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PDF ADT7461 Data sheet ( Hoja de datos )
| Número de pieza | ADT7461 | |
| Descripción | Temperature Monitor | |
| Fabricantes | Analog Devices | |
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±1°C Temperature Monitor with
Series Resistance Cancellation
ADT7461
FEATURES
On-chip and remote temperature sensor
0.25°C resolution/1°C accuracy on remote channel
1°C resolution/3°C accuracy on local channel
Automatically cancels up to 3 kΩ (typ) of resistance in series
with remote diode to allow noise filtering
Extended, switchable temperature measurement range
0°C to +127°C (default) or –55°C to +150°C
Pin- and register-compatible with the ADM1032
2-wire SMBus serial interface with SMBus alert support
Two SMBus address versions available:
ADT7461 SMBus address is 0x4C
ADT7461-2 SMBus address is 0x4D
Programmable over/under temperature limits
Offset registers for system calibration
Up to two over temperature fail-safe THERM outputs
Small 8-lead SOIC or8-lead MSOP packages
170 μA operating current, 5.5 μA standby current
APPLICATIONS
Desktop and notebook computers
Industrial controllers
Smart batteries
Embedded systems
Instrumentation
GENERAL DESCRIPTION
The ADT74611 is a dual-channel digital thermometer and
under/over temperature alarm intended for use in PCs and
thermal management systems. It is pin- and register-compatible
with the ADM1032. The ADT7461 has three additional
features: series resistance cancellation (where up to 3 kΩ
(typical) of resistance in series with the temperature monitoring
diode may be automatically cancelled from the temperature
result, allowing noise filtering); configurable ALERT output;
and an extended, switchable temperature measurement range.
The ADT7461 can accurately measure the temperature of a
remote thermal diode to ±1°C and the ambient temperature to
±3°C. The temperature measurement range defaults to 0°C to
+127°C, compatible with the ADM1032, but can be switched to
a wider measurement range of −55°C to +150°C. The ADT7461
communicates over a 2-wire serial interface compatible with
system management bus (SMBus) standards. An ALERT output
signals when the on-chip or remote temperature is out of range.
The THERM output is a comparator output that allows on/off
control of a cooling fan. The ALERT output can be reconfigured
as a second THERM output, if required.
The SMBus address of the ADT7461 is 0x4C. An ADT7461-2
is also available, which uses SMBus Address 0x4D.
1 Protected by U.S. Patents 5,195,827; 5,867,012; 5,982,221; 6,097,239;
6,133,753; 6,169,442; other patents pending.
ON-CHIP
TEMPERATURE
SENSOR
CONVERSION RATE
REGISTER
LOCAL TEMPERATURE
VALUE REGISTER
D+ 2
D– 3
ANALOG
MUX
ADC
SRC
BLOCK
BUSY
RUN/STANDBY
REMOTE TEMPERATURE
VALUE REGISTER
REMOTE OFFSET
REGISTER
EXTERNAL DIODE OPEN CIRCUIT
ADT7461
STATUS REGISTER
SMBus INTERFACE
ADDRESS POINTER
REGISTER
LOCAL TEMPERATURE
LOW LIMIT REGISTER
LOCAL TEMPERATURE
HIGH LIMIT REGISTER
REMOTE TEMPERATURE
LOW LIMIT REGISTER
REMOTE TEMPERATURE
HIGH LIMIT REGISTER
LOCAL THERM LIMIT
REGISTER
EXTERNAL THERM LIMIT
REGISTER
CONFIGURATION
REGISTER
INTERRUPT
MASKING
1
VDD
5
GND
7
SDATA
8
SCLK
Figure 1. Functional Block Diagram
4
THERM
6
ALERT/
THERM2
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.
Specifications subject to change without notice. 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 owners.
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 © 2005 Analog Devices, Inc. All rights reserved.
1 page  
ABSOLUTE MAXIMUM RATINGS
Table 3.
Parameter
Rating
Positive Supply Voltage (VDD) to GND
D+
D− to GND
−0.3 V, +5.5 V
−0.3 V to VDD + 0.3 V
−0.3 V to +0.6 V
SCLK, SDATA, ALERT
−0.3 V to +5.5 V
THERM
Input Current, SDATA, THERM
Input Current, D−
ESD Rating, All Pins (Human Body Model)
Maximum Junction Temperature (TJ max)
Storage Temperature Range
−0.3 V to VDD + 0.3 V
−1 mA, +50 mA
±1 mA
2000 V
150°C
−65°C to +150°C
IR Reflow Peak Temperature
220°C
Pb-Free Parts Only
260°C (±0.5°C)
Lead Temperature (Soldering 10 sec)
300°C
ADT7461
THERMAL CHARACTERISTICS
8-lead SOIC package
θJA = 121°C/W
8-lead MSOP package
θJA = 142°C/W
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.
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. B | Page 5 of 24
5 Page 
The user can switch between measurement ranges at any time.
Switching the range also switches the data format. The next
temperature result following the switching is reported back to
the register in the new format. However, the contents of the
limit registers are not changed. The user must ensure that the
limit registers are reprogrammed, as necessary, when the data
format changes. See the Limit Registers section for more
information.
ADT7461 REGISTERS
The ADT7461 contains a total of 22 8-bit registers. These regis-
ters are used to store the results of remote and local temperature
measurements and high and low temperature limits and to
configure and control the device. A description of these registers
follows. Additional details are provided in Table 7 to Table 11.
Address Pointer Register
The address pointer register does not have or require an
address, as the first byte of every write operation is automati-
cally written to this register. The data in this first byte always
contains the address of another register on the ADT7461, which
is stored in the address pointer register. This register address is
written to by the second byte of a write operation or is used for
a subsequent read operation.
The power-on default value of the address pointer register is
0x00. Therefore, if a read operation is performed immediately
after power-on, without first writing to the address pointer, the
value of the local temperature is returned, since its register
address is 0x00.
Temperature Value Registers
The ADT7461 has three registers to store the results of local and
remote temperature measurements. These registers can only be
written to by the ADC and can be read by the user over the
SMBus. The local temperature value register is at Address 0x00.
The external temperature value high byte register is at
Address 0x01, with the low byte register at Address 0x10.
The power-on default for all three registers is 0x00.
Configuration Register
The configuration register is Address 0x03 at read and
Address 0x09 at write. Its power-on default is 0x00. Only four
bits of the configuration register are used. Bits 0, 1, 3, and 4 are
reserved and should not be written to by the user.
Bit 7 of the configuration register is used to mask the ALERT
output. If Bit 7 is 0, the ALERT output is enabled. This is the
power-on default. If Bit 7 is set to 1, the ALERT output is
disabled. This only applies if Pin 6 is configured as ALERT. If
Pin 6 is configured as THERM2, the value of Bit 7 has no effect.
ADT7461
If Bit 6 is set to 0 (the power-on default), the device is in
operating mode with the ADC converting. If Bit 6 is set to 1, the
device is in standby mode and the ADC does not convert. The
SMBus does, however, remain active in standby mode, so values
can be read from or written to the ADT7461 via the SMBus in
this mode. The ALERT and THERM outputs are also active in
standby mode. Changes made to the registers in standby mode
that affect the THERM or ALERT outputs cause these signals to
be updated.
Bit 5 determines the configuration of Pin 6 on the ADT7461. If
Bit 5 is 0 (default), then Pin 6 is configured as an ALERT
output. If Bit 5 is 1, then Pin 6 is configured as a THERM2
output. Bit 7, the ALERT mask bit, is only active when Pin 6 is
configured as an ALERT output. If Pin 6 is set up as a THERM2
output, then Bit 7 has no effect.
Bit 2 sets the temperature measurement range. If Bit 2 is 0
(default), the temperature measurement range is set between
0°C to +127°C. Setting Bit 2 to 1 means that the measurement
range is set to the extended temperature range.
Table 7. Configuration Register Bit Assignments
Bit Name
Function
Power-On
Default
7 MASK1
0 = ALERT enabled
1 = ALERT masked
0
6 RUN/STOP
0 = Run
1 = Standby
0
5
ALERT/THERM2
0 = ALERT
1 = THERM2
0
4, 3 Reserved
0
2
Temperature
Range Select
0 = 0°C to 127°C
1 = Extended range
0
1, 0 Reserved
0
Conversion Rate Register
The conversion rate register is Address 0x04 at read and
Address 0x0A at write. The lowest four bits of this register are
used to program the conversion rate by dividing the internal
oscillator clock by 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, or 1024 to
give conversion times from 15.5 ms (Code 0x0A) to 16 seconds
(Code 0x00). For example, a conversion rate of 8 conversions
per second means that beginning at 125 ms intervals, the device
performs a conversion on the internal and external temperature
channels.
This register can be written to and read back over the SMBus.
The higher four bits of this register are unused and must be set
to 0. The default value of this register is 0x08, giving a rate of
16 conversions per second. Use of slower conversion times
greatly reduces the device power consumption, as shown
in Table 8.
Rev. B | Page 11 of 24
11 Page | ||
| Páginas | Total 24 Páginas | |
| PDF Descargar | [ Datasheet ADT7461.PDF ] | |
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