aSC7512
D
IGITAL
T
EMPERATURE
S
ENSOR
W
ITH
I
NTEGRATED
F
AN
C
ONTROL
Fully Released Specification
Product Description
The aSC7512 has a two wire digital interface compatible
with SMBus 2.0. Using a 10-bit
ΣΔ-
ADC, the aSC7512
measures the temperature of a remote diode connected
transistor as well as its own die.
Using temperature information from these two zones, an
automatic fan speed control algorithm is employed to
minimize acoustic impact while achieving recommended
CPU temperature under varying operational loads.
To set fan speed, the aSC7512 has a pulse width
modulation (PWM) output that is controlled by one of two
temperature zones. Both high- and low-frequency PWM
ranges are supported. The aSC7512 also includes a digital
filter that can be invoked to smooth temperature readings
for better control of fan speed and minimum acoustic
impact. The aSC7512 has a tachometer input to measure
fan speed or alternatively, an alert pin that may be
triggered by exceeding a temperature limit setting. Limit
and status registers for all measured values are included to
alert the system host that any measurements are outside of
programmed limits.
P
RODUCT
S
PECIFICATION
Measurement System
Temperature:
•
0.25°C resolution, ±1°C accuracy on remote diode
•
0.25°C resolution, ±3°C accuracy on local sensor
•
Extended temperature measurement range on
remote sensor –55°C to +125°C using or 2’s
complement coding.
Fan Tachometer:
•
16-bit count of 90KHz clock periods
Limit alarms for all measured values
Applications
•
•
•
Desktop Computers – Motherboards and Graphics
Cards
Laptop Computers
Microprocessor based equipment (e.g. Base-
stations, Routers, ATMs, Point of Sales)
Features
•
•
•
•
•
•
•
•
•
•
2-wire, SMBus 2.0 compliant, serial digital
interface
10-bit
ΣΔ-ADC
Monitors internal and remote thermal diodes
Programmable autonomous fan control based on
temperature readings
Noise filtering of temperature reading for fan
control
0.25°C digital temperature sensor resolution
PWM fan speed control output for 2-, 3- or 4-wire
fans.
Provides high and low PWM frequency ranges
Fan tachometer input or
ALERT
output
8-lead MSOP or SOIC package
Connection Diagram
V
DD
D+
D-
PWM
1
2
8
SMBCLK
SMBDAT
TACH /
ALERT
GND
7
aSC7512
3
6
4
5
Ordering Information
Part Number
aSC7512D8
aSC7512M8
Package
8-lead SOIC
8-lead MSOP
Temperature Range
and Operating Voltage
-40°C to +125°C, 3.3V
-40°C to +125°C, 3.3V
Marking
aSC7512
Ayww
7512
Ayww
How Supplied
2500 units Tape & Reel
2500 units Tape & Reel
Ayww – Assembly site, year, workweek
© Andigilog, Inc. 2006
-1-
www.andigilog.com
August 2006 - 70A05003
aSC7512
Block Diagram
SMBus Interface
SMBDAT
SMBCLK
PWM
Fan PWM Control Register
ID Registers
Fan
Speed
TACH /
ALERT
Pin
MUX
Limit Registers
Limit Comparators
Status Registers
Tach Signal
Conditioner
Address
Pointer
Fan T-min, T-range & T-Hyst
Configuration Register
Spike Smoothing
D+
D-
Internal
Sensor
Diode
Signal
Con-
ditioning
&
Analog
Mux
ADC
Digital
Filter
Fan Control Registers
Fan Characteristic Registers
Bandgap
Reference
Fan Speed Configuration
Figure 1 Block Diagram
Pin Descriptions
Symbol
SMBus
SMBDAT
SMBCLK
V
DD
Pin
7
8
1
Type
Digital I/O
(Open-Drain)
Digital Input
POWER
Name and Function/Connection
System Management Bus Data. Open-drain output. 5V
tolerant, SMBus 2.0 compliant.
System Management Bus Clock. Tied to Open-drain output.
5V tolerant, SMBus 2.0 compliant.
+3.3V pin. Can be powered by +3.3V Standby power if
monitoring in low power states is required. This pin should
be bypassed with a 0.1μF capacitor in parallel with 100pF
Ground for all analog and digital circuitry.
Positive input (current source) from the remote thermal
diode serves as the positive input into the A/D. Connected
to the anode of a CPU thermal diode or the base-collector of
a diode connected MMBT3904 NPN transistor.
Negative input (current sink) from the remote thermal diode
serves as the negative input into the A/D. Connected to
cathode of a CPU thermal diode or the emitter of a diode
connected MMBT3904 NPN transistor.
Input for monitoring tachometer output of fan (default) or
ALERT
output selectable by configuration register 09h, bit 5.
Power
GND
D+
Remote
5
2
GROUND
Remote Thermal Diode
Positive Input
D-
3
Remote Thermal Diode
Negative Input
Digital Input / Digital
Open-Drain Output
Digital Open-Drain
Output
Fan / Alert
TACH /
ALERT
6
4
PWM
Fan speed control, Pulse Width Modulated.
© Andigilog, Inc. 2006
-2-
www.andigilog.com
August 2006 - 70A05003
aSC7512
Absolute Maximum Ratings
1
Parameter
Supply Voltage, V
DD
Voltage on Any Digital Input or
Output Pin
Voltage on Remote +
Current on Remote -
Input Current on Any Pin
2
Package Input Current
Storage Temperature
ESD
4
Human Body Model
Machine Model
2
Notes:
Rating
-0.5V to 6.0V
-0.5V to 6.0V
-0.5V to (V
DD
+
0.50V)
±1mA
±5mA
±20mA
See (Note 3)
-65°C to +150°C
2500 V
250 V
Package Dissipation at T
A
= 25°C
Operating Ratings
1
Parameter
aSC7512 Operating
Temperature Range
Remote Diode Temperature
Range
Supply Voltage (3.3V
nominal)
All Other Inputs
Typical Supply Current
Rating
-40°C
≤
T
A
≤
+125°C
-55°C
≤
T
D
≤
+125°C
+3.0V to +3.6V
-0.05V to V
DD
+ 0.05V
TBDmA
1. Absolute maximum ratings are limits beyond which
operation may cause permanent damage to the device.
These are stress ratings only; functional operation at or
above these limits is not implied.
2. When the input voltage (V
IN
) at any pin exceeds the
power supplies (V
IN
< GND or V
IN
> V
DD
), the current at
that pin should be limited to 5mA. The 20mA maximum
package input current rating limits the number of pins
that can safely exceed the power supplies with an input
current of 5mA to four. Parasitic components and/or
ESD protection circuitry are present on the aSC7512
pins. Care should be taken not to forward bias the
parasitic diode present on pins D+ and D-. Doing so by
more than 50mV may corrupt temperature
measurements.
3. Thermal resistance junction-to-ambient when attached to
a double-sided printed circuit board with 1oz. foil is
TBD
°
C/W
4. Human Body Model: 100pF capacitor discharged
through a 1.5kΩ resistor into each pin. Machine Model:
200pF capacitor discharged directly into each pin.
© Andigilog, Inc. 2006
-3-
www.andigilog.com
August 2006 - 70A05003
aSC7512
DC Electrical Characteristics
5
The following specifications apply for V
DD
= 3.3V, and all analog input source impedance R
s
= 50Ω unless otherwise
specified in conditions.
Boldface limits apply for T
A
= T
J
over T
MIN
to 85°C;
all other limits T
A
= T
J
= 25°C. T
A
is the
ambient temperature of the aSC7512; T
J
is the junction temperature of aSC7512; T
D
is the remote thermal diode junction
temperature. Specifications subject to change without notice
Parameter
POWER SUPPLY CHARACTERISTICS
Supply Current
Power-On Reset Threshold
Voltage
TEMPERATURE TO DIGITAL CONVERTER CHARACTERISTICS
Resolution
Local Sensor Accuracy
6
-40°C
≤
T
A
≤
+100°C,
3V≤ V
D D
≤
3.6V
0°C
≤
T
A
≤
+100°C,
-55°C≤T
D
≤+125°C,
3V≤V
DD
≤3.6V
-40°C
≤
T
A
≤
+120°C,
-55°C≤T
D
≤+125°C,
3V≤V
DD
≤3.6V
I
DS
High Level
Low Level
96
6
16
I
OL
V
OL
V
OL
I
OH
V
IH
V
IL
V
HYST
300
V
OL
= 0.4V
I
OUT
= +8mA
I
OUT
= +4mA
V
OUT
= V+
2.1
0.8
0.1
8
0.4
mA (min)
V (max)
V (max)
µA(max)
V (min)
V (max)
mV
0.25
10
±1
±1
±3
±2
°C
Bits
°C
°C
Converting, Interface and Fans
Inactive, Peak Current
Converting, Interface and Fans
inactive, Average Current
1.6
1.8
0.5
2.8
3.5
mA(max)
mA
V
Conditions
Min
Typ
Max
Units
Remote Sensor Accuracy
7
±3
°C
µA
µA
External Diode Current Source
External Diode Current Ratio
DIGITAL OPEN-DRAIN OUTPUT: PWM
Logic Low Sink Current
Logic Low Level
Logic Low Output Voltage
High Level Output Current
Logic Input High Voltage
Logic Input Low Voltage
Logic Input Hysteresis Voltage
DIGITAL INPUTS: ALL
Logic Input High Voltage
Logic Input Low Voltage
Logic Input Threshold Voltage
Logic High Input Current
Logic Low Input Current
Digital Input Capacitance
V
IH
V
IL
V
TH
I
IH
I
IL
C
IN
V
IN
= V+
V
IN
= GND
1.5
0.005
-0.005
20
10
-10
2.1
0.8
V (min)
V (max)
V
µA(max)
µA(max)
pF
SMBUS OPEN-DRAIN OUTPUT: SMBDAT
0.4
10
SMBUS INPUTS: SMBCLK, SMBDAT
© Andigilog, Inc. 2006
-4-
www.andigilog.com
August 2006 - 70A05003
aSC7512
AC Electrical Characteristics
The following specifications apply for V
DD
= 3.3V unless otherwise specified in conditions.
Boldface limits apply for T
A
= T
J
over T
MIN
to 85°C;
all other limits T
A
= T
J
= 25°C.
Parameter
TACHOMETER
Fan Full-Scale Count
Fan Counter Clock Frequency
Fan Count Conversion Time
FAN PWM OUTPUT
Low-Frequency Range
Frequency Range
High-Frequency Range
Duty-Cycle Range
Duty-Cycle Resolution (8-bits)
Spin-Up Time Interval Range
0.3906
0
4000
10
94
22.5
30
0 to
100
Hz
Hz
kHz
kHz
%(max)
%/count
ms
ms
90
0.7
1.46
65535
(max)
kHz
sec(max)
Conditions
Min
Typ
Max
Units
Logic Electrical Characteristics
(T
A
= 25 °C, V
DD
= 3.3V unless otherwise noted)
Parameter
Input Voltage Logic High
Input Voltage Logic Low
Output Voltage Logic Low
(
ALERT
)
Output Low Sink Current
(
ALERT
)
Input Leakage Current
SMBus Output Sink Current
SMBus Logic Input Current
Output Leakage Current
Output Transition Time
Input Capacitance
Symbol
V
IH
V
IL
V
OL
I
OL
I
IN
I
OL
I
IH,
I
IL
I
OH
t
F
C
IN
V
OH
= V
DD
= 5.5V
C
L
= 400pF, I
OL
= -3mA
All Digital Inputs
Conditions
3V≤ V
D D
≤
3.6V
3V≤ V
D D
≤
3.6V
V
DD
=5V, I
OL
= -6mA
ALERT
forced to 0.4V
Min
2.1
Typ
Max
0.8
0.4
Units
V
V
V
mA
6
±1.0
6
-1
0.1
+1
1
250
5
V
IN
= 0V or 5.5V,
-40°C
≤
T
A
≤
+125°C
T
A
= 25 °C, V
OL
= 0.6V
µA
mA
µA
µA
ns
pF
© Andigilog, Inc. 2006
-5-
www.andigilog.com
August 2006 - 70A05003
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