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PDF ADT7476A Data sheet ( Hoja de datos )
| Número de pieza | ADT7476A | |
| Descripción | dBCool Remote Thermal Controller and Voltage Monitor | |
| Fabricantes | Analog Devices | |
| Logotipo |  |
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dBCool™ Remote Thermal
Controller and Voltage Monitor
ADT7476A
FEATURES
Monitors up to five voltages
Improved TACH and PWM performance
Controls and monitors up to four fans
High and low frequency fan drive signal
One on-chip and two remote temperature sensors
Extended temperature measurement range up to 191°C
Automatic fan speed control mode controls system
cooling based on measured temperature
Enhanced acoustic mode dramatically reduces user
perception of changing fan speeds
Thermal protection feature via THERM output
Monitors performance impact of Intel® Pentium® 4 processor
Thermal control circuit via THERM input
3-wire and 4-wire fan speed measurement
Limit comparison of all monitored values
5 V support on all TACH and PWM channels
Meets SMBus 2.0 electrical specifications
GENERAL DESCRIPTION
The ADT7476A dBCOOL controller is a thermal monitor
and multiple PWM fan controller for noise-sensitive or power-
sensitive applications requiring active system cooling. The
ADT7476A can drive a fan using either a low or high frequency
drive signal and can monitor the temperature of up to two
remote sensor diodes plus its own internal temperature. The
part also measures and controls the speed of up to four fans, so
the fans operate at the lowest possible speed for minimum
acoustic noise.
The automatic fan speed control loop optimizes fan speed
for a given temperature. The effectiveness of the system’s
thermal solution can be monitored using the THERM input.
The ADT7476A also provides critical thermal protection to
the system using the bidirectional THERM pin as an output
to prevent system or component overheating.
VID5/GPIO5
VID4/GPIO4
VID3/GPIO3
VID2/GPIO2
VID1/GPIO1
VID0/GPIO0
GPIO6
PWM1
PWM2
PWM3
TACH1
TACH2
TACH3
TACH4
THERM
VCC
D1+
D1–
D2+
D2–
+5VIN
+12VIN
+2.5VIN
VCCP
FUNCTIONAL BLOCK DIAGRAM
ADDR
ADDREN SELECT SCL SDA SMBALERT
PWM
REGISTERS
AND
CONTROLLERS
(HF AND LF)
VCC TO ADT7476A
BAND GAP
TEMP. SENSOR
VID/GPIO
REGISTER
AUTOMATIC
FAN SPEED
CONTROL
FAN
SPEED
COUNTER
PERFORMANCE
MONITORING
THERMAL
PROTECTION
INPUT
SIGNAL
CONDITIONING
AND
ANALOG
MULTIPLEXER
SMBus
ADDRESS
SELECTION
SERIAL BUS
INTERFACE
ADT7476A
ADDRESS
POINTER
REGISTER
PWM
CONFIGURATION
REGISTERS
INTERRUPT
MASKING
ACOUSTIC
ENHANCEMENT
CONTROL
10-BIT
ADC
BAND GAP
REFERENCE
INTERRUPT
STATUS
REGISTERS
LIMIT
COMPARATORS
VALUE AND
LIMIT
REGISTERS
GND
Figure 1.
Rev. 0
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. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
Trademarksandregisteredtrademarksarethepropertyoftheirrespectiveowners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
www.analog.com
Fax: 781.461.3113
©2006 Analog Devices, Inc. All rights reserved.
1 page  
ABSOLUTE MAXIMUM RATINGS
Table 2.
Parameter
Rating
Positive Supply Voltage (VCC)
Maximum Voltage on +12 VIN Pin
Maximum Voltage on +5 VIN Pin
Maximum Voltage on All Open-Drain Outputs
3.6 V
16 V
6.25 V
3.6 V
Max Voltage on TACH/PWM Pins
+5.5 V
Voltage on Remaining Input or Output Pins
Input Current at Any Pin
Package Input Current
Maximum Junction Temperature (TJMAX)
Storage Temperature Range
−0.3 V to +4.2 V
±5 mA
±20 mA
150°C
−65°C to +150°C
Lead Temperature, Soldering
IR Reflow Peak Temperature
220°C
Pb-Free Peak Temperature
260°C
Lead Temperature (Soldering, 10 sec)
ESD Rating
300°C
1500 V
ADT7476A
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
JA is specified for the worst-case conditions, that is, a device
soldered in a circuit board for surface-mount packages.
Table 3. Thermal Resistance
Package Type
θJA
24-lead QSOP
122
θJC
31.25
Unit
°C/W
ESD 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 this product 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. 0 | Page 5 of 72
5 Page 
ADT7476A
FRONT
CHASSIS
FAN
ADT7476A
TACH2
PWM1
TACH1
REAR
CHASSIS
FAN
AMBIENT
TEMPERATURE
PWM3
TACH3 VID[0:4]/VID[0:5]
D2+
5(VRM9)/6(VRM10)
D2–
THERM
D1+ PROCHOT
D1–
VCC
SDA
+5VIN
SCL
+12VIN/VID5 SMBALERT
GND
Figure 13. ADT7476A Configuration
SERIAL BUS INTERFACE
Control of the ADT7476A is carried out using the serial system
management bus (SMBus). The ADT7476A is connected to this
bus as a slave device, under the control of a master controller.
The ADT7476A has a 7-bit serial bus address. When the device
is powered up with Pin 13 (PWM3/ADDREN) high, the
ADT7476A has a default SMBus address of 0101110 or 0x2E.
The read/write bit must be added to get the 8-bit address.
If more than one ADT7476A is to be used in a system, each
ADT7476A is placed in ADDR SELECT mode by strapping
Pin 13 low on power-up. The logic state of Pin 14 then
determines the device’s SMBus address. The logic of these
pins is sampled on power-up.
The device address is sampled on power-up and latched on
the first valid SMBus transaction, more precisely on the low-to-
high transition at the beginning of the eighth SCL pulse, when
the serial bus address byte matches the selected slave address.
The selected slave address is chosen using the ADDREN pin/
ADDR SELECT pin. Any attempted changes in the address
have no effect after this.
Table 5. Hardwiring the ADT7476A SMBus Device Address
Pin 13 State Pin 14
Address
0
Low (10 kΩ to GND)
0101100 (0x2C)
0
High (10 kΩ pull-up)
0101101 (0x2D)
1 Don’t Care 0101110 (0x2E)
ADT7476A
VCC
ADDR SELECT 14
PWM3/ADDREN 13
10kΩ
ADDRESS = 0x2E
Figure 14. Default SMBus Address = 0x2E
ADT7476A
ADDR SELECT
14 10kΩ
13
PWM3/ADDREN
ADDRESS = 0x2C
Figure 15. SMBus Address = 0x2C (Pin 14 = 0)
ADT7476A
ADDR SELECT
VCC
10kΩ
14
PWM3/ADDREN 13
ADDRESS = 0x2D
Figure 16. SMBus Address = 0x2D (Pin 14 = 1)
Rev. 0 | Page 11 of 72
11 Page | ||
| Páginas | Total 30 Páginas | |
| PDF Descargar | [ Datasheet ADT7476A.PDF ] | |
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