Datasheet MIC384-1BM, MIC384-1BMM, MIC384-2BM, MIC384-2BMM, MIC384-0BMM Datasheet (MICREL)

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Page 1

MIC384 Micrel

MIC384

Three-Zone Thermal Supervisor

Advance Information

General Description

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 2wire 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.

*SMBus and Pentium III are trademarks of Intel Corporation.

**I2C is a trademark of Philips Electronics, N.V.

Ordering Information

Part Number Base Address(* MIC384-0BM 100 100x –55°C to +125°C 8-Lead SOP MIC384-1BM 100 101x –55°C to +125°C 8-Lead SOP Contact Factory MIC384-2BM 100 110x –55°C to +125°C 8-Lead SOP Contact Factory MIC384-3BM 100 111x –55°C to +125°C 8-Lead SOP Contact Factory MIC384-0BMM 100 100x –55°C to +125°C 8-Lead MSOP MIC384-1BMM 100 101x –55°C to +125°C 8-Lead MSOP Contact Factory MIC384-2BMM 100 110x –55°C to +125°C 8-Lead MSOP Contact Factory MIC384-3BMM 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.

Features

• 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

• Desktop, Server and Notebook Computers

• Power Supplies

• Test and Measurement Equipment

• Wireless Systems

• Networking/Datacom Hardware

)

Junction Temp. Range Package Notes

T ypical Application

3.3V 3 × 10k

FROM

SERIAL BUS

HOST

pull-ups

DATA CLK /INT GND

MIC384

VDD

T1 T2 A0

3-Channel SMBus Temperature Measurement System

Micrel, Inc. • 1849 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 944-0970 • http://www.micrel.com

September 2000 1 MIC384

0.1µF

2200pF

REMOTE DIODE

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MIC384 Micrel

Pin Configuration

CLK /INT

GND

Pin Description

Pin Number Pin Name Pin Function

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. MIC284 Slave

8 VDD Analog Input: Power supply input to the IC.

1DATA 2 3 4

Address Setings.

8 VDD

MIC384 2 September 2000

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MIC384 Micrel

Absolute Maximum Ratings (Note 1)

Power Supply Voltage, V

Voltage on Any Pin................................–0.3V to V

Current Into Any Pin.................................................±10mA

Power Dissipation, T

Junction Temperature ............................................. +150°C

................................................... 6.0V

+0.3V

= +125°C ...............................30mW

Operating Ratings (Note 2)

Power Supply Voltage, V Ambient Temperature Range (T Package Thermal Resistance (θ

SOP.................................................................+152°C/W

MSOP..............................................................+206°C/W

.............................. +2.7V to +5.5V

) ............-55°C to +125°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

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 Min Typ Max Units Power Supply

POR

HYST

Temperature-to-Digital Converter Characteristics

CONV0

CONV1

Remote Temperature Inputs (T1, T2)

Address Input (A0)

LEAK

Supply Current /INT, open, A0 = VDD or GND, 350 750 µA

CLK = DATA = high, normal mode /INT, open, A0 = V

shutdown mode, CLK = 100kHz /INT, open, A0 = V

shutdown mode, CLK = DATA = high

Power-On Reset Time; Note 7 VDD > V

POR

or GND, 3 µA

or GND, 1 10 µA

200 µs

Power-On Reset Voltage all registers reset to default values, 2.0 2.7 V

A/D conversions initiated

Power-On Reset Hysteresis Voltage 250 mV

Accuracy—Local Temperature 0°C ≤ T

≤ +100°C, /INT open, ±1 ±2 °C

Note 4, 9 3V ≤ VDD ≤ 3.6V

–55°C ≤ T

≤ +125°C, /INT open, ±2 ±3 °C

3V ≤ VDD ≤ 3.6V

Accuracy—Remote Temperature 0°C ≤ T

≤ +100°C, /INT open, ±1 ±3 °C

Note 5, 4, 9 3V ≤ VDD ≤ 3.6V, 0°C ≤ TA ≤ +85°C

–55°C ≤ T

≤ +125°C, /INT open, ±2 ±5 °C

3V ≤ VDD ≤ 3.6V, 0°C ≤ TA ≤ +85°C

Conversion Time, local zone 50 80 ms Note 7, 8

Conversion Time, remote zone Note 7, 8 100 160 ms

Current to External Diode high level, T1 or T2 forced to 1.5V 224 400 µA

Note 7

low level 7.5 14 µA

Low Input Voltage 2.7V ≤ VDD ≤ 5.5V 0.6 V High Input Voltage 2.7V ≤ VDD ≤ 5.5V 2.0 V Input Capacitance 10 pF Input Current ±0.01 ±1 µA

September 2000 3 MIC384

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MIC384 Micrel

Symbol Parameter Condition Min Typ Max Units Serial Data I/O Pin (DATA)

LEAK

Serial Clock Input (CLK)

LEAK

Status Output (/INT)

INT

nINT

T_SET0 Default T_SET0 Value t T_HYST0 Default T_HYST0 Value t T_SET1 Default T_SET1 Value t T_HYST1 Default T_HYST1 Value t T_SET2 Default T_SET2 Value t T_HYST2 Default T_HYST2 Value t

Serial Interface Timing (Note 7)

Low Output Voltage IOL = 3mA 0.4 V Note 6 IOL = 6mA 0.8 V Low Input Voltage 2.7V ≤ VDD ≤ 5.5V 0.3V High Input Voltage 2.7V ≤ VDD ≤ 5.5V 0.7V

V V

Input Capacitance 10 pF Input current ±0.01 ±1 µA

Low Input Voltage 2.7V ≤ VDD ≤ 5.5V 0.3V High Input Voltage 2.7V ≤ VDD ≤ 5.5V 0.7V

V V

Input Capacitance 10 pF Input current ±0.01 ±1 µA

Low Output Voltage, IOL = 3mA 0.4 V

Note 6

Interrupt Propagation Delay, Note 7, 8 to /INT < VOL, FQ = 00, R

IOL = 6mA 0.8 V from

TEMPx > T_SETx or TEMPx < T_HYSTx

= 10kΩ

PULLUP

CONV

µs

Interrupt Reset Propagation Delay, from any register read to /INT > VOH, 1 µs Note 7 R

POR POR POR POR POR POR

= 10kΩ

PULLUP

after VDD > V after VDD > V after VDD > V after VDD > V after VDD > V after VDD > V

POR POR POR POR POR POR

81 81 81 °C 76 76 76 °C 97 97 97 °C 92 92 92 °C 97 97 97 °C 92 92 92 °C

CLK (Clock) Period 2.5 µs Data In Setup Time to CLK High 100 ns Data Out Stable After CLK Low 0 ns DATA Low Setup Time to CLK Low start condition 100 ns DATA High Hold Time stop condition 100 ns

After CLK High

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.

Note 4. Final test on outgoing product is performed at TA = TBD°C. Note 5. 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. Note 6. Current into this pin will result in self-heating of the MIC384. Sink current should be minimized for best accuracy. Note 7. Guaranteed by design over the operating temperature range. Not 100% production tested. Note 8. t

Human body model: 1.5k in series with 100pF. Machine model: 200pF, no series resistance.

CONV

= t

CONV0

+(2 X t

CONV1

). t

is the conversion time for the local zone; t

CONV0

is the conversion time for the remote zones.`

CONV1

MIC384 4 September 2000

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MIC384 Micrel

Note 9. Accuracy specification does not include quantization noise, which may be as great as ±1⁄2LSB (±0.5°C).

Timing Diagram

SCL

SDA Data In

SDA Data Out

Serial Interface Timing

September 2000 5 MIC384

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MIC384 Micrel

Functional Diagram

VDD

8-Bit Sigma-Delta ADC

T1 T2

3:1

MUX

∑

∫

DATA

CLK

MIC384

Bandgap

Sensor

and

Reference

2-Wire

Serial Bus

Interface

Pointer

1-Bit DAC

Registers

Temperature

Setpoint

Registers

Temperature

Hysteresis

Registers

Configuration

Result

GND

Digital Filter

and

Control

Logic

State

Machine

and

Digital

Comparator

Open-Drain

Output

/INT

Functional Description

Pin Descriptions VDD: Power supply input. See electrical specifications. GND: Ground return for all MIC384 functions. 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 Power On" for more information. A0 determines the slave address as shown in Table 1:

rebmuNtraP

0-483CIM0 0001001

1-483CIM0 0101001

2-483CIM0 0011001

3-483CIM0 0111001

stupnIsserddAevalS483CIM

0AyraniBxeH

11001001

11101001

11011001

11111001

b b b b b b b

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 is

MIC384 6 September 2000

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MIC384 Micrel

set, it prevents the /INT output from sinking current. In I 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

value less than 127°C (7F 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.

= 0111 1111b). An interrupt will

connection to an external diode is lost or the sense line (T1 or T2) is shorted to V

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

etyB_dnammoCretsigeRtegraT

yraniBxeHlebaLnoitpircseD

00000000

10000000

01000000

11000000

00001000

01001000

11001000

00000100

01000100

11000100

0PMETerutarepmetlacol

GIFNOCretsigernoitarugifnoc

0TSYH_Tsiseretsyherutarepmetlacol

0TES_Ttniopteserutarepmetlacol

1PMETerutarepmet1enozetomer

1TSYH_Tsiseretsyherutarepmet1enozetomer

1TES_Ttniopteserutarepmet1enozetomer

2PMETerutarepmet2enozetomer

2TSYH_Tsiseretsyherutarepmet2enozetomer

2TES_Ttniopteserutarepmet2enozetomer

Table 2. MIC384 Register Addresses

September 2000 7 MIC384

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MIC384 Micrel

S1001

XXA0

0A00XXXXXXA

XXX XXXXX

/A P

MIC384 Slave Address

DATA

CLK

Command Byte

Data Byte to MIC384

START

STOP

R/W = WRITE

ACKNOWLEDGE ACKNOWLEDGE

NOT ACKNOWLEDGE

Master-to-slave transmission Slave-to-master response

S1001

XXA0 XXA0

0A00XXXXXXAS1 1 100

XXX XXXX

/A P

MIC384 Slave Address

DATA

CLK

Command Byte

MIC384 Slave Address

Data Read From MIC384

START

STOP

R/W = WRITE

R/W = READ

ACKNOWLEDGE ACKNOWLEDGE ACKNOWLEDGE

NOT ACKNOWLEDGE

Master-to-slave transmission Slave-to-master response

S1001

XXA0

1A /A

XXX XXX PXX

MIC384 Slave Address

DATA

CLK

Data Byte from MIC384

START

STOP

R/W = READ

ACKNOWLEDGE NOT ACKNOWLEDGE

Master-to-slave transmission Slave-to-master response

Figure 1. WRITE_BYTE Protocol

Figure 2. READ_BYTE Protocol

Figure 3. RECEIVE_BYTE

MIC384 8 September 2000

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MIC384 Micrel

S1001

XXX

AXX XXXXXXXA

MIC384 Slave Address

First Byte of Transaction

START

ACKNOWLEDGE ACKNOWLEDGE

R/W = DONT CARE

/A PXX XXXXXX

Last Byte of Transaction

A/D Converter

in Standby

Conversion

in Progress

New Conversion

in Progress

New Conversion

Begins

Conversion Interrupted

By MIC384 Acknowledge

First

Result

Ready

CONV1

STOP

NOT ACKNOWLEDGE

…

Master-to-slave transmission Slave-to-master response

SS1000

XXA0 XXA0

0A00000001A 10 100 XX XXXXXX/AP

MIC384 Slave Address

Temperature event occurs

MIC384 Slave Address

INT

Command Byte = 01

= CONFIG

CONFIG Value*

START

STOP

R/W = WRITE

ACKNOWLEDGE

R/W = READ

NOT ACKNOWLEDGE

Master-to-slave transmission Slave-to-master response

n/INT

/INT

* Status bits in CONFIG are cleared to zero following this operation

Figure 4. A/D Converter Timing

Figure 5. Responding to Interrupts

September 2000 9 MIC384

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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 t another t

CONV1

, results for zone two will be ready after

CONV1

, and for the local zone t

later. Figure 4

CONV0

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

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.

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

MIC384 10 September 2000

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MIC384 Micrel

erutarepmeTyraniBxeH

C°521+10111110 C°001+00100110

C°52+10011000

C°0.1+10000000

C°000000000

C°0.1– 11111111 C°52– 11100111 C°04– 00011011 C°55– 10010011

b b b b b b b b b

Table 3. Digital Temperature Format

September 2000 11 MIC384

Page 12

MIC384 Micrel

is in 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).

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 10

. 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 t

to detect a temperature event. The depth of

CONV

Fault_Queue vs. D[4:3] of the configuration register is shown in Table 4.

]3:4[GIFNOChtpeDeueuQ_tluaF

00*noisrevnoc1

10snoisrevnoc2

01snoisrevnoc4

11snoisrevnoc6

gnittestluafeD*

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 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 under-temperature condition still exists. In addition, more than one temperature event may have occurred simultaneously or in rapid succession between the assertion of /INT and servicing of the 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.

MIC384 12 September 2000

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MIC384 Micrel

tnevE*noitidnoC**esnopser482CIM

lacol,erutarepmethgih0TES_T>0PMETTNI/tressa,GIFNOCni0Stes

,erutarepmethgih

1enozetomer

,erutarepmethgih

2enozetomer

1TES_T>1PMETTNI/tressa,GIFNOCni1Stes

2TES_T>1PMETTNI/tressa,GIFNOCni2Stes

lacol,erutarepmetwol0TSYH_T<0PMETTNI/tressa,GIFNOCni0Stes

,erutarepmetwol

1enozetomer

,erutarepmetwol

2enozetomer

tluafedoid

delbaneerastpurretnisemussA**

DNG

1TSYH_T<1PMETTNI/tressa,GIFNOCni1Stes

2TSYH_T<1PMETTNI/tressa,GIFNOCni2Stes

roDDVotdetrohsronepo2Tro1T

dezingocerebotnoisrevnocEUEUQ_TLUAFrofeurtebtsumnoitidnoC*

f7=C°721+nehtsseleulavynaottesera2TES_Tdna1TES_TtahtsemussA***

,GIFNOCni2Sro/dna1SdnaTIRCtes

***TIRC/dnaTNI/tressa

11111110=

Table 5. MIC384 Temperature Events

September 2000 13 MIC384

Page 14

MIC384 Micrel

Internal Register Set

emaNnoitpircseDetyBdnammoCnoitarepOtluafeDpU-rewoP

0PMET

GIFNOCretsigernoitarugifnoc10

0TSYH_T

0TES_T

1PMET

enoz

1enoz

1TSYH_T1enoz,gnittessiseretsyh21

1TES_T

2PMET

1enoz

2enoz

,erutarepmetderusaem

enozlacol

lacol,gnittessiseretsyh

lacol,tniopteserutarepmet

,erutarepmetderusaem

,tniopteserutarepmet

,erutarepmetderusaem

ylnodaertib-800 etirw/daertib-800 etirw/daertib-8C4

etirw/daertib-815

ylnodaertib-800 etirw/daertib-8C5 etirw/daertib-816

h02ylnodaertib-800

2TSYH_T2enoz,gnittessiseretsyhh22etirw/daertib-8C5

2TES_T

2enoz

,tniopteserutarepmet

h32etirw/daertib-816

)1(

)C°0(

)2(

)C°67+(

)C°18+(

)1(

)C°0(

)C°29+(

)C°79+(

)1(

)C°0(

)C°29+(

)C°79+(

(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

]7[D]6[D]5[D]4[D]3[D]2[D]1[D]0[D

ylnodaerylnodaerylnodaeretirw/daeretirw/daeretirw/daeretirw/daer

0enoz

sutats

)0S(

stiBnoitcnuFnoitarepO

0S)ylnodaer(sutatstpurretnilacol tneveon=0,deruccotneve=1

1S)ylnodaer(sutatstpurretni1enozetomer tneveon=0,deruccotneve=1

2S)ylnodaer(sutatstpurretni2enozetomer tneveon=0,deruccotneve=1

]0:1[QFhtpedeueuQ_tluaF

MIksamtpurretni delbanestpurretni=0,delbasid=1

EDOM

NDHS

)GIFNOC(RETSIGERNOITARUGIFNOC

etirW/daeRtiB-8

1enoz

sutats

)1S(

2enoz

sutats

)2S(

eueuqtluaf

htped

)]0:1[QF(

tpurretni

ksam

)MI(

TNI/PMC

edom

)EDOM(

nwodtuhS

)NDHS(

,snoisrevnoc2=10,noisrevnoc1=00 snoisrevnoc6=11,snoisrevnoc4=01

tpurretni/rotarapmoc

nipTNI/rofnoitcelesedom

nwodtuhs/lamron

noitcelesedomgnitarepo

lamron=0

,edomtpurretni=1

edomrotarapmoc=0

,nwodtuhs=1

CONFIG Power-Up Value: 0000 0000b = 00

(*)

• not in shutdown mode

• comparator mode

• Fault_Queue depth = 1

• interrupts enabled.

• no temperature events pending

CONFIG Command Byte Value: 0000 0001b = 01

* Following the first Fault_Queue conversions, one or more of the status bits may be set.

MIC384 14 September 2000

Page 15

MIC384 Micrel

Local Temperature Result Register

)0PMET(STLUSERERUTAREPMETLACOL

ylnOdaeRtiB-8

]7[D]6[D]5[D]4[D]3[D]2[D]1[D]0[D

BSM6tib5tib4tib3tib2tib1tibBSL

*CDAmorfataderutarepmetlacol

stiBnoitcnuFnoitarepO

]0:7[D

*enoz

lacolehtrofataderutarepmetderusaem

ylnodaer

TEMP0 Power-Up Value: 0000 0000b = 00h (0°C) TEMP0 Command Byte Value: 0000 0000b = 00

†

Local Hysteresis Register

]7[D]6[D]5[D]4[D]3[D]2[D]1[D]0[D

BSM6tib5tib4tib3tib2tib1tibBSL

stiBnoitcnuFnoitarepO

]0:7[D*gnittessiseretsyherutarepmetlacoletirw/daer

T_HYST0 Power-Up Value: 0100 1100b = 4Ch (+76°C) T_HYST0 Command Byte Value: 0000 0010b = 02

* Each LSB represents one degree Centigrade. The values are

in a two's complement format such that 0°C is reported as 0000 0000

†

TEMP0 will contain measured temperature data after the completion of one conversion.

etirW/daeRtiB-8

* 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.

. See "Temperature Data Format" for more details.

)0TSYH_T(SISERETSYHERUTAREPMETLACOL

gnittessiseretsyherutarepmetlacol

Local Temperature Setpoint Register

)0TES_T(TNIOPTESERUTAREPMETLACOL

etirW/daeRtiB-8

]7[D]6[D]5[D]4[D]3[D]2[D]1[D]0[D

BSM6tib5tib4tib3tib2tib1tibBSL

tniopteserutarepmetlacol

stiBnoitcnuFnoitarepO

]0:7[D*tniopteserutarepmetlacoletirw/daer

T_SET0 Power-Up Value: 0101 0001b = 51h (+81°C) T_SET0 Command Byte Value: 0000 0011b = 03

* 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.

September 2000 15 MIC384

Page 16

MIC384 Micrel

Remote Zone 1 Temperature Result Register

)1PMET(TLUSERERUTAREPMET1ENOZETOMER

ylnOdaeRtiB-8

]7[D]6[D]5[D]4[D]3[D]2[D]1[D]0[D

BSM6tib5tib4tib3tib2tib1tibBSL

*CDAmorfataderutarepmet1enozetomer

stiBnoitcnuFnoitarepO

]0:7[D

*enoenoz

etomerrofataderutarepmetderusaem

ylnodaer

TEMP1 Power-Up Value: 0000 0000b = 00h (0°C) TEMP1 Command Byte Value: 0001 0000b = 10

†

Remote Zone 1 Hysteresis Register

]7[D]6[D]5[D]4[D]3[D]2[D]1[D]0[D

BSM6tib5tib4tib3tib2tib1tibBSL

stiBnoitcnuFnoitarepO

]0:7[D*siseretsyherutarepmetenoenozetomeretirw/daer

T_HYST1 Power-Up Value: 0101 1100b = 5Ch (+92°C) T_HYST1 Command Byte Value: 0001 0010b = 12

* Each LSB represents one degree Centigrade. The values are

in a two's complement format such that 0°C is reported as 0000 0000

†

TEMP1 will contain measured temperature data for the selected zone after the completion of one conversion.

etirW/daeRtiB-8

* 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.

. See "Temperature Data Format" for more details.

)1TSYH_T(RETSIGERSISERETSYHERUTAREPMET1ENOZETOMER

*siseretsyherutarepmet1enozetomer

Remote Zone 1 Temperature Setpoint Register

)1TES_T(TNIOPTESERUTAREPMET1ENOZETOMER

etirW/daeRtiB-8

]7[D]6[D]5[D]4[D]3[D]2[D]1[D]0[D

BSM6tib5tib4tib3tib2tib1tibBSL

tniopteserutarepmet1enozetomer

stiBnoitcnuFnoitarepO

]0:7[D*tniopteserutarepmetenoenozetomeretirw/daer

T_SET1 Power-Up Value: 0110 0001b = 61h (+97°C) T_SET1 Command Byte Value: 0001 0011b = 13

* 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.

MIC384 16 September 2000

Page 17

MIC384 Micrel

Remote Zone 2 Temperature Result Register

)2PMET(RETSIGERSTLUSERERUTAREPMET2ENOZETOMER

ylnOdaeRtiB-8

]7[D]6[D]5[D]4[D]3[D]2[D]1[D]0[D

BSM6tib5tib4tib3tib2tib1tibBSL

*CDAmorfataderutarepmet2enozetomer

stiBnoitcnuFnoitarepO

]0:7[D

*2enoz

etomerrofataderutarepmetderusaem

ylnodaer

TEMP2 Power-Up Value: 0000 0000b = 00h (0°C) TEMP2 Command Byte Value: 0010 0000b = 20

†

Remote Zone 2 Hysteresis Register

]7[D]6[D]5[D]4[D]3[D]2[D]1[D]0[D

BSM6tib5tib4tib3tib2tib1tibBSL

stiBnoitcnuFnoitarepO

]0:7[D

*gnittes

T_HYST2 Power-Up Value: 0101 1100b = 5Ch (+92°C) T_HYST2 Command Byte Value: 0010 0010b = 22

* Each LSB represents one degree Centigrade. The values are

in a two's complement format such that 0°C is reported as 0000 0000

†

TEMP2 will contain measured temperature data for the selected zone after the completion of one conversion.

etirW/daeRtiB-8

siseretsyherutarepmet2enozetomer

* 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.

. See "Temperature Data Format" for more details.

)2TSYH_T(RETSIGERSISERETSYH2ENOZETOMER

gnittessiseretsyherutarepmet2enozetomer

etirw/daer

Remote Zone 2 Setpoint Register

)2TES_T(TNIOPTESERUTAREPMET2ENOZETOMER

etirW/daeRtiB-8

]7[D]6[D]5[D]4[D]3[D]2[D]1[D]0[D

BSM6tib5tib4tib3tib2tib1tibBSL

tniopteserutarepmet2enozetomer

stiBnoitcnuFnoitarepO

]0:7[D*tniopteserutarepmet2enozetomeretirw/daer

T_SET2 Power-Up Value: 0110 0001b = 61h (+97°C) T_SET2 Command Byte Value: 0010 0011b = 23

* 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.

September 2000 17 MIC384

Page 18

MIC384 Micrel

Applications

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 I the temperature error due to self-heating.

) will give a good estimate of

OL(INT)

P [(I V ) (I ) (I V )]

=×+ + ×

DDDDD

P [(0.75mA 5.5V) (6mA 0.8V) (6mA 0.8V)]

= ×+×+×

P 13.73mW

R of MSOP-08 package is 206 C/ W

−

q(j a)

Maximum T relative to T due to self-heating is 13.73mW 206 C/ W = 2.83 C

∆×°°

OL(DATA) OL(/INT) OL(/INT)

Equation 1. Worst-Case Self-Heating

In any application, the best test is to verify performance against calculation in the final application environment. This is especially true when dealing with systems for which some 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 ∆V

of a diode-connected PNP transistor (“diode”) at two

CB-E

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.

[(0.350mA I 3.3V) (25% 1.5mA I 0.3V) (1% 1.5mA I 0.3V)]=1.27mW

T (1.27mW 206 C / W)

∆= × °

∆= °0.262 C

×+× ×+× ×

DD(typ)

OL(DATA) OL(/INT)

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 2000

Page 19

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 ∆V

, 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

DATA

CLK

/INT

GND

VDD

A0 T1 T2

8 7 6 54

GUARD/RETURN

REMOTE DIODE (T1)

GUARD/RETURN

REMOTE DIODE (T2)

GUARD/RETURN

Figure 6. Guard Traces/Kelvin Ground Returns

September 2000 19 MIC384

Page 20

MIC384 Micrel

3.3V

FROM

SERIAL BUS

HOST

10k pull-ups

100

4.7µF0.1µF

MIC384

DATA CLK / INT GND

VDD

T1 T2

2200pF

Figure 7. VDD Decoupling for Very Noisy Supplies

Remote Diode

MIC384 20 September 2000

Page 21

MIC384 Micrel

Package Information

0.026 (0.65) MAX)

PIN 1

0.157 (3.99)

0.150 (3.81)

0.064 (1.63)

0.045 (1.14)

0.122 (3.10)

0.112 (2.84)

0.036 (0.90)

0.032 (0.81)

0.050 (1.27) TYP

0.197 (5.0)

0.189 (4.8)

0.020 (0.51)

0.013 (0.33)

0.0098 (0.249)

0.0040 (0.102)

SEATING

PLANE

8-Lead SOP (M)

0.199 (5.05)

0.187 (4.74)

0.120 (3.05)

0.116 (2.95)

0.043 (1.09)

0.038 (0.97)

DIMENSIONS:

INCHES (MM)

0°–8°

0.012 (0.30) R

45°

0.050 (1.27)

0.016 (0.40)

0.244 (6.20)

0.228 (5.79)

DIMENSIONS:

INCH (MM)

0.010 (0.25)

0.007 (0.18)

0.005 (0.13)

0.012 (0.03)

0.0256 (0.65) TYP

0.008 (0.20)

0.004 (0.10)

5° MAX

0° MIN

0.012 (0.03) R

0.039 (0.99)

0.035 (0.89)

0.021 (0.53)

8-Lead MSOP (MM)

MICREL INC. 1849 FORTUNE DRIVE SAN JOSE, CA 95131 USA

TEL + 1 (408) 944-0800 FAX + 1 (408) 944-0970 WEB http://www.micrel.com

This information is believed to be accurate and reliable, however no responsibility is assumed by Micrel for its use nor for any infringement of patents or

other rights of third parties resulting from its use. No license is granted by implication or otherwise under any patent or patent right of Micrel Inc.

September 2000 21 MIC384