MIC281-0YM6-TR [MICROCHIP]
SPECIALTY ANALOG CIRCUIT, PDSO6;
| 型号： | MIC281-0YM6-TR |
| 厂家： | 
MICROCHIP |
| 描述： | SPECIALTY ANALOG CIRCUIT, PDSO6 光电二极管 |
| 文件： | 总14页 (文件大小：645K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
MIC281
Low-Cost IttyBitty™ Thermal Sensor
General Description
Features
The MIC281 is a digital thermal sensor capable of
measuring the temperature of a remote PN junction. It is
optimized for applications favoring low cost and small size.
The remote junction may be an inexpensive commodity
transistor, e.g., 2N3906, or an embedded thermal diode
such as found in Intel Pentium® II/III/IV CPUs, AMD
Athlon® CPUs, and Xilinx Virtex® FPGAs.
Remote temperature measurement using embedded
thermal diodes or commodity transistors
Accurate remote sensing: ±3°C max., 0°C to 100°C
Excellent noise rejection
I2C and SMBus 2.0-compatible serial interface
SMBus timeout to prevent bus lockup
Voltage tolerant I/Os
The MIC281 is 100% software and hardware backward
compatible with the MIC280 and features the same
industry-leading noise performance and small size. The
advanced integrating A/D converter and analog front-end
reduce errors due to noise for maximum accuracy and
minimum guardbanding.
Low power shutdown mode
Failsafe response to diode faults
3.0V to 3.6V power supply range
Available in IttyBitty SOT23-6 package
A 2-wire SMBus 2.0-compatible serial interface is provided
for host communication. The clock and data pins are 5V-
tolerant regardless of the value of VDD. They will not clamp
the bus lines low even if the device is powered down.
Applications
Desktop, server, and notebook computers
Set-top boxes
Game consoles
Superior performance, low power, and small size make the
MIC281 an excellent choice for cost-sensitive thermal
management applications.
Appliances
Datasheets and support documentation are available on
Micrel’s website at: www.micrel.com.
Typical Application
IttyBitty is a trademark of Micrel, Inc. All other trademarks are the property of their respective owners.
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
Revision 2.0
April 23, 2014
Micrel, Inc.
MIC281
Ordering Information
Part Number
Marking(1)
TB00
Slave Address
1001 000xb
1001 001xb
1001 010xb
1001 011xb
1001 100xb
1001 101xb
1001 110xb
1001 111xb
Ambient Temp. Range
–55° to +125°C
–55° to +125°C
–55° to +125°C
–55° to +125°C
–55° to +125°C
–55° to +125°C
–55° to +125°C
–55° to +125°C
Package
SOT23-6
SOT23-6
SOT23-6
SOT23-6
SOT23-6
SOT23-6
SOT23-6
SOT23-6
MIC281-0YM6
MIC281-1YM6
MIC281-2YM6
MIC281-3YM6
MIC281-4YM6
MIC281-5YM6
MIC281-6YM6
MIC281-7YM6
Note:
TB01
TB02
TB03
TB04
TB05
TB06
TB07
1. Underbar (_) may not be to scale.
Pin Configuration
SOT23-6 (M6)
Top View
Pin Description
Pin Number
Pin Name
VDD
GND
T1
Pin Function
1
2
3
4
5
6
Analog input: Power supply input to the IC.
Ground return for all IC functions.
Analog input: Connection to remote diode junction.
Digital input: Serial bit clock input.
CLK
DATA
NC
Digital input/output: Open-drain. Serial data input/output.
No connection: Must be left unconnected.
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MIC281
Absolute Maximum Ratings(2)
Operating Ratings(3)
Power Supply Voltage (VDD)........................................+3.8V
Voltage on T1....................................... –0.3V to VDD + 0.3V
Voltage on CLK, DATA ..................................... –0.3V to 6V
Current into Any Pin..................................................±10mA
Power Dissipation, TA = +125°C ..............................109mW
Storage Temperature (Ts).........................–65°C to +150°C
ESD Ratings(4)
Power Supply Voltage (VDD) ........................ +3.0V to +3.6V
Ambient Temperature Range (TA) ............–55°C to +125°C
Package Thermal Resistance
SOT23-6 (JA) ..................................................230°C/W
Human Body Model.....................................................1.5kV
Machine Model.............................................................200V
Soldering (SOT23-6 package)
Vapor Phase (60s) ........................................... 220°C+5/-0°C
Infrared (15s).................................................... 235°C+5/-0°C
Electrical Characteristics(5)
VDD = 3.3V; TA = 25°C, unless noted. Bold values indicate TMIN ≤ TA ≤ TMAX, unless noted(3).
Symbol
Parameter
Condition
Min.
Typ.
Max.
0.4
Units
Power Supply
T1 open; CLK = DATA = High;
Normal mode
0.23
9
mA
µA
Shutdown mode; T1 open; Note 7
CLK = 100kHz
IDD
Supply Current
Shutdown mode; T1 open;
CLK = DATA = High
6
µA
µs
V
tPOR
Power-on Reset Time, Note 7
Power-on Reset Voltage
VDD > VPOR
200
2.65
All registers reset to default values;
A/D conversions initiated
2.95
VPOR
Power-on Reset Hysteresis
Voltage, Note 7
VHYST
300
mV
Temperature-to-Digital Converter Characteristics
0°C ≤ TD ≤ 100°C, 0°C < TA < 85°C;
3.15V < VDD < 3.45V
±1
±2
±3
±5
°C
°C
ms
Accuracy, Notes 7, 8, 9
–40°C ≤ TD ≤ 125°C, 0°C < TA < 85°C;
3.15V < VDD < 3.45V
Conversion Time
Note 7
240
tCONV
200
Remote Temperature Input, T1
400
T1 forced to 1.0V, high level
Low level
192
12
µA
µA
Current into External Diode,
Note 7
IF
7
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MIC281
Electrical Characteristics(5) (Continued)
VDD = 3.3V; TA = 25°C, unless noted. Bold values indicate TMIN ≤ TA ≤ TMAX, unless noted(3).
Symbol
Parameter
Condition
Min.
Typ.
Max.
Units
Serial Data I/O Pin, DATA
IOL = 3mA
0.3
0.5
0.8
5.5
V
V
VOL
Low Output Voltage, Note 6
IOL = 6mA
VIL
Low Input Voltage
High Input Voltage
Input Capacitance
Input Current
3V ≤ VDD ≤ 3.6V
3V ≤ VDD ≤ 3.6V
Note 7
V
2.1
VIH
V
CIN
ILEAK
10
10
pF
µA
±1
Serial Clock Input, CLK
0.8
5.5
VIL
Low Input Voltage
3V ≤ VDD ≤ 3.6V
3V ≤ VDD ≤ 3.6V
Note 7
V
V
2.1
VIH
High Input Voltage
Input Capacitance
Input Current
CIN
ILEAK
pF
µA
±1
Serial Interface Timing
2.5
100
300
t1
t2
t3
CLK (clock) Period
µs
ns
ns
Data In Setup Time to CLK High
Data Out Stable after CLK Low
Data Low Setup Time to CLK
Low
100
t4
t5
Start Condition
Stop Condition
ns
Data High Hold Time after CLK
High
100
25
ns
35
tTO
Bus Timeout
30
ms
Notes:
2. Exceeding the absolute maximum ratings may damage the device.
3. The device is not guaranteed to function outside its operating ratings. Final test on outgoing product is performed at TA = 25°C.
4. Devices are ESD sensitive. Handling precautions are recommended. Human body model, 1.5kΩ in series with 100pF.
5. Specification for packaged product only.
6. Current into the DATA pin will result in self-heating of the device. Sink current should be minimized for best accuracy.
7. Guaranteed by design over the operating temperature range. Not 100% production tested.
8. Accuracy specification does not include quantization noise, which may be up to ±1/2 LSB.
9. TD is the temperature of the remote diode junction. Testing is performed using a single unit of one of the transistors listed in Table 4.
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MIC281
Timing Diagram
Serial Interface Timing
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MIC281
Typical Characteristics
VDD = 3.3V; TA = 25˚C, unless otherwise noted.
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MIC281
Functional Description
Serial Port Operation
The MIC281 uses standard SMBus Write_Byte and Read_Byte operations for communication with its host. The SMBus
Write_Byte operation involves sending the device’s slave address (with the R/W bit low to signal a write operation),
followed by a command byte and the data byte. The SMBus Read_Byte operation is a composite write and read
operation: the host first sends the device’s slave address followed by the command byte, as in a write operation. A new
start bit must then be sent to the MIC281, followed by a repeat of the slave address with the R/W bit (LSB) set to the high
(read) state. The data to be read from the part may then be clocked out. These protocols are shown in Figures 1 and 2.
The Command byte is eight bits (one byte) wide. This byte carries the address of the MIC281 register to be operated
upon. The command byte values corresponding to the various MIC281 registers are shown in Table 1. Other command
byte values are reserved, and should not be used.
Figure 1. Write_Byte Protocol
Figure 2. Read_Byte Protocol
Table 1. MIC281 Register Addresses
Target Register
Description
Command Byte Value
Power-on Default
Label
TEMP
Read
01h
Write
N/A
03h
Remote temperature result
Configuration
00h (0°C)
80h
CONFIG
MFG_ID
DEV_ID
03h
Manufacturer identification
Device and revision identification
FEh
FFh
N/A
N/A
2Ah
(10)
0xh
Note:
10. The lower nibble contains the die revision level (e.g., Rev. 0 = 00h).
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MIC281
Slave Address
The MIC281 will only respond to its own unique slave address. A match between the MIC281’s address and the address
specified in the serial bit stream must be made to initiate communication. The MIC281’s slave address is fixed at the time
of manufacture. Eight different slave addresses are available as determined by the part number. See Table 2 and the
Ordering Information table.
Table 2. MIC281 Slave Addresses
Part Number
MIC281-0YM6
MIC281-1YM6
MIC281-2YM6
MIC281-3YM6
MIC281-4YM6
MIC281-5YM6
MIC281-6YM6
MIC281-7YM6
Slave Address
1001 000b = 90h
1001 001b = 92h
1001 010b = 94h
1001 011b = 96h
1001 100b = 98h
1001 101b = 9Ah
1001 110b = 9Ch
1001 111b = 9Eh
Temperature Data Format
The least-significant bit of the temperature register represents one degree Centigrade. The values are in a two’s
complement format, wherein the most significant bit (D7) represents the sign: zero for positive temperatures and one for
negative temperatures. Table 3 shows examples of the data format used by the MIC281 for temperatures.
Table 3. Digital Temperature Format
Temperature
+127°C
+125°C
+25°C
Binary
Hex
7F
7D
19
0111 1111
0111 1101
0001 1001
0000 0001
0000 0000
1111 1111
1110 0111
1000 0011
1000 0000
+1°C
01
0°C
00
–1°C
FF
E7
83
–25°C
–125°C
–128°C
80
Diode Faults
The MIC281 is designed to respond in a failsafe manner to diode faults. If an internal or external fault occurs in the
temperature sensing circuitry, such as T1 being open or shorted to VDD or GND, the temperature result will be reported
as the maximum full-scale value of +127°C. Note that diode faults will not be detected until the first A/D conversion cycle
is completed following power-up or exiting shutdown mode.
Shutdown Mode
Setting the shutdown bit in the configuration register will cause the MIC281 to cease operation. The A/D converter will
stop and power consumption will drop to the ISHDN level. No registers will be affected by entering shutdown mode. The last
temperature reading will persist in the TEMP register.
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MIC281
Detailed Register Descriptions
Remote Temperature Result (TEMP) 8-bits, Read Only
Local Temperature Result Register
D[7]
read-only
D[6]
read-only
D[5]
read-only
D[4]
read-only
D[3]
read-only
D[2]
read-only
D[1]
read-only
D[0]
read-only
Temperature data from ADC.
Bit
Function
Operation
D[7:0]
Measured temperature data for the remote zone.
Read only
Power-up default value: 0000 0000b = 00h = (0°C)(11)
Read command byte: 0000 0001b = 01h
Each LSB represents one degree centigrade. The values are in a twos complement binary format such that 0°C is
reported as 0000 0000b. See the Temperature Data Format section for more details.
Note:
11. TEMP will contain measured temperature data after the completion of one conversion.
Configuration Register (CONFIG) 8-bits, Read/Write
Configuration Register
D[7]
D[6]
D[5]
D[4]
D[3]
D[2]
D[1]
D[0]
reserved
reserved
reserved
reserved
reserved
reserved
reserved
write-only
Reserved
Shutdown
(SHDN)
Reserved
Bit
D7
Function
Reserved
Shutdown bit
Reserved
Operation(12)
Always writes as zero; reads undefined
0 = normal operation; 1 = shutdown
Always writes as zero; reads undefined
D6
D[5:0]
Note:
12. Any write to CONFIG will result in any A/D conversion in progress being aborted and the result discarded. The A/D will begin a new conversion
sequence once the write operation is complete.
Power-up default value: x0xx xxxxb (not in shutdown mode)
Command byte: 0000 0011b = 03h
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MIC281
Manufacturer ID Register (MFG_ID) 8-bits, Read only
Manufacturer ID Register
D[7]
read-only
D[6]
read-only
D[5]
read-only
D[4]
read-only
D[3]
read-only
D[2]
read-only
D[1]
read-only
D[0]
read-only
0
0
1
0
1
0
1
0
Bit
Function
Operation
D[7:0]
Identifies Micrel, Inc. as the manufacturer of the device
Read only. Always returns 2Ah
Power-up default value: 0010 1010b = 2Ah
Read command byte: 1111 1110b = FEh
Die Revision Register (DIE_REV) 8-bits, Read only
Die Revision Register
D[7]
D[6]
D[5]
D[4]
D[3]
D[2]
D[1]
D[0]
read-only
read-only
read-only
read-only
read-only
read-only
read-only
read-only
MIC281 die revision number
Bit
Function
Operation
D[7:0]
Identifies the device revision number.
Read only
Power-up default value: [device revision number]h
Read command byte: 1111 1111b = FFh
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MIC281
In most applications, the DATA pin will have a duty cycle
of substantially below 25% in the low state. These
considerations, combined with more typical device and
application parameters, give a better system-level view of
device self-heating. This is illustrated by the next equation.
In any application, the best approach is to verify
performance against calculation in the final application
environment. This is especially true when dealing with
systems for which some temperature data may be poorly
defined or unobtainable except by empirical means.
Application Information
Remote Diode Section
Most small-signal PNP transistors with characteristics
similar to the JEDEC 2N3906 will perform well as remote
temperature sensors. Table 4 lists several examples of
such parts that Micrel has tested for use with the MIC281.
Other transistors equivalent to these should also work well.
Table 4. Transistors suitable for use as remote diodes
Part
PD = [(IDD × VDD)+(IOL(DATA) × VOL(DATA))]
Vendor
Package
Number
PD = [(0.23mA× 3.3V)+(25% × 1.5mA× 0.15V)] PD =
0.815mW
Fairchild Semiconductor
On Semiconductor
MMBT3906
MMBT3906L
SMBT3906
KST3906-TF
SOT-23
SOT-23
SOT-23
SOT-23
Rθ(J-A) of SOT23-6 package is 230°C/W, therefore the
typical self-heating is:
Philips Semiconductor
Samsung Semiconductor
0.815mW × 230°C/W = 0.188°C
Series Resistance
The operation of the MIC281 depends upon sensing the
VCB-E of a diode-connected PNP transistor (diode) at two
different current levels. For remote temperature
measurements, this is done using an external diode
connected between T1 and ground. Because this
technique relies upon measuring the relatively small
voltage difference resulting from two levels of current
through the external diode, any resistance in series with
the external diode will cause an error in the temperature
reading from the MIC281. A good rule of thumb is that for
each ohm in series with the external transistor, there will
Minimizing Errors
Self-Heating
One concern when using a part with the temperature
accuracy and resolution of the MIC281 is to avoid errors
induced by self-heating (VDD × IDD) + (VOL × IOL). In order to
understand what level of error this might represent, and
how to reduce that error, the dissipation in the MIC281
must be calculated and its effects reduced to a
temperature offset. The worst-case operating condition for
the MIC281 is when VDD = 3.6V.The maximum power
dissipated in the part is given in the following equation:
be
a
0.9°C error in the MIC281’s temperature
measurement. It is not difficult to keep the series
resistance well below an ohm (typically <0.1Ω), so this will
rarely be an issue.
PD = [(IDD × VDD)+(IOL(DATA) × VOL(DATA))]
PD = [(0.4mA× 3.6V)+(6mA× 0.5V)]
PD = 4.44mW
Filter Capacitor Selection
It is usually desirable to employ a filter capacitor between
the T1 and GND pins of the MIC281. The use of this
capacitor is recommended in environments with a lot of
high frequency noise (such as digital switching noise), or if
long traces or wires are used to connect to the remote
diode. The recommended total capacitance from the T1
pin to GND is 2200pF. If the remote diode is to be at a
distance of more than six-to-twelve inches from the
MIC281, using twisted pair wiring or shielded microphone
cable for the connections to the diode can significantly
reduce noise pickup. If using a long run of shielded cable,
remember to subtract the cable’s conductor-to-shield
capacitance from the 2200pF total capacitance.
Rθ(J-A) of SOT23-6 package is 230°C/W, therefore the
theoretical maximum self-heating is:
4.44mW × 230°C/W = 1.02°C
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MIC281
4. Due to the small currents involved in the measurement
of the remote diode’s ∆VBE, it is important to
adequately clean the PC board after soldering to
prevent current leakage. This is most likely to show up
as an issue in situations where water-soluble soldering
fluxes are used.
Layout Considerations
The following guidelines should be kept in mind when
designing and laying out circuits using the MIC281.
1. Place the MIC281 as close to the remote diode as
possible, while taking care to avoid severe noise
sources such as high frequency power transformers,
CRTs, memory and data busses, and the like.
5. In general, wider traces for the ground and T1 lines will
help reduce susceptibility to radiated noise (wider
traces are less inductive). Use trace widths and
spacing of 10mm wherever possible and provide a
ground plane under the MIC281 and under the
connections from the MIC281 to the remote diode.
This will help guard against stray noise pickup.
2. Because any conductance from the various voltages
on the PC board and the T1 line can induce serious
errors, it is good practice to guard the remote diode's
emitter trace with a pair of ground traces. These
ground traces should be returned to the MIC281's own
ground pin. They should not be grounded at any other
part of their run. However, it is highly desirable to use
these guard traces to carry the diode's own ground
return back to the ground pin of the MIC281, thereby
providing a Kelvin connection for the base of the
diode. See Figure 3.
6. Always place a good quality power supply bypass
capacitor directly adjacent to, or underneath, the
MIC281. This should be a 0.1µF ceramic capacitor.
Surface-mount parts provide the best bypassing
because of their low inductance.
3. When using the MIC281 to sense the temperature of a
processor or other device which has an integral
thermal diode, e.g., Intel's Pentium III, connect the
emitter and base of the remote sensor to the MIC281
using the guard traces and Kelvin return shown in
Figure 3. The collector of the remote diode is typically
inaccessible to the user on these devices.
Figure 3. Guard Traces/Kelvin Ground Returns
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MIC281
Package Information(13)
6-Pin SOT23 (M6)
Note:
13. Package information is correct as of the publication date. For updates and most current information, go to www.micrel.com.
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MIC281
MICREL, INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA
TEL +1 (408) 944-0800 FAX +1 (408) 474-1000 WEB http://www.micrel.com
Micrel makes no representations or warranties with respect to the accuracy or completeness of the information furnished in this data sheet. This
information is not intended as a warranty and Micrel does not assume responsibility for its use. Micrel reserves the right to change circuitry,
specifications and descriptions at any time without notice. No license, whether express, implied, arising by estoppel or otherwise, to any intellectual
property rights is granted by this document. Except as provided in Micrel’s terms and conditions of sale for such products, Micrel assumes no liability
whatsoever, and Micrel disclaims any express or implied warranty relating to the sale and/or use of Micrel products including liability or warranties
relating to fitness for a particular purpose, merchantability, or infringement of any patent, copyright or other intellectual property right.
Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product
can reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant
into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A
Purchaser’s use or sale of Micrel Products for use in life support appliances, devices or systems is a Purchaser’s own risk and Purchaser agrees to fully
indemnify Micrel for any damages resulting from such use or sale.
© 2014 Micrel, Incorporated.
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