTE
FUNCTION
REGISTER

ADDRESS

POINTER

REGISTER

ALERT

STATUS

REGISTER

ADC

2.5V

BANDGAP

REFERENCE

SERIAL BUS

INTERFACE

ANALOG O/P

REGISTER,

COUNTER

AND 8-BIT DAC

VALUE AND

LIMIT

REGISTERS

LIMIT

COMPARATORS

INTERRUPT

STATUS

REGISTERS

INT MASK

REGISTER

MASK

GATING

CONFIGURATION

REGISTER

SDA

SCL

FAN_SPD/NTEST_IN

INT

FAN_OFF

REV. A

Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties that
may result from its use. No license is granted by implication or otherwise
under any patent or patent rights of Analog Devices.

GPI

GND

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: [phone] www.analog.com
Fax: [phone] © Analog Devices, Inc., 2002

1, 2

ADM1028–SPECIFICATIONS

(TA = T

Parameter Min Typ Max Unit Test Conditions

POWER SUPPLY

Supply Voltage, V
Supply Current, I

CC

CC

3.0 3.30 5.5 V

TEMPERATURE-TO-DIGITAL CONVERTER

Internal Sensor Accuracy ± 3 °C

Resolution 1 °C
External Diode Sensor Accuracy ± 5 °C

Resolution 1 °C
Remote Sensor Source Current 120 µA High Level (D+ = D– + 0.65 V)

ANALOG OUTPUT

Output Voltage Range 0 2.5 V
Total Unadjusted Error, TUE ± 3%I
Full-Scale Error ± 1 ±3%
Zero Error ± 2 LSB No Load
Differential Nonlinearity, DNL ± 1 LSB Monotonic by Design
Integral Nonlinearity ± 1 LSB
Output Source Current 2 mA
Output Sink Current 1 mA

THERMA OUTPUT

THERMA Pull-Up Resistance 9 12 14 kΩ

DIGITAL OUTPUT THERMA/NTEST_OUT,

R_OFF

Output High Voltage, V
Output Low Voltage, V

OL

OH

2.4 V I

OPEN-DRAIN DIGITAL OUTPUTS

(INT, THERMB, FAN_OFF, R_RST)

Output Low Voltage, V
High Level Output Leakage Current, I

OL

OH

FAN SPEED RAMP RATES

Counter Frequency 1 ± 50% 16 ± 50% Hz

OPEN-DRAIN SERIAL DATA

BUS OUTPUT (SDA)

Output Low Voltage, V
High Level Output Leakage Current, I

OL

OH

SERIAL BUS DIGITAL INPUTS

(SCL, SDA)

Input High Voltage, V
Input Low Voltage, V

IL

IH

2.1 V

Input Leakage Current ±5 µA
Hysteresis 500 mV Note 4

DIGITAL INPUT LOGIC LEVELS

(FAN_SPD/TEST_IN, GPI)

Input High Voltage, V
Input Low Voltage, V

IL

IH

2.2 V

DIGITAL INPUT LEAKAGE CURRENT

(ALL DIGITAL INPUTS)

Input High Current, I
Input Low Current, I
Input Capacitance, C

IL

IN

IH

–1 –0.005 µAV

3 6 9 pF Note 4

to T

MIN

, VCC = V

MAX

MIN

to V

, unless otherwise noted.)

MAX

2 3.2 mA Interface Inactive, ADC Active

± 2 °C60°C ≤ T

± 3 °C60°C ≤ T

≤ 100°C

A

≤ 100°C

A

7 µA Low Level (D+ = D– + 0.65 V)

= 2 mA

L

= 3.0 mA

OUT

0.4 V

0.4 V I

0.1 1 µAV

0.4 V I

0.1 1 µAV

= –3.0 mA

OUT

= V

OUT

= –3.0 mA

OUT

= V

OUT

CC

CC

3

0.8 V

0.8 V

= V

IN

+0.005 +1 µAV

IN

CC

= 0

–2–

REV. A

Parameter Min Typ Max Unit Test Conditions

SCLK

BUF

SU;STA

HD;STA

LOW

HIGH

SU;DAT

HD;DAT

4

100 kHz See Figure 1

4.7 µs See Figure 1

4.7 µs See Figure 1

4.0 µs See Figure 1

SU;STO

4.0 µs See Figure 1

4.7 µs See Figure 1

4.0 µs See Figure 1

r

f

1000 ns See Figure 1

300 ns See Figure 1
250 ns See Figure 1
300 ns See Figure 1

= 0.8 V for a falling edge and V

IL

= 2.2 V for a rising edge.

IH

SERIAL BUS TIMING

Clock Frequency, f
Bus Free Time, t
Start Setup Time, t
Start Hold Time, t
Stop Condition Setup Time, t
SCL Low Time, t
SCL High Time, t
SCL, SDA Rise Time, t
SCL, SDA Fall Time, t
Data Setup Time, t
Data Hold Time, t

NOTES

1

Typicals are at TA = 25°C and represent most likely parametric norm. Standby current typ is measured with VCC = 3.3 V.

2

Timing specifications are tested at logic levels of V

3

IOH for FAN_OFF guaranteed by design, not production tested.

4

Guaranteed by design, not production tested.

Specifications subject to change without notice.

ADM1028

ABSOLUTE MAXIMUM RATINGS

*

Positive Supply Voltage (VCC) . . . . . . . . . . . . . . . . . . . . . 6.5 V

Voltage on Digital Inputs Except Therm

and D– . . . . . . . . . . . . . . . . . . . . . . . . . . . . –0.3 V to +6.5 V

Voltage on Therm Pin . . . . . . . . . . . . . . –0.3 V to V

+ 0.3 V

CC

Voltage on D– Pin . . . . . . . . . . . . . . . . . . . . –0.3 V to + 0.6 V

Voltage on Any Other Input . . . . . . . . . . –0.3 V to V

+ 0.3 V

CC

or Output Pin

Input Current at Any Pin . . . . . . . . . . . . . . . . . . . . . . . ± 5 mA

Package Input Current . . . . . . . . . . . . . . . . . . . . . . . ± 20 mA

Maximum Junction Temperature (T

max) . . . . . . . . . . 150°C

J

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

Lead Temperatures

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

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

ESD Rating (Human Body Model) . . . . . . . . . . . . . . . 4000 V

*Stresses above those listed under Absolute Maximum Ratings may cause perma-

nent 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.

t

t

F

HIGH

SCL

t

LOW

t

HD; STA

t

R

t

HD; DAT

THERMAL CHARACTERISTICS

16-Lead QSOP Package:

θ

= 105°C/W, θJC = 39°C/W

JA

ORDERING GUIDE

Temperature Package Package

Model Range Description Option

ADM1028ARQ 0°C to 100°C Shrink Small Outline RQ-16

Package (QSOP)

t

HD; STA

t

SU; DAT

t

SU; STA

t

SU; STO

REV. A

SDA

t

BUF

PS

S

Figure 1. Serial Bus Timing Diagram

–3–

P

ADM1028

PIN CONFIGURATION

FAN_OFF

GPI

AUXRST

GND

V

CC3AUX

RST

R_RST

FAN_SPD/NTEST_IN

1

2

3

ADM1028

4

TOP VIEW

5

(Not to Scale)

6

7

8

16

SDA

15

SCL

14

INT

13

R_OFF

12

THERMB

11

THERMA/NTEST_OUT

10

D+

9

D–

PIN FUNCTION DESCRIPTIONS

Pin No. Mnemonic Description

1 FAN_OFF Digital Output (Open Drain) Fan Off Request. When asserted low, this indicates a

request to shut off the fan independent of the FAN_SPD output. When negated (output
FET off) it indicates that the fan may be turned on.

2 GPI Digital Input (12 V tolerant). This pin is a general-purpose logic input with 12 V toler-

ance. It can be programmed as an active high or active low input that sets Bit 4 of the
Interrupt Status Register. A voltage >2.2 V on this pin, represents a Logic “1,” while a
floating condition is interpreted as Logic “0.”

3 AUXRST Digital Input. This pin can be driven low as an input to reset the ADM1028.
4 GND Ground. Power and signal ground.
5V

CC3AUX

Power 3.3 V Aux. Power source and voltage monitor input for power-on reset.

6 RST Digital Input. This pin can be pulled low externally to indicate to the ADM1028 that the

main system power has been removed. The ADM1028 will shut off the FAN_SPD out­put and reset its R_OFF output.

7 R_RST Digital Output (Open Drain). This pin is a remote reset output that pulses low on

receipt of a specific SMBus message.

8 FAN_SPD/NTEST_IN Analog Output/Test Input. An active-high input that enables NAND board-level

connectivity testing. Refer to section on NAND testing.
Used as an analog output for fan speed control when NAND test is not selected.

9 D– Remote Thermal Diode Negative Input. This is the negative input (current sink) from

the remote thermal diode. This also serves as the negative input into the A/D.

10 D+ Remote Thermal Diode Positive Input. This is the positive input (current source) from

the remote thermal diode. This serves as the positive input into the A/D.

11 THERMA/NTEST_OUT Digital Output (Open Drain with Integrated V

Pull-Up). An active low thermal

CC3AUX

overload output that indicates a violation of a temperature setpoint (over temperature).
The fan is on full-speed whenever this pin is asserted low. Acts as the output of the NAND
Tree when the ADM1028 is in NAND Tree Test Mode.

12 THERMB Digital Output (Open Drain). This pin is a second THERM signal. It can be used to

drive external circuitry with a different external pull-up supply rail.

13 R_OFF Digital Output or Open Drain with Integrated V

Pull-Up. Remote off (power-

CC3AUX

down) output. This pin is driven high on receipt of a specific SMBus message. The pin
(and its associated register bit) remain high until the RST input is asserted low.

14 INT Digital Output (Open Drain), System Interrupt Output. This signal indicates a violation

of a set trip point. The output is enabled when Bit 1 of the Configuration Register is set

to 1. The default state is disabled.
15 SCL Digital Input. SMBus Clock.
16 SDA Digital I/O (Open Drain). SMBus Bidirectional Data.

–4–

REV. A

Typical Performance Characteristics–ADM1028

SCLK FREQUENCY – kHz

SUPPLY CURRENT – mA

1.77

1 5 10 25 50 75 100

1.67

1.72

1.82

1.87

1.92

1.97

2.02

250 500 750 1000

VDD = 5V

VDD = 3.3V

30

20

10

0

–10

TEMPERATURE ERROR – ⴗC

–20

–30

1

D+ TO GND

D+ TO V

DD

LEAKAGE RESISTANCE – M⍀

10 100

TPC 1. Temperature Error vs. PC Board Track Resistance
(D+ to V

)

DD

14

12

10

8

6

4

TEMPERATURE ERROR – ⴗC

2

0

1

10 100k 1000M

VIN = 250mV p-p

= 100mV p-p

V

IN

10k 100M1k 10M100 1M

FREQUENCY – Hz

TPC 2. Temperature Error vs. Power Supply
Noise Frequency

4

3

2

1

0

–1

ERROR – ⴗC

–2

–3

–4

–5

0 102030405060708090

LOWER SPEC LEVEL

UPPER SPEC LEVEL

100

TEMPERATURE – ⴗC

TPC 4. Temperature Error of ADM1028 vs. Pentium® III
Temperature

40

35

30

25

20

15

10

TEMPERATURE ERROR – ⴗC

5

0

–5

010203040506070

CAPACITANCE – nF

TPC 5. Temperature Error vs. Capacitance Between
D+ and D–

14

13

12

11

10

9

8

7

6

5

4

3

TEMPERATURE ERROR – ⴗC

2

1

0

1 10 100 1k 10k 100k 1M 10M 100M 1G

TPC 3. Temperature Error vs. Common-Mode
Noise Frequency

REV. A

VIN = 100mV p-p

VIN = 50mV p-p

VIN = 25mV p-p

FREQUENCY – Hz

TPC 6. Standby Current vs. Clock Frequency

–5–