MIC281
Micrel
MIC281
Low-Cost IttyBitty™ Thermal Sensor IttyBitty®
REV 11/04
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 com-
patible 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 man-
agement applications.
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
2
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
• IttyBitty™ SOT23-6 Package
Applications
•
•
•
•
Desktop, server and notebook computers
Set-top boxes
Game consoles
Appliances
Typical Application
3.3V
10k
pull-ups
5
TO
SERIAL BUS
HOST
4
MIC281
DATA
CLK
NC
VDD
T1
GND
1
3
2
0.1µF
2000pF
CPU DIODE
MIC281 Typical Application
IttyBitty is a registered trademark of Micrel, Inc.
*All 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
November 2004
1
MIC281
MIC281
Micrel
Part Number
Slave Address
Marking
TB00
TB01
TB02
TB03
TB05
TB05
TB06
TB07
1001 000x
b
1001 001x
b
1001 010x
b
1001 100x
b
1001 101x
b
1001 110x
b
1001 111x
b
1001 011x
b
-55°C to +125°C
-55°C to +125°C
-55°C to +125°C
-55°C to +125°C
-55°C to +125°C
-55°C to +125°C
-55°C to +125°C
-55°C to +125°C
SOT23-6
SOT23-6
SOT23-6
SOT23-6
SOT23-6
SOT23-6
SOT23-6
SOT23-6
Ambient Temp. Range
Package
Ordering Information
Standard
Marking
Pb-FREE
MIC281-0YM6*
MIC281-1YM6*
MIC281-2YM6*
MIC281-3YM6*
MIC281-4YM6
MIC281-5YM6*
MIC281-6YM6*
MIC281-7YM6*
MIC281-0BM6* TB00
MIC281-1BM6* TB01
MIC281-2BM6* TB02
MIC281-3BM6* TB03
MIC281-4BM6
TB04
MIC281-5BM6* TB05
MIC281-6BM6* TB06
MIC281-7BM6* TB07
* Contact Micrel regarding availability
Pin Configuration
VDD 1
GND 2
T1 3
6 NC
5 DATA
4 CLK
SOT23-6
Pin Description
Pin
1
2
3
4
5
6
Pin Name
VDD
GND
T1
CLK
DATA
NC
Pin Description
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 I/O: Open-drain. Serial data input/output.
No Connection: Must be left unconnected.
MIC281
2
November 2004
MIC281
Micrel
Absolute Maximum Ratings
(Note 1)
Power Supply Voltage, V
DD .....................................................
3.8V
Voltage on T1 ........................................ –0.3V to V
DD
+0.3V
Voltage on CLK, DATA....................................–0.3V to 6.0V
Current Into Any Pin ................................................. ±10mA
Power Dissipation, T
A
= 125°C ................................ 109mW
Junction Temperature ................................................ 150°C
Storage Temperature ................................ –65°C to +150°C
ESD Ratings,
Note 7
Human Body Model ................................................ 1.5kV
Machine Model ........................................................ 200V
Soldering (SOT23-6 Package)
Vapor Phase (60s) ......................................... 220
+5
/
–0
°C
Infrared (15s) ................................................. 235
+5
/
–0
°C
Operating Ratings
(Note 2)
Power Supply Voltage, V
DD
......................... +3.0V to +3.6V
Ambient Temperature Range (T
A
) .............. –40°C to +85°C
Package Thermal Resistance (θ
JA
)
SOT-23-6 ........................................................... 230°C/W
Electrical Characteristics
For typical values, T
A
=25°C, V
DD
=3.3V unless otherwise noted.
Bold
values are for T
MIN
≤ T
A
≤ T
MAX
unless otherwise noted.
Note 2
Symbol
Parameter
Condition
Min
Typ
Max
0.4
Power Supply
I
DD
Supply Current
T1 open; CLK=DATA=High; Normal Mode
Shutdown mode; T1 open; CLK = 100kHz;
Note 5
Shutdown Mode; T1 open; CLK=DATA=High
t
POR
Power-on reset time,
Note 5
Power-on reset voltage
Power-on reset hysteresis voltage
Note 5
Accuracy,
Notes 3, 5, 6
0°C ≤ T
D
≤ 100°C; 0°C ≤ T
A
≤ 85°C;
3.15V ≤ V
DD
≤ 3.45V
V
POR
V
HYST
V
DD
> V
POR
All registers reset to default values; A/D
conversions initiated
0.23
9
6
200
2.65
300
2.95
mA
µA
µA
µs
V
mV
Units
Temperature-to-Digital Converter Characteristics
±1
±2
200
192
7
12
0.3
0.5
0.8
2.1
10
±1
5.5
±3
±5
240
400
°C
°C
ms
µA
µA
V
V
V
V
pF
µA
t
CONV
I
F
Conversion time,
Note 5
Current into External Diode
Note 5
Low Output Voltage,
Note 4
Low Input Voltage
High Input Voltage
Input Capacitance,
Note 5
Input Current
–40°C ≤ T
D
≤ 125°C; 0°C ≤ T
A
≤ 85°C;
3.15V ≤ V
DD
≤ 3.45V
Remote Temperature Input, T1
T1 forced to 1.0V, high level
Low level
I
OL
= 3mA
Serial Data I/O Pin, DATA
V
OL
V
IL
I
OL
= 6mA
V
IH
3.0V ≤ V
DD
≤ 5.5V
3.0V ≤ V
DD
≤ 5.5V
C
IN
I
LEAK
November 2004
3
MIC281
MIC281
Symbol
V
IL
Parameter
Low Input Voltage
High Input Voltage
Input Capacitance,
Note 5
Input current
CLK (clock) period
Data in Setup Time to CLK High
Data Out Stable After CLK Low
DATA Low Setup Time to CLK Low
Bus timeout
Start Condition
DATA High Hold Time After CLK High Stop Condition
2.5
100
300
100
100
25
30
35
Condition
3.0V ≤ V
DD
≤ 3.6V
3.0V ≤ V
DD
≤ 3.6V
Min
Typ
Max
0.8
2.1
10
±1
5.5
Serial Clock Input, CLK
Micrel
Units
V
V
pF
µA
µs
ns
ns
ns
ns
ms
V
IH
C
IN
I
LEAK
t
1
t
2
t
3
t
4
t
5
t
TO
Serial Interface Timing
Note 1.
The device is not guaranteed to function outside its operating range.
Note 2.
Final test on outgoing product is performed at T
A
= 25°C.
Note 3.
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 5.
Note 4.
Current into the DATA pin will result in self-heating of the device. Sink current should be minimized for best accuracy.
Note 5.
Guaranteed by design over the operating temperature range. Not 100% production tested.
Note 6.
Accuracy specifications do not include quantization noise which may be up to ± 0.5LSB.
Note 7.
Devices are ESD sensitive. Observe appropriate handling precautions.
Timing Diagram
t
1
SCL
SDA
DATA INPUT
SDA
DATA OUTPUT
t
4
t
2
t
3
t
5
Serial Interface Timing
MIC281
4
November 2004
MIC281
Micrel
Typical Characteristics
V
DD
= 3.3V; T
A
= 25°C, unless otherwise noted.
2
1.5
MEASUREMENT ERROR (°C)
SUPPLY CURRENT (µA)
1
0.5
0
-0.5
-1
-1.5
-2
100
0
20
40
60
80
REMOTE DIODE TEMPERATURE (°C)
R emote T emperature
Meas urement E rror
400
350
S upply C urrent vs .
T emperature for V
DD
= 3.3V
20
Quies c ent C urrent vs .
C loc k F requenc y in
S hutdown Mode
T 1 open
DAT A = HIG H
QUIESCENT CURRENT (µA)
300
250
200
150
100
50
0
-55 -35 -15 5 25 45 65 85 105 125
TEMPERATURE (°C)
15
10
5
0
0
100
200
300
FREQUENCY (kHz)
400
Quies c ent C urrent vs .
T emperature in S hutdown Mode
30
Quies c ent C urrent vs .
S upply V oltage in S hutdown Mode
10
T 1 open
9
C LK = DAT A = HIG H
8
7
6
5
4
3
2
1
0
2.6
2.8
3.0
3.2
3.4
SUPPLY VOLTAGE (V)
8
6
MEASUREMENT ERROR (°C)
4
2
0
-2
-4
-6
Meas urement E rror vs .
P C B L eakage to +3.3V /G ND
T 1 open
C LK = DAT A = HIG H
25
QUIESCENT CURRENT (µA)
20
15
10
5
0
-55 -35 -15 5 25 45 65 85 105 125
TEMPERATURE (°C)
QUIESCENT CURRENT (µA)
G ND
3.3V
3.6
-8
1x10
6
1x10
7
1x10
8
RESISTANCE FROM T1 (Ω)
1x10
9
R emote T emperature E rror vs .
C apac itanc e on T 1
5
0
-5
-10
-15
-20
E rror Due to Nois e on the B as e
of R emote T rans is tor
7
6
REMOTE TEMP. ERROR (°C)
5
4
3
2
1
0
1
E rror Due to Nois e on the
C ollec tor of R emote T rans is tor
1.6
1.4
TEMPERTURE ERROR (°C)
1.2
1.0
0.8
0.6
0.4
0.2
0
1
25mV
P -P
100mV
P -P
TEMPERATURE ERROR (°C)
10mV
P -P
3mV
P -P
10 100 1k 10k 100k 1M 10M100M
FREQUENCY (Hz)
50mV
P -P
25mV
P -P
10 100 1k 10k 100k 1M 10M100M
FREQUENCY (Hz)
0
1000
2000
3000
4000
5000
6000
7000
CAPACITANCE (pF)
November 2004
8000
5
MIC281
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