MICREL MIC384-0YMM

MIC384
Micrel
MIC384
Three-Zone Thermal Supervisor
General Description
Features
The MIC384 is a versatile digital thermal supervisor capable
of measuring temperature using its own internal sensor and
two inexpensive external sensors or embedded silicon diodes
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. The open-drain interrupt output
pin can be used as either an over-temperature alarm or a
thermostatic control signal.
Interrupt mask and status bits are provided for reduced software overhead. Fault queues prevent nuisance tripping due
to thermal or electrical noise. 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 MIC384 an excellent
choice for multiple zone thermal management applications.
•
•
•
•
•
•
•
•
•
•
Measures Local and Two Remote Temperatures
2-Wire SMBus-compatible Interface
Programmable Thermostat Settings for All Three Zones
Open-Drain Interrupt Output Pin
Interrupt Mask and Status Bits
Fault Queues to Prevent Nuisance Tripping
Low Power Shutdown Mode
Failsafe response to diode faults
2.7V to 5.5V Power Supply Range
8-Lead SOIC and MSOP Packages
Applications
•
•
•
•
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*SMBus and Pentium III are trademarks of Intel Corporation.
**I2C is a trademark of Philips Electronics, N.V.
Desktop, Server and Notebook Computers
Power Supplies
Test and Measurement Equipment
Wireless Systems
Networking/Datacom Hardware
Ordering Information
Part Number
Base Address (*) Junction Temp. Range
Package
Availability
Standard
Pb-Free
MIC384-0BM
MIC384-0YM
100 100x
-55°C to +125°C
8-Lead SOIC
MIC384-1BM
MIC384-1YM
100 101x
-55°C to +125°C
8-Lead SOIC
Contact Factory
MIC384-2BM
MIC384-2YM
100 110x
-55°C to +125°C
8-Lead SOIC
Contact Factory
MIC384-3BM
MIC384-3YM
100 111x
-55°C to +125°C
8-Lead SOIC
Contact Factory
MIC384-0BMM
MIC384-0YMM
100 100x
-55°C to +125°C
8-Lead MSOP
MIC384-1BMM
MIC384-1YMM
100 101x
-55°C to +125°C
8-Lead MSOP
Contact Factory
MIC384-2BMM
MIC384-2YMM
100 110x
-55°C to +125°C
8-Lead MSOP
Contact Factory
MIC384-3BMM
MIC384-3YMM
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.
Typical Application
3.3V
3 × 10k
pull-ups
FROM
SERIAL BUS
HOST
0.1µF
MIC384
DATA
VDD
CLK
T1
/INT
GND
T2
A0
2200pF
2200pF
REMOTE
DIODE
REMOTE
DIODE
3-Channel SMBus Temperature Measurement System
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
MIC384
MIC384
Micrel
Pin Configuration
DATA
1
8 VDD
CLK 2
7 A0
/INT 3
6 T1
GND 4
5 T2
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
T2
Analog Input: Connection to remote temperature sensor (diode junction)
6
T1
Analog Input: Connection to remote temperature sensor (diode junction)
7
A0
Digital Input: Slave address selection input. See Table 1. MIC384 Slave
Address Settings.
8
VDD
MIC384
Pin Function
Analog Input: Power supply input to the IC.
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September 2005
MIC384
Micrel
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 ................................................. ±10mA
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, open, A0 = VDD or GND,
shutdown mode, CLK = 100kHz
3
/INT, 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 5, 4, 9
tCONV0
tCONV1
3V ≤ VDD ≤ 3.6V, 0°C ≤ TA ≤ +85°C
0°C ≤ TA ≤ +100°C, /INT open,
3V ≤ VDD ≤ 3.6V
±1
±2
°C
–55°C ≤ TA ≤ +125°C, /INT open,
±2
±3
°C
0°C ≤ TD ≤ +100°C, /INT 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 open,
Conversion Time, local zone
Note 7, 8
Conversion Time, remote zone
Note 7, 8
Remote Temperature Inputs (T1, T2)
IF
Current to External Diode
Note 7
high level, T1 or T2 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
MIC384
MIC384
Micrel
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
±0.01
V
pF
±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
±0.01
V
V
pF
±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
T_SET2
Default T_SET2 Value
T_HYST2
Default T_HYST2 Value
Serial Interface Timing (Note 7)
IOL = 3mA
IOL = 6mA
from TEMPx > T_SETx or TEMPx < T_HYSTx
to /INT < VOL, FQ = 00, RPULLUP = 10kΩ
from any register read to /INT > VOH,
RPULLUP = 10kΩ
tPOR after VDD > VPOR
0.8
V
tCONV+1
µs
1
µs
81
81
81
°C
tPOR after VDD > VPOR
76
76
76
°C
tPOR after VDD > VPOR
97
97
97
°C
tPOR after VDD > VPOR
92
92
92
°C
tPOR after VDD > VPOR
97
97
97
°C
tPOR after VDD > VPOR
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.
MIC384
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 MIC384. Sink current should be minimized for best accuracy.
Guaranteed by design over the operating temperature range. Not 100% production tested.
tCONV = tCONV0 +(2 X tCONV1). tCONV0 is the conversion time for the local zone; tCONV1 is the conversion time for the remote zones.`
Accuracy specification does not include quantization noise, which may be as great as ±1⁄ 2LSB (±0.5°C).
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September 2005
MIC384
Micrel
Timing Diagram
t1
SCL
t4
t5
t2
SDA Data In
t3
SDA Data Out
Serial Interface Timing
September 2005
5
MIC384
MIC384
Micrel
Functional Diagram
VDD
8-Bit Sigma-Delta ADC
T1
3:1
MUX
T2
Bandgap
Sensor
and
Reference
Digital Filter
and
Control
Logic
1-Bit
DAC
Result
Registers
A0
2-Wire
Serial Bus
Interface
DATA
Pointer
Register
CLK
Temperature
Setpoint
Registers
State
Machine
and
Digital
Comparator
Temperature
Hysteresis
Registers
Configuration
Register
Open-Drain
Output
/INT
MIC384
GND
Functional Description
Power On" for more information. A0 determines the slave
address as shown in Table 1:
Pin Descriptions
VDD: Power supply input. See electrical specifications.
GND: Ground return for all MIC384 functions.
P a r t N u m be r
MI C 3 8 4 -0
CLK: Clock input to the MIC384 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 MIC384’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 MIC384 will only respond to
its own unique slave address, allowing up to eight MIC384’s to
share a single bus. A match between the MIC384’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
MIC384
MI C 3 8 4 -1
MI C 3 8 4 -2
MI C 3 8 4 -3
I n p u ts
MI C 3 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
0
100 1010b
4Ah
1
1 0 0 1 0 11 b
4B h
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
Table 1. MIC384 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 MIC384’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
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September 2005
MIC384
Micrel
is set, it prevents the /INT output from sinking current. In
I2C and SMBus systems, the IM bit is therefore an interrupt
mask bit.
T1 and T2: The T1 and T2 pins connect to off-chip PN diode
junctions, for monitoring the temperature at remote locations.
The remote diodes may be embedded thermal sensing
junctions in integrated circuits so equipped (such as Intel's
Pentium III), or discrete 2N3906-type bipolar transistors 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. The
temperature is calculated by measuring the forward voltage of
a diode junction at two different bias current levels. An internal
multiplexer directs the current source’s output to either the
internal or one of the external diode junctions. The MIC384
uses two’s-complement 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 any
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 MIC384 continuously performs
temperature-to-digital conversions, compares the results
against the setpoint and hysteresis registers, and updates
the state of /INT and the status bits accordingly. The remote
zones are converted first, followed by the local zone (T1⇒
T2⇒LOCAL). The states of /INT and the status bits are
updated after each measurement is taken.
Diode Faults
The MIC384 is designed to respond in a failsafe manner
to hardware faults in the external sensing circuitry. If the
connection to an external diode is lost or the sense line (T1
or T2) 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 the setpoint register for the corresponding zone is 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 MIC384 complete the number of conversion
cycles specified by Fault_Queue (see below). 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 MIC384 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 MIC384, 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 MIC384 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 MIC384 registers
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 MIC384 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 MIC384, and then retrieves the data byte. Figures
1 through 3 show the formats for these procedures.
C o m m a n d _ B y te
T a r g e t R e g i s te r
B ina r y
Hex
L a be l
D e s c r i p ti o n
0000 0000b
00h
T E MP 0
loc a l te mpe ra ture
0000 0001b
01h
C O N F IG
c onfigura tion re gis te r
0000 0010b
02h
T _HY S T 0
loc a l te mpe ra ture hys te re s is
0000 0011b
03h
T _S E T 0
loc a l te mpe ra ture s e tpoint
0001 0000b
10h
T E MP 1
re mote z one 1 te mpe ra ture
0001 0010b
12h
T _ H Y S T 1 re mote z one 1 te mpe ra ture hys te re s is
0001 0011b
13h
T _S E T 1
0010 0000b
20h
T E MP 2
re mote z one 1 te mpe ra ture s e tpoint
re mote z one 2 te mpe ra ture
0010 0010b
22h
T _HY S T 2
re mote z one 2 te mpe ra ture hys te re s is
0010 0011b
23h
T _S E T 2
re mote z one 2 te mpe ra ture s e tpoint
Table 2. MIC384 Register Addresses
September 2005
7
MIC384
MIC384
CLK
DATA
Command Byte
Data Byte to MIC384
START
ACKNOWLEDGE
NOT ACKNOWLEDGE
STOP
START
8
CLK
DATA
R/W = WRITE
R/W = READ
Master-to-slave transmission
START
R/W = READ
NOT ACKNOWLEDGE
Slave-to-master response
ACKNOWLEDGE
Figure 3. RECEIVE_BYTE
Master-to-slave transmission
START
STOP
NOT ACKNOWLEDGE
Slave-to-master response
ACKNOWLEDGE
S 1 0 0 1 X X A0 1 A X X X X X X X X /A P
Data Byte from MIC384
Figure 2. READ_BYTE Protocol
ACKNOWLEDGE
MIC384 Slave Address
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
Data Read From MIC384
Slave-to-master response
MIC384 Slave Address
Figure 1. WRITE_BYTE Protocol
Master-to-slave transmission
ACKNOWLEDGE
Command Byte
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
MIC384 Slave Address
CLK
DATA
MIC384 Slave Address
STOP
MIC384
Micrel
September 2005
September 2005
9
START
R/W = DONT CARE
Slave-to-master response
MIC384 Slave Address
Figure 4. A/D Converter Timing
Command Byte = 01h = CONFIG
STOP
CONFIG Value*
New Conversion�
in Progress
tCONV1
New Conversion
First
Begins
Result�
Ready
NOT ACKNOWLEDGE
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
MIC384 Slave Address
Last Byte of Transaction
X X X X X X X X /A P
A/D Converter�
in Standby
ACKNOWLEDGE
…
Master-to-slave transmission
ACKNOWLEDGE
Conversion Interrupted
By MIC384 Acknowledge
Conversion�
in Progress
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
MIC384 Slave Address
STOP
MIC384
Micrel
MIC384
MIC384
Micrel
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 MIC384
for temperatures.
A/D Converter Timing
Whenever the MIC384 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 MIC384.
Upon powering up or coming out of shutdown mode, the ADC
will begin acquiring temperature data starting with the first
external zone, zone 1, then the second external zone, zone
2, and finally the internal zone, zone 0. Results for zone 1 will
be valid after tCONV1, results for zone two will be ready after
another tCONV1, 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
allws the use of a filter capacitor on T1 and/or T2 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 aquiring temperature data with the first external zone
(zone 1), followed by the second external zone (zone 2), and
then the internal zone (zone 0). If the ADC in 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 MIC384 is shut
down, powered off, or is interrupted by a serial bus transaction as described above.
Power On
When power is initially applied, the MIC384’s internal registers
are set to their default states. Also at this time, the level on
the address input, A0, is read to establish the device’s slave
address. The MIC384’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
• T_SET2 = 97°C; T_HYST2 = 92°C
• Initialized to recognize overtemperature faults
MIC384
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 any
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 bit(s) 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 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 MIC384’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 MIC384 backward compatible with that of the LM75 and similar devices. In both modes,
the MIC384 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
MIC384’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.
However, if the device is shut down while in interrupt mode,
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 MIC384 is in
10
September 2005
MIC384
Micrel
T e m p e r a tu r e
B ina ry
Hex
+1 2 5 ° C
0 1 1 1 1 1 01 b
7Dh
+1 0 0 ° C
0110 0100 b
64h
+2 5 ° C
0001 1001b
19h
+1 . 0 ° C
0000 000 1b
01h
0° C
0000 0000 b
00h
– 1. 0° C
1111 1111b
FFh
– 25° C
1 1 1 0 0 1 11 b
E 7h
– 40° C
1 1 0 1 1 0 00 b
D 8h
– 55° C
1 1 0 0 1 0 01 b
C 9h
Table 3. Digital Temperature Format
September 2005
11
MIC384
MIC384
Micrel
shutdown mode, and the interrupt status will not be retained.
Since entering shutdown mode stops A/D conversions, the
MIC384 is incapable of detecting or reporting temperature
events of any kind while in shutdown. Diode faults require
one or more A/D conversion cycles to be recognized, and
therefore will not be reported either while the device is in
shutdown (see "Diode Faults" above).
S2, in CONFIG and assert its /INT 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 CONFIG). Following an
interrupt, the host should read the contents of the configuration register to confirm that the MIC384 was the source of the
interrupt. A read operation on any register will cause /INT to
be de-asserted. This is shown in Figure 5. The status bits
will only be cleared once CONFIG has been read.
Since temperature-to-digital conversions continue while /INT
is asserted, the measured temperature could change between
the MIC384’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 MIC384 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 status bits (S0, S1, and S2). This should not
be done before completing the appropriate interrupt service
routine(s).
Polling
The MIC384 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 MIC384,
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
MIC384 and prevent the /INT pin from sinking current.
Fault_Queue
Fault queues (programmable digital filters) are provided
in the MIC384 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,
or TEMPx < T_HYSTx) which must occur in order for the
condition to be considered valid. There are separate fault
queues for each zone. 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 then 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.
C O N F IG [4: 3]
F a u l t_ Q u e u e D e p th
00
1 c onve rs ion*
01
2 c onve rs ions
10
4 c onve rs ions
11
6 c onve rs ions
* D e fa ult s e tting
Table 4. Fault_Queue Depth Settings
Interrupt Generation
Assuming the MIC384 is in interrupt mode and interrupts
are enabled, there are seven different conditions that will
cause the MIC384 to set one of the status bits, S0, S1, or
MIC384
12
September 2005
MIC384
Micrel
E v ent
C o n d i ti o n *
MI C 3 8 4 r e s p o n s e **
high te mpe ra ture , loc a l
T E MP 0 > T _ S E T 0
s e t S 0 in C O N F I G , a s s e rt /I N T
high te mpe ra ture ,
re mote z one 1
T E MP 1 > T _ S E T 1
s e t S 1 in C O N F I G , a s s e rt /I N T
high te mpe ra ture ,
re mote z one 2
T E MP 2 > T _ S E T 2
s e t S 2 in C O N F I G , a s s e rt /I N T
low te mpe ra ture , loc a l
T E MP 0 < T _ H Y S T 0
s e t S 0 in C O N F I G , a s s e rt /I N T
low te mpe ra ture ,
re mote z one 1
T E MP 1 < T _ H Y S T 1
s e t S 1 in C O N F I G , a s s e rt /I N T
low te mpe ra ture ,
re mote z one 2
T E MP 2 < T _ H Y S T 2
s e t S 2 in C O N F I G , a s s e rt /I N T
diode fa ult
T 1 or T 2 ope n or s horte d to V D D or
G ND
s e t S 1 a nd/or S 2 in C O N F I G , a s s e rt /I N T
a nd /C R I T ***
* C ondition mus t be true for F A U L T _ Q U E U E c onve rs ion to be re c ogniz e d
** A s s ume s inte rrupts e na ble d
*** A s s ume s the T _ S E T 1 a nd/or C R I T 1 a re s e t to a ny va lue le s s the n +1 2 7 ° C = 7 fh = 0 1 1 1 1 1 1 1 b
Table 5. MIC384 Temperature Events
September 2005
13
MIC384
MIC384
Micrel
Register Set and Programmer’s Model
Internal Register Set
Na me
D e s c r i p ti o n
C o m m a n d B y te
O p e r a ti o n
P o w e r -U p D e f a u l t
T E MP 0
me a s ure d te mpe ra ture ,
loc a l z one
00h
8 -bit re a d only
0 0h ( 0° C ) (1)
C O N F IG
c onfigura tion re gis te r
01h
8 -bit re a d/write
0 0 h( 2 )
T _HY S T 0
hys te re s is s e tting, loc a l
z o ne
02h
8 -bit re a d/write
4 C h ( +7 6 ° C )
T _S E T 0
te mpe ra ture s e tpoint, loc a l
z o ne
03h
8 -bit re a d/write
5 1 h ( +8 1 ° C )
T E MP 1
me a s ure d te mpe ra ture ,
z o ne 1
10h
8 -bit re a d only
0 0h ( 0° C ) (1)
T _HY S T 1
hys te re s is s e tting, z one 1
1 2h
8 -bit re a d/write
5 C h ( +9 2 ° C )
T _S E T 1
te mpe ra ture s e tpoint,
z o ne 1
13h
8 -bit re a d/write
6 1 h ( +9 7 ° C )
T E MP 2
me a s ure d te mpe ra ture ,
z o ne 2
20h
8 -bit re a d only
0 0h ( 0° C ) (1)
T _HY S T 2
hys te re s is s e tting, z one 2
22h
8 -bit re a d/write
5 C h ( +9 2 ° C )
T _S E T 2
te mpe ra ture s e tpoint,
z o ne 2
23h
8 -bit re a d/write
6 1 h ( +9 7 ° C )
(1)
TEMPx 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.
Detailed Register Descriptions
Configuration Register
C O N F IG U R A T IO N R E G IS T E R (C O N F IG )
8 -B i t R e a d /W r i te
D [7]
D [ 6]
D [ 5]
re a d only
re a d only
re a d only
loc a l
s ta tus
(S 0)
re mote
s ta tus
(S 1)
/C R I T
s ta tus
(C R IT 1)
B i ts
D [ 4]
D [ 3]
D [ 2]
D [ 1]
D [ 0]
re a d/write
re a d/write
re a d/write
re a d/write
fa ult que ue
de pth
( F Q [1 : 0 ])
inte rrupt
ma s k
( I M)
C MP /I N T
mode
( MO D E )
S hutdown
(S H DN )
F u n c ti o n
O p e r a ti o n
S0
loc a l inte rrupt s ta tus ( re a d only)
1 = e ve nt oc c ure d, 0 = no e ve nt
S1
re mote inte rrupt s ta tus ( re a d only)
1 = e ve nt oc c ure d, 0 = no e ve nt
re mote ove r-te mpe ra ture s ta tus ( re a d only)
1 = ove r-te mpe ra ture , 0 = no e ve nt
C R IT 1
0 0 = 1 c onve rs ion, 0 1 = 2 c onve rs ions ,
1 0 = 4 c onve rs ions , 1 1 = 6 c onve rs ions
F Q [1 : 0 ] F a ult_ Q ue ue de pth
IM
inte rrupt ma s k
1 = dis a ble d, 0 = inte rrupts e na ble d
MO D E
c ompa ra tor/inte rrupt
mode s e le c tion for /I N T pin
1 = inte rrupt mode ,
0 = c ompa ra tor mode
S HDN
norma l/s hutdown
ope ra ting mode s e le c tion
1 = s hutdown,
0 = norma l
CONFIG Power-Up Value: 0000 0000b = 00h(*)
• not in shutdown mode
• comparator mode
• 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.
MIC384
14
September 2005
MIC384
Micrel
Local Temperature Result Register
L O C A L T E MP E R A T U R E R E S U L T R E G I S T E R ( T E MP 0 )
8 -B i t R e a d /W r i te
D [7]
D [ 6]
D [ 5]
MS B
bit 6
bit 5
D [ 4]
D [ 3]
D [ 2]
D [ 1]
D [ 0]
bit 4
bit 3
bit 2
bit 1
LS B
te mpe ra ture da ta from A D C *
B i ts
D [7 : 0 ]
F u n c ti o n
O p e r a ti o n
me a s ure d te mpe ra ture da ta for the loc a l
z o ne *
TEMP0 Power-Up Value: 0000 0000b = 00h (0°C)†
TEMP0 Command Byte Value: 0000 0000b = 00h
re a d only
* 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 Hysteresis Register
L O C A L T E MP E R A T U R E H Y S T E R E S I S ( T _ H Y S T 0 )
8 -B i t R e a d /W r i te
D [7]
D [ 6]
D [ 5]
D [ 4]
D [ 3]
D [ 2]
D [ 1]
D [ 0]
MS B
bit 6
bit 5
bit 4
bit 3
bit 2
bit 1
LS B
loc a l te mpe ra ture hys te re s is s e tting
B i ts
D [7 : 0 ]
F u n c ti o n
O p e r a ti o n
loc a l te mpe ra ture hys te re s is s e tting*
T_HYST0 Power-Up Value: 0100 1100b = 4Ch (+76°C)
T_HYST0 Command Byte Value: 0000 0010b = 02h
re a d/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
L O C A L T E MP E R A T U R E S E T P O I N T ( T _ S E T 0 )
8 -B i t R e a d /W r i te
D [7]
D [ 6]
D [ 5]
D [ 4]
D [ 3]
D [ 2]
D [ 1]
D [ 0]
MS B
bit 6
bit 5
bit 4
bit 3
bit 2
bit 1
LS B
loc a l te mpe ra ture s e tpoint
B i ts
D [7 : 0 ]
F u n c ti o n
O p e r a ti o n
loc a l te mpe ra ture s e tpoint*
re a d/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
MIC384
MIC384
Micrel
Remote Zone 1 Temperature Result Register
R E MO T E Z O N E 1 T E MP E R A T U R E R E S U L T ( T E MP 1 )
8 -B i t R e a d O n l y
D [7]
D [ 6]
MS B
bit 6
D [ 5]
D [ 4]
D [ 3]
D [ 2]
D [ 1]
D [ 0]
bit 5
bit 4
bit 3
bit 2
bit 1
LS B
re mote z one 1 te mpe ra ture da ta from A D C *
B i ts
D [7 : 0 ]
F u n c ti o n
O p e r a ti o n
me a s ure d te mpe ra ture da ta for re mote
z o ne o ne *
TEMP1 Power-Up Value: 0000 0000b = 00h (0°C)†
TEMP1 Command Byte Value: 0001 0000b = 10h
re a d only
* 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 Zone 1 Hysteresis Register
R E MO T E Z O N E 1 T E MP E R A T U R E H Y S T E R E S I S R E G I S T E R ( T _ H Y S T 1 )
8 -B i t R e a d /W r i te
D [7]
D [ 6]
D [ 5]
D [ 4]
D [ 3]
D [ 2]
D [ 1]
D [ 0]
MS B
bit 6
bit 5
bit 4
bit 3
bit 2
bit 1
LS B
re mote z one 1 te mpe ra ture hys te re s is *
B i ts
D [7 : 0 ]
F u n c ti o n
O p e r a ti o n
re mote z one one te mpe ra ture hys te re s is *
T_HYST1 Power-Up Value: 0101 1100b = 5Ch (+92°C)
T_HYST1 Command Byte Value: 0001 0010b = 12h
re a d/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 Zone 1 Temperature Setpoint Register
R E MO T E Z O N E 1 T E MP E R A T U R E S E T P O I N T ( T _ S E T 1 )
8 -B i t R e a d /W r i te
D [7]
D [ 6]
D [ 5]
D [ 4]
D [ 3]
D [ 2]
D [ 1]
D [ 0]
MS B
bit 6
bit 5
bit 4
bit 3
bit 2
bit 1
LS B
re mote z one 1 te mpe ra ture s e tpoint
B i ts
D [7 : 0 ]
F u n c ti o n
O p e r a ti o n
re mote z one one te mpe ra ture s e tpoint*
T_SET1 Power-Up Value: 0110 0001b = 61h (+97°C)
T_SET1 Command Byte Value: 0001 0011b = 13h
MIC384
re a d/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.
16
September 2005
MIC384
Micrel
Remote Zone 2 Temperature Result Register
R E MO T E Z O N E 2 T E MP E R A T U R E R E S U L T S R E G I S T E R ( T E MP 2 )
8 -B i t R e a d O n l y
D [7]
D [ 6]
MS B
bit 6
D [ 5]
D [ 4]
D [ 3]
D [ 2]
D [ 1]
D [ 0]
bit 5
bit 4
bit 3
bit 2
bit 1
LS B
re mote z one 2 te mpe ra ture da ta from A D C *
B i ts
F u n c ti o n
D [7 : 0 ]
me a s ure d te mpe ra ture da ta for re mote
z o ne 2 *
O p e r a ti o n
TEMP2 Power-Up Value: 0000 0000b = 00h (0°C)†
TEMP2 Command Byte Value: 0010 0000b = 20h
re a d only
* 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.
†
TEMP2 will contain measured temperature data for the selected zone after the completion of one conversion.
Remote Zone 2 Hysteresis Register
R E MO T E Z O N E 2 H Y S T E R E S I S R E G I S T E R ( T _ H Y S T 2 )
8 -B i t R e a d /W r i te
D [7]
D [ 6]
D [ 5]
D [ 4]
D [ 3]
D [ 2]
D [ 1]
D [ 0]
MS B
bit 6
bit 5
bit 4
bit 3
bit 2
bit 1
LS B
re mote z one 2 te mpe ra ture hys te re s is s e tting
B i ts
F u n c ti o n
D [7 : 0 ]
re mote z one 2 te mpe ra ture hys te re s is
s e tting*
O p e r a ti o n
T_HYST2 Power-Up Value: 0101 1100b = 5Ch (+92°C)
T_HYST2 Command Byte Value: 0010 0010b = 22h
re a d/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 Zone 2 Setpoint Register
R E MO T E Z O N E 2 T E MP E R A T U R E S E T P O I N T ( T _ S E T 2 )
8 -B i t R e a d /W r i te
D [7]
D [ 6]
D [ 5]
D [ 4]
D [ 3]
D [ 2]
D [ 1]
D [ 0]
MS B
bit 6
bit 5
bit 4
bit 3
bit 2
bit 1
LS B
re mote z one 2 te mpe ra ture s e tpoint
B i ts
F u n c ti o n
O p e r a ti o n
D [7 : 0 ]
re mote z one 2 te mpe ra ture s e tpoint*
T_SET2 Power-Up Value: 0110 0001b = 61h (+97°C)
T_SET2 Command Byte Value: 0010 0011b = 23h
September 2005
re a d/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
MIC384
MIC384
Micrel
Applications
against calculation in the final application environment. This
is especially true when dealing with systems for which some
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 MIC384 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 external diodes connected between
T1, T2 and ground.
Since this technique relies upon measuring the relatively
small voltage difference resulting from two levels of current
through the external diodes, any resistance in series with
those diodes will cause an error in the temperature reading from the MIC384. A good rule of thumb is this: for each
ohm in series with a zone's external transistor, there will be
a 0.9°C error in the MIC384’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
It is sometimes desirable to use a filter capacitor between
the T1 and/or T2 pins and the GND pin of the MIC384. The
use of these capacitors 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 diodes. The maximum recommended total capacitance from
the T1 or T2 pin to GND is 2700pF. This typically suggests
the use of 2200pF NP0 or C0G ceramic capacitors with a
10% tolerance.
If a remote diode is to be at a distance of more than ≈ 6"—12"
from the MIC384, 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.
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 MIC384. 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 MIC384 is to avoid errors in measuring
the local temperature induced by self-heating. Self-heating
is caused by the power naturally dissipated inside the device
due to operating supply current and I/O sink currents (VDD ×
IDD ) + (VOL × IOL). In order to understand what level of error
this represents, and how to reduce that error, the dissipation
in the MIC384 must be calculated and its effects reduced to
a temperature offset.
The worst-case operating condition for the MIC384 is when
VDD = 5.5V, MSOP-08 package. The 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 MIC384 is negligible. Similarly, the DATA
pin will in all likelihood have a duty cycle of substantially less
than 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 interruptmode. This is illustrated in Equation 2.
If the part is to be used in comparator mode, calculations
similar to those shown above (accounting for the expected
value and duty cycle of IOL(INT)) will give a good estimate of
the temperature error due to self-heating.
In any application, the best test is to verify performance
PD = [(IDD x VDD) + (IOL(DATA)) x VOL(DATA) + (IOL(/INT) x VOL(/INT))]
PD = [(0.75mA x 5.5V) + (6mA x 0.8V) + (6mA x 0.8V)]
PD = 13.73mW
Rq(j-a) of MSOP - 08 package is 206°C/W
Maximum ∆TJ relative to TA due to self heating is 13.73mW x 206°C/W = 2.83°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)] = 1.27mW
∆TJ = (1.27mW x 206°C/W)
∆TJ = 0.262°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
MIC384
18
September 2005
MIC384
Micrel
Layout Considerations
The following guidelines should be kept in mind when designing and laying out circuits using the MIC384:
1. Place the MIC384 as close to the remote diodes
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 to the T1 or T2 line can
induce serious errors, it is good practice to guard
the remote diodes’ emitter traces with pairs of
ground traces. These ground traces should be
returned to the MIC384’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 diodes’ own ground
return back to the ground pin of the MIC384,
thereby providing a Kelvin connection for the
base of the diodes. See Figure 6.
3. When using the MIC384 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 MIC384 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
MIC384 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
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/T2 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 MIC384 and under the connections from
the MIC384 to the remote diodes. This will help
guard against stray noise pickup.
6. Always place a good quality 0.1µF power supply
bypass capacitor directly adjacent to, or underneath, the MIC384. Surface-mount capacitors
are preferable because of their low inductance.
7. When the MIC384 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 an additional 4.7µF,
6.3V electrolytic capacitor from VDD to GND.
See Figure 7.
MIC384
1 DATA
VDD 8
2 CLK
A0 7
3 /INT
T1 6
4 GND
T2 5
GUARD/RETURN
REMOTE DIODE (T1)
GUARD/RETURN
GUARD/RETURN
REMOTE DIODE (T2)
GUARD/RETURN
Figure 6. Guard Traces/Kelvin Ground Returns
September 2005
19
MIC384
MIC384
Micrel
100
3.3V
10k pull-ups
FROM
SERIAL BUS
HOST
0.1µF
4.7µF
MIC384
DATA
VDD
CLK
/ INT
GND
T1
T2
A0
2200pF
2200pF
Remote
Diode
Remote
Diode
Figure 7. VDD Decoupling for Very Noisy Supplies
MIC384
20
September 2005
MIC384
Micrel
Package Information
8-Lead SOIC (M)
8-Lead MSOP (MM)
September 2005
21
MIC384
MIC384
Micrel
MICREL INC.
2180 FORTUNE DRIVE
SAN JOSE, CA 95131
USA
TEL + 1 (408) 944-0800 FAX + 1 (408) 474-1000 WEB http://www.micrel.com
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
MIC384
22
September 2005