Micrel MIC284-3YMM Two-zone thermal supervisor Datasheet

MIC284
Micrel, Inc.
MIC284
Two-Zone Thermal Supervisor
General Description
The MIC284 is a versatile digital thermal supervisor capable of
measuring temperature using its own internal sensor and an
inexpensive external sensor or embedded silicon diode such
as those found in the Intel Pentium III™ CPU. A 2-wire serial
interface is provided to allow communication with either I2C™
or SMBus™ masters. Features include an open-drain overtemperature output with dedicated registers for implementing
fan control or over-temperature shutdown circuits.
Interrupt status and mask bits are provided for reduced software overhead. The open-drain interrupt output pin can be
used as either an overtemperature alarm or a thermostatic
control signal. A programmable address pin permits two
devices to share the bus. (Alternate base addresses available-contact Micrel.) Superior performance, low power and
small size makes the MIC284 an excellent choice for the most
demanding thermal management applications. The MIC284
is part of the SilentSense™ family of thermal supervisors.
Data sheets and support documentation can be found on
Micrel’s web site at www.micrel.com.
SilentSense™
Features
• Optimized for CPU Thermal Supervision in Computing
Applications
• Measures Local and Remote Temperature
• Sigma-Delta ADC for 8-Bit Temperature Results
• 2-Wire SMBus-compatible Interface
• Programmable Thermostat Settings for both Internal and
External Zones
• Open-Drain Interrupt Output Pin
• Open-Drain Over Temperature Output Pin for Fan Control or Hardware Shutdown
• Interrupt Mask and Status Bits
• Low Power Shutdown Mode
• Failsafe response to diode faults
• 2.7V to 5.5V Power Supply Range
• 8-Lead SOIC and MSOP Packages
Applications
•
•
•
•
•
Desktop, Server and Notebook Computers
Power Supplies
Test and Measurement Equipment
Wireless Systems
Networking/Datacom Hardware
Typical Application
3.3V
4  10k
pull-ups
0.1F
MIC284
DATA
CLK
FROM
SERIAL BUS
HOST
/INT
/CRIT
OVER-TEMP
SHUTDOWN
VDD
T1
A0
GND
2200pF
REMOTE
DIODE
2-Channel SMBus Temperature Measurement System
SMBus and Pentium III are trademarks of Intel Corporation.
I2C is a trademark of Philips Electronics, N.V.
SilentSense is a trademark of Micrel, Inc.
Micrel, Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
September 2005
1
MIC284
MIC284
Micrel, Inc
Ordering Information
Part Number
Base Address (*) Junction Temp. Range
Package
Availability
Standard
Pb-Free
MIC284-0BM
MIC284-0YM
100 100x
-55°C to +125°C
8-Lead SOIC
MIC284-1BM
MIC284-1YM
100 101x
-55°C to +125°C
8-Lead SOIC
Contact Factory
MIC284-2BM
MIC284-2YM
100 110x
-55°C to +125°C
8-Lead SOIC
Contact Factory
MIC284-3BM
MIC284-3YM
100 111x
-55°C to +125°C
8-Lead SOIC
Contact Factory
MIC284-0BMM
MIC284-0YMM
100 100x
-55°C to +125°C
8-Lead MSOP
MIC284-1BMM
MIC284-1YMM
100 101x
-55°C to +125°C
8-Lead MSOP
Contact Factory
MIC284-2BMM
MIC284-2YMM
100 110x
-55°C to +125°C
8-Lead MSOP
Contact Factory
MIC284-3BMM
MIC284-3YMM
100 111x
-55°C to +125°C
8-Lead MSOP
Contact Factory
* The least-significant bit of the slave address is determined by the state of the A0 pin.
Pin Configuration
DATA
1
8 VDD
CLK 2
7 A0
/INT 3
6 T1
GND 4
5 /CRIT
Pin Description
Pin Number
Pin Name
1
DATA
Digital I/O: Open-drain. Serial data input/output.
2
CLK
Digital Input: The host provides the serial bit clock on this input.
3
/INT
Digital Output: Open-drain. Interrupt or thermostat output.
4
GND
Ground: Power and signal return for all IC functions.
5
/CRIT
6
T1
Analog Input: Connection to remote temperature sensor (diode junction)
7
A0
Digital Input: Slave address selection input. See Table 1. MIC284 Slave
Address Settings.
8
VDD
MIC284
Pin Function
Digital Output: Open-Drain. Over-temperature indication
Analog Input: Power supply input to the IC.
2
September 2005
MIC284
Micrel, Inc.
Absolute Maximum Ratings (Note 1)
Operating Ratings (Note 2)
Power Supply Voltage, VDD .......................................... 6.0V
Voltage on Any Pin ................................ –0.3V to VDD+0.3V
Current Into Any Pin ................................................ ±10 mA
Power Dissipation, TA = +125°C ................................ 30mW
Junction Temperature .............................................. +150°C
Storage Temperature ................................ –65°C to +150°C
ESD Ratings (Note 3)
Human Body Model ...................................................TBD V
Machine Model ..........................................................TBD V
Soldering
Vapor Phase (60 sec.) .............................. +220°C +5⁄–0°C
Infrared (15 sec.) ...................................... +235°C +5⁄–0°C
Power Supply Voltage, VDD ......................... +2.7V to +5.5V
Ambient Temperature Range (TA) ............. -55°C to +125°C
Package Thermal Resistance (θJA)
SOP ................................................................. +152°C/W
MSOP .............................................................. +206°C/W
Electrical Characteristics
2.7V ≤ VDD ≤ 5.5; TA = +25°C, bold values indicate –55°C ≤ TA ≤ +125°C, Note 4; unless noted.
Symbol
Parameter
Condition
Supply Current
/INT, open, A0 = VDD or GND,
CLK = DATA = high, normal mode
Min
Typ
Max
Units
350
750
µA
Power Supply
IDD
tPOR
Power-On Reset Time, Note 7
VPOR
Power-On Reset Voltage
VHYST
Power-On Reset
Hysteresis Voltage
/INT, /CRIT open, A0 = VDD or GND
shutdown mode, CLK = 100kHz
3
/INT, /CRIT open, A0 = VDD or GND
shutdown mode, CLK = DATA = high
1
VDD > VPOR
all registers reset to default values,
A/D conversions initiated
2.0
µA
10
µA
200
µs
2.7
V
250
mV
Temperature-to-Digital Converter Characteristics
Accuracy—Local Temperature
Note 4, 9
3V ≤ VDD ≤ 3.6V
Accuracy—Remote Temperature
Note 4, 5, 9
tCONV0
tCONV1
3V ≤ VDD ≤ 3.6V, 0°C ≤ TA ≤ +85°C
0°C ≤ TA ≤ +100°C, /INT and /CRIT open,
3V ≤ VDD ≤ 3.6V
±1
±2
°C
–55°C ≤ TA ≤ +125°C, /INT and /CRIT open,
±2
±3
°C
0°C ≤ TD ≤ +100°C, /INT and /CRIT open,
3V ≤ VDD ≤ 3.6V, 0°C ≤ TA ≤ +85°C
±1
±3
°C
±2
±5
°C
50
80
ms
100
160
ms
224
400
µA
–55°C ≤ TD ≤ +125°C, /INT and /CRIT open,
Conversion Time, local zone
Note 7
Conversion Time, remote zone
Note 7
Remote Temperature Input (T1)
IF
Current to External Diode
Note 7
high level, T1 forced to 1.5V
7.5
low level
14
µA
Address Input (A0)
VIL
Low Input Voltage
CIN
Input Capacitance
VIH
High Input Voltage
ILEAK
Input Current
September 2005
2.7V ≤ VDD ≤ 5.5V
2.7V ≤ VDD ≤ 5.5V
0.6
2.0
V
10
±0.01
3
V
pF
±1
µA
MIC284
MIC284
Micrel, Inc
Symbol
Parameter
Condition
Min
Typ
Max
Units
0.4
V
0.8
V
0.3VDD
V
Serial Data I/O Pin (DATA)
VOL
Low Output Voltage
VIL
Low Input Voltage
CIN
Input Capacitance
Note 6
VIH
High Input Voltage
ILEAK
Input current
VIL
Low Input Voltage
IOL = 3mA
IOL = 6mA
2.7V ≤ VDD ≤ 5.5V
2.7V ≤ VDD ≤ 5.5V
0.7VDD
10
V
pF
±0.01
±1
µA
Serial Clock Input (CLK)
VIH
High Input Voltage
ILEAK
Input current
VOL
Low Output Voltage,
Note 6
tINT
Interrupt Propagation Delay,
Note 7, 8
tnINT
Interrupt Reset Propagation Delay,
Note 7
CIN
Input Capacitance
2.7V ≤ VDD ≤ 5.5V
2.7V ≤ VDD ≤ 5.5V
0.7VDD
0.3VDD
10
V
V
pF
±0.01
±1
µA
0.4
V
Status Output (/INT)
T_SET0
Default T_SET0 Value
T_HYST0
Default T_HYST0 Value
T_SET1
Default T_SET1 Value
T_HYST1
Default T_HYST1 Value
Over-Temperature Output (/CRIT)
VOL
Low Output Voltage,
Note 6
tCRIT
/CRIT Propagation Delay,
Note 7, 8
tnCRIT
/CRIT Reset Propagation Delay,
Note 7
CRIT1
Default CRIT1 Value
nCRIT1
Default nCRIT1 Value
Serial Interface Timing (Note 7)
IOL = 3mA
IOL = 6mA
from TEMP > T_SET or TEMPx < T_HYSTx
to INT < VOL, FQ = 00, RPULLUP = 10kΩ
from any register read to /INT > VOH
FQ = 00, RPULLUP = 10kΩ
tPOR after VDD > VPOR
tPOR after VDD > VPOR
0.8
V
tCONV+1
µs
1
µs
81
81
81
°C
tPOR after VDD > VPOR
76
76
76
°C
97
97
97
°C
tPOR after VDD > VPOR
92
92
92
°C
0.4
V
IOL = 3mA
IOL = 6mA
from TEMPx > T_SETx or TEMPx < T_HYSTx
to INT < VOL, FQ = 00, RPULLUP = 10kΩ
from TEMPx < nCRITx to /CRIT > VOH
FQ = 00, RPULLUP = 10kΩ
tPOR after VDD > VPOR
tPOR after VDD > VPOR
0.8
V
tCONV+1
µs
1
µs
97
97
97
°C
92
92
92
°C
t1
CLK (Clock) Period
2.5
t2
Data In Setup Time to CLK High
100
ns
t3
Data Out Stable After CLK Low
0
ns
t4
DATA Low Setup Time to CLK Low
start condition
100
ns
t5
DATA High Hold Time
After CLK High
stop condition
100
ns
Note 1.
Exceeding the absolute maximum rating may damage the device.
Note 2.
The device is not guaranteed to function outside its operating rating.
Note 3.
Devices are ESD sensitive. Handling precautions recommended.
Human body model: 1.5k in series with 100pF. Machine model: 200pF, no series resistance.
Note 4.
Final test on outgoing product is performed at TA = TBD°C.
Note 5.
Note 6.
Note 7.
Note 8.
Note 9.
MIC284
µs
TD is the temperature of the remote diode junction. Testing is performed using a single unit of one of the transistors listed in Table 6.
Current into this pin will result in self-heating of the MIC284. Sink current should be minimized for best accuracy.
Guaranteed by design over the operating temperature range. Not 100% production tested.
tCONV = tCONV0 + tCONV1. tCONV0 is the conversion time for the local zone; tCONV1 is the conversion time for the remote zone.`
Accuracy specification does not include quantization noise, which may be as great as ±1⁄ 2LSB (±0.5°C).
4
September 2005
MIC284
Micrel, Inc.
Timing Diagram
t1
SCL
t4
t2
SDA Data In
t5
t3
SDA Data Out
Serial Interface Timing
September 2005
5
MIC284
MIC284
Micrel, Inc
Functional Diagram
VDD
TEMPERATURE-TO-DIGITAL
CONVERTER
2:1
MUX
T1
Bandgap
Sensor
and
Reference
Digital Filter
and
Control
Logic
1-Bit
DAC
Result
Registers
A0
2-Wire
Serial Bus
Interface
DATA
Pointer
Register
CLK
T_SET & /CRIT
Setpoint
Registers
State
Machine
and
Digital
Comparator
Temperature
Hysteresis
Registers
Configuration
Register
/INT
Open-Drain
Output
/CRIT
MIC284
GND
Functional Description
Pin Descriptions
VDD: Power supply input. See electrical specifications.
GND: Ground return for all MIC284 functions.
CLK: Clock input to the MIC284 from the two-wire serial bus.
The clock signal is provided by the host, and is shared by all
devices on the bus.
DATA: Serial data I/O pin that connects to the two-wire serial
bus. DATA is bi-directional and has an open-drain output driver.
An external pull-up resistor or current source somewhere in
the system is necessary on this line. This line is shared by
all devices on the bus.
A0: This inputs sets the least significant bit of the MIC284’s
7-bit slave address. The six most-significant bits are fixed and
are determined by the part number ordered. (See ordering
information table above.) Each MIC284 will only respond to
its own unique slave address, allowing up to eight MIC284s to
share a single bus. A match between the MIC284’s address
and the address specified in the serial bit stream must be
made to initiate communication. A0 should be tied directly
to VDD or ground. See "Temperature Measurement and
Power On" for more information. A0 determines the slave
address as shown in Table 1:
MIC284
6
P a r t N u m be r
I n p u ts
MI C 2 8 4 S l a v e A d d r e s s
A0
B ina r y
Hex
0
100 1000b
48h
1
1 0 0 1 0 01 b
49h
MI C 2 8 4 -1
0
100 1010b
4Ah
1
1 0 0 1 0 11 b
4B h
MI C 2 8 4 -2
0
100 1100b
4C h
1
1 0 0 1 1 01 b
4D h
0
100 1110b
4E h
1
1 0 0 1 1 11 b
4F h
MI C 2 8 4 -0
MI C 2 8 4 -3
Table 1. MIC284 Slave Address Settings
/INT: Temperature events are indicated to external circuitry
via this output. Operation of the /INT output is controlled by
the MODE and IM bits in the MIC284’s configuration register.
See "Comparator and Interrupt Modes" below. This output
is open-drain and may be wire-OR’ed with other open-drain
signals. Most systems will require a pull-up resistor or current
source on this pin. If the IM bit in the configuration register
is set, it prevents the /INT output from sinking current. In
I2C and SMBus systems, the IM bit is therefore an interrupt
September 2005
MIC284
Micrel, Inc.
mask bit.
/CRIT: Over-temperature events are indicated to external
circuitry via this output. This output is open-drain and may
be wire-OR’ed with other open-drain signals. Most systems
will require a pull-up resistor or current source on this pin.
T1: This pin connects to an off-chip PN diode junction, for
monitoring the junction temperature at a remote location.
The remote diode may be an embedded thermal sensing junction in an integrated circuit so equipped (such
as Intel's Pentium III), or a discrete 2N3906-type bipolar
transistor with base and collector tied together.
Temperature Measurement
The temperature-to-digital converter is built around a switched
current source and an eight-bit analog-to-digital converter.
Each diode's temperature is calculated by measuring its forward voltage drop at two different current levels. An internal
multiplexer directs the MIC284's current source output to either
an internal or external diode junction. The MIC284 uses two’scomplement data to represent temperatures. If the MSB of a
temperature value is zero, the temperature is zero or positive.
If the MSB is one, the temperature is negative. More detail
on this is given in the "Temperature Data Format" section
below. A “temperature event” results if the value in either of
the temperature result registers (TEMPx) becomes greater
than the value in the corresponding temperature setpoint
register (T_SETx). Another temperature event occurs if and
when the measured temperature subsequently falls below
the temperature hysteresis setting in T_HYSTx.
During normal operation the MIC284 continuously performs
temperature-to-digital conversions, compares the results
against the setpoint registers, and updates the states of /INT,
/CRIT, and the status bits accordingly. The remote zone is
converted first, followed by the local zone. The states of /INT,
/CRIT, and the status bits are updated after each measurement is taken. The remote diode junction connected to T1
may be embedded in an integrated circuit such as a CPU,
ASIC, or graphics processor, or it may be a diode-connected
discrete transistor.
Diode Faults
The MIC284 is designed to respond in a failsafe manner to
hardware faults in the external sensing circuitry. If the con-
September 2005
nection to the external diode is lost or the sense line (T1) is
shorted to VDD or ground, the temperature data reported
by the A/D converter will be forced to its full-scale value
(+127°C). This will cause a temperature event to occur if
T_SET1 or CRIT1 are set to any value less than 127°C (7Fh
= 0111 1111b). An interrupt will be generated on /INT if so
enabled. The temperature reported for the external zone will
remain +127°C until the fault condition is cleared. This fault
detection mechanism requires that the MIC284 complete
the number of conversion cycles specified by Fault_Queue.
The part will therefore require one or more conversion cycles
following power-on or a transition from shutdown to normal
operation before reporting an external diode fault.
Serial Port Operation
The MIC284 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 a data byte. The SMBus
Read_Byte operation is similar, but 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 MIC284, 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.
The command byte is eight bits wide. This byte carries the
address of the MIC284 register to be operated upon, and is
stored in the part’s pointer register. The pointer register is
an internal write-only register. The command byte (pointer
register) values corresponding to the various MIC284 register
addresses are shown in Table 2. Command byte values other
than those explicitly shown are reserved, and should not be
used. Any command byte sent to the MIC284 will persist in
the pointer register indefinitely until it is overwritten by another
command byte. If the location latched in the pointer register
from the last operation is known to be correct (i.e., points
to the desired register), then the Receive_Byte procedure
may be used. To perform a Receive_Byte, the host sends
an address byte to select the MIC284, and then retrieves the
data byte. Figures 1 through 3 show the formats for these
procedures.
7
MIC284
MIC284
Micrel, Inc
Command_Byte
Target Registe r
Binary
He x
Labe l
Descriptio n
0000 0000b
00h
TEMP0
local temperatur e
0000 0001b
01h
CONFIG
configuration registe r
0000 0010b
02h
T_HYST0
local temperature hysteresi s
0000 0011b
03h
T_SET0
local temperature setpoin t
0001 0000b
10h
TEMP1
remote temperatur e
0001 0010b
12h
0001 0011b
13h
T_SET1
remote temperature setpoin t
0010 0010b
22h
nCRIT1
over-temperature hysteresis
0010 0011b
23h
CRIT1
over-temperature setpoin t
T_HYST1 remote temperature hysteresi s
Table 2. MIC284 Register Addresses
MIC284
8
September 2005
September 2005
CLK
DATA
Command Byte
Data Byte to MIC284
START
ACKNOWLEDGE
ACKNOWLEDGE
MIC284 Slave Address
STOP
Data Read From MIC284
NOT ACKNOWLEDGE
START
9
CLK
DATA
R/W = WRITE
ACKNOWLEDGE
R/W = READ
Data Byte from MIC284
R/W = READ
STOP
Slave-to-master response
ACKNOWLEDGE NOT ACKNOWLEDGE
Figure 3. RECEIVE_BYTE
Master-to-slave transmission
START
S 1 0 0 1 X X A0 1 A X X X X X X X X /A P
MIC284 Slave Address
STOP
Slave-to-master response
ACKNOWLEDGE NOT ACKNOWLEDGE
Master-to-slave transmission
START
Figure 2. READ_BYTE Protocol
ACKNOWLEDGE
S 1 0 0 1 X X A0 0 A 0 0 X X X X X X A S 1 0 0 1 X X A0 1 A X X X X X X X X /A P
Command Byte
Figure 1. WRITE_BYTE Protocol
R/W = WRITE
S 1 0 0 1 X X A0 0 A 0 0 X X X X X X A X X X X X X X X /A P
MIC284 Slave Address
CLK
DATA
MIC284 Slave Address
MIC284
Micrel, Inc.
MIC284
MIC284
10
START
ACKNOWLEDGE
Command Byte = 01h = CONFIG
MIC284 Slave Address
CONFIG Value*
First
Result
Ready
START
ACKNOWLEDGE
ACKNOWLEDGE
tn/INT
R/W = READ
ACKNOWLEDGE
Master-to-slave transmission
START
Figure 5. Responding to Interrupts
* Status bits in CONFIG are cleared to zero following this operation
R/W = WRITE
Slave-to-master response
NOT ACKNOWLEDGE
S 1 0 0 0 X X A0 0 A 0 0 0 0 0 0 0 1 A S 1 0 0 0 X X A0 1 A X X X X X X X X /A P
MIC284 Slave Address
Figure 4. A/D Converter Timing
Slave-to-master response
tCONV1
New Conversion
in Progress
New Conversion
Begins
NOT ACKNOWLEDGE
STOP
X X X X X X X X /A P
Last Byte of Transaction
A/D Converter
in Standby
ACKNOWLEDGE
…
Master-to-slave transmission
Conversion Interrupted
By MIC284 Acknowledge
Conversion
in Progress
R/W = DONT CARE
Temperature event occurs
INT
t/INT
First Byte of Transaction
S 1 0 0 1 X X X X A X X X X X X X X A
MIC284 Slave Address
STOP
MIC284
Micrel, Inc
September 2005
MIC284
Micrel, Inc.
Temperature Data Format
The LSB of each 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 MIC284
for temperatures.
A/D Converter Timing
Whenever the MIC284 is not in its low power shutdown mode,
the internal A/D converter (ADC) attempts to make continuous
conversions unless interrupted by a bus transaction accessing
the MIC284. When the part is accessed, the conversion in
progress will be halted, and the partial result discarded. When
the access to the MIC284 is complete, the ADC will begin a
new conversion cycle with results for the remote zone valid
tCONV1 after that, and for the local zone tCONV0 later. Figure
4 shows this behavior. The conversion time is twice as long
for external conversions as it is for internal conversions. This
allows the use of a filter capacitor on T1 without a loss of
accuracy due to the resulting longer settling times.
Upon powering-up, coming out of shutdown mode, or resuming operation following a serial bus transaction, the ADC will
begin acquiring temperature data starting with the external
zone (zone 1), followed by the internal zone (zone 0). If the
ADC is interrupted by a serial bus transaction, it will restart
the conversion that was interrupted and then continue in the
normal sequence. This sequence will repeat indefinitely until
the MIC284 is shut down, powered off, or is interrupted by a
serial bus transaction as described above.
Power-On
When power is initially applied, the MIC284’s internal registers
are set to their default states, and A0 is read to establish
the device’s slave address. The MIC284’s power-up default
state can be summarized as follows:
• Normal Mode operation (i.e., part is not in shutdown)
• /INT function is set to Comparator Mode
• Fault Queue depth = 1 (FQ=00)
• Interrupts are enabled (IM = 0)
• T_SET0 = 81°C; T_HYST0 = 76°C
• T_SET1 = 97°C; T_HYST1 = 92°C
• CRIT1 = 97°C; nCRIT1 = 92°C
• Initialized to recognize overtemperature faults
September 2005
Comparator and Interrupt Modes
Depending on the setting of the MODE bit in the configuration register, the /INT output will behave either as an interrupt
request signal or a thermostatic control signal. Thermostatic
operation is known as comparator mode. The /INT output
is asserted when the measured temperature, as reported
in either of the TEMPx registers, exceeds the threshold
programmed into the corresponding T_SETx register for the
number of conversions specified by Fault_Queue (described
below). In comparator mode, /INT will remain asserted and
the status bits will remain high unless and until the measured
temperature falls below the value in the T_HYSTx register
for Fault_Queue conversions. No action on the part of the
host is required for operation in comparator mode. Note that
entering shutdown mode will not affect the state of /INT when
the device is in comparator mode.
In interrupt mode, once a temperature event has caused a
status bit (Sx) to be set, and the /INT output to be asserted,
they will not be automatically de-asserted when the measured
temperature falls below T_HYSTx. They can only be de-asserted by reading any of the MIC284’s internal registers or
by putting the device into shutdown mode. If the most recent
temperature event was an overtemperature condition, Sx will
not be set again, and /INT cannot be reasserted, until the
device has detected that TEMPx < T_HYSTx. Similarly, if
the most recent temperature event was an undertemperature
condition, Sx will not be set again, and /INT cannot be reasserted, until the device has detected that TEMPx > T_SETx.
This keeps the internal logic of the MIC284 backward compatible with that of the LM75 and similar devices. In both modes,
the MIC284 will be responsive to over-temperature events at
power-up. See "Interrupt Generation", below.
Shutdown Mode
Setting the SHDN bit in the configuration register halts the
otherwise continuous conversions by the A/D converter. The
MIC284’s power consumption drops to 1µA typical in shutdown
mode. All registers may be read from or written to while in
shutdown mode. Serial bus activity will slightly increase the
part’s power consumption.
Entering shutdown mode will not affect the state of /INT
when the device is in comparator mode (MODE = 0). It will
retain its state until after the device exits shutdown mode and
resumes A/D conversions.
If the device is shut down while in interrupt mode (mode =
Temperature
Binar y
He x
+125° C
0111 1101b
7Dh
+25° C
0001 1001b
19h
+1.0° C
0000 0001b
01h
0° C
0000 000 0b
00h
– 1.0° C
1111 111 1b
FFh
– 25° C
1110 011 1b
E7h
– 40° C
1101 100 0b
D8h
– 55° C
1100 100 1b
C9h
Table 3. Digital Temperature Format
11
MIC284
MIC284
Micrel, Inc
1), the /INT pin will be unconditionally de-asserted and the
internal latches holding the interrupt status will be cleared.
Therefore, no interrupts will be generated while the MIC284
is in shutdown mode, and the interrupt status will not be retained. Regardless of the setting of the MODE bit, the state
of /CRIT and its corresponding status bit, CRIT1, does not
change when the MIC284 enters shutdown mode. They will
retain their states until after the device exits shutdown mode
and resumes A/D conversions. Since entering shutdown
mode stops A/D conversions, the MIC284 is incapable of
detecting or reporting temperature events of any kind while
in shutdown. Diode fault detection requires one or more A/D
conversion cycles to detect external sensor faults, therefore
diode faults will not be reported until the MIC284 exits shutdown (see "Diode Faults" above).
Fault Queues
Fault queues (programmable digital filters) are provided
in the MIC284 to prevent false tripping due to thermal or
electrical noise. The two bits in CONFIG[4:3] set the depth
of Fault_Queue. Fault_Queue then determines the number
of consecutive temperature events (TEMPx > T_SETx,
TEMPx < T_HYSTx, TEMP1 > CRIT1, or TEMP1 < nCRIT1)
which must occur in order for the condition to be considered
valid. There are separate fault queues for each zone and
for the over-temperature detect function. As an example,
assume the part is in comparator mode, and CONFIG[4:3] is
programmed with 10b. The measured temperature in zone
one would have to exceed T_SET1 for four consecutive A/D
conversions before /INT would be asserted or the S1 status bit
set. Similarly, TEMP1 would have to be less than T_HYST1
for four consecutive conversions before /INT would be reset.
Like any filter, the fault queue function also has the effect of
delaying the detection of temperature events. In this example,
it would take 4 x tCONV to detect a temperature event. The
depth of Fault_Queue vs. D[4:3] of the configuration register
is shown in Table 4:
CONFIG[4:3]
Fault_Queue Dept h
00
1 conversion *
01
2 conversion s
10
4 conversion s
11
6 conversion s
A read operation on any register will cause /INT to be deasserted. This is shown in Figure 5. The status bits will be
cleared once CONFIG has been read.
Since temperature-to-digital conversions continue while
/INT is asserted, the measured temperature could change
between the MIC284’s assertion of /INT or /CRIT and the
host’s response. It is good practice for the interrupt service
routine to read the value in TEMPx, to verify that the overtemperature or under-temperature condition still exists. In
addition, more than one temperature event may have occurred
simultaneously or in rapid succession between the assertion
of /INT and servicing of the MIC284 by the host. The interrupt service routine should allow for this eventuality. Keep
in mind that clearing the status bits and deasserting /INT
is not sufficient to allow further interrupts to occur. TEMPx
must become less than T_HYSTx if the last event was an
over-temperature condition, or greater than T_SETx if the
last event was an under-temperature condition, before /INT
can be asserted again.
Putting the device into shutdown mode will de-assert /INT and
clear the S0 and S1 status bits. This should not be done before
completing the appropriate interrupt service routine(s).
/CRIT Output
If and when the measured remote temperature exceeds
the value programmed into the CRIT1 register, the /CRIT
output will be asserted and CRIT1 in the configuration register will be set. If and when the measured temperature in
zone one subsequently falls below the value programmed
into nCRIT1, the /CRIT output will be de-asserted and the
CRIT1 bit in CONFIG will be cleared. This action cannot be
masked and is completely independent of the settings of the
mode bit and interrupt mask bit. The host may poll the state
of the /CRIT output at any time by reading the configuration
register. The state of the CRIT1 bit exactly follows the state
of the /CRIT output. The states of /CRIT and CRIT1 do not
change when the MIC284 enters shutdown mode. Entering
shutdown mode stops A/D conversions, however, so their
states will not change while the device is shut down.
Polling
The MIC284 may either be polled by the host, or request the
host’s attention via the /INT pin. In the case of polled operation, the host periodically reads the contents of CONFIG to
check the state of the status bits. The act of reading CONFIG clears the status bits. If more than one event that sets
a given status bit occurs before the host polls the MIC284,
only the fact that at least one such event has occurred will be
apparent to the host. For polled systems, the interrupt mask
bit should be set (IM = 1). This will disable interrupts from
the MIC284, and prevent the /INT pin from sinking current.
The host may poll the state of the /CRIT output at any time
by reading the configuration register. The state of the CRIT1
bit exactly follows the state of the /CRIT output.
* Default setting
Table 4. Fault_Queue Depth Settings
Interrupt Generation
Assuming the MIC284 is in interrupt mode and interrupts are
enabled, there are five different conditions that will cause
the MIC284 to set one of the status bits (S0, S1, or CRIT1)
in CONFIG and assert its /INT output and/or /CRIT output.
These conditions are listed in Table 5. When a temperature event occurs, the corresponding status bit will be set
in CONFIG. This action cannot be masked. However, a
temperature event will only generate an interrupt signal on
/INT if it is specifically enabled by the interrupt mask bit (IM
=0 in the configuration register). Following an interrupt, the
host should read the contents of the configuration register
to confirm that the MIC284 was the source of the interrupt.
MIC284
12
September 2005
MIC284
Micrel, Inc.
Event
Condition* *
MIC284 response *
high temperature, remote
TEMP1 > T_SET1
set S1 in CONFIG, assert /IN T
high temperature, local
TEMP0 > T_SET0
set S0 in CONFIG, assert /IN T
low temperature, remote
TEMP1 > T_HYST1
set S1 in CONFIG, assert /IN T
low temperature, local
TEMP0 > T_HYST0
set S0 in CONFIG, assert /IN T
over-temperatue, remote
TEMP1 > CRIT1
set CRIT in CONFIG, assert /CRIT
NOT over-temperature,
remote
TEMP1 > nCRIT1
clear CRIT in CONFIG, de-assert /CRIT
diode fault
T1 open or T1 shorted to VDD or GND
set CRIT and S1 in CONFIG, assert /INT
and /CRIT***
*
Assumes interrupts enabled
** Condition must be true for FAULT_QUEUE conversion to be recognized
*** Assumes the T_SET1 and CRIT1 are set yo any value less then +127° C = 7fh = 0111 1111b
Table 5. MIC284 Temperature Events
September 2005
13
MIC284
MIC284
Micrel, Inc
Register Set and Programmer’s Model
Internal Register Set
Name
Descriptio n
Command Byt e
Operatio n
Power-Up Defaul t
TEMP0
local temperatur e
00h
8-bit read only
0 0h (0° C)(1)
CONFIG
configuration registe r
0 1h
8-bit read/write
0 0h (2)
T_HYST0
local hysteresi s
02h
8-bit read/write
4 Ch (+76° C)
T_SET0
local temperature setpoin t
03h
8-bit read/write
5 1h (+81° C)
TEMP1
remote temperatur e
10h
8-bit read only
0 0h (0° C)(1)
T_HYST1
remote hysteresi s
8-bit read/write
5 Ch (+92° C)
T_SET1
remote temperature
setpoint
12h
13h
8-bit read/write
6 1h (+97° C)
nCRIT1
over-temperature
hysteresis
22h
8-bit read/write
5 Ch (+92° C)
CRIT1
over-temperature
temperature setpoint
23h
8-bit read/write
6 1h (+97° C)
(1)
TEMP0 and TEMP1 will contain measured temperature data after the completion of one conversion cycle.
(2)
After the first Fault_Queue conversions are complete, status bits will be set if TEMPx > T_SETx or TEMP1 > CRIT1.
Detailed Register Descriptions
Configuration Register
CONFIGURATION REGISTER (CONFIG)
8-Bit Read/Write
D[7]
D[6 ]
D[5 ]
read only
read only
read only
local
status
(S0)
remote
status
(S1)
/CRIT
status
(CRIT1)
Bits
D[4 ]
D[3 ]
D[2 ]
D[1 ]
D[0 ]
read/write
read/write
read/write
read/write
fault queue
depth
(FQ[1:0])
interrupt
mask
(IM)
CMP/INT
mode
(MODE)
Shutdown
(SHDN)
Functio n
Operatio n
S0
local interrupt status (read only )
1 = event occured, 0 = no event
S1
remote interrupt status (read only )
1 = event occured, 0 = no event
CRIT1 remote over-temperature status (read only )
1 = over-temperature, 0 = no event
FQ[1:0] Fault_Queue dept h
00 = 1 conversion, 01 = 2 conversions,
10 = 4 conversions, 11 = 6 conversions
IM
interrupt mas k
1 = disabled, 0 = interrupts enabled
MODE
comparator/interrupt
mode selection for /INT pin
1 = interrupt mode,
0 = comparator mode
SHDN
normal/shutdown
operating mode selection
1 = shutdown,
0 = normal
CONFIG Power-Up Value: 0000 0000b = 00h(*)
• not in shutdown mode
• comparator mode
• /INT = active low
• Fault_Queue depth = 1
• interrupts enabled.
• no temperature events pending
CONFIG Command Byte Value: 0000 0001b = 01h
* Following the first Fault_Queue conversions, one or more of the status bits may be set.
MIC284
14
September 2005
MIC284
Micrel, Inc.
Local Temperature Result Register
LOCAL TEMPERATURE SETPOINT (T_SET0)
8-Bit Read/Write
D[7]
D[6 ]
D[5 ]
MSB
bit 6
bit 5
D[4 ]
D[3 ]
D[2 ]
D[1 ]
D[0 ]
bit 4
bit 3
bit 2
bit 1
LSB
local temperature setpoint
Bits
D[7:0]
Functio n
Operatio n
local temperature setpoint *
read/write
TEMP0 Power-Up Value: 0000 0000b = 00h (0°C)†
TEMP0 Command Byte Value: 0000 0000b = 00h
* Each LSB represents one degree Centigrade. The values are
in a two's complement format such that 0°C is reported as
0000 0000b. See "Temperature Data Format" for more details.
†
TEMP0 will contain measured temperature data after the
completion of one conversion.
Local Temperature Hysteresis Register
LOCAL TEMPERATURE HYSTERESIS (T_HYST0)
8-Bit Read/Write
D[7]
D[6 ]
D[5 ]
D[4 ]
D[3 ]
D[2 ]
D[1 ]
D[0 ]
MSB
bit 6
bit 5
bit 4
bit 3
bit 2
bit 1
LSB
local temperature hysteresis setting
Bits
D[7:0]
Functio n
Operatio n
local temperature hysteresis setting *
T_HYST0 Power-Up Value: 0100 1100b = 4Ch (+76°C)
T_HYST0 Command Byte Value: 0000 0010b = 02h
read/write
* Each LSB represents one degree Centigrade. The values are
in a two's complement format such that 0°C is reported as
0000 0000b. See "Temperature Data Format" for more details.
Local Temperature Setpoint Register
LOCAL TEMPERATURE SETPOINT (T_SET0)
8-Bit Read/Write
D[7]
D[6 ]
D[5 ]
D[4 ]
D[3 ]
D[2 ]
D[1 ]
D[0 ]
MSB
bit 6
bit 5
bit 4
bit 3
bit 2
bit 1
LSB
local temperature setpoint
Bits
D[7:0]
Functio n
Operatio n
local temperature setpoint *
read/write
T_SET0 Power-Up Value: 0101 0001b = 51h (+81°C)
T_SET0 Command Byte Value: 0000 0011b = 03h
September 2005
* Each LSB represents one degree Centigrade. The values are
in a two's complement format such that 0°C is reported as
0000 0000b. See "Temperature Data Format" for more details.
15
MIC284
MIC284
Micrel, Inc
Remote Temperature Result Register
REMOTE TEMPERATURE RESULT (TEMP1)
8-Bit Read Only
D[7]
D[6 ]
D[5 ]
D[4 ]
D[3 ]
D[2 ]
D[1 ]
D[0 ]
MSB
bit 6
bit 5
bit 4
bit 3
bit 2
bit 1
LSB
remote temperature data from ADC*
Bits
D[7:0]
Functio n
Operatio n
measured temperature data for the remote
read only
zone*
TEMP1 Power-Up Value: 0000 0000b = 00h (0°C)†
TEMP1 Command Byte Value: 0001 0000b = 10h
* Each LSB represents one degree Centigrade. The values are
in a two's complement format such that 0°C is reported as
0000 0000b. See "Temperature Data Format" for more details.
†
TEMP1 will contain measured temperature data for the selected zone after the completion of one conversion.
Remote Temperature Hysteresis Register
REMOTE TEMPERATURE HYSTERESIS (T_HYST1)
8-Bit Read/Write
D[7]
D[6 ]
D[5 ]
D[4 ]
D[3 ]
D[2 ]
D[1 ]
D[0 ]
MSB
bit 6
bit 5
bit 4
bit 3
bit 2
bit 1
LSB
remote temperature hysteresis setting
Bits
D[7:0]
Functio n
Operatio n
remote temperature hysteresis setting *
T_HYST1 Power-Up Value: 0101 1100b = 5Ch (+92°C)
T_HYST1 Command Byte Value: 0001 0010b = 12h
read/write
* Each LSB represents one degree Centigrade. The values are
in a two's complement format such that 0°C is reported as
0000 0000b. See "Temperature Data Format" for more details.
Remote Temperature Setpoint Register
REMOTE TEMPERATURE SETPOINT (T_SET1)
8-Bit Read/Write
D[7]
D[6 ]
D[5 ]
D[4 ]
D[3 ]
D[2 ]
D[1 ]
D[0 ]
MSB
bit 6
bit 5
bit 4
bit 3
bit 2
bit 1
LSB
remote temperature setpoint
Bits
D[7:0]
Functio n
Operatio n
remote temperature setpoint *
read/write
T_SET1 Power-Up Value: 0110 0001b = 61h (+97°C)
T_SET1 Command Byte Value: 0001 0011b = 13h
MIC284
* Each LSB represents one degree Centigrade. The values are
in a two's complement format such that 0°C is reported as
0000 0000b. See "Temperature Data Format" for more details.
16
September 2005
MIC284
Micrel, Inc.
Remote Over-Temperature Hysteresis Register
REMOTE OVER-TEMPERATURE HYSTERESIS (nCRIT1)
8-Bit Read/Write
D[7]
D[6 ]
MSB
bit 6
D[5 ]
D[4 ]
D[3 ]
D[2 ]
D[1 ]
D[0 ]
bit 5
bit 4
bit 3
bit 2
bit 1
LSB
remote over-temperature hysteresis setting
Bits
D[7:0]
Functio n
Operatio n
remote temperature hysteresis setting *
nCRIT Power-Up Value: 0101 1100b = 5Ch (+92°C)
nCRIT1 Command Byte Value: 0010 0010b = 22h
read/write
* Each LSB represents one degree Centigrade. The values are
in a two's complement format such that 0°C is reported as
0000 0000b. See "Temperature Data Format" for more details.
Remote Over-Temperature Setpoint Register
REMOTE OVER-TEMPERATURE HYSTERESIS (nCRIT1)
8-Bit Read/Write
D[7]
D[6 ]
MSB
bit 6
D[5 ]
D[4 ]
D[3 ]
D[2 ]
D[1 ]
D[0 ]
bit 5
bit 4
bit 3
bit 2
bit 1
LSB
remote over-temperature hysteresis setting
Bits
D[7:0]
Functio n
Operatio n
remote temperature hysteresis setting *
CRIT1 Power-Up Value: 0110 0001b = 61h (+97°C)
CRIT1 Command Byte Value: 0010 0011b = 23h
September 2005
read/write
* Each LSB represents one degree Centigrade. The values are
in a two's complement format such that 0°C is reported as
0000 0000b. See "Temperature Data Format" for more details.
17
MIC284
MIC284
Micrel, Inc
Applications
of the thermal data (e.g., PC board thermal conductivity and
ambient temperature) may be poorly defined or unobtainable
except by empirical means.
Series Resistance
The operation of the MIC284 depends upon sensing the
ΔVCB-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.
Since 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 MIC284. A good rule of thumb is this: for each ohm
in series with the external transistor, there will be a 0.9°C error
in the MIC284’s temperature measurement. It isn’t difficult
to keep the series resistance well below an ohm (typically <
0.1Ω), so this will rarely be an issue.
Filter Capacitor Selection
Remote Diode Selection
Most small-signal PNP transistors with characteristics similar
to the JEDEC 2N3906 will perform well as remote temperature
sensors. Table 6 lists several examples of such parts that
Micrel has tested for use with the MIC284. Other transistors
equivalent to these should also work well.
Minimizing Errors
Self-Heating
One concern when using a part with the temperature accuracy
and resolution of the MIC284 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 MIC284 must be calculated
and its effects reduced to a temperature offset.
The worst-case operating condition for the MIC284 is when
VDD = 5.5V, MSOP-08 package. T he maximum power dissipated in the part is given in Equation 1 below.
In most applications, the /INT output will be low for at most
a few milliseconds before the host resets it back to the high
state, making its duty cycle low enough that its contribution to
self-heating of the MIC284 is negligible. Similarly, the DATA
pin will in all likelihood 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 in interrupt-mode
usage. This is illustrated by Equation 2.
If the part is to be used in comparator mode, calculations
similar to those shown in Equation 2 (accounting for the
expected value and duty cycle of IOL(/INT) and IOL(/CRIT))
will give a good estimate of the device’s self-heating error.
In any application, the best test is to verify performance
against calculation in the final application environment. This
is especially true when dealing with systems for which some
It is sometimes desirable to use a filter capacitor between the
T1 and GND pins of the MIC284. The use of this capacitor
is recommended in environments with a lot of high frequency
noise (such as digital switching noise), or if long wires are used
to attach to the remote diode. The maximum recommended
total capacitance from the T1 pin to GND is 2700pF. This
typically suggests the use of a 2200pF NP0 or C0G ceramic
capacitor with a 10% tolerance.
If the remote diode is to be at a distance of more than ≈ 6"
— 12" from the MIC284, using twisted pair wiring or shielded
microphone cable for the connections to the diode can significantly help reduce noise pickup. If using a long run of shielded
cable, remember to subtract the cable’s conductor-to-shield
capacitance from the 2700pF maximum total capacitance.
Layout Considerations
The following guidelines should be kept in mind when designing and laying out circuits using the MIC284:
PD = [(IDD x VDD) + (IOL(DATA)) x VOL(DATA) + (IOL(/INT) x VOL(/INT)) + (IOL(/CRIT) x VOL(/CRIT))]
PD = [(0.75mA x 5.5V) + (6mA x 0.8V) + (6mA x 0.8V) + (6mA x 0.8V)]
PD = 18.53mW
Rθ(j-a) of MSOP - 08 package is 206°C/W
Maximum ∆TJ relative to TA due to self heating is 18.53mW x 206°C/W = 3.82°C
Equation 1. Worst-case self-heating
[(0.35mA IDD(typ) x 3.3V) + (25% x 1.5mA IOL(DATA)) x 0.3V) + (1% x 1.5mA IOL(/INT) x 0.3V) + (25% x 1.5mA IOL(/CRIT) x 0.3V) = 1.38mW
∆TJ = (1.38mW x 206°C/W) = 0.29°C
Equation 2. Real-world self-heating example
Vendor
Part Number
Package
Fairchild
MMBT3906
SOT-23
On Semiconductor
MMBT3906L
SOT-23
Phillips Semiconductor
PMBT3906
SOT-23
Samsung
KST3906-TF
SOT-23
Table 6. Transistors Suitable for Remote Temperature Sensing Use
MIC284
18
September 2005
MIC284
Micrel, Inc.
most likely to show up as an issue in situations
where water-soluble soldering fluxes are used.
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 10 mils wherever
possible and provide a ground plane under
the MIC284 and under the connections from
the MIC284 to the remote diode. This will help
guard against stray noise pickup.
6. Always place a good quality power supply
bypass capacitor directly adjacent to, or underneath, the MIC284. This should be a 0.1µF
ceramic capacitor. Surface-mount parts provide
the best bypassing because of their low inductance.
7. When the MIC284 is being powered from particularly noisy power supplies, or from supplies
which may have sudden high-amplitude spikes
appearing on them, it can be helpful to add additional power supply filtering. This should be
implemented as a 100Ω resistor in series with
the part’s VDD pin, and a 4.7µF, 6.3V electrolytic
capacitor from VDD to GND. See Figure 7.
1. Place the MIC284 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.
2. Since 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 MIC284’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 MIC284,
thereby providing a Kelvin connection for the
base of the diode. See Figure 6.
3. When using the MIC284 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 MIC284 using the guard traces and
Kelvin return shown in Figure 6. The collector
of the remote diode is typically inaccessible to
the user on these devices. To allow for this, the
MIC284 has superb rejection of noise appearing
from collector to GND, as long as the base to
ground connection is relatively quiet.
4. Due to the small currents involved in the measurement of the remote diode’s ΔVBE, it is
important to adequately clean the PC board after
soldering to prevent current leakage. This is
MIC284
1 DATA
2 CLK
3 /INT
4 GND
VDD 8
A0 7
GUARD/RETURN
T1 6
REMOTE DIODE (T1)
GUARD/RETURN
/CRIT 5
Figure 6. Guard Traces/Kelvin Ground Returns
100
3.3V
10k pull-ups
FROM
SERIAL BUS
HOST
OVER-TEMP
SHUTDOWN
0.1F
MIC284
DATA
VDD
T1
CLK
/INT
A0
/CRIT
4.7F
2200pF
GND
Remote
Diode
Figure 7. VDD Decoupling for Very Noisy Supplies
September 2005
19
MIC284
MIC284
Micrel, Inc
Package Information
8-Lead SOIC (M)
8-Lead MSOP (MM)
MICREL INC.
TEL
2180 FORTUNE DRIVE
SAN JOSE, CA 95131
USA
+ 1 (408) 944-0800 FAX + 1 (408) 474-1000 WEB http://www.micrel.com
This information furnished by�
Micrel reserves the right to change circuitry and specifications at any time without notification to the customer.
Micrel Products are not�
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 Pr�
Micrel for any damages resulting from such use or sale.
© 2005 Micrel Incorporated
MIC284
20
September 2005
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