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PDF ADT7476 Data sheet ( Hoja de datos )
| Número de pieza | ADT7476 | |
| Descripción | dBCool Remote Thermal Controller and Voltage Monitor | |
| Fabricantes | Analog Devices | |
| Logotipo |  |
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dBCool™ Remote Thermal
Controller and Voltage Monitor
ADT7476
FEATURES
Monitors up to 5 voltages
Controls and monitors up to 4 fans
High and low frequency fan drive signal
1 on-chip and 2 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
Meets SMBus 2.0 electrical specifications
GENERAL DESCRIPTION
The ADT7476 dBCool controller is a thermal monitor
and multiple PWM fan controller for noise-sensitive or power-
sensitive applications requiring active system cooling. The
ADT7476 can drive a fan using either a low or high frequency
drive signal, monitor the temperature of up to two remote
sensor diodes plus its own internal temperature, and measure
and control the speed of up to four fans, so they 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 ADT7476 also provides critical thermal protection to
the system using the bidirectional THERM pin as an output
to prevent system or component overheating.
FUNCTIONAL BLOCK DIAGRAM
ADDR
ADDREN SELECT SCL SDA SMBALERT
VID5
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
PWM
REGISTERS
AND
CONTROLLERS
(HF AND LF)
VCC TO ADT7476
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
ADT7476
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. 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. 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  
ADT7476
Parameter
SMBUS DIGITAL INPUTS (SCL, SDA)
Input High Voltage, VIH
Input Low Voltage, VIL
Hysteresis
DIGITAL INPUT LOGIC LEVELS (TACH INPUTS)
Input High Voltage, VIH
Input Low Voltage, VIL
Hysteresis
DIGITAL INPUT LOGIC LEVELS (THERM) ADTL+
Input High Voltage, VIH
Input Low Voltage, VIL
DIGITAL INPUT CURRENT
Input High Current, IIH
Input Low Current, IIL
Input Capacitance, CIN
SERIAL BUS TIMING2
Clock Frequency, fSCLK
Glitch Immunity, tSW
Bus Free Time, tBUF
SCL Low Time, tLOW
SCL High Time, tHIGH
SCL, SDA Rise Time, tr
SCL, SDA Fall Time, tf
Data Setup Time, tSU;DAT
Detect Clock Low Timeout, tTIMEOUT
Min Typ Max
Unit Test Conditions/Comments
2.0
0.4
500
V
V
mV
2.0
−0.3
0.5
3.6
0.8
V
V
V
V
V p-p
Maximum input voltage
Minimum input voltage
0.75 × VCC V
0.4 V
±1 μA VIN = VCC
±1 μA VIN = 0
5 pF
See Figure 2
10 400 kHz
50 ns
4.7 μs
4.7 μs
4.0 50 μs
1000
ns
300 μs
250 ns
15 35 ms Can be disabled
1 All voltages are measured with respect to GND, unless otherwise specified. Typical voltages are TA = 25°C and represent a most likely parametric norm. Logic inputs
accept input high voltages up to VMAX, even when the device is operating down to VMIN. Timing specifications are tested at logic levels of VIL = 0.8 V for a falling edge,
and VIH = 2.0 V for a rising edge.
2 SMBus timing specifications are guaranteed by design and are not production tested.
TIMING DIAGRAM
SCL
tLOW tR
tHD; STA
tHD; DAT
SDA
tBUF
PS
tF
tHIGH
tSU; DAT
tHD; STA
tSU; STA
S
Figure 2. Serial Bus Timing Diagram
tSU; STO
P
Rev. A | Page 5 of 72
5 Page 
PRODUCT DESCRIPTION
The ADT7476 is a complete thermal monitor and multiple fan
controller for any system requiring thermal monitoring and
cooling. The device communicates with the system via a serial
system management bus. The serial bus controller has a serial
data line for reading and writing addresses and data (Pin 1),
and an input line for the serial clock (Pin 2). All control and
programming functions for the ADT7476 are performed over
the serial bus. In addition, a pin can be reconfigured as an
SMBALERT output to signal out-of-limit conditions.
FEATURE COMPARISONS BETWEEN ADT7476
AND ADT7468
• Dynamic TMIN , dynamic operating point, and associated
registers are no longer available on the ADT7476. The
following related registers are not available in the
ADT7476:
• Calibration Control 1 and Calibration Control 2
(Register 0x36 and Register 0x37)
• Operating Point (Register 0x33, Register 0x34, and
Register 0x35)
• Previously, TRANGE defined the slope of the automatic fan
control algorithm. For the ADT7476, TRANGE now defines a
true temperature range.
ADT7476
• For the ADT7476, acoustic filtering is now assigned to
temperature zones and not to fans. Smoothing times have
been increased for better acoustic performance.
• For the ADT7476, temperature measurements are made
with two switching currents instead of three. SRC is not
available in the ADT7476.
• For the ADT7476, high frequency PWM can now be
enabled/disabled on each PWM output individually.
• For the ADT7476, THERM can now be enabled/disabled
on each temperature channel individually.
• The ADT7476 does not support full shutdown mode.
• The ADT7476 defaults to twos complement temperature
measurement mode.
• Some pins have swapped/added functions.
• The power-up routine for the ADT7476 is simplified.
Other minor changes in the ADT7476 include the following:
• Vcore_low_enable has been reallocated to Bit 7 of
Configuration Register 1 (0x40).
• Dev ID register reads 0x76.
Rev. A | Page 11 of 72
11 Page | ||
| Páginas | Total 70 Páginas | |
| PDF Descargar | [ Datasheet ADT7476.PDF ] | |
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