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MIC280
Micrel
MIC280
Precision IttyBittyTM Thermal Supervisor REV. 11/04
General Description
The MIC280 is a digital thermal supervisor capable of measuring its own internal temperature and that of a remote PN junction. 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* FPGA's. A 2-wire SMBus* 2.0 compatible serial interface is provided for host communication. Remote temperature is measured with 1C accuracy and 9-bit to 12-bit resolution (programmable). Independent high, low, and over-temperature thresholds are provided for each zone. The advanced integrating A/D converter and analog front-end reduce errors due to noise for maximum accuracy and minimum guardbanding. The interrupt output signals temperature events to the host, including data-ready and diode faults. Critical device settings can be locked to prevent changes and insure failsafe operation. The clock, data, and interrupt 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. Superior accuracy, failsafe operation, and small size make the MIC280 an excellent choice for the most demanding thermal management applications.
Features
* Measures local and remote temperature * Highly accurate remote sensing 1C max., 60C to 100C * Superior noise immunity for reduced temperature guardbands * 9-bit to 12-bit temperature resolution for remote zone * Fault queues to further reduce nuisance tripping * Programmable high, low, and over-temperature thresholds for each zone * SMBus 2 compatible serial interface including device timeout to prevent bus lockup * Voltage tolerant I/O's * Open-drain interrupt output pin - supports SMBus Alert Response Address protocol * Low power shutdown mode * Locking of critical functions to insure failsafe operation * Failsafe response to diode faults * Enables ACPI compliant thermal management * 3.0V to 3.6V power supply range * IttyBittyTM SOT23-6 package
Applications
* * * * * * * Desktop, server and notebook computers Printers and copiers Test and measurement equipment Thermal supervision of Xilinx Virtex FPGA's Wireless/RF systems Intelligent power supplies Datacom/telecom cards
Typical Application
3V to 3.6V 3x 10k
5 TO SERIAL BUS HOST 4 6
MIC280 DATA CLK /INT VDD T1 GND
1 3 2
0.1F ceramic
1800pF
2N3906/ CPU DIODE
MIC280 Typical Application
IttyBiity is a 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
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MIC280
MIC280
Micrel Part Number Slave Address Marking TA00 TA01 TA02 TA03 TA05 TA05 TA06 TA07 100 1000b 100 1001b 100 1010b 100 1011b 100 1100b 100 1101b 100 1110b 100 1111b -55C to +125C -55C to +125C -55C to +125C -55C to +125C -55C to +125C -55C to +125C -55C to +125C -55C to +125C SOT23-6 SOT23-6 SOT23-6 SOT23-6 SOT23-6 SOT23-6 SOT23-6 SOT23-6 Ambient Temp. Range Package
Ordering Information
Standard MIC280-0BM6 MIC280-1BM6 MIC280-2BM6 MIC280-3BM6 MIC280-4BM6 MIC280-5BM6 MIC280-6BM6 MIC280-7BM6 Marking TA00 TA01 TA02 TA03 TA04 TA05 TA06 TA07 Pb-FREE MIC280-0YM6 MIC280-1YM6 MIC280-2YM6 MIC280-3YM6 MIC280-4YM6 MIC280-5YM6 MIC280-6YM6 MIC280-7YM6
Pin Configuration
VDD 1 GND 2 T1 3 6 /INT 5 DATA 4 CLK
SOT23-6
Pin Description
Pin Number 1 2 3 4 5 6 Pin Name VDD GND T1 CLK DATA /INT Pin Function Power Supply Input. Ground. Analog Input. Connection to remote diode junction. Digital Input. Serial bit clock input. Digital Input/Output. Open-drain. Serial data input/output. Digital Output. Open-drain. Interrupt output.
MIC280
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MIC280
Micrel
Absolute Maximum Ratings (Note 1)
Power Supply Voltage, VDD ..................................................... 3.8V Voltage on T1 ........................................ -0.3V to VDD+0.3V Voltage on CLK, DATA, /INT ..............................-0.3V to 6V Current Into Any Pin ................................................. 10mA Power Dissipation, TA = 125C ................................ 109mW Storage Temperature ................................ -65C to +150C ESD Ratings, Note 3 Human Body Model ................................................ 1.5kV Machine Model ........................................................ 200V Soldering (SOT23-6 Package) Vapor Phase (60s) .....................................220C +5/-0C Infrared (15s) .............................................235C +5/-0C
Operating Ratings (Note 2)
Power Supply Voltage, VDD ............................ +3V to +3.6V Ambient Temperature Range (TA) .......... -55C to +125C Junction Temperature ................................................ 150C Package Thermal Resistance (JA) SOT23-6 ............................................................ 230C/W
Electrical Characteristics
For typical values TA = 25C, VDD = 3.3V, unless otherwise noted. Symbol IDD Bold values indicate -55C TA 125C, 3.0V VDD 3.6V, unless otherwise noted. Note 2 Parameter Conditions Power Supply Supply Current /INT, T1 open; CLK = DATA = High; Normal Mode Shutdown Mode; /INT, T1 open; Note 5 CLK = 100kHz, DATA = High Shutdown Mode; /INT, T1 open; CLK = DATA = High tPOR Power-on Reset Time, Note 5 Power-on Reset Voltage Power-on Reset Hysteresis Voltage Note 5 Accuracy, Remote Temperature Notes 2, 7, 10, 11 60C TD 100C, 3.15V < VDD < 3.45V, 25C < TA < 85C 0C TD 100C, 3.15V < VDD < 3.45V, 25C < TA < 85C -55C TD 125C, 3.15V < VDD < 3.45V, 25C < TA < 85C VPOR VHYST VDD > VPOR All registers reset to default values; A/D conversions initiated 0.23 9 6 200 2.65 300 2.95 [TBD] 0.4 mA A A s V mV Min. Typ Max Units
Temperature-to-Digital Converter Characteristics 0.25 1 2 1 1.5 200 330 570 1000 192 7 12 1 2 4 2 2.5 240 390 670 1250 400 C C C C C ms ms ms ms A A
Accuracy, Local Temperature Note 2, 10
0C TA 100C, 3.15V < VDD < 3.45V -55C TA 125C, 3.15V < VDD < 3.45V
tCONV
Conversion Time, Notes 2, 8
RES[1:0]=00 (9 bits) RES[1:0]=01 (10 bits) RES[1:0]=10 (11 bits) RES[1:0]=11 (12 bits)
Remote Temperature Input, T1 IF Current into External Diode Note 5 T1 forced to 1.0V, High level Low level
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MIC280
MIC280
Symbol VOL VIL Parameter Low Output Voltage, Note 4 Low Input Voltage High Input Voltage Input Capacitance Input Current Low Input Voltage High Input Voltage Input Capacitance Input Current Low Output Voltage, Note 4 Interrupt Propagation Delay Notes 5, 6 Interrupt Reset Propagation Delay Note 5, 9 IOL = 3mA 3V VDD 3.6V 3V VDD 3.6V Note 5 Condition IOL = 3mA 3V VDD 3.6V 3V VDD 3.6V Note 5 IOL = 6mA Min Typ Max 0.3 0.5 0.8 2.1 10 1 0.8 2.1 10 1 0.3 0.5 [tCONV] 1 1 2.5 100 300 Start Condition Stop Condition 100 100 25 30 35 5.5 5.5 Serial Data I/O Pin, DATA
Micrel
Units V V V V pF A V V pF A V V ms
VIH
CIN
ILEAK VIL
Serial Clock Input, CLK VIH
CIN
ILEAK VOL tINT tnINT ILEAK t1 t2 t3 t4 t5 tTO
Interrupt Output, /INT IOL = 6mA
from read of STATUS or A.R.A. to /INT > VOH; RPULLUP = 10k
from TEMPx < TLOWx or TEMPx > THIGHx or TEMPx > CRITx to /INT < VOL; RPULLUP = 10k
s A s ns ns ns ns ms
Serial Interface Timing 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
Exceeding the absolute maximum rating may damage the device. The device is not guaranteed to function outside its operating range. Final test on outgoing product is performed at TA = 25C. Devices are ESD sensitive. Handling precautions recommended. Current into the /INT or DATA pins will result in self heating of the device. Sink current should be minimized for best accuracy. Guaranteed by design over the operating temperature range. Not 100% production tested. tINT and tCRIT are equal to tCONV. TD is the temperature of the remote diode junction. Testing is performed using a single unit of one of the transistors listed in Table 8.
Note 1. Note 2. Note 3. Note 4. Note 5. Note 6. Note 7. Note 8. Note 9.
tCONV = tCONV(local) + tCONV(remote). Following the acquisition of either remote or local temperature data, the limit comparisons for that zone are performed and the device status updated; Status bits will be set and /INT driven active, if applicable. The interrupt reset propogation delay is dominated by the capacitance on the bus.
Note 11. Tested at 10-bit resolution.
Note 10. Accuracy specification does not include quantization noise, which may be up to 1/2 LSB.
MIC280
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MIC280
Micrel
Timing Diagrams
t1
CLK
t4
DATA INPUT
t2
t3
t5
DATA OUTPUT
Serial Interface Timing
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MIC280
MIC280
Micrel
Typical Characteristics
VDD = 3.3V; TA = 25C, unless otherwise noted.
2.5 2 1.5 1 0.5 0 -0.5 -1 -1.5 -2 -2.5 -55 -35 -15 5 25 45 65 85 105 125 JUNCTION TEMPERATURE (C)
A c c urac y vs . T emperature, Internal S ens or
2 1.5 MEASUREMENT ERROR (C)
R emote T emperature Meas urement E rror
400 350 SUPPLY CURRENT (A) QUIESCENT CURRENT (A) 300 250 200 150 100 50
S upply C urrent vs . T emperature for V DD = 3.3V
MEASURMENT ERROR (C)
1 0.5 0 -0.5 -1 -1.5 -2 100 0 20 40 60 80 REMOTE DIODE TEMPERATURE (C)
0 -55 -35 -15 5 25 45 65 85 105 125 TEMPERATURE (C)
20
Quies c ent C urrent vs . C loc k F requenc y in S hutdown Mode
/INT , T 1 open DAT A = HIG H
QUIESCENT CURRENT (A)
Quies c ent C urrent vs . T emperature in S hutdown Mode
30
/INT , T 1 open 25 C LK = DAT A = HIG H
Quies c ent C urrent vs . S upply V oltage in S hutdown Mode
10 /INT , 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)
QUIESCENT CURRENT (A)
15
20 15 10 5 0 -55 -35 -15 5 25 45 65 85 105 125 TEMPERATURE (C)
10
5
0
0
100 200 300 FREQUENCY (kHz)
400
3.6
140 MEASURED LOCAL TEMPERATURE (C) 120
R es pons e to Immers ion in 125C F luid B ath
8 6 MEASUREMENT ERROR (C)
Meas urement E rror vs . P C B L eakage to +3.3V /G ND
R emote T emperature E rror vs . C apac itanc e on T 1
5 0 -5 -10 -15 -20
100 80 60 40 20 0 0 1 2 3 4 5 6 7 8 9 10 TIME (sec)
2 0 -2 -4 -6
G ND
3.3V
-8 1x10 6 1x10 7 1x10 8 RESISTANCE FROM T1 ()
1000
2000
3000
4000
5000
6000
7000
CAPACITANCE (pF)
Nois e Injec ted into the B as e of R emote T rans is tor
7 6 REMOTE TEMP. ERROR (C) 5 4 3 2 1 0 1
1.6 1.4 TEMPERTURE ERROR (C) 1.2 1.0 0.8 0.6 0.4 0.2
Nois e Injec ted into the C ollec tor of R emote T rans is tor
100mV P -P
25mV P -P
10mV P -P
3mV P -P
10 100 1k 10k 100k 1M 10M100M FREQUENCY (Hz)
50mV P -P
0 1
25mV P -P
10 100 1k 10k 100k 1M 10M100M FREQUENCY (Hz)
MIC280
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8000
1x10 9
TEMPERATURE ERROR (C)
4
0
MIC280
Micrel initiate communication. The MIC280'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 below and the Ordering Information table above.
Part Number MIC280-0BM6 MIC280-1BM6 MIC280-2BM6 MIC280-3BM6 MIC280-4BM6 MIC280-5BM6 MIC280-6BM6 MIC280-7BM6 Slave Address 100 1000b = 48h 100 1001b = 49h 100 1010b = 4Ah 100 1011b = 4Bh 100 1100b = 4Ch 100 1110b = 4Eh 100 1111b = 4Fh 100 1101b = 4Dh
Functional Description
Serial Port Operation The MIC280 uses standard SMBus Write_Byte, Read_Byte, and Read_Word 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 MIC280, 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. A Read_Word is similar, but two successive data bytes are clocked out rather than one. These protocols are shown in Figure 1, Figure 2, and Figure 3. The Command byte is eight bits (one byte) wide. This byte carries the address of the MIC280 register to be operated upon. The command byte values corresponding to the various MIC280 registers are shown in Table 1. Other command byte values are reserved, and should not be used. Slave Address The MIC280 will only respond to its own unique slave address. A match between the MIC280's address and the address specified in the serial bit stream must be made to
Table 2: MIC280 Slave Addresses Alert Response Address In addition to the Read_Byte, Write_Byte, and Read_Word protocols, the MIC280 adheres to the SMBus protocol for response to the Alert Response Address (ARA). The MIC280 expects to be interrogated using the ARA when it has asserted its /INT output. Temperature Data Format The least-significant bit of each temperature register (high bytes) represents one degree Centigrade. The values are in a two's complement format, wherein the most significant bit
Target Register Label TEMP0 TEMP1h STATUS CONFIG IMASK THIGH0 TLOW0 THIGH1h TLOW1h LOCK TEMP1l THIGH1l TLOW1l CRIT1 CRIT0 MFG_ID DEV_ID Description Local temperature result Remote temperature result, high byte Status Configuration Interrupt mask register Local temperature high limit Local temperature low limit Remote temperature high limit, high byte Remote temperature low limit, high byte Security register Remote temperature result, low byte Remote temperature high limit, low byte Remote temperature low limit, low byte Remote over-temperature limit Local over-temperature limit Manufacturer Identification Device and revision identification
Command Byte Value Read 00h 01h 02h 04h 05h 07h 09h 10h 06h 03h Write n/a n/a n/a 03h 04h 05h 06h 07h 08h 09h n/a 13h 14h 19h 20h n/a n/a
Power-on Default 00h (0C) 00h (0C) 00h 80h 07h
3Ch (60C) 50h (80C) 00h (0C) 00h 00h 00h 00h 00h (0C)
08h
13h 14h 20h 19h
64h (100C) 46h (70C) 0xh* 2Ah
FEh FFh
* The lower nibble contains the die revision level, e.g., Rev 0 = 00h.
Table 1: MIC280 Register Addresses
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MIC280
MIC280 (D7) represents the sign: zero for positive temperatures and one for negative temperatures. Table 3 shows examples of the data format used by the MIC280 for temperatures:
Temperature +127C +125C +25C +1C 0C -1C -25C -125C -128C Binary 0111 1111 0111 1101 0001 1001 0000 0001 0000 0000 1111 1111 1110 0111 1000 0011 1000 0000 Hex 7F 7D 19 01 00 FF E7 83 80
Micrel register is shown in Table 5. Note: there is no fault queue for over-temperature events (CRIT0 and CRIT1) or diode faults. The fault queue applies only to high-temperature and low-temperature events as determined by the THIGHx and TLOWx registers. Any write to CONFIG will result in the fault queues being purged and reset. Writes to any of the limit registers, TLOWx or THIGHx, will result in the fault queue for the corresponding zone being purged and reset.
CONFIG[5:4] 00 01 10 11 FAULT QUEUE DEPTH 1 (Default) 2 4 6
Table 3: Digital Temperature Format, High Bytes Extended temperature resolution is provided for the external zone. The high and low temperature limits and the measured temperature for zone one are reported as 12-bit values stored in a pair of 8-bit registers. The measured temperature, for example, is reported in registers TEMP1h, the high-order byte, and TEMP1l, the low-order byte. The values in the low-order bytes are left-justified four-bit binary values representing one-sixteenth degree increments. The A-D converter resolution for zone 1 is selectable from nine to twelve bits via the configuration register. Low-order bits beyond the resolution selected will be reported as zeroes. Examples of this format are shown below in Table 4. FAULT QUEUE A set of fault queues (programmable digital filters) are provided in the MIC280 to prevent false tripping due to thermal or electrical noise. Two bits, CONFIG[5:4], set the depth of the fault queues. The fault queue setting then determines the number of consecutive temperature events (TEMPx > THIGHx or TEMPx < TLOWx) which must occur in order for the condition to be considered valid. As an example, assume CONFIG[5:4] is programmed with 10b. The measured temperature for a given zone would have to exceed THIGHx for four consecutive A/D conversions before /INT would be asserted or the status bit set. 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 fault queue depth vs. CONFIG[5:4] of the configuration
Extended Temperature, Low Byte 0.0000 0.0625 0.1250 0.2500 0.5625 0.9375 9 BITS Binary 0000 0000 0000 0000 0000 0000 0000 0000 1000 0000 1000 0000 Hex 00 00 00 00 80 80
Table 5: Fault Queue Depth Settings Interrupt Generation There are eight different conditions that will cause the MIC280 to set one of the bits in STATUS and assert its /INT output, if so enabled. These conditions are listed in Table 6. Unlike previous generations of thermal supervisor IC's, there are no interdependencies between any of these conditions. That is, if CONDITION is true, the MIC280 will respond accordingly, regardless of any previous or currently pending events. Normally when a temperature event occurs, the corresponding status bit will be set in STATUS, the corresponding interrupt mask bit will be cleared, and /INT will be asserted. Clearing the interrupt mask bit(s) prohibits continuous interrupt generation while the device is being serviced. (It is possible to prevent events from clearing interrupt mask bits by setting bits in the lock register. See Table 7 for Lockbit functionality.) A temperature event will only set bits in the status register if it is specifically enabled by the corresponding bit in the interrupt mask register. An interrupt signal will only be generated on /INT if interrupts are also globally enabled (IE =1 in CONFIG). The MIC280 expects to be interrogated using the Alert Response Address once it has asserted its interrupt output. Following an interrupt, a successful response to the A.R.A. or a read operation on STATUS will cause /INT to be de-asserted. STATUS will also be cleared by the read operation. Reading STATUS following an interrupt is an acceptable substitute for
Resolution 10 BITS Binary 0000 0000 0000 0000 0000 0000 0100 0000 1000 0000 1100 0000 Hex 00 00 00 40 80 C0 11 BITS Binary 0000 0000 0000 0000 0010 0000 0100 0000 1000 0000 1110 0000 Hex 00 00 20 40 80 E0 12 BITS Binary 0000 0000 0001 0000 0010 0000 0100 0000 1001 0000 1111 0000 Hex 00 10 20 40 90 F0
Table 4: Digital Temperature Format, Low Bytes
MIC280
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MIC280
November 2004
MIC280Slave Address
Command Byte
Data Byte to MIC280
DATA
START
STOP
R/W = WRITE
ACKNOWLEDGE
ACKNOWLEDGE
S 1 0 0 1 A2 A1 A0 0 A X X X X X X X X A D7 D6 D5 D4 D3 D2 D1 D0 A P
ACKNOWLEDGE
CLK
Master-to-slave transmission Slave-to-master response
Figure 1. WRITE_BYTE Protocol
MIC280Slave Address
Command Byte
MIC280Slave Address
Data Read From MIC280
DATA
START
START
R/W = WRITE
ACKNOWLEDGE ACKNOWLEDGE
S 1 0 0 1 A2 A1 A0 0 A X X X X X X X X A S 1 0 0 1 A2 A1 A0 1 A X X X X X X X X /A P
R/W = READ
ACKNOWLEDGE
NOT ACKNOWLEDGE
9
Master-to-slave transmission
STOP
CLK
Slave-to-master response
Figure 2. READ_BYTE Protocol
High-Order Byte (TEMP1h) from MIC280
MIC280Slave Address
Command Byte
MIC280Slave Address
Low-Order Byte (TEMP1L) from MIC280
DATA
R/W = WRITE
S 1 0 0 1 A2 A1 A0 0 A 0 0 0 0 0 0 0 1 A S 1 0 0 1 A2 A1 A0 1 A D11 D10 D9 D8 D7 D6 D5 D4 A D3 D2 D1 D0 0 0 0 0 /A P
ACKNOWLEDGE ACKNOWLEDGE
START
START
R/W = READ
ACKNOWLEDGE
ACKNOWLEDGE
NOT ACKNOWLEDGE
STOP
CLK
Master-to-slave transmission
Slave-to-master response
Figure 3. READ_WORD Protocol for Accessing TEMP1h : TEMP1l
Micrel
MIC280
MIC280
Alert Response Address DATA
0
R/W = READ
STOP
MIC280
MIC280 respond with its slave address
1A1
0
NOT ACKNOWLEDGE
S00011
0
ACKNOWLEDGE
0
1 A2 A1 A0 0 /A P
START Event Occurs
/INT
tINT
tINT
Master-to-slave transmission
Slave-to-master response
Figure 4. MIC280 Alert Response Address Protocol
10
MIC280 Slave Address S 1 0 0 1 A2 A1 A0 0 A 0
0
ACKNOWLEDGE
Command Byte = 03h = CONFIG
0 0 0 0 1 1A1
MIC280 Slave Address
Value in STATUS**
DATA
START
R/W = READ
ACKNOWLEDGE
0 0 1 A2 A1 A0 1 X X X X X X X X /A P
NOT ACKNOWLEDGE
STOP
Event Occurs
/INT
** All status bits are cleared to zero following this operation
tINT
tINT
Master-to-slave transmission
Slave-to-master response
Figure 5. Reading Status in response to an interrupt
November 2004
Micrel
MIC280 using the A.R.A. if the host system does not implement the A.R.A protocol. Figure 4 and Figure 5 illustrate these two methods of responding to MIC280 interrupts. Since temperature-to-digital conversions continue while /INT is asserted, the measured temperature could change between the MIC280's assertion of /INT and the host's response. It is good practice for the interrupt service routine to read the value in TEMPx, to verify that the over-temperature or undertemperature 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 MIC280 by the host. The interrupt service routine should allow for this eventuality. At the end of the interrupt service routine, the interrupt enable bits should be reset to permit future interrupts. Reading the Result Registers All MIC280 registers are eight bits wide and may be accessed using the standard Read_Byte protocol. The temperature result for the local zone, zone 0, is a single 8-bit value in register TEMP0. A single Read_Byte operation by the host is sufficient for retrieving this value. The temperature result for the remote zone is a twelve-bit value split across two eight-bit registers, TEMP1h and TEMP1l. A series of two Read_Byte operations are needed to obtain the entire twelvebit temperature result for zone 1. It is possible under certain conditions that the temperature result for zone 1 could be updated between the time TEMP1l or TEMP1h is read and the companion register is read. In order to insure coherency, TEMP1h supports the use of the Read_Word protocol for accessing both TEMP1h and TEMP1l with a single operation. This insures that the values in both result registers are from the same ADC cycle. This is illustrated in Figure 3 above. Read_Word operations are only supported for TEMP1h: TEMP1l, i.e., only for command byte values of 01h. Polling The MIC280 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 STATUS to check the state of the status bits. The act of reading STATUS clears it. If more than one event that sets a given status bit occurs before the host polls STATUS, only the fact that at least one such event has occurred will be apparent
EVENT Data ready Over-temperature, remote Over-temperature, local High temperature, remote High temperature, local Low temperature, remote Low temperature, local Diode fault CONDITION A/D conversions complete for both zones; result registers updated; state of /INT updated ([TEMP1h:TEMP1l]) > CRIT1 TEMP0 > CRIT0 ([TEMP1h:TEMP1l]) > THIGH1h:THIGH1l]** TEMP0 > THIGH0** ( [TEMP1h:TEMP1l]) < TLOW1h:TLOW1l]** TEMP0 < TLOW0** T1 open or T1 shorted to VDD or GND
Micrel to the host. For polled systems, the global interrupt enable bit should be clear (IE = 0). This will disable interrupts from the MIC280 (prevents the /INT pin from sinking current). For interrupt-driven systems, IE must be set to enable the /INT output. Shutdown Mode Putting the device into shutdown mode by setting the shutdown bit in the configuration register will unconditionally deassert /INT, clear STATUS, and purge the fault queues. Therefore, this should not be done before completing the appropriate interrupt service routine(s). No other registers will be affected by entering shutdown mode. The last temperature readings will persist in the TEMPx registers. The MIC280 can be prevented from entering shutdown mode using the shutdown lockout bit in the lock register. If L3 in LOCK is set while the MIC280 is in shutdown mode, it will immediately exit shutdown mode and resume normal operation. It will not be possible to subsequently re-enter shutdown mode. If the reset bit is set while the MIC280 is shut down, normal operation resumes from the reset state. (see below) Warm Resets The MIC280 can be reset to its power-on default state during operation by setting the RST bit in the configuration register. When this bit is set, /INT will be deasserted, the fault queues will be purged, the limit registers will be restored to their normal power-on default values, and any A/D conversion in progress will be halted and the results discarded. This includes resetting bits L3 - L0 in the security register, LOCK. The state of the MIC280 following this operation is indistinguishable from a power-on reset. If the reset bit is set while the MIC280 is shut down, the shutdown bit is cleared and normal operation resumes from the reset state. If bit 4 of LOCK, the Warm Reset Lockout Bit, is set, warm resets cannot be initiated, and writes to the RST bit will be completely ignored. Setting L4 while the MIC280 is shut down will result in the device exiting shutdown mode and resuming normal operation, just as if the shutdown bit had been cleared.
MIC280 RESPONSE* Set S7, clear IM7, assert /INT Set S1, assert /INT Set S0, assert /INT Set S4, clear IM4, assert /INT Set S6, clear IM6, assert /INT Set S3, clear IM3, assert /INT Set S5, clear IM5, assert /INT Set S2, clear IM2, assert /INT
* Assumes interrupts enabled. **CONDITION must be true for Fault_Queue conversions to be recognized.
Table 6: MIC280 Temperature Events
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MIC280
MIC280 Configuration Locking The security register, LOCK, provides the ability to disable configuration changes as they apply to the MIC280's most critical functions: shutdown mode, and reporting diode faults and over-temperature events. LOCK provides a way to prevent malicious or accidental changes to the MIC280 registers that might prevent a system from responding properly to critical events. Once L0, L1, or L2 has been set, the global interrupt enable bit, IE, will be set and fixed. It cannot subsequently be cleared. Its state will be reflected in the configuration register. The bits in LOCK can only be set once. That is, once a bit is set, it cannot be reset until the MIC280 is power-cycled or a warm reset is performed by setting RST in the configuration register. The warm reset function can be disabled by setting L4 in LOCK. If L4 is set, locked settings cannot be changed during operation and warm resets cannot be performed; only a power-cycle will reset the locked state(s). If L0 is set, the values of IM0 and CRIT0 become fixed and unchangeable. That is, writes to CRIT0 and the corresponding interrupt enable bit are locked out. A local over-temperature event will generate an interrupt regardless of the setting of IE or its interrupt mask bit. If L1 is set, the values of IM1 and CRIT1 become fixed and unchangeable. A remote over-temperature event will generate an interrupt regardless of the setting of IE or its interrupt
LOCK BIT L0 L1 L2 L3 L4 FUNCTION LOCKED Local over-temperature detection Remote over-temperature detection Diode fault interrupts locked on or off Shutdown mode Warm resets
Micrel mask bit. Similarly, setting L2 will fix the state of IM2, allowing the system to permanently enable or disable diode fault interrupts. A diode fault will generate an interrupt regardless of the setting of IE or its interrupt mask bit. L3 can be used to lock out shutdown mode. If L3 is set, the MIC280 will not shut down under any circumstances. Attempts to set the SHDN bit will be ignored and all chip functions will remain operational. If L3 is set while the MIC280 is in shutdown mode, it will immediately exit shutdown mode and resume normal operation. It will not be possible to subsequently reenter shutdown mode. Setting L4 disables the RST bit in the configuration register, preventing the host from initiating a warm reset. Writes to RST will be completely ignored if L4 is set.
RESPONSE WHEN SET IM0 fixed at 1, writes to CRIT0 locked-out; IE permanently set IM1 fixed at 1; writes to CRIT1 locked-out; IE permanently set IM2 fixed at current state; IE permanently set if IM2=1 SHDN fixed at 0; exit shutdown if SHDN=1 when L3 is set RST bit disabled; cannot initiate Warm resets
Table 7: Lock bit functionality
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Detailed Register Descriptions
Local Temperature Result Register (TEMP0) 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 D[7:0] Function Measured temperature data for the local zone. Operation Read only
Power-up default value: 0000 0000b = 00h (0C)** Read command byte: 0000 0000b = 00h Each LSB represents one degree centigrade. The values are in a two's complement binary format such that 0C is reported as 0000 0000b. See Temperature Data Format (above) for more details.
**TEMP0 will contain measured temperature data after the completion of one conversion.
Remote Temperature Result High-Byte Register (TEMP1h) 8-bits, read only
Remote Temperature Result High-Byte 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 D[7:0] Function Measured temperature data for the remote zone, most significant byte. Operation Read only
Power-up default value: 0000 0000b = 00h (0C)** Read command byte: 0000 0001b = 01h Each LSB represents one degree centigrade. The values are in a two's complement binary format such that 0C is reported as 0000 0000b. See Temperature Data Format (above) for more details. TEMP1h can be read using either a Read_Byte operation or a Read_Word operation. Using Read_Byte will yield the 8-bit value in TEMP1h. The complete remote temperature result in both TEMP1h and TEMP1l may be obtained by performing a Read_Word operation on TEMP1h. The MIC280 will respond to a Read_Word with a command byte of 01h (TEMP1h) by returning the value in TEMP1h followed by the value in TEMP1l. This guarantees that the data in both registers is from the same temperature-to-digital conversion cycle. The Read_Word operation is diagramed in Figure 3. This is the only MIC280 register that supports Read_Word.
**TEMP1h will contain measured temperature data after the completion of one conversion.
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MIC280
MIC280 Status Register (STATUS) 8-bits, read-only
Status Register D[7] read-only S7 Bit(s) S7 S6 S5 S4 S3 S2 S1 S0 D[6] read-only S6 Function Data ready Local high temperature event Local low temperature event Remote high temperature event Remote low temperature event Diode fault Remote over-temperature event Local over-temperature event D[5] read-only S5 D[4] read-only S4 D[3] read-only S3 D[2] read-only S2 D[1] read-only S1 Operation* 1 = data available 0 = ADC busy 1 = event occurred, 0 = none 1 = event occurred, 0 = none 1 = event occurred, 0 = none 1 = event occurred, 0 = none 1 = fault, 0 = none 1 = event occurred, 0 = none 1 = event occurred, 0 = none D[0] read-only S0
Micrel
* All status bits are cleared after any read operation is performed on STATUS.
Power-up default value: 0000 0000b = 00h (no events pending) Read command byte: 0000 0010b = 02h The power-up default value is 00h. Following the first conversion, however, any of the status bits may be set depending on the measured temperature results or the existence of a diode fault. Configuration Register (CONFIG) 8-bits, read/write
Configuration Register D[7] read/write Interrupt Enable (IE) Bits(s) IE SHDN FQ[1:0] RES[1:0] D[1] RST D[6] read/write Shut-down (SHDN) Function Interrupt enable Selects operating mode: normal/shutdown Depth of fault queue* A/D converter resolution for external zone - affects conversion rate Reserved Resets all MIC280 functions and restores the power-up default state D[5] reserved D[4] reserved D[3] reserved D[2] reserved D[1] reserved Reserved D[0] reserved Reset (RST) Operation* 1 = interrupts enabled, 0 = disabled 1 = shutdown, 0 = normal [00]=1, [01]=2, [10]=4, [11]=6 [00]=9-bits, [01]=10-bits, [10]=11-bits, [11]=12-bits always write as zero! write only; 1 = reset, 0 = normal operation; disabled by setting L4
Fault Queue (FQ[1:0])
Resolution (RES[1:0])
Power-up default value: Read/Write command byte:
1000 0000b = 80h (Not in shutdown mode; Interrupts enabled; Fault queue depth=1; Resolution = 9 bits) 0000 0011b = 03h
* Any write to CONFIG will result in the fault queues being purged and reset and 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.
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Interrupt Mask Register (IMASK) 8-bits, read/write
Interrupt Mask Register D[7] read/write IM7 Bit(s) IM7 IM6 IM5 IM4 IM3 IM2 IM1 IM0 D[6] read/write IM6 Function Data ready event mask Local high temperature event mask Local low temperature event mask Remote high temperature event mask Remote low temperature event mask Diode fault mask Remote over-temperature event mask Local over-temperature event mask D[5] read/write IM 5 D[4] read/write IM 4 D[3] read/write IM 3 D[2] read/write IM 2 D[1] read/write IM 1 Operation* 1 = enabled, 0 = disabled 1 = enabled, 0 = disabled 1 = enabled, 0 = disabled 1 = enabled, 0 = disabled 1 = enabled, 0 = disabled 1 = enabled, 0 = disabled 1 = enabled, 0 = disabled 1 = enabled, 0 = disabled D[0] read/write IM0
Power-up default value: Read/Write command byte:
0000 0111b = 07h (Over-temp. and diode faults enabled) 0000 0100b = 04h
Local Temperature High Limit Register (THIGH0) 8-bits, read/write
Local Temperature High Limit Register D[7] read/write D[6] read/write D[5] read/write D[4] read/write D[3] read/write D[2] read/write D[1] read/write D[0] read/write
High temperature limit for local zone. Bit D[7:0] Function High temperature limit for the local zone. Operation Read/write
Power-up default value: 0011 1100b = 3Ch (60C) Read/Write command byte: 0000 0101b = 05h Each LSB represents one degree centigrade. The values are in a two's complement binary format such that 0C is reported as 0000 0000b. See Temperature Data Format (above) for more details. Any writes to a temperature limit register will result in the corresponding fault queue being purged and reset.
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Local Temperature Low Limit Register (TLOW0) 8-bits, read/write
Local Temperature Low Limit Register D[7] read/write D[6] read/write D[5] read/write D[4] read/write D[3] read/write D[2] read/write D[1] read/write D[0] read/write
Low temperature limit for local zone Bit D[7:0] Function Low temperature limit for the local zone Operation Read/write
Power-up default value: 0000 0000b = 00h (0C) Read/Write command byte: 0000 0110b = 06h Each LSB represents one degree centigrade. The values are in a two's complement binary format such that 0C is reported as 0000 0000b. See TEMPERATURE DATA FORMAT (above) for more details. Any writes to a temperature limit register will result in the corresponding fault queue being purged and reset. Remote Temperature High Limit High-Byte Register (THIGH1h) 8-bits, read/write
Remote Temperature High Limit High-Byte Register D[7] read/write D[6] read/write D[5] read/write D[4] read/write D[3] read/write D[2] read/write D[1] read/write D[0] read/write
High temperature limit for remote zone, most significant byte. Bit D[7:0] Function High temperature limit for the remote zone, most significant byte. Operation Read/write
Power-up default value: 0101 0000b = 50h (80C) Read/Write command byte: 0000 0111b = 07h Each LSB represents one degree centigrade. The values are in a two's complement binary format such that 0C is reported as 0000 0000b. See TEMPERATURE DATA FORMAT (above) for more details. Any writes to a temperature limit register will result in the corresponding fault queue being purged and reset.
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Remote Temperature Low Limit High-Byte Register (TLOW1h) 8-bits, read/write
Remote Temperature Low Limit High-Byte Register D[7] read/write D[6] read/write D[5] read/write D[4] read/write D[3] read/write D[2] read/write D[1] read/write D[0] read/write
Low temperature limit for remote zone, most significant byte. Bit D[7:0] Function Low temperature limit for the remote zone, most significant byte. Operation Read/write
Power-up default value: 0000 0000b = 00h (0C) Read/Write command byte: 0000 1000b = 08h Each LSB represents one degree centigrade. The values are in a two's complement binary format such that 0C is reported as 0000 0000b. See Temperature Data Format (above) for more details. Any writes to a temperature limit register will result in the corresponding fault queue being purged and reset. Security Register (LOCK) 8-bits, write once
Security Register D[7] reserved D[6] reserved Reserved Bit D[7:5] L4 L3 L2 L1 L0 Function Reserved Warm reset lockout bit Shutdown mode lockout bit* Diode fault event lock bit Remote over-temperature event lock bit Local over-temperature event lock bit D[5] reserved D[4] read/ write-once L4 D[3] read/ write-once L3 D[2] read/ write-once L2 D[1] read/ write-once L1 Operation* Always write as zero 1 = RST bit disabled; 0 = unlocked 1= shutdown disabled; 0 = unlocked 1 = locked, 0 = unlocked 1 = locked, 0 = unlocked 1 = locked, 0 = unlocked D[0] read/ write-once L0
Power-up default value: Read/Write command byte:
0000 0000b = 00h (All events unlocked) 0000 1001b = 09h
* If the chip is shutdown when L3 is set, the chip will exit shutdown mode and resume normal operation. It will not be possible to subsequently re-enter shutdown mode.
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Remote Temperature Result Low-Byte Register (TEMP1l) 8-bits, read only
Remote Temperature Result Low-Byte Register D[7] read-only D[6] read-only D[5] read-only D[4] read-only D[3] reserved D[2] reserved D[1] reserved D[0] reserved
Temperature data from ADC, least significant bits Bit D[7:4] D[3:0] Function
Reserved - always reads zero Operation Read only Always reads as zeroes
Measured temperature data for the remote zone, least significant bits. Reserved
Power-up default value: 0000 0000b = 00h (0C)** Read command byte: 0001 0000b = 10h Each LSB represents one-sixteenth degree centigrade. The values are in a binary format such that 1/16thC (0.0625C) is reported as 0001 0000b. See Temperature Data Format (above) for more details. TEMP1l can be accessed using a Read_Byte operation. However, the complete remote temperature result in both TEMP1h and TEMP1l may be obtained by performing a Read_Word operation on TEMP1h. The MIC280 will respond to a Read_Word with a command byte of 01h (TEMP1h) by returning the value in TEMP1h followed by the value in TEMP1l. This guarantees that the data in both registers is from the same temperature-to-digital conversion cycle. The Read_Word operation is diagramed in Figure 3. TEMP1h is the only MIC280 register that supports Read_Word. **TEMP1l will contain measured temperature data after the completion of one conversion. Remote Temperature High Limit Low-Byte Register (THIGH1l) 8-bits, read/write
Remote Temperature High Limit Low-Byte Register D[7] read/write D[6] read/write D[5] read/write D[4] read/write D[3] reserved D[2] reserved D[1] reserved D[0] reserved
High temperature limit for remote zone, least significant bits. Bit D[7:4] D[3:0] Function
Reserved - always reads zero Operation Read/write Always reads as zeros
High temperature limit for the remote zone, least significant bits. Reserved.
Power-up default value: 0000 0000b = 00h (0C) Read/Write command byte: 0001 0011b = 13h Each LSB represents one-sixteenth degree centigrade. The values are in a binary format such that 1/16thC (0.0625C) is reported as 0001 0000b. See Temperature Data Format (above) for more details. Any writes to a temperature limit register will result in the corresponding fault queue being purged and reset.
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Remote Temperature Low Limit Low-Byte Register (TLOW1l) 8-bits, read/write
Remote Temperature Low Limit Low-Byte Register D[7] read/write D[6] read/write D[5] read/write D[4] read/write D[3] reserved D[2] reserved D[1] reserved D[0] reserved
Low temperature limit for remote zone, least significant bits. Bit D[7:4] D[3:0] Function
Reserved - always reads zero. Operation Read/write Always reads as zeros.
Low temperature limit for the remote zone, least significant bits. Reserved
Power-up default value: 0000 0000b = 00h (0C) Read/Write command byte: 0001 0100b = 14h Each LSB represents one-sixteenth degree centigrade. The values are in a binary format such that 1/16thC (0.0625C) is reported as 0001 0000b. See Temperature Data Format (above) for more details. Any writes to a temperature limit register will result in the corresponding fault queue being purged and reset. Remote Over-Temperature Limit Register (CRIT1) 8-bit, read/write
Remote Over-Temperature Limit Register D[7] read/write D[6] read/write D[5] read/write D[4] read/write D[3] read/write D[2] read/write D[1] read/write D[0] read/write
Over-temperature limit for remote zone. Bit D[7:0] Function Over-temperature limit for the remote zone. Operation Read/write
Power-up default value: 0110 0100b = 64h (100C) Read/Write command byte: 0001 1001b = 19h Each LSB represents one degree centigrade. The values are in a two's complement binary format such that 0C is reported as 0000 0000b. SeeTemperature Data Format (above) for more details. Any writes to a temperature limit register will result in the corresponding fault queue being purged and reset.
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Local Over-Temperature Limit Register (CRIT0) 8-bits, read/write
Local Over-Temperature Limit Register D[7] read/write D[6] read/write D[5] read/write D[4] read/write D[3] read/write D[2] read/write D[1] read/write D[0] read/write
Over-temperature limit for local zone. Bit D[7:0] Function Over-temperature limit for the local zone. Operation Read/write
Power-up default value: 0100 0110b = 46h (70C) Read/Write command byte: 0010 0000b = 20h Each LSB represents one degree centigrade. The values are in a two's complement binary format such that 0C is reported as 0000 0000b. SeeTemperature Data Format (above) for more details. Any writes to a temperature limit register will result in the corresponding fault queue being purged and reset. Manufacturer ID Register (MFG_ID) 8-bits, read only
Manufacturer ID Register D[7] read only 0 BIT(S) D[7:0] D[6] read only 0 FUNCTION Identifies Micrel as the manufacturer of the device. Always returns 2Ah. D[5] read only 1 D[4] read only 0 D[3] read only 1 D[2] read only 0 D[1] read only 1 Operation* Read only. Always returns 2Ah D[0] read only 0
Power-up default value: Read command byte:
0010 1010b = 2Ah 1111 1110b = FEh Die Revision Register (DIE_REV) 8-bits, read only
Die Revision Register D[3] reserved
D[7] read-only
D[6] read-only
D[5] read-only
D[4] read-only
D[2] reserved
D[1] reserved
D[0] reserved
MIC280 DIE REVISION NUMBER Bit(s) D[7:0] Function Identifies the device revision number Operation* Read only.
Power-up default value: Read command byte:
[Device revision number]h 1111 1111b = FFh
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Series Resistance
Application Information
Remote Diode Selection Most small-signal PNP transistors with characteristics similar to the JEDEC 2N3906 will perform well as remote temperature sensors. Table 8 lists several examples of such parts that Micrel has tested for use with the MIC280. Other transistors equivalent to these should also work well.
Vendor Fairchild Semiconductor On Semiconductor Philips Semiconductor Samsung Semiconductor Part Number MMBT3906 MMBT3906L PMBT3906 KST3906-TF Package SOT-23 SOT-23 SOT-23 SOT-23
Table 8: Transistors suitable for use as remote diodes Minimizing Errors
Self-Heating
One concern when using a part with the temperature accuracy and resolution of the MIC280 is to avoid errors induced by self-heating (VDD x IDD) + (VOL x IOL). In order to understand what level of error this might represent, and how to reduce that error, the dissipation in the MIC280 must be calculated and its effects reduced to a temperature offset. The worstcase operating condition for the MIC280 is when VDD = 3.6V. The maximum power dissipated in the part is given in the following equation: PD = [(IDD x VDD)+(IOL(DATA)xVOL(DATA))+(IOL(/INT)xVOL(/INT)] PD = [(0.4mA x 3.6V)+(6mA x 0.5V)+(6mA x 0.5V)] PD = 7.44mW R(J-A) of SOT23-6 package is 230C/W Theoretical Maximum TJ due to self-heating is: 7.44mW x 230C/W = 1.7112C Worst-case self-heating 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 MIC280 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 given in the following equation: (0.23mA IDD(typ) x 3.3V) + (25% x 1.5mA IOL(DATA) x 0.15V) + (1% x 1.5mA IOL(/INT) x 0.15V) = 0.817mW TJ = (0.8175mW x 230C/W) = 0.188C Real-world self-heating example 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 temperature data may be poorly defined or unobtainable except by empirical means.
The operation of the MIC280 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. 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 MIC280. A good rule of thumb is this: for each ohm in series with the external transistor, there will be a 0.8C error in the MIC280's temperature measurement. It is not difficult to keep the series resistance well below an ohm (typically < 0.1), so this will rarely be an issue. Filter Capacitor Selection It is usually desirable to employ a filter capacitor between the T1 and GND pins of the MIC280. 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 conect to the remote diode. The maximum recommended total capacitance from the T1 pin to GND is 2200pF. This typically suggests the use of a 1800pF 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 MIC280, 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 maximum total capacitance. Layout Considerations The following guidelines should be kept in mind when designing and laying out circuits using the MIC280: 1. Place the MIC280 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 MIC280'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 MIC280, thereby providing a Kelvin connection for the base of the diode. See Figure 6. 3. When using the MIC280 to sense the temperature of a processor or other device which has an integral thermal diode, e.g., Intel's Pentium II, III, IV, AMD Athlon CPU, Xilinx Virtex FPGAs, connect the emitter and base of the remote sensor to the MIC280 using the guard traces and Kelvin return shown in Figure 6. The collector of the remote diode is typically inaccessible to the user 21 MIC280
November 2004
MIC280 on these devices. To allow for this, the MIC280 has superb rejection of noise appearing from collector to GND. 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. 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 MIC280 and under the connections from the MIC280 to the remote diode. This will help guard against stray noise pickup.
Micrel 6. Always place a good quality power supply bypass capacitor directly adjacent to, or underneath, the MIC280. This should be a 0.1 F ceramic capacitor. Surface-mount parts provide the best bypassing because of their low inductance. 7. When the MIC280 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 100 resistor in series with the part's VDD pin, and a 4.7 F, 6.3V electrolytic capacitor from VDD to GND. See Figure 7.
MIC280
1 VDD 2 GND
/INT 6 DATA 5 CLK 4
GUARD/RETURN REMOTE DIODE (T1)
3 T1
GUARD/RETURN
Figure 6. Guard Traces/Kelvin Ground Returns
3V to 3.6V 3x 10k
5 TO SERIAL BUS HOST 4 6
100 MIC280 DATA CLK /INT VDD T1 GND
1 3 2 2N3906/ CPU DIODE
0.1F ceramic
4.7F
1800pF
Figure 7. VDD Decoupling for Very Noisy Supplies
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Package Information
1.90 (0.075) REF 0.95 (0.037) REF
1.75 (0.069) 3.00 (0.118) 1.50 (0.059) 2.60 (0.102)
DIMENSIONS: MM (INCH) 3.00 (0.118) 2.80 (0.110) 1.30 (0.051) 0.90 (0.035) 10 0 0.15 (0.006) 0.00 (0.000) 0.60 (0.024) 0.10 (0.004) 0.20 (0.008) 0.09 (0.004)
0.50 (0.020) 0.35 (0.014)
6-Lead SOT23 (M6)
MICREL INC.
TEL + 1 (408) 944-0800 FAX + 1 (408) 474-1000 WEB http://www.micrel.com
2180 FORTUNE DRIVE
SAN JOSE, CA 95131
USA
This information furnished by Micrel in this data sheet is believed to be accurate and reliable. However no responsibility is assumed by Micrel for its use. Micrel reserves the right to change circuitry and specifications at any time without notification to the customer. 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. (c) 2004 Micrel Incorporated
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MIC280

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