aSC7621
H
ARDWARE
M
ONITOR
W
ITH
I
NTEGRATED
F
AN
C
ONTROL
Preliminary Specification
Product Description
The aSC7621 has a two wire digital interface compatible
with SMBus 2.0. Using a 10-bit
ΣΔ-
ADC, the aSC7621
measures the temperature of two remote diode connected
transistors as well as its own die. Support for Platform
Environmental Control Interface (PECI) is included.
Using temperature information from these four 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 aSC7621 has three independent
pulse width modulation (PWM) outputs that are controlled
by one, or a combination of three, temperature zones.
Both high- and low-frequency PWM ranges are supported.
The aSC7621 also includes a digital filter that can be
invoked to smooth temperature readings for better control
of fan speed and minimum acoustic impact. The aSC7621
has tachometer inputs to measure fan speed on up to four
fans. Limit and status registers for all measured values are
included to alert the system host that any measurements
are outside of programmed limits via status registers.
System voltages of VCCP, 2.5V, 3.3V, 5.0V, and 12V
motherboard power are monitored efficiently with internal
scaling resistors.
P
RODUCT
S
PECIFICATION
Measurement System
Temperature:
•
0.25°C resolution, ±2°C accuracy on remote diode
•
0.25°C resolution, ±3°C accuracy on local sensor
•
Temperature measurement range on remote
sensor –55°C to +125°C using 2’s complement
coding.
Voltage:
•
10-bit Resolution, ±2% (TUE)
Fan Tachometer:
•
16-bit count of 90kHz clock periods
Limit alarms for all measured values
Preliminary Specification – Subject to change without notice
Preliminary Specification – Subject to change without notice
Applications
•
•
Desktop Computers – Motherboards and Graphics
Cards
Microprocessor based equipment (e.g. Base-
stations, Routers, ATMs, Point of Sales)
Features
•
•
•
•
•
•
•
•
•
•
•
•
Supports PECI interface and monitors internal and
remote thermal diodes
2-wire, SMBus 2.0 compliant, serial interface
10-bit
ΣΔ-ADC
Monitors VCCP, 2.5V, 3.3V, 5.0V, and 12V
motherboard/processor supplies
Programmable autonomous fan control based on
temperature readings
Noise filtering of temperature reading for fan
speed control
0.25°C digital temperature sensor resolution
3 PWM fan speed control outputs for 2-, 3- or 4-
wire fans and up to 4 fan tachometer inputs
Enhanced measured temperature to Temperature
Zone assignment.
Provides high and low PWM frequency ranges
3 GPIO pins for custom use
24-Lead QSOP package
Connection Diagram
SMBDAT
SMBCLK
GND
3.3V
GPIO2
GPIO1
PECI
Vtt
TACH3
PWM2
TACH1
TACH2
1
2
3
4
5
6
7
8
9
10
11
12
24
23
22
21
20
PWM1/
XTESTOUT
VCCP
2.5V
12V
5V
GPIO3
REMOTE 1+
REMOTE 1-
REMOTE 2+
REMOTE 2-
TACH4/
AddressSelect
PWM3/
AddressEnable
aSC7621
19
18
17
16
15
14
13
Ordering Information
Part Number
aSC7621QS24
Package
24-lead QSOP
Temperature Range
and Operating Voltage
0°C to +120°C, 3.3V
Marking
aSC7621
Ayww
How Supplied
2500 units Tape & Reel
Ayww – Assembly site, year, workweek
© Andigilog, Inc. 2006
-1-
www.andigilog.com
October 2006 - 70A06010
aSC7621
Block Diagram
PECI
Vtt
PECI
INTERFACE
SERIAL BUS
INTERFACE
SMBDAT
SMBCLK
GPIO1
GPIO2
GPIO3
TACH1
TACH2
TACH3
TACH4/
Address
Select
3.3V
5V
12V
2.5V
VCCP
REMOTE 1+
REMOTE 1-
REMOTE 2-
REMOTE 2+
GPIO
REGISTER
VOLTAGE FAN
SPEED
TEMPERATURE, AND
LIMIT VALUE
REGISTERS
FAN SPEED
COUNTER
STEPPING
AND DEVICE
ID REGISTERS
LIMIT
COMPARATORS
Preliminary Specification – Subject to change without notice
Preliminary Specification – Subject to change without notice
STATUS REGISTERS
ADDRESS
POINTER
REGISTERS
CONFIGURATION
REGISTERS
SPIKE SMOOTHING
FAN TMIN/TRANGE/
HYST REGISTERS
FAN
CHARACTERISTICS
FAN SPEED CONFIG
REGISTERS
FAN PWM CONTROL
& PWM VALUE
REGISTERS
PWM3/
AddressEnable
PWM2
INPUT
ATTENUATORS,
EXTERNAL
DIODE SIGNAL
CONDITIONING,
AND
ANALOG
MULTIPLEXER
PWM1
10-bit
ΣΔ
-ADC
INTERNAL
TEMP
SENSOR
BANDGAP
REFERENCE
Figure 1 Block Diagram
© Andigilog, Inc. 2006
-2-
www.andigilog.com
October 2006 - 70A06010
aSC7621
Pin Descriptions
Symbol
SMBus
SMBDAT
SMBCLK
PECI
Vtt
Pin
1
2
7
8
Type
Digital I/O
(Open-Drain)
Digital Input
Digital I/O
Analog Input
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.
Platform Environmental Control Interface (PECI). PECI 1.0
compliant, CPU digital thermometer input
PECI reference voltage.
+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.
A bulk capacitance of approximately 10μF needs to be in
near vicinity of the aSC7621.
Ground for all analog and digital circuitry.
Analog Input for +5V monitoring.
Analog Input for +12V monitoring.
Analog Input for +2.5V monitoring..
Analog Input for VCCP (processor voltage) monitoring.
Positive input (current source) from the first remote thermal
diode Serves as the positive input into the A/D. Connected
to THERMDA pin of Pentium processor.
Negative input (current sink) from the first remote thermal
diode Serves as the negative input into the A/D. Connected
to THERMDC pin of Pentium processor.
Positive input (current source) from the second remote
thermal diode Serves as the positive input into the A/D.
Connected to the base of a diode connected MMBT3904
NPN transistor.
Negative input (current sink) from the second remote
thermal diode Serves as the negative input into the A/D.
Connected to the emitter of a diode connected MMBT3904
NPN transistor.
Input for monitoring tachometer output of fan 1.
Input for monitoring tachometer output of fan 2.
Input for monitoring tachometer output of fan 3. During
power-up, if held low through a 10KΩ resistor, SMBus
address may be selected based on the state of TACH4 pin.
Input for monitoring tachometer output of fan 4. If in
Address Select Mode, determines the SMBus address of
aSC7621.
Fan speed control 1. When in XOR tree test mode,
functions as XOR Tree output.
Fan speed control 2.
Fan speed control 3. Pull to ground at power on to enable
Address Select Mode (Address Select pin controls SMBus
address of the device).
Power
PECI
3.3V
4
POWER
Preliminary Specification – Subject to change without notice
GND
5V
Voltage
Inputs
12V
2.5V
VCCP
Remote 1+
3
20
21
22
23
18
GROUND
Analog Input
Analog Input
Analog Input
Analog Input
Remote Thermal
Diode Positive
Input
Remote Thermal
Diode Negative
Input
Remote Thermal
Diode Positive
Output
Remote Thermal
Diode Negative
Input
Digital Input
Digital Input
Digital Input
Preliminary Specification – Subject to change without notice
Remote 1-
Remote
17
Remote 2+
16
Remote 2-
TACH1
Fan Tachometer
Inputs
TACH2
TACH3
15
11
12
9
TACH4/AddressSelect
PWM1/XTESTOUT
14
24
10
13
Digital Input
Digital Open-
Drain Output
Digital Open-
Drain Output
Digital Open-
Drain Output
Fan Control
PWM2
PWM3/Address Enable
© Andigilog, Inc. 2006
-3-
www.andigilog.com
October 2006 - 70A06010
aSC7621
Symbol
GPIO1
GPIO
GPIO2
GPIO3
Pin
6
5
19
Type
Digital I/O
Digital I/O
Digital I/O
Name and Function/Connection
Alert Out / Zone # THERM Out. Default is GPIO input
Alert Out / Zone # THERM Out. Default is GPIO input
Alert Out / Zone # THERM Out. Default is GPIO input
Absolute Maximum Ratings
1
Parameter
Supply Voltage, V
DD
Voltage on Any Digital Input or
Output Pin other than PWM Outputs
Voltage on PWM Outputs
Rating
3.6V
-0.3V to V
DD
+0.3V
-0.3V to 5.5V
-0.5V to 16V
-0.5V to 6.5V
-0.5V to (V
DD
+
0.50V)
-0.5V to 6.0V
±1mA
±5mA
±20mA
See (Note 3)
-65°C to +150°C
4000 V
250 V
2000V
Operating Ratings
1
Parameter
aSC7621 Operating
Temperature Range, Ambient
Temperature, T
MIN
to T
MAX
Remote Diode Temperature
Range
Supply Voltage (3.3V
nominal)
V
IN
Voltage Range
+12V V
IN
+5V V
IN
+3.3V V
IN
VCCP and All Other Inputs
Typical Supply Current
-0.05V to 16V
-0.05V to 6.5V
3.0V to 4.4V
-0.05V to V
DD
+ 0.05V
1.8mA
Rating
0°C
≤
T
A
≤
+120°C
-55°C
≤
T
D
≤
+125°C
+3.0V to +3.6V
Preliminary Specification – Subject to change without notice
Preliminary Specification – Subject to change without notice
Voltage on 12V Analog Input
Voltage on 5V Analog Input
Voltage on Remote 1 +, Remote 2 +
Voltage on Other Analog Inputs
Current on Remote 1 -, Remote 2 -
Input Current on Any Pin
2
Package Input Current
2
Package Dissipation at T
A
= 25°C
Storage Temperature
Human Body Model
ESD
4
Machine Model
Charged Device Model
Notes:
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 aSC7621
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 115°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. Charged-Device Model is per JESD22-
C101C.
© Andigilog, Inc. 2006
-4-
www.andigilog.com
October 2006 - 70A06010
aSC7621
DC Electrical Characteristics
5
The following specifications apply for V
DD
= 3.0V to 3.6V, 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 T
MAX
; all other limits T
A
= T
J
= 25°C. T
A
is the ambient temperature of the aSC7621; T
J
is the junction temperature of aSC7621; T
D
is the remote thermal diode
junction temperature. Specifications subject to change without notice
Parameter
POWER SUPPLY CHARACTERISTICS
Supply Current
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
Preliminary Specification – Subject to change without notice
Preliminary Specification – Subject to change without notice
Power-On Reset Threshold
Voltage
TEMPERATURE TO DIGITAL CONVERTER CHARACTERISTICS
Resolution
0°C
≤
T
A
≤
+100°C,
0°C≤T
D
≤+100°C,
3V≤V
DD
≤3.6V
0°C
≤
T
A
≤
+120°C,
-55°C≤T
D
≤+125°C,
3V≤V
DD
≤3.6V
0°C
≤
T
A
≤
+120°C,
3V≤ V
D D
≤
3.6V
I
DS
High Level
Low Level
0.25
10
±2
°C
Bits
°C
Remote Sensor Accuracy
6
±3
±1
96
6
16
±3
°C
°C
µA(max)
µA
Temperature Accuracy using
7
Internal Diode
External Diode Current Source
External Diode Current Ratio
ANALOG TO DIGITAL CONVERTER CHARACTERISTICS
Total Unadjusted Error
8
Differential Non-linearity
Power Supply Sensitivity
Total Monitoring Cycle Time
9
Input Resistance, all analog
inputs
DIGITAL OUTPUT: PWM1, PWM2, PWM3, XTESTOUT
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
© Andigilog, Inc. 2006
TUE
DNL
All Voltage and Temperature
readings
140
1
±1
200
210
±2
%(max)
LSB
%/V
250
400
ms (max)
kΩ
I
OL
V
OL
V
OL
I
OH
V
IH
V
IL
V
HYST
V
IH
V
OL
= 0.4V
I
OUT
= +8mA
I
OUT
= +4mA
V
OUT
= V+
8
0.4
0.4
0.1
2.1
0.8
300
2.1
10
mA (min)
V (max)
V (max)
µA(max)
V (min)
V (max)
mV
V (min)
October 2006 - 70A06010
SMBUS OPEN-DRAIN OUTPUT: SMBDAT
SMBUS INPUTS: SMBCLK, SMBDAT
-5-
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