ADT7485AARMZ-R [ONSEMI]
Temperature Sensor and Voltage Monitor with Simple Serial Transport; 温度传感器和电压监视器用简单串行传输型号: | ADT7485AARMZ-R |
厂家: | ONSEMI |
描述: | Temperature Sensor and Voltage Monitor with Simple Serial Transport |
文件: | 总12页 (文件大小:330K) |
中文: | 中文翻译 | 下载: | 下载PDF数据表文档文件 |
ADT7485A
Temperature Sensor and
Voltage Monitor with
Simple Serial Transport
The ADT7485A is a digital temperature sensor and voltage monitor
for use in PC applications with Simple Serial Transport (SST)
interface. It can monitor its own temperature as well as the
temperature of a remote sensor diode. It can also monitor four external
voltage channels and its own supply voltage. The ADT7485A is
controlled by a single SST bidirectional data line. This device is a
fixed−address SST client where the target address is chosen by the
state of the address pin, ADD.
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MARKING
DIAGRAM
10
T21
RYWG
G
Features
1
MSOP−10
CASE 846AC
1
• 1 On−Chip Temperature Sensor
• 1 Remote Temperature Sensor
• Monitors Up to 5.0 Voltages
• SST Interface
T21 = Device Code
R
Y
W
G
= Assembly Location
= Year
= Work Week
= Pb−Free Package
• This is a Pb−Free Device
(Note: Microdot may be in either location)
Applications
• Personal Computers
• Portable Personal Devices
• Industrial Sensor Nets
PIN ASSIGNMENT
V
1
2
3
4
5
10 SST
CC
GND
D1+
D1–
12 V
9
8
7
6
ADD
2.5 V
ADT7485A
V
CCP
5.0 V
(Top View)
ORDERING INFORMATION
See detailed ordering and shipping information in the package
dimensions section on page 11 of this data sheet.
ADT7485A
ON−CHIP
TEMPERATURE
SENSOR
OFFSET REGISTERS
TEMPERATURE
VALUE REGISTERS
V
CC
12 V
INPUT
ATTENUATORS
AND
SST INTERFACE
SST
5.0 V
A/D
CONVERTER
V
CCP
ANALOG
MULTIPLEXER
2.5 V
D1+
D1−
VOLTAGE
VALUE REGISTERS
ADDRESS
SELECTION
ADD
GND
Figure 1. Functional Block Diagram
© Semiconductor Components Industries, LLC, 2010
1
Publication Order Number:
April, 2010 − Rev. 3
ADT7485A/D
ADT7485A
ABSOLUTE MAXIMUM RATINGS
Parameter
Rating
Unit
Supply Voltage (V
)
4.0
V
V
CC
Voltage on 12 V Pin
Voltage on 5.0 V Pin
16
7.0
V
Voltage on 2.5 V and V
Pins
3.6
V
CCP
Voltage on Any Other Pin (Including SST Pin)
Input Current at Any Pin
−0.3 to +3.6
5.0
V
mA
mA
°C
°C
°C
Package Input Current
20
Maximum Junction Temperature (T Max)
150
J
Storage Temperature Range
−65 to +150
Lead Temperature, Soldering
IR Peak Re−flow Temperature
Lead Temperature (10 sec)
260
300
ESD Rating
1500
V
Stresses exceeding Maximum Ratings may damage the device. Maximum Ratings are stress ratings only. Functional operation above the
Recommended Operating Conditions is not implied. Extended exposure to stresses above the Recommended Operating Conditions may affect
device reliability.
NOTE: This device is ESD sensitive. Use standard ESD precautions when handling.
THERMAL CHARACTERISTICS
Package Type
q
JA
q
JC
Unit
10−Lead MSOP
206
44
°C/W
NOTE: is specified for the worst−case conditions, that is, a device soldered in a circuit board for surface−mount packages.
q
JA
PIN ASSIGNMENT
Pin No.
Mnemonic
Type
Power supply
Ground
Description
1
2
V
CC
3.3 V 10%. V is also monitored through this pin.
CC
GND
D1+
Ground Pin.
3
Analog input
Analog input
Analog input
Analog input
Analog input
Analog input
Digital input
Digital input/output
Positive Connection to Remote 1 Temperature Sensor.
Negative Connection to Remote 1 Temperature Sensor.
12 V Supply Monitor.
4
D1−
5
12 V
5.0 V
6
5.0 V Supply Monitor.
7
V
CCP
Processor Core Voltage Monitor.
2.5 V Supply Monitor.
8
2.5 V
ADD
SST
9
SST Address Select.
10
SST Bidirectional Data Line.
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2
ADT7485A
ELECTRICAL CHARACTERISTICS T = T
to T
, V = V
to V , unless otherwise noted.
MAX
A
MIN
MAX
CC
MIN
Parameter
Test Conditions/Comments
Min
Typ
Max
3.6
Unit
Power Supply
Supply Voltage, V
3.0
3.3
2.8
3.8
V
V
CC
Undervoltage Lockout Threshold
Average Operating Supply Current, I
Continuous conversions
5.0
mA
DD
Temperature−to−Digital Converter
Local Sensor Accuracy
40°C ≤ T ≤ 70°C; V = 3.3 V 5%
+1.0
+1.0
1.75
4.0
°C
°C
A
CC
−40°C ≤ T ≤ +100°C
A
Remote Sensor Accuracy
−40°C ≤ T ≤ +125°C; T = 25°C; V = 3.3 V
1.0
1.75
D
A
CC
−40°C ≤ T ≤ +125°C; −40 ≤ T ≤ 70°C;
D
A
V
CC
= 3.3 V 5%
−40°C ≤ T ≤ +125°C; −40 ≤ T ≤ +100°C
4.0
D
A
Remote Sensor Source Current
Low level
Mid level
High level
12
80
204
mA
Resolution
0.016
1.5
°C
Series Resistance Cancellation
The ADT7485A cancels 1.5 kW in series with
the remote thermal diode
kW
Digital Input (ADD)
Input High Voltage, V
2.3
V
IH
Input Low Voltage, V
0.8
1.0
V
IL
Input High Current, I
V
V
= V
= 0
−1.0
mA
mA
pF
IH
IN
CC
Input Low Current, I
IL
IN
Pin Capacitance
5.0
0.1
Analog−to−Digital Converter (Including Multiplexer and Attenuators)
Total Unadjusted Error (TUE)
12 V and 5.0 V channels
For all other channels
2.0
1.5
%
Differential Non−linearity (DNL)
10 bits
1.0
LSB
%/V
ms
Power Supply Sensitivity
Conversion Time (Voltage Input)
(Note 1)
Averaging enabled
Averaging enabled
Averaging enabled
Averaging enabled
11
12
38
Conversion Time
(Local Temperature) (Note 1)
ms
ms
ms
kW
Conversion Time
(Remote Temperature) (Note 1)
Total Monitoring Cycle Time (Note 1)
Input Resistances
145
V
CCP
and 2.5V Channels
80
95
180
110
120
230
140
150
280
5.0 V Channel
12 V Channel
Digital I/O (SST Pin)
Input High Voltage , V
1.1
1.1
V
V
IH
Input Low Voltage, V
Hysteresis (Note 1)
0.4
1.9
IL
Between input switching levels
150
mV
V
Output High Voltage, V
I
= 6 mA (maximum)
OH
SOURCE
1. Guaranteed by design, not production tested.
2. Minimum and maximum bit times are relative to t
defined in the timing negotiation pulse.
BIT
3. Device is compatible with hold time specification as driven by SST originator.
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ADT7485A
ELECTRICAL CHARACTERISTICS T = T
to T
, V = V
to V , unless otherwise noted.
MAX
A
MIN
MAX
CC
MIN
Parameter
Test Conditions/Comments
Min
Typ
Max
Unit
Digital I/O (SST Pin)
High Impedance State Leakage, I
Device powered on SST bus;
= 1.1 V, V = 3.3 V
1.0
10
mA
mA
LEAK
LEAK
V
SST
CC
High Impedance State Leakage, I
Device non−powered on SST bus;
= 1.1 V, V = 0 V
V
SST
CC
Signal Noise Immunity, V
Noise glitches from 10 MHz to 100 MHz;
width up to 50 ns
300
mV
p−p
NOISE
SST Timing
Bitwise Period, t
0.495
0.6 x
500
ms
ms
BIT
High Level Time for Logic 1, t
(Note 2)
t
defined in speed negotiation
0.75 x
BIT
0.8 x
H1
BIT
t
t
t
BIT
BIT
High Level Time for Logic 0, t
(Note 2)
0.2 x
BIT
0.25 x
BIT
0.4 x
BIT
ms
ms
ms
ms
H0
t
t
t
Time to Assert SST High for Logic 1,
0.2 x
t
t
SU, HIGH
BIT
Hold Time, t
(Note 3)
See SST Specification Rev 1.0
0.5 x
HOLD
STOP
t
BIT−M
Stop Time, t
Device responding to a constant low level
driven by originator
1.25 x
2 x t
2 x t
BIT
BIT
t
BIT
Time to Respond After a Reset, t
0.4
ms
RESET
Response Time to Speed Negotiation
After Powerup
Time after powerup when device can participate
in speed negotiation
500
ms
1. Guaranteed by design, not production tested.
2. Minimum and maximum bit times are relative to t
defined in the timing negotiation pulse.
BIT
3. Device is compatible with hold time specification as driven by SST originator.
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ADT7485A
TYPICAL CHARACTERISTICS
1.55
1.50
1.45
1.40
1.35
1.30
1.25
1.20
3.56
3.55
3.54
3.53
3.52
3.51
3.50
3.49
3.48
3.47
3.46
3.45
DEV3
DEV2
750Ω (~2mA)
270Ω (~5.2mA)
120Ω (~10.6mA)
DEV1
95
2.6
2.8
3.0
3.2
3.4
3.6
–45
–25
–5
15
35
55
75
115
V
(V)
TEMPERATURE (5C)
CC
Figure 2. SST O/P Level vs. Supply Voltage
Figure 3. Supply Current vs. Temperature
7
6
5
4
1.55
1.50
1.45
1.40
1.35
1.30
1.25
1.20
750Ω (~2mA)
270Ω (~5.2mA)
3
2
HI SPEC (V = 3.0 V)
CC
MEAN (V = 3.3 V)
CC
1
120Ω (~10.6mA)
0
LO SPEC (V = 3.6 V)
CC
–1
–60 –40 –20
0
20
40
60
80
100 120 140
–50
0
50
100
150
TEMPERATURE (5C)
TEMPERATURE (5C)
Figure 4. Local Temperature Error
Figure 5. SST O/P Level vs. Temperature
3.9
3.7
3.5
3.3
3.1
2.9
7
6
5
4
3
2
DEV2
DEV3
DEV1
HI SPEC (V = 3.0 V)
CC
1
MEAN (V = 3.3 V)
CC
0
–1
–2
LO SPEC (V = 3.6 V)
CC
2.65
2.85
3.05
3.25
3.45
3.65
–60 –40 –20
0
20
40
60
80
100 120 140
V
(V)
TEMPERATURE (5C)
CC
Figure 6. Supply Current vs. Voltage
Figure 7. Remote Temperature Error
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ADT7485A
TYPICAL CHARACTERISTICS
15
10
5
30
DEV1_EXT1
DEV1_EXT2
DEV2_EXT1
DEV2_EXT2
DEV3_EXT1
DEV3_EXT2
D+ TO GND
25
20
0
100mV
60mV
–5
–10
–15
–20
–25
–30
–35
–40
15
10
5
DEV1_EXT1
DEV1_EXT2
DEV2_EXT1
DEV2_EXT2
DEV3_EXT1
DEV3_EXT2
D+ TO V
CC
40mV
1M
0
–5
10k
100k
10M
100M
1G
0
20
40
60
80
100
NOISE FREQUENCY (Hz)
RESISTANCE (MΩ)
Figure 8. Remote Temperature Error vs. PCB
Resistance
Figure 9. Temperature Error vs. Common−Mode
Noise Frequency
20
15
10
5
0
–10
–20
–30
EXT2
–40
–50
EXT1
125mV
0
–60
–70
–80
–90
50mV
−5
–10
10k
100k
1M
10M
100M
1G
0
10
20
30
40
50
POWER SUPPLY NOISE FREQUENCY (Hz)
CAPACITANCE (nF)
Figure 10. Local Temperature Error vs. Power
Supply Noise
Figure 11. Remote Temperature Error vs.
Capacitance Between D1+ and D1−
7
5
4
3
2
40mV
6
5
4
3
5
125mV
4
50mV
20mV
2
–1
1
–2
–3
10mV
0
10k
100k
1M
10M
100M
1G
10k
100k
1M
10M
100M
1G
NOISE FREQUENCY (Hz)
POWER SUPPLY NOISE FREQUENCY (Hz)
Figure 12. Temperature Error vs.
Differential−Mode Noise Frequency
Figure 13. Remote Temperature Error vs. Power
Supply Noise
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ADT7485A
Product Description
ADT7485A Client Address
The ADT7485A is a temperature− and voltage−monitoring
device. The ADT7485A can monitor the temperature of one
remote sensor diode, plus its own internal temperature. It can
also monitor up to five voltage channels, including its own
supply voltage.
The client address for the ADT7485A is selected using the
address pin. The address pin is connected to a float detection
circuit, which allows the ADT7485A to distinguish between
three input states: high, low (GND), and floating. The
address range for the fixed address, discoverable device is
0x48 to 0x4A.
SST Interface
Table 1. ADT7485A Selectable Addresses
SST is a one−wire serial bus and a communications
protocol between components intended for use in personal
computers, personal hand−held devices, or other industrial
sensor nets. The ADT7485A supports SST Rev 1.0.
SST is a licensable bus technology from Analog Devices,
Inc., and Intel Corporation. To inquire about obtaining a
copy of the Simple Serial Transport Specification or an SST
technology license, please email Analog Devices at
sst_licensing@analog.com or write to Analog Devices,
3550 North First Street, San Jose, CA 95134, Attention: SST
Licensing, M/S B7−24.
ADD
Low (GND)
Address Selected
0x48
0x49
0x4A
Float
High
Command Summary
Table 2 summarizes the commands supported by the
ADT7485A device when directed at the target address
selected by the fixed address pin. It contains the command
name, command code (CC), write data length (WL), read
data length (RL), and a brief description.
Table 2. Command Code Summary
Command
Code, CC
Write
Length, WL
Read
Length, RL
Command
Ping()
Description
0x00
0x00
0x01
0x00
0x10
0x11
0x12
0x13
0x14
0x10
0xe0
0xe0
0x00
0x01
0x01
0x01
0x01
0x01
0x01
0x01
0x01
0x01
0x02
0x01
0x00
0x02
0x02
0x04
0x02
0x02
0x02
0x02
0x02
0x10
0x00
0x01
Shows a nonzero FCS over the header if present.
Shows the temperature of the device’s internal thermal diode.
Shows the temperature of External Thermal Diode.
Returns a 4−byte block of data (GetIntTemp, GetExt1Temp).
Shows the voltage attached to 12 V input.
GetIntTemp()
GetExtTemp()
GetAllTemps()
GetVolt12V()
GetVolt5V()
Shows the voltage attached to 5.0 V input.
GetVoltVCC()
GetVolt2.5V()
GetVoltVCCP()
GetAllVolts()
SetExtOffset()
GetExtOffset()
Shows the voltage attached to V input.
CC
Shows the voltage attached to 2.5 V input.
Shows the voltage attached to V
input.
CCP
Shows all voltage measurement values.
Sets the offset used to correct errors in External Diode.
Shows the offset that the device is using to correct errors in
External Diode.
ResetDevice()
GetDIB()
0xf6
0x01
0x00
Functional reset. The ADT7485A also responds to this
command when directed to the Target Address 0x00.
0xf7
0xf7
0x01
0x01
0x08
0x10
Shows information used by SW to identify the device’s
capabilities. Can be in 8− or 16−byte format.
Command Code Details
ADT7485A Device Identifier Block
The GetDIB() command retrieves the device identifier
block (DIB), which provides information to identify the
capabilities of the ADT7485A. The data returned can be in
8− or 16−byte format. The full 16 bytes of DIB is detailed in
Table 3. The 8−byte format involves the first eight bytes
described in this table. Byte−sized data is returned in the
respective fields as it appears in Table 3. Word−sized data,
including vendor ID, device ID, and data values use little
endian format, that is, the LSB is returned first, followed by
the MSB.
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ADT7485A
GetAllTemps()
Table 3. 16−Byte DIB Details
The ADT7485A shows the local and remote temperatures
in a 4−byte block of data (internal temperature first,
followed by external temperature) in response to a
GetAllTemps() command.
Byte
Name
Value
Description
0
Device
Capabilities
0xc0
Fixed address
device
1
Version/Revision
0x10
Meets Version 1 of
SST specification
SetExtOffset()
This command sets the offset that the ADT7485A will use
to correct errors in the external diode. The offset is set in little
endian, 16−bit, twos complement format. The maximum
offset is 128°C with +0.25°C resolution.
2, 3
Vendor ID
00x11d
4
Contains company
ID number in little
endian format
4, 5
Device ID
0x7485
Contains device ID
number in little
endian format
GetExtOffset()
6
7
Device Interface
0x01
0x00
SST device
Reserved
This command causes the ADT7485A to show the offset
that it is using to correct errors in the external diode. The
offset value is returned in little endian format, that is, LSB
before MSB.
Function
Interface
8
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Revision ID
0x00
0x00
0x00
0x00
0x00
0x00
0x05
Reserved
9
Reserved
ADT7485A Response to Unsupported Commands
A full list of command codes supported by the
ADT7485A is given in Table 2. The offset registers
(Command Code 0xe0) are the only registers that the user
can write to. The other defined registers are read only.
Writing to Register Addresses 0x02, 0x09, and 0x15 to 0xdf
shows a valid FSC, but no action is taken by the ADT7485A.
The ADT7485A shows an invalid FSC if the user attempts
to write to the device between Command Codes 0xe2 to
0xee. These registers are reserved for the manufacturer’s use
only, and no data can be written to the device via these
addresses.
10
11
12
13
14
15
Reserved
Reserved
Reserved
Reserved
Contains revision ID
Client Device
Address
0x48 to
0x4a
Dependent on the
state of address pin
Ping()
The Ping() command verifies if a device is responding at
a particular address. The ADT7485A shows a valid
non−zero FCS in response to the Ping() command when
correctly addressed.
Voltage Measurement
The ADT7485A has four external voltage measurement
Table 4. Ping() Command
channels. It can also measure its own supply voltage, V
.
CC
Target Address
Write Length
Read Length
FCS
Pins 5 and 8 measure the supplies of the 12 V, 5.0 V,
processor core voltage (V ), and 2.5 V pins, respectively.
(Not necessary)
0x00
0x00
CCP
The V supply voltage measurement is carried out through
CC
ResetDevice()
the V pin (Pin 1). The 2.5 V pin can be used to monitor a
CC
This command resets the register map and conversion
controller. The reset command can be global or directed at
the client address of the ADT7485A.
chip−set supply voltage in a computer system.
Analog−to−Digital Converter
All analog inputs are multiplexed into the on−chip,
successive approximation, analog−to−digital converter
(ADC). This has a resolution of 10 bits. The basic input
range is 0 V to 2.25 V, but the inputs have built−in
attenuators to allow measurement of 2.5 V, 3.3 V, 5.0 V,
Table 5. ResetDevice() Command
Write
Length
Read
Length Command
Reset
Target Address
FCS
Device Address
0x01
0x00 0xf6
12 V, and the processor core voltage (V
external components.
) without any
CCP
GetIntTemp()
The ADT7485A shows the local temperature of the device
in response to the GetIntTemp() command. The data has a
little endian, 16−bit, twos complement format.
To allow for the tolerance of these supply voltages, the
ADC produces a specific output for each nominal input
voltage and therefore has adequate headroom to cope with
overvoltage. The full−scale voltage that can be recorded for
each channel is shown in Table 6.
GetExtTemp()
Prompted by the GetExtTemp() command, the ADT7485A
shows the temperature of the remote diode in little endian,
16−bit, twos complement format. The ADT7485A shows
0x8000 in response to this command if the external diode is
an open or short circuit.
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ADT7485A
Table 6. Maximum Reported Input Voltages
Table 8. Analog−to−Digital Output vs. VIN
Twos Complement
Voltage Channel
Full−Scale Voltage
Voltage
MSB
LSB
12 V
16 V
8.0 V
4.0 V
4.0 V
4.0 V
12
5.0
3.3
3.0
2.5
1.0
0
0011 0000
0001 0100
0000 1101
0000 1100
0000 1010
0000 0100
0000 0000
0000 0000
0000 0000
0011 0011
0000 0000
0000 0000
0000 0000
0000 0000
5.0 V
V
CC
2.5 V
V
CCP
Input Circuitry
The internal structure for the analog inputs is shown in
Figure 14. The input circuit consists of an input protection
diode and an attenuator, plus a capacitor that forms a
first−order, low−pass filter to provide input immunity to
high frequency noise.
Temperature Measurement
The ADT7485A has two dedicated temperature
measurement channels: one for measuring the temperature
of an on−chip band gap temperature sensor, and one for
measuring the temperature of a remote diode, usually
located in the CPU or GPU.
The ADT7485A monitors one local and one remote
temperature channel. Monitoring of each of the channels is
done in a round−robin sequence. The monitoring sequence
is in the order shown in Table 9.
120kW
12V
IN
20kW
47kW
71kW
94kW
30pF
30pF
30pF
30pF
35pF
93kW
68kW
45kW
5V
IN
3.3V
2.5V
IN
MUX
Table 9. Temperature Monitoring Sequence
Channel
Number
Conversion
Time (ms)
Measurement
IN
0
1
Local temperature
12
38
Remote 1 temperature
17.5kW
52.5kW
V
CCP
Temperature Measurement Method
A simple method for measuring temperature is to exploit
the negative temperature coefficient of a diode by measuring
Figure 14. Internal Structure of Analog Inputs
the base−emitter voltage (V ) of a transistor operated at
BE
constant current. Unfortunately, this technique requires
Voltage Measurement Command Codes
calibration to null the effect of the absolute value of V
which varies from device to device.
,
BE
The voltage measurement command codes are detailed in
Table 7. Each voltage measurement has a read length of two
bytes in little endian format (LSB followed by MSB). All
voltages can be read together by addressing Command Code
0x10 with a read length of 0x10. The data is retrieved in the
order listed in Table 7.
The technique used in the ADT7485A measures the
change in V when the device is operated at three different
BE
currents.
Figure 15 shows the input signal conditioning used to
measure the output of a remote temperature sensor. This
figure shows the remote sensor as a substrate transistor,
which is provided for temperature monitoring on some
microprocessors, but it could also be a discrete transistor. If
a discrete transistor is used, the collector is not grounded and
should be linked to the base. To prevent ground noise from
interfering with the measurement, the more negative
terminal of the sensor is not referenced to ground, but is
biased above ground by an internal diode at the D1− input.
If the sensor is operating in an extremely noisy environment,
C1 can be added as a noise filter. Its value should not exceed
1000 pF.
Table 7. Voltage Measurement Command Code
Voltage Channel
Command Code
Returned Data
LSB, MSB
LSB, MSB
LSB, MSB
LSB, MSB
LSB, MSB
12 V
0x10
0x11
0x12
0x13
0x14
5.0 V
V
CC
2.5 V
V
CCP
Voltage Data Format
The returned voltage value is in twos complement, 16−bit,
binary format. The format is structured so that voltages in
the range of 32 V can be reported. In this way, the reported
value represents the number of 1/1024 V in the actual
reading, allowing a resolution of approximately 1 mV.
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9
ADT7485A
N1× I N2× I
V
Table 11. SST Temperature Data Format
DD
I
I
BIAS
Twos Complement
Temperature (5C)
REMOTE
SENSING
MSB
LSB
V
V
OUT+
TRANSISTOR
−125
−80
−40
−20
−5
1110 0000
1110 1100
1111 0110
1111 1011
1111 1110
1111 1111
0000 0000
0000 0000
0000 0001
0000 0100
0000 1010
0001 0100
0001 1111
1100 0000
0000 0000
0000 0000
0011 1110
1100 0000
1100 0000
0000 0000
0100 0000
0100 0000
1100 0010
0000 0000
0000 0000
0100 0000
D1+
D1–
C1*
TO
ADC
BIAS
DIODE
LOW−PASS FILTER
OUT–
fC = 65kHz
*CAPACITOR C1 IS OPTIONAL.
IT SHOULD ONLY BE USED
IN NOISY ENVIRONMENTS.
−1
0
Figure 15. Signal Conditioning for Remote Diode
Temperature Sensors
+1
+5
To measure DV , the operating current through the
BE
+20
+40
+80
+125
sensor is switched between three related currents. Figure 15
shows N1 x I and N2 x I as different multiples of the
current I. The currents through the temperature diode are
switched between I and N1 x I, giving DV , and then
BE1
between I and N2 x I, giving DV . The temperature can
BE2
Using Discrete Transistors
then be calculated using the two DV measurements. This
BE
If a discrete transistor is used, the collector is not grounded
and should be linked to the base. If a PNP transistor is used,
the base is connected to the D− input and the emitter is
connected to the D+ input. If an NPN transistor is used, the
emitter is connected to the D− input and the base is
connected to the D+ input.
method can also cancel the effect of series resistance on the
temperature measurement. The resulting DV waveforms
BE
are passed through a 65 kHz low−pass filter to remove noise
and then through a chopper−stabilized amplifier to amplify
and rectify the waveform, producing a dc voltage
proportional to DV . The ADC digitizes this voltage, and
BE
Figure 16 shows how to connect the ADT7485A to an NPN
or PNP transistor for temperature measurement. To prevent
ground noise from interfering with the measurement, the
more negative terminal of the sensor is not referenced to
ground, but is biased above ground by an internal diode at the
D1− input.
a temperature measurement is produced. To reduce the
effects of noise, digital filtering is performed by averaging
the results of 16 measurement cycles for low conversion
rates. Signal conditioning and measurement of the internal
temperature sensor is performed in the same manner.
Reading Temperature Measurements
2N3904
NPN
ADT7485A
ADT7485A
The temperature data returned is two bytes in little endian
format, that is, LSB before MSB. All temperatures can be
read together by using Command Code 0x00 with a read
length of 0x04. The command codes and returned data are
described in Table 10.
D1+
D1+
2N3906
PNP
D1–
D1–
Figure 16. Connections for NPN and PNP Transistors
The ADT7485A shows an external temperature value of
0x8000 if the external diode is an open or short circuit.
Table 10. Temperature Channel Command Codes
Temp
Command
Code
Returned Data
Layout Considerations
Channel
Digital boards can be electrically noisy environments.
Take the following precautions to protect the analog inputs
from noise, particularly when measuring the very small
voltages from a remote diode sensor:
Internal
External
All Temps
0x00
0x01
0x00
LSB, MSB
LSB, MSB
Internal LSB, Internal MSB;
External LSB, External MSB
• Place the ADT7485A as close as possible to the remote
sensing diode. Provided that the worst noise sources,
such as clock generators, data/address buses, and CRTs,
are avoided, this distance can be four to eight inches.
• Route the D1+ and D1− tracks close together in parallel
with grounded guard tracks on each side. Provide a
ground plane under the tracks if possible.
SST Temperature Sensor Data Format
The data for temperature is structured to allow values in
the range of 512°C to be reported. Thus, the temperature
sensor format uses a twos complement, 16−bit binary value
to represent values in this range. This format allows
temperatures to be represented with approximately a
0.016°C resolution.
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10
ADT7485A
cables. Connect the twisted pair cable to D+ and D−
• Use wide tracks to minimize inductance and reduce
noise pickup. A 5 mil track minimum width and
spacing is recommended.
and the shield to GND, close to the ADT7485A. Leave
the remote end of the shield unconnected to avoid
ground loops.
5mil
5mil
5mil
5mil
5mil
5mil
5mil
GND
Because the measurement technique uses switched
current sources, excessive cable and/or filter capacitance
can affect the measurement. When using long cables, the
filter capacitor can be reduced or removed. Cable resistance
can also introduce errors. A 1 W series resistance introduces
about 0.5°C error.
D1+
D1–
GND
Temperature Offset
As CPUs run faster, it is more difficult to avoid high
frequency clocks when routing the D+ and D− tracks around
a system board. Even when the recommended layout
guidelines are followed, there may still be temperature
errors, attributed to noise being coupled onto the D+ and D−
lines. High frequency noise generally has the effect of
producing temperature measurements that are consistently
too high by a specific amount. The ADT7485A has
temperature offset command code of 0xe0 through which a
desired offset can be set. By doing a one−time calibration of
the system, the offset caused by system board noise can be
calculated and nulled by specifying it in the ADT7485A.
The offset is automatically added to every temperature
measurement. The maximum offset is 128°C with 0.25°C
resolution. The offset format is the same as the temperature
data format; 16−bit, twos complement notation, as shown in
Table 11. The offset should be programmed in little endian
format, that is, LSB before MSB. The offset value is also
returned in little endian format when read.
Figure 17. Arrangements of Signal Tracks
• Try to minimize the number of copper/solder joints,
which can cause thermocouple effects. Where
copper/solder joints are used, make sure that they are in
both the D1+ and D1− paths and are at the same
temperature.
• Thermocouple effects should not be a major problem
because 1°C corresponds to about 240 mV, and
thermocouple voltages are about 3 mV/°C of the
temperature difference. Unless there are two
thermocouples with a big temperature differential
between them, thermocouple voltages should be much
less than 200 mV.
• Place a 0.1 mF bypass capacitor close to the ADT7485A.
• If the distance to the remote sensor is more than eight
inches, the use of a twisted pair cable is recommended.
This works for distances of about 6 feet to 12 feet.
• For very long distances (up to 100 feet), use shielded
twisted pair cables, such as Belden #8451 microphone
ORDERING INFORMATION
†
Device Order Number*
ADT7485AARMZ−R
ADT7485AARMZ−R7
Package Type
Package Option
Shipping
3000 Tape & Reel
1000 Tape & Reel
10−Lead MSOP
RM−10
†For information on tape and reel specifications, including part orientation and tape sizes, please refer to our Tape and Reel Packaging
Specifications Brochure, BRD8011/D.
*These are Pb−Free packages.
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11
ADT7485A
PACKAGE DIMENSIONS
MSOP−10
CASE 486AC−01
ISSUE O
NOTES:
1. DIMENSIONING AND TOLERANCING PER
ANSI Y14.5M, 1982.
−A−
2. CONTROLLING DIMENSION: MILLIMETER.
3. DIMENSION “A” DOES NOT INCLUDE MOLD
FLASH, PROTRUSIONS OR GATE BURRS.
MOLD FLASH, PROTRUSIONS OR GATE
BURRS SHALL NOT EXCEED 0.15 (0.006)
PER SIDE.
4. DIMENSION “B” DOES NOT INCLUDE
INTERLEAD FLASH OR PROTRUSION.
INTERLEAD FLASH OR PROTRUSION
SHALL NOT EXCEED 0.25 (0.010) PER SIDE.
5. 846B−01 OBSOLETE. NEW STANDARD
846B−02
−B−
K
G
PIN 1 ID
D 8 PL
M
S
S
A
0.08 (0.003)
T B
MILLIMETERS
INCHES
DIM MIN
MAX
3.10
3.10
MIN
MAX
0.122
0.122
0.043
0.012
A
B
C
D
G
H
J
2.90
2.90
0.95
0.20
0.114
0.114
1.10 0.037
0.30 0.008
0.50 BSC
0.020 BSC
0.05
0.10
4.75
0.40
0.15 0.002
0.21 0.004
5.05 0.187
0.70 0.016
0.006
0.008
0.199
0.028
C
0.038 (0.0015)
K
L
−T−
SEATING
PLANE
L
H
J
SOLDERING FOOTPRINT*
1.04
0.041
0.32
0.0126
10X
10X
3.20
4.24
5.28
0.126
0.167 0.208
0.50
mm
inches
ǒ
Ǔ
8X0.0196
SCALE 8:1
*For additional information on our Pb−Free strategy and soldering
details, please download the ON Semiconductor Soldering and
Mounting Techniques Reference Manual, SOLDERRM/D.
SST is a licensable bus technology from Analog Devices, Inc., and Intel Corporation.
ON Semiconductor and
are registered trademarks of Semiconductor Components Industries, LLC (SCILLC). SCILLC reserves the right to make changes without further notice
to any products herein. SCILLC makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does SCILLC assume any liability
arising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including without limitation special, consequential or incidental damages.
“Typical” parameters which may be provided in SCILLC data sheets and/or specifications can and do vary in different applications and actual performance may vary over time. All
operating parameters, including “Typicals” must be validated for each customer application by customer’s technical experts. SCILLC does not convey any license under its patent rights
nor the rights of others. SCILLC products are not designed, intended, or authorized for use as components in systems intended for surgical implant into the body, or other applications
intended to support or sustain life, or for any other application in which the failure of the SCILLC product could create a situation where personal injury or death may occur. Should
Buyer purchase or use SCILLC products for any such unintended or unauthorized application, Buyer shall indemnify and hold SCILLC and its officers, employees, subsidiaries, affiliates,
and distributors harmless against all claims, costs, damages, and expenses, and reasonable attorney fees arising out of, directly or indirectly, any claim of personal injury or death
associated with such unintended or unauthorized use, even if such claim alleges that SCILLC was negligent regarding the design or manufacture of the part. SCILLC is an Equal
Opportunity/Affirmative Action Employer. This literature is subject to all applicable copyright laws and is not for resale in any manner.
PUBLICATION ORDERING INFORMATION
LITERATURE FULFILLMENT:
N. American Technical Support: 800−282−9855 Toll Free
USA/Canada
Europe, Middle East and Africa Technical Support:
Phone: 421 33 790 2910
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Phone: 81−3−5773−3850
ON Semiconductor Website: www.onsemi.com
Order Literature: http://www.onsemi.com/orderlit
Literature Distribution Center for ON Semiconductor
P.O. Box 5163, Denver, Colorado 80217 USA
Phone: 303−675−2175 or 800−344−3860 Toll Free USA/Canada
Fax: 303−675−2176 or 800−344−3867 Toll Free USA/Canada
Email: orderlit@onsemi.com
For additional information, please contact your local
Sales Representative
ADT7485A/D
相关型号:
ADT7486AARMZ-U5
Switch/Digital Output Temperature Sensor, DIGITAL TEMP SENSOR-SERIAL, 16BIT(s), 4Cel, SQUARE, SURFACE MOUNT, LEAD FREE, MO-187-AA, MSOP-10
ONSEMI
ADT7486ARMZ
Switch/Digital Output Temperature Sensor, DIGITAL TEMP SENSOR-SERIAL, 16BIT(s), 1Cel, SQUARE, SURFACE MOUNT, LEAD FREE, PLASTIC, MO-187-BA, MSOP-10
ADI
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