MIC281
Low-Cost IttyBitty™ Thermal Sensor
General Description
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.
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.
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 V
DD
. They will not clamp
the bus lines low even if the device is powered down.
Superior performance, low power, and small size make the
MIC281 an excellent choice for cost-sensitive thermal
management applications.
Datasheets and support documentation are available on
Micrel’s website at:
www.micrel.com.
Features
Remote temperature measurement using embedded
thermal diodes or commodity transistors
Accurate remote sensing: ±3°C max., 0°C to 100°C
Excellent noise rejection
I C and SMBus 2.0-compatible serial interface
SMBus timeout to prevent bus lockup
Voltage tolerant I/Os
Low power shutdown mode
Failsafe response to diode faults
3.0V to 3.6V power supply range
Available in IttyBitty SOT23-6 package
2
Applications
Desktop, server, and notebook computers
Set-top boxes
Game consoles
Appliances
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
April 23, 2014
Revision 2.0
Micrel, Inc.
MIC281
Ordering Information
Part Number
MIC281-0YM6
MIC281-1YM6
MIC281-2YM6
MIC281-3YM6
MIC281-4YM6
MIC281-5YM6
MIC281-6YM6
MIC281-7YM6
Note:
1. Underbar (_) may not be to scale.
Marking
TB00
TB01
TB02
TB03
TB04
TB05
TB06
TB07
(1)
Slave Address
1001 000x
b
1001 001x
b
1001 010x
b
1001 011x
b
1001 100x
b
1001 101x
b
1001 110x
b
1001 111x
b
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
Pin Configuration
SOT23-6 (M6)
Top View
Pin Description
Pin Number
1
2
3
4
5
6
Pin Name
VDD
GND
T1
CLK
DATA
NC
Pin Function
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.
Digital input/output: Open-drain. Serial data input/output.
No connection: Must be left unconnected.
April 23, 2014
2
Revision 2.0
Micrel, Inc.
MIC281
Absolute Maximum Ratings
(2)
Power Supply Voltage (V
DD
)........................................ +3.8V
Voltage on T1 ....................................... –0.3V to V
DD
+ 0.3V
Voltage on CLK, DATA ..................................... –0.3V to 6V
Current into Any Pin .................................................. ±10mA
Power Dissipation, T
A
= +125°C .............................. 109mW
Storage Temperature (Ts)......................... –65°C to +150°C
(4)
ESD Ratings
Human Body Model ..................................................... 1.5kV
Machine Model ............................................................. 200V
Soldering (SOT23-6 package)
+5
Vapor Phase (60s) ........................................... 220°C /
-0
°C
+5
Infrared (15s) .................................................... 235°C /
-0
°C
Operating Ratings
(3)
Power Supply Voltage (V
DD
) ........................ +3.0V to +3.6V
Ambient Temperature Range (T
A
) ............ –55°C to +125°C
Package Thermal Resistance
SOT23-6 (
JA
) .................................................. 230°C/W
Electrical Characteristics
(5)
V
DD
= 3.3V; T
A
= 25°C, unless noted.
Bold
values indicate T
MIN
≤ T
A
≤ T
MAX
, unless noted .
Symbol
Parameter
Condition
Min.
Typ.
Max.
Units
(3)
Power Supply
T1 open; CLK = DATA = High;
Normal mode
I
DD
Supply Current
Shutdown mode; T1 open;
Note 7
CLK = 100kHz
Shutdown mode; T1 open;
CLK = DATA = High
t
POR
V
POR
V
HYST
Power-on Reset Time,
Note 7
Power-on Reset Voltage
Power-on Reset Hysteresis
Voltage,
Note 7
0°C ≤ T
D
≤ 100°C, 0°C < T
A
< 85°C;
3.15V < V
DD
< 3.45V
–40°C ≤ T
D
≤ 125°C, 0°C < T
A
< 85°C;
3.15V < V
DD
< 3.45V
V
DD
> V
POR
All registers reset to default values;
A/D conversions initiated
0.23
9
6
200
2.65
300
2.95
0.4
mA
µA
µA
µs
V
mV
Temperature-to-Digital Converter Characteristics
±1
±2
200
±3
±5
240
°C
°C
ms
Accuracy,
Notes 7, 8, 9
t
CONV
Conversion Time
Note 7
Remote Temperature Input, T1
I
F
Current into External Diode,
Note 7
T1 forced to 1.0V, high level
Low level
7
192
12
400
µA
µA
April 23, 2014
3
Revision 2.0
Micrel, Inc.
MIC281
Electrical Characteristics
(5)
(Continued)
V
DD
= 3.3V; T
A
= 25°C, unless noted.
Bold
values indicate T
MIN
≤ T
A
≤ T
MAX
, unless noted .
Symbol
Parameter
Condition
Min.
Typ.
Max.
Units
(3)
Serial Data I/O Pin, DATA
V
OL
V
IL
V
IH
C
IN
I
LEAK
Low Output Voltage,
Note 6
Low Input Voltage
High Input Voltage
Input Capacitance
Input Current
3V ≤ V
DD
≤ 3.6V
3V ≤ V
DD
≤ 3.6V
Note 7
2.1
10
±1
I
OL
= 3mA
I
OL
= 6mA
3V ≤ V
DD
≤ 3.6V
3V ≤ V
DD
≤ 3.6V
Note 7
2.1
10
±1
0.3
0.5
0.8
5.5
V
V
V
V
pF
µA
Serial Clock Input, CLK
V
IL
V
IH
C
IN
I
LEAK
Low Input Voltage
High Input Voltage
Input Capacitance
Input Current
0.8
5.5
V
V
pF
µA
Serial Interface Timing
t
1
t
2
t
3
t
4
t
5
t
TO
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 T
A
= 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. T
D
is the temperature of the remote diode junction. Testing is performed using a single unit of one of the transistors listed in Table 4.
CLK (clock) Period
Data In Setup Time to CLK High
Data Out Stable after CLK Low
Data Low Setup Time to CLK
Low
Data High Hold Time after CLK
High
Bus Timeout
Start Condition
Stop Condition
2.5
100
300
100
100
25
30
35
µs
ns
ns
ns
ns
ms
April 23, 2014
4
Revision 2.0
Micrel, Inc.
MIC281
Timing Diagram
Serial Interface Timing
April 23, 2014
5
Revision 2.0
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