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PDF ADT7461 Data sheet ( Hoja de datos )
| Número de pieza | ADT7461 | |
| Descripción | Temperature Monitor | |
| Fabricantes | ON Semiconductor | |
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ADT7461
+15C Temperature Monitor
with Series Resistance
Cancellation
The ADT7461 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 kW (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.
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 kW (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/Undertemperature Limits
• Offset Registers for System Calibration
• Up to Two Overtemperature Fail−Safe THERM Outputs
• Small 8-lead SOIC NB or 8-lead MSOP Packages
• 170 mA Operating Current, 5.5 mA Standby Current
• These are Pb-Free Devices*
Applications
• Desktop and Notebook Computers
• Industrial Controllers
• Smart Batteries
• Embedded Systems
• Instrumentation
http://onsemi.com
SOIC−8 NB
CASE 751
MSOP8
CASE 846AB
PIN ASSIGNMENT
VDD 1
D+ 2
D− 3
THERM 4
8 SCLK
7 SDATA
6 ALERT/THERM2
5 GND
(Top View)
MARKING DIAGRAMS
8
ADT74
61A
#YWW
1
SOIC−8
ADT7461A
#
Y
W
= Specific Device Code
= Pb-Free Package
= Year
= Work Week
8
T1x
AYWG
G
1
MSOP8
T1x = Refer to Order Info Table
A = Assembly Location
Y = Year
W = Work Week
G = Pb-Free Package
(Note: Microdot may be in either location)
ORDERING INFORMATION
See detailed ordering and shipping information in the package
dimensions section on page 18 of this data sheet.
* For additional information on our Pb-Free strategy and soldering details, please download the ON Semiconductor Soldering and Mounting
Techniques Reference Manual, SOLDERRM/D.
© Semiconductor Components Industries, LLC, 2014
March, 2014 − Rev. 8
1
Publication Order Number:
ADT7461/D
1 page  
ADT7461
TYPICAL PERFORMANCE CHARACTERISTICS
60
40
D+ To GND
20
0
−20
−40 D+ To VCC
−60
−80
0
20 40 60 80 100
LEAKAGE RESISTANCE (MW)
Figure 3. Temperature Error vs. Leakage Resistance
4
40mV NO FILTER
60mV NO FILTER
3
40mV WITH FILTER
60mV WITH FILTER
2
1
−0
−1
−2
0
100 200 300 400 500 600
FREQUENCY (MHz)
Figure 5. Temperature Error vs. Differential Mode
Noise Frequency (With and Without R-C-R Filter
of 100 W - 2.2 nF - 100 W)
0
−10
−20
−30
−40
−50
−60
−70
0
5 10 15 20 25
CAPACITANCE (nF)
Figure 7. Temperature Error vs. Capacitance
Between D+ and D−
0
−0.1
−0.2
−0.3
−0.4
−0.5
−0.6
−0.7
−0.8
−3 −10 10 30 50 70 90 110 130 150
TEMPERATURE (°C)
Figure 4. Temperature Error vs. Actual
Temperature Using 2N3906
20
250 mV EXTERNAL
15
10
100 mV INTERNAL
5
0
−5 100 mV EXTERNAL
−10 250 mV INTERNAL
−15
0
20 40
FREQUENCY (MHz)
Figure 6. Temperature Error vs. Power Supply
Noise Frequency
180
160 100 mV
140 NO FILTER
120
100
80
60
40
20
0
−20
0
100 mV WITH FILTER
100 200 300 400 500 600
FREQUENCY (MHz)
Figure 8. Temperature Error vs. 100 mV
Differential Mode Noise Frequency (With and
Without R-C-R Filter of 100 W - 2.2 nF - 100 W)
http://onsemi.com
5
5 Page 
ADT7461
When Pin 6 is configured as THERM2, only the high
temperature limits are relevant. If Flag 6 and/or Flag 4 are
set, the THERM2 output goes low to indicate the
temperature measurements are outside the programmed
limits. Flag 5 and Flag 3 have no effect on THERM2. The
behavior of THERM2 is otherwise the same as THERM.
Table 10. STATUS REGISTER BIT ASSIGNMENTS
Bit Name
Function
7
BUSY
1 when ADC is converting
(Note 1)
6 LHIGH 1 when local high temperature limit is
(Note 2) tripped
5
LLOW
1 when local low temperature limit is
(Note 2) tripped
4 RHIGH 1 when remote high temperature limit is
(Note 2) tripped
3 RLOW 1 when remote low temperature limit is
(Note 2) tripped
2
OPEN
1 when remote sensor is an open circuit
(Note 2)
1 RTHRM 1 when remote THERM limit is tripped
0 LTHRM 1 when local THERM limit is tripped
1. Polling of the BUSY bit is not recommended.
2. These flags stay high until the status register is read or they are
reset by POR.
Offset Register
Offset errors may be introduced into the remote
temperature measurement by clock noise or by the thermal
diode being located away from the hot spot. To achieve the
specified accuracy on this channel, these offsets must be
removed.
The offset value is stored as a 10-bit, twos complement
value in Registers 0x11 (high byte) and 0x12 (low byte, left
justified). Only the upper 2 bits of Register 0x12 are used.
The MSB of Register 0x11 is the sign bit. The minimum
offset that can be programmed is −128°C, and the maximum
is +127.75°C. The value in the offset register is added to the
measured value of the remote temperature.
The offset register powers up with a default value of 0°C
and has no effect unless the user writes a different value to it.
Table 11. SAMPLE OFFSET REGISTER CODES
Offset Value
0x11
0x12
−128°C
−4°C
−1°C
−0.25°C
0°C
+0.25°C
+1°C
+4°C
+127.75°C
1000 0000
1111 1100
1111 1111
1111 1111
0000 0000
0000 0000
0000 0001
0000 0100
0111 1111
00 00 0000
00 00 0000
00 000000
11 00 0000
00 00 0000
01 00 0000
00 00 0000
00 00 0000
11 00 0000
One-Shot Register
The one-shot register is used to initiate a conversion and
comparison cycle when the ADT7461 is in standby mode,
after which the device returns to standby. Writing to the
one-shot register address (0x0F) causes the ADT7461 to
perform a conversion and comparison on both the internal
and the external temperature channels. This is not a data
register as such; the write operation to Address 0x0F causes
the one-shot conversion. The data written to this address is
irrelevant and is not stored.
Consecutive ALERT Register
The value written to this register determines how many
out-of-limit measurements must occur before an ALERT is
generated. The default value is that one out-of-limit
measurement generates an ALERT. The maximum value that
can be chosen is 4. The purpose of this register is to allow the
user to perform some filtering of the output. This is
particularly useful at the fastest three conversion rates, where
no averaging takes place. This register is at Address 0x22.
Table 12. CONSECUTIVE ALERT REGISTER CODES
Register Value
Number of Out-of-Limit
Measurements Required
NOTE:
yxxx 000x
1
yxxx 001x
2
yxxx 011x
3
yxxx 111x
4
x = don’t care bits, and y = SMBus timeout bit.
Default = 0. See SMBus section for more information.
http://onsemi.com
11
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| PDF Descargar | [ Datasheet ADT7461.PDF ] | |
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