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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
Remote Thermal Diode
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.
FUNCTIONAL BLOCK DIAGRAM
V
CC3AUX
V
CC3AUX
10k
R_OFF
R_RST
ADM1028
POWER-ON
RESET
SERIAL BUS
INTERFACE
REMOTE
FUNCTION
REGISTER
ANALOG O/P
REGISTER,
COUNTER
AND 8-BIT DAC
VALUE AND
LIMIT
REGISTERS
LIMIT
COMPARATORS
SDA
SCL
AUXRST
RESET
FAN_SPD SHUTOFF
AND R_OFF RESET
ADDRESS
POINTER
REGISTER
ALERT
STATUS
REGISTER
FAN_SPD/NTEST_IN
RST
D+
ANALOG
SIGNAL
CONDITIONING
D–
V
CC3AUX
10k
THERMA/NTEST_OUT
ADC
INTERRUPT
STATUS
REGISTERS
INT
MASK
REGISTER
MASK
GATING
2.5V
BANDGAP
REFERENCE
INT
THERMB
CONFIGURATION
REGISTER
FAN_OFF
REV. B
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. Trademarks and
registered trademarks are the property of their respective companies.
GPI
GND
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700
www.analog.com
Fax: 781/326-8703
© 2003 Analog Devices, Inc. All rights reserved.
ADM1028–SPECIFICATIONS
Parameter
POWER SUPPLY
Supply Voltage, V
CC
Supply Current, I
CC
TEMPERATURE-TO-DIGITAL CONVERTER
Internal Sensor Accuracy
Resolution
External Diode Sensor Accuracy
Resolution
Remote Sensor Source Current
ANALOG OUTPUT
Output Voltage Range
Total Unadjusted Error, TUE
Full-Scale Error
Zero Error
Differential Nonlinearity, DNL
Integral Nonlinearity
Output Source Current
Output Sink Current
THERMA
OUTPUT
THERMA
Pull-Up Resistance
DIGITAL OUTPUT
THERMA/NTEST_OUT,
R_OFF
Output High Voltage, V
OH
Output Low Voltage, V
OL
OPEN-DRAIN DIGITAL OUTPUTS
(INT,
THERMB, FAN_OFF, R_RST)
Output Low Voltage, V
OL
High Level Output Leakage Current, I
OH
FAN SPEED RAMP RATES
Counter Frequency
OPEN-DRAIN SERIAL DATA
BUS OUTPUT (SDA)
Output Low Voltage, V
OL
High Level Output Leakage Current, I
OH
SERIAL BUS DIGITAL INPUTS
(SCL, SDA)
Input High Voltage, V
IH
Input Low Voltage, V
IL
Input Leakage Current
Hysteresis
DIGITAL INPUT LOGIC LEVELS
(FAN_SPD/TEST_IN, GPI)
Input High Voltage, V
IH
Input Low Voltage, V
IL
DIGITAL INPUT LEAKAGE CURRENT
(ALL DIGITAL INPUTS)
Input High Current, I
IH
Input Low Current, I
IL
Input Capacitance, C
IN
1, 2
Min
3.0
(T
A
= T
MIN
to T
MAX
, V
CC
= V
MIN
to V
MAX
, unless otherwise noted.)
Typ
3.30
2
Max
5.5
3.2
±
3
±
2
±
5
±
3
Unit
V
mA
∞C
∞C
∞C
∞C
∞C
∞C
mA
mA
V
%
%
LSB
LSB
LSB
mA
mA
kW
Test Conditions
Interface Inactive, ADC Active
1
60∞C
£
T
A
£
100∞C
60∞C
£
T
A
£
100∞C
High Level (D+ = D– + 0.65 V)
Low Level (D+ = D– + 0.65 V)
1
120
7
0
±
1
±
2
±
1
2
1
9
12
2.5
±
3
±
3
±
1
I
L
= 2 mA
No Load
Monotonic by Design
14
2.4
0.4
V
V
I
OUT
= 3.0 mA
0.1
1
±
50%
0.4
1
16
±
50%
V
mA
Hz
I
OUT
= –3.0 mA
V
OUT
= V
CC3
0.1
0.4
1
V
mA
I
OUT
= –3.0 mA
V
OUT
= V
CC
2.1
0.8
±
5
500
V
V
mA
mV
Note 4
2.2
0.8
V
V
–1
3
–0.005
+0.005
6
+1
9
mA
mA
pF
V
IN
= V
CC
V
IN
= 0
Note 4
–2–
REV. B
ADM1028
Parameter
SERIAL BUS TIMING
4
Clock Frequency, f
SCLK
Bus Free Time, t
BUF
Start Setup Time, t
SU;STA
Start Hold Time, t
HD;STA
Stop Condition Setup Time, t
SU;STO
SCL Low Time, t
LOW
SCL High Time, t
HIGH
SCL, SDA Rise Time, t
r
SCL, SDA Fall Time, t
f
Data Setup Time, t
SU;DAT
Data Hold Time, t
HD;DAT
Min
Typ
Max
100
4.7
4.7
4.0
4.0
4.7
4.0
1000
300
250
300
Unit
kHz
ms
ms
ms
ms
ms
ms
ns
ns
ns
ns
Test Conditions
See Figure 1
See Figure 1
See Figure 1
See Figure 1
See Figure 1
See Figure 1
See Figure 1
See Figure 1
See Figure 1
See Figure 1
See Figure 1
NOTES
1
Typicals are at T
A
= 25∞C and represent most likely parametric norm. Standby current typ is measured with V
CC
= 3.3 V.
2
Timing specifications are tested at logic levels of V
IL
= 0.8 V for a falling edge and V
IH
= 2.2 V for a rising edge.
3
I
OH
for
FAN_OFF
guaranteed by design, not production tested.
4
Guaranteed by design, not production tested.
Specifications subject to change without notice.
ABSOLUTE MAXIMUM RATINGS
*
THERMAL CHARACTERISTICS
Positive Supply Voltage (V
CC
) . . . . . . . . . . . . . . . . . . . . . 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
CC
+ 0.3 V
Voltage on D– Pin . . . . . . . . . . . . . . . . . . . . –0.3 V to + 0.6 V
Voltage on Any Other Input . . . . . . . . . –0.3 V to V
CC
+ 0.3 V
or Output Pin
Input Current at Any Pin . . . . . . . . . . . . . . . . . . . . . . .
±
5 mA
Package Input Current . . . . . . . . . . . . . . . . . . . . . . .
±
20 mA
Maximum Junction Temperature (T
J
max) . . . . . . . . . . 150∞C
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.
16-Lead QSOP Package:
q
JA
= 105∞C/W,
q
JC
= 39∞C/W
ORDERING GUIDE
Model
Temperature
Range
Package
Description
Package
Option
ADM1028ARQ 0∞C to 100∞C
Shrink Small Outline RQ-16
Package (QSOP)
t
LOW
t
R
SCL
t
F
t
HD; STA
t
HD; STA
t
HD; DAT
t
HIGH
t
SU; DAT
t
SU; STA
t
SU; STO
SDA
t
BUF
P
S
S
P
Figure 1. Serial Bus Timing Diagram
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 the ADM1028 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. B
–3–
ADM1028
PIN CONFIGURATION
FAN_OFF
1
GPI
2
AUXRST
3
GND
4
16
SDA
15
SCL
14
INT
13
R_OFF
TOP VIEW
V
CC3AUX 5
(Not to Scale)
12
THERMB
ADM1028
RST
6
R_RST
7
FAN_SPD/NTEST_IN
8
11
THERMA/NTEST_OUT
10
D+
9
D–
PIN FUNCTION DESCRIPTIONS
Pin No.
1
Mnemonic
FAN_OFF
Description
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.
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.”
Digital Input. This pin can be driven low as an input to reset the ADM1028.
Ground. Power and signal ground.
Power 3.3 V Aux. Power source and voltage monitor input for power-on reset.
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 out-
put and reset its
R_OFF
output.
Digital Output (Open Drain). This pin is a remote reset output that pulses low on
receipt of a specific SMBus message.
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.
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.
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.
Digital Output (Open Drain with Integrated V
CC3AUX
Pull-Up). An active low thermal
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.
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.
Digital Output or Open Drain with Integrated V
CC3AUX
Pull-Up. Remote off (power-
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.
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.
Digital Input. SMBus Clock.
Digital I/O (Open Drain). SMBus Bidirectional Data.
2
GPI
3
4
5
6
AUXRST
GND
V
CC3AUX
RST
7
8
R_RST
FAN_SPD/NTEST_IN
9
10
11
D–
D+
THERMA/NTEST_OUT
12
13
THERMB
R_OFF
14
INT
15
16
SCL
SDA
–4–
REV. B
