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MIC280

Precision IttyBitty™ Thermal Supervisor

IttyBitty is a trademark of Micrel, Inc. All other 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

May 5, 2014

Revision 2.0

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 those found in Intel

Pentium® II/III/IV CPUs, AMD Athlon® CPUs, and Xilinx

Virtex® FPGAs. A 2-wire SMBus® 2.0-compatible serial

interface is provided for host communication. Remote

temperature is measured with ±1°C accuracy and 9-bit to

12-bit resolution (programmable). Independent high, low,

and overtemperature 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 ensure 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.

Datasheets and support documentation are available on

Micrel’s web site at: www.micrel.com.

Features

 Measures local and remote temperature

 Highly accurate remote sensing: ±1°C max., 60°C to

100°C

 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 overtemperature

thresholds for each zone

 SMBus 2.0-compatible serial interface including device

timeout to prevent bus lockup

 Voltage-tolerant I/Os

 Open-drain interrupt output pin – supports SMBus Alert

Response Address protocol

 Low power shutdown mode

 Locking of critical functions to ensure failsafe operation

 Failsafe response to diode faults

 Enables ACPI-compliant thermal management

 3.0V to 3.6V power supply range

 Available in IttyBitty™ SOT23-6 package

Applications

 Desktop, server, and notebook computers

 Printers and copiers

 Test and measurement equipment

 Thermal supervision of Xilinx Virtex FPGAs

 Wireless/RF systems

 Intelligent power supplies

 Datacom/telecom cards

Typical Application

Micrel, Inc.

MIC280

May 5, 2014

Revision 2.0

Ordering Information

Part Number

Marking

Slave Address

Ambient Temp. Range

Package

MIC280-0YM6

TA00

100 1000b

–55° to +125°C

SOT23-6

MIC280-1YM6

TA01

100 1001b

–55° to +125°C

SOT23-6

MIC280-2YM6

TA02

100 1010b

–55° to +125°C

SOT23-6

MIC280-3YM6

TA03

100 1011b

–55° to +125°C

SOT23-6

MIC280-4YM6

TA04

100 1100b

–55° to +125°C

SOT23-6

MIC280-5YM6

TA05

100 1101b

–55° to +125°C

SOT23-6

MIC280-6YM6

TA06

100 1110b

–55° to +125°C

SOT23-6

MIC280-7YM6

TA07

100 1111b

–55° to +125°C

SOT23-6

Note:

1. Underbar (_) may not be to scale.

Pin Configuration

SOT23-6 (M6)

(Top View)

Pin Description

Pin Number

Pin Name

Pin Function

VDD

Power supply input.

GND

Ground.

Analog input. Connection to remote diode junction.

CLK

Digital input. Serial bit clock input.

DATA

Digital input/output. Open-drain. Serial data input/output.

/INT

Digital output. Open-drain. Interrupt output.

Micrel, Inc.

MIC280

May 5, 2014

Revision 2.0

Absolute Maximum Ratings(2)

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 = +125°C .............................. 109mW

Storage Temperature (Ts) ......................... –65°C to +150°C

ESD Ratings(4)

Human Body Model ..................................................... 1.5kV

Machine Model ............................................................. 200V

Soldering (SOT23-6 package)

Vapor Phase (60s) ........................................... 220°C+5/-0°C

Infrared (15s) .................................................... 235°C+5/-0°C

Operating Ratings(3)

Power Supply Voltage (VDD) ........................ +3.0V to +3.6V

Ambient Temperature Range (TA) ............ –55°C to +125°C

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

Junction Thermal Resistance

SOT23-6 (JA) .................................................. 230°C/W

Electrical Characteristics(5, 6)

VDD = 3.3V; TA = 25°C, unless noted. Bold values indicate –55°C ≤ TA ≤ +125°C, 3.0V ≤ VDD ≤ 3.6V, unless noted(3).

Symbol

Parameter

Condition

Min.

Typ.

Max.

Units

Power Supply

IDD

Supply Current

/INT, T1 open; CLK = DATA = High;

Normal mode

0.23

0.4

Shutdown mode; /INT, T1 open; Note 7

CLK = 100kHz, DATA = High

µA

Shutdown mode; /INT, T1 open;

CLK = DATA = High

µA

tPOR

Power-on Reset Time, Note 7

VDD > VPOR

200

µs

VPOR

Power-on Reset Voltage

All registers reset to default values;

A/D conversions initiated

2.65

2.95

VHYST

Power-on Reset Hysteresis

Voltage, Note 7

300

Temperature-to-Digital Converter Characteristics

Accuracy, Remote Temperature

Notes 3, 9, 12, 13

60°C ≤ TD ≤ 100°C

3.15V < VDD < 3.45V, 25°C < TA < 85°C

±0.25

±1

°C

0°C ≤ TD ≤ 100°C

3.15V < VDD < 3.45V, 25°C < TA < 85°C

±1

±2

°C

–55°C ≤ TD ≤ 125°C

3.15V < VDD < 3.45V, 25°C < TA < 85°C

±2

±4

°C

Accuracy, Local Temperature

Notes 3, 12

0°C ≤ TA ≤ 100°C, 3.15V < VDD < 3.45V

±1

±2

°C

–55°C ≤ TA ≤ 125°C, 3.15V < VDD < 3.45V

±1.5

±2.5

°C

tCONV

Conversion Time

Notes 3, 10

RES[1:0]=00 (9 bits)

200

240

RES[1:0]=01 (10 bits)

330

390

RES[1:0]=10 (11 bits)

570

670

RES[1:0]=11 (12 bits)

1000

1250

Micrel, Inc.

MIC280

May 5, 2014

Revision 2.0

Electrical Characteristics(5, 6) (Continued)

VDD = 3.3V; TA = 25°C, unless noted. Bold values indicate –55°C ≤ TA ≤ +125°C, 3.0V ≤ VDD ≤ 3.6V, unless noted(3).

Symbol

Parameter

Condition

Min.

Typ.

Max.

Units

Remote Temperature Input, T1

Current into External Diode

Note 7

T1 forced to 1.0V, High level

192

400

µA

Low level

µA

Serial Data I/O Pin, DATA

VOL

Low Output Voltage, Note 6

IOL = 3mA

0.3

IOL = 6mA

0.5

VIL

Low Input Voltage

3V ≤ VDD ≤ 3.6V

0.8

VIH

High Input Voltage

3V ≤ VDD ≤ 3.6V

2.1

5.5

CIN

Input Capacitance

Note 7

ILEAK

Input Current

±1

µA

Serial Clock Input, CLK

VIL

Low Input Voltage

3V ≤ VDD ≤ 3.6V

0.8

VIH

High Input Voltage

3V ≤ VDD ≤ 3.6V

2.1

5.5

CIN

Input Capacitance

Note 7

ILEAK

Input Current

±1

µA

Interrupt Output, /INT

VOL

Low Output Voltage, Note 6

IOL = 3mA

0.3

IOL = 6mA

0.5

tINT

Interrupt Propagation Delay

Notes 7, 8

From TEMPx < TLOWx or TEMPx > THIGHx

or TEMPx > CRITx to /INT < VOL,

RPULLUP = 10kΩ

[tCONV]

tnINT

Interrupt Reset Propagation

Delay, Notes 7, 11

From read of STATUS or A.R.A. to /INT > VOH

RPULLUP = 10kΩ

µs

ILEAK

±1

µA

Micrel, Inc.

MIC280

May 5, 2014

Revision 2.0

Electrical Characteristics(5, 6) (Continued)

VDD = 3.3V; TA = 25°C, unless noted. Bold values indicate –55°C ≤ TA ≤ +125°C, 3.0V ≤ VDD ≤ 3.6V, unless noted(3).

Symbol

Parameter

Condition

Min.

Typ.

Max.

Units

Serial Interface Timing

CLK (clock) Period

2.5

µs

Data In Setup Time to CLK High

100

Data Out Stable after CLK Low

300

Data Low Setup Time to CLK

Low

Start Condition

100

Data High Hold Time after CLK

High

Stop Condition

100

tTO

Bus Timeout

Notes:

2. Exceeding the absolute maximum ratings may damage the device.

3. The device is not guaranteed to function outside its operating ratings. Final test on outgoing product is performed at TA = 25°C.

4. Devices are ESD sensitive. Handling precautions are recommended. Human body model, 1.5kΩ in series with 100pF.

5. Specification for packaged product only.

6. Current into the /INT or DATA pins will result in self heating of the device. Sink current should be minimized for best accuracy.

7. Guaranteed by design over the operating temperature range. Not 100% production tested.

8. tINT and tCRIT are equal to tCONV.

9. 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.

10. 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.

11. The interrupt reset propagation delay is dominated by the capacitance on the bus.

12. Accuracy specification does not include quantization noise, which may be up to ±1/2 LSB.

13. Tested at 10-bit resolution.

Micrel, Inc.

MIC280

May 5, 2014

Revision 2.0

Timing Diagram

Serial Interface Timing

Micrel, Inc.

MIC280

May 5, 2014

Revision 2.0

Typical Characteristics

Micrel, Inc.

MIC280

May 5, 2014

Revision 2.0

Typical Characteristics (Continued)

Micrel, Inc.

MIC280

May 5, 2014

Revision 2.0

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 2.

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 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 1 below and the Ordering Information

table.

Table 1. MIC280 Slave Addresses

Part Number

Slave Address

MIC280-0YM6

100 1000b = 48h

MIC280-1YM6

100 1001b = 49h

MIC280-2YM6

100 1010b = 4Ah

MIC280-3YM6

100 1011b = 4Bh

MIC280-4YM6

100 1100b = 4Ch

MIC280-5YM6

100 1101b = 4Dh

MIC280-6YM6

100 1110b = 4Eh

MIC280-7YM6

100 1111b = 4Fh

Table 2. MIC280 Register Addresses

Target Register

Command Byte Value

Power-on

Default

Label

Description

Read

Write

TEMP0

Local temperature result

00h

n/a

00h (0°C)

TEMP1h

Remote temperature result, high byte

01h

n/a

00h (0°C)

STATUS

Status

02h

n/a

00h

CONFIG

Configuration

03h

80h

IMASK

Interrupt mask register

04h

07h

THIGH0

Local temperature high limit

05h

3Ch (60°C)

TLOW0

Local temperature low limit

06h

00h (0°C)

THIGH1h

Remote temperature high limit, high byte

07h

50h (80°C)

TLOW1h

Remote temperature low limit, high byte

08h

00h (0°C)

LOCK

Security register

09h

00h

TEMP1l

Remote temperature result, low byte

10h

n/a

00h

THIGH1l

Remote temperature high limit, low byte

13h

00h

TLOW1l

Remote temperature low limit, low byte

14h

00h

CRIT1

Remote overtemperature limit

19h

64h (100°C)

CRIT0

Local overtemperature limit

20h

46h (70°C)

MFG_ID

Manufacturer identification

FEh

n/a

2Ah

DEV_ID

Device and revision identification

FFh

n/a

0xh*

*The lower nibble contains the die revision level, e.g., Rev 0 = 00h.

Micrel, Inc.

MIC280

May 5, 2014

Revision 2.0

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 as- serted 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 (D7) represents the sign: zero for

positive temperatures and one for negative temperatures.

Table 3 shows examples of the data used by the MIC280

for temperatures.

Table 3. Digital Temperature Format, High Bytes

Temperature

Binary

Hex

+127°C

0111 1111

+125°C

0111 1101

+25°C

0001 1001

+1°C

0000 0001

0°C

0000 0000

–1°C

1111 1111

–25°C

1110 0111

–125°C

1000 0011

–128°C

1000 0000

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 in

Table 5.

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 × tCONV to detect a temperature

event. The fault queue depth versus CONFIG[5:4] of the

conﬁguration register is shown in Table 4. Note: there is

no fault queue for overtemperature 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.

Table 4. Fault Queue Depth Settings

CONFIG[5:4]

Fault Queue Depth

1 (Default)

Micrel, Inc.

MIC280

May 5, 2014

Revision 2.0

Table 5. Digital Temperature Format, Low Bytes

Extended Temperature

Low Byte

Resolution

9 BITS

10 BITS

11 Bits

12 BITS

Binary Hex

0.0000

0000 0000 00

0.0625

0000 0000 00

0001 0000 10

0.1250

0000 0000 00

0010 0000 20

0.2500

0000 0000 00

0100 0000 40

0.5625

1000 0000 80

1001 0000 90

0.9375

1000 0000 80

1100 0000 C0

1110 0000 E0

1111 0000 F0

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 ICs, 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

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 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.

Because 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 overtemperature 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 twelve-bit 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

supports the use of the Read_Word protocol for

accessing both TEMP1h and TEMP1l with a single

operation. This ensures that the values in both result

registers are from the same ADC cycle. This is illustrated

in Figure 3. 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 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.

Micrel, Inc.

MIC280

May 5, 2014

Revision 2.0

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.

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 reset- ting 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.

Table 6. MIC280 Temperature Events

Event

Condition

MIC280 Response(14)

Data ready

A/D conversions complete for both zones; result

registers updated; state of /INT updated

Set S7, clear IM7, assert /INT

Overtemperature, remote

([TEMP1h:TEMP1l]) >CRIT1

Set S1, assert /INT

Overtemperature, local

TEMP0 >CRIT0

Set S0, assert /INT

High temperature, remote

([TEMP1h:TEMP1l]) >[THIGH1h:THIGH1l](15)

Set S4, clear IM4, assert /INT

High temperature, local

TEMP0 >THIGH0(15)

Set S6, clear IM6, assert /INT

Low temperature, remote

([TEMP1h:TEMP1l]) <[TLOW1h:TLOW1l](15)

Set S3, clear IM3, assert /INT

Low temperature, local

TEMP0 <TLOW0(15)

Set S5, clear IM5, assert /INT

Diode fault

T1 open or T1 shorted to VDD or GND

Set S2, clear IM2, assert /INT

Notes:

14. Assumes interrupts enabled.

15. CONDITION must be true for Fault_Queue conversions to be recognized.

Micrel, Inc.

MIC280

May 5, 2014

Revision 2.0

Figure 1. WRITE_BYTE Protocol

Figure 2. READ_BYTE Protocol

Figure 3. READ_WORD Protocol for Accessing TEMP1h : TEMP1l

Micrel, Inc.

MIC280

May 5, 2014

Revision 2.0

Figure 4. MIC280 Alert Response Address Protocol

Figure 5. Reading Status in Response to an Interrupt

Micrel, Inc.

MIC280

May 5, 2014

Revision 2.0

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 overtemperature 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

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

overtemperature 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 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 re-enter shutdown mode.

Setting L4 disables the RST bit in the conﬁguration

Writes to RST will be completely ignored if L4 is set.

Table 7. Lock bit functionality

Lock Bit

Function Locked

Response When Set

Local over-temperature detection

IM0 ﬁxed at 1, writes to CRIT0 locked-out; IE permanently set

Remote over-temperature detection

IM1 ﬁxed at 1; writes to CRIT1 locked-out; IE permanently set

Diode fault interrupts locked on or off

IM2 ﬁxed at current state; IE permanently set if IM2=1

Shutdown mode

SHDN ﬁxed at 0; exit shutdown if SHDN=1 when L3 is set

Warm resets

RST bit disabled; cannot initiate Warm resets

Micrel, Inc.

MIC280

May 5, 2014

Revision 2.0

Detailed Register Descriptions

Local Temperature Result Register (TEMP0) 8-bits, Read-Only

Temperature Data from ADC

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

Bit

Function

Operation

D[7:0]

Measured temperature data for the local zone.

Read-only

Power-up default value: 0000 0000b = 00h = (0°C)(16)

Read command byte: 0000 0000b = 00h

Each LSB represents one degree centigrade. The values are in a twos complement binary format such that 0°C is

reported as 0000 0000b. See the Temperature Data Format section for more details.

Note:

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

Remote Temperature Result High-Byte Register (TEMP1h) 8-bits, Read-Only

Temperature Data from ADC

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

Bit

Function

Operation

D[7:0]

Measured temperature data for the remote zone, most significant byte.

Read-only

Power-up default value: 0000 0000b = 00h = (0°C)(17)

Read command byte: 0000 0001b = 01h

Each LSB represents one degree centigrade. The values are in a twos complement binary format such that 0°C is

reported as 0000 0000b. See the Temperature Data Format section 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 diagrammed in Figure 3. This is the only

MIC280 register that supports Read_Word.

Note:

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

Micrel, Inc.

MIC280

May 5, 2014

Revision 2.0

Status Register (STATUS) 8-bits, Read-Only

Status 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

Bit

Function

Operation(18)

Data ready

1 = data available, 0 = ADC busy

Local high temperature event

1 = event occurred, 0 = none

Local low temperature event

1 = event occurred, 0 = none

Remote high temperature event

1 = event occurred, 0 = none

Remote low temperature event

1 = event occurred, 0 = none

Diode fault

1 = fault, 0 = none

Remote overtemperature event

1 = event occurred, 0 = none

Local overtemperature event

1 = event occurred, 0 = none

Note:

18. 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.

Micrel, Inc.

MIC280

May 5, 2014

Revision 2.0

Configuration Register (CONFIG) 8-bits, Read/Write

Configuration Register

D[7]

read/write

D[6]

read/write

D[5]

reserved

D[4]

reserved

D[3]

reserved

D[2]

reserved

D[1]

reserved

D[0]

reserved

Interrupt

Enable (IE)

Shut-down

(SHDN)

Fault Queue

(FQ[1:0])

Resolution

(RES[1:0])

Reserved

Reset

(RST)

Bit

Function

Operation

Interrupt enable

1 = interrupts enabled, 0 = disabled

SHDN

Selects operating mode: normal/shutdown

1 = shutdown, 0 = normal

FQ[1:0]

Depth of fault queue(19)

[00] = 1, [01] = 2, [10] = 4, [11] = 6

RES[1:0]

A/D converter resolution for external zone; affects conversion rate

[00] = 9-bits, [01] = 10-bits,

[10] = 11-bits, [11] = 12-bits

D[1]

Reserved

Always write as zero

RST

Resets all MIC280 functions and restores the power-up default state

Write only; 1 = reset, 0 = normal

Operation; disabled by setting L4

Note:

19. 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.

Power-up default value: 1000 0000b = 80h (not in shutdown mode; interrupts enabled; fault queue depth = 1; resolution =

9-bits)

Read/write command byte: 0000 0011b = 03h

Micrel, Inc.

MIC280

May 5, 2014

Revision 2.0

Interrupt Mask Register (IMASK) 8-bits, Read/Write

Interrupt Mask Register

D[7]

read/write

D[6]

read/write

D[5]

reserved

D[4]

reserved

D[3]

reserved

D[2]

reserved

D[1]

reserved

D[0]

reserved

IM7

IM6

IM5

IM4

IM3

IM2

IM1

IM0

Bit

Function

Operation

IM7

Data-ready event mask

1 = enabled, 0 = disabled

IM6

Local high temperature event mask

1 = enabled, 0 = disabled

IM5

Local low temperature event mask

1 = enabled, 0 = disabled

IM4

Remote high temperature event mask

1 = enabled, 0 = disabled

IM3

Remote low temperature event mask

1 = enabled, 0 = disabled

IM2

Diode fault mask

1 = enabled, 0 = disabled

IM1

Remote overtemperature event mask

1 = enabled, 0 = disabled

IM0

Local overtemperature event mask

1 = enabled, 0 = disabled

Power-up default value: 0000 0111b = 07h (overtemperature and diode faults enabled)

Read/write command byte: 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

Function

Operation

D[7:0]

High temperature limit for the local zone.

Read/write

Power-up default value: 0011 1100b = 3Ch (60°C)

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 0°C is

reported as 0000 0000b. See Temperature Data Format for more details.

Any writes to a temperature limit register will result in the corresponding fault queue being purged and reset.

Micrel, Inc.

MIC280

May 5, 2014

Revision 2.0

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

Function

Operation

D[7:0]

Low temperature limit for the local zone.

Read/write

Power-up default value: 0000 0000b = 00h (0°C)

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 0°C is

reported as 0000 0000b. See Temperature Data Format 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

Function

Operation

D[7:0]

High temperature limit for the remote zone, most signiﬁcant byte.

Read/write

Power-up default value: 0101 0000b = 50h (80°C)

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 0°C is

reported as 0000 0000b. See Temperature Data Format for more details.

Any writes to a temperature limit register will result in the corresponding fault queue being purged and reset.

Micrel, Inc.

MIC280

May 5, 2014

Revision 2.0

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

Function

Operation

D[7:0]

Low temperature limit for the remote zone, most signiﬁcant byte.

Read/write

Power-up default value: 0000 0000b = 00h (0°C)

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 0°C is

reported as 0000 0000b. See Temperature Data Format 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

D[5]

reserved

D[4]

read/write-

once

D[3]

read/write-

once

D[2]

read/write-

once

D[1]

read/write-

once

D[0]

read/write-

once

Reserved

Bit

Function

Operation

D[7:5]

Reserved

Always write as zero

Warm-reset lockout bit

1 = RST bit disabled; 0 = unlocked

Shutdown mode lockout bit(Error! Reference source not found.)

1 = shutdown disabled; 0 = unlocked

Diode fault event lock bit

1 = locked; 0 = unlocked

Remote overtemperature event lock bit

1 = locked; 0 = unlocked

Local overtemperature event lock bit

1 = locked; 0 = unlocked

Power-up default value: 0000 0000b = 00h (all event unlocked)

Write command byte: 0000 1001b = 09h

Micrel, Inc.

MIC280

May 5, 2014

Revision 2.0

Remote Temperature Result Low-Byte Register (TLOW1l) 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 significat bits. Reserved always reads zero.

Bit

Function

Operation

D[7:4]

Measured temperature data for the remote zone, least significant bits.

Read only

D[3:0]

Reserved

Always reads as zero

Power-up default value: 0000 0000b = 00h (0°C)(20)

Read command byte: 0001 0000b = 10h

Each LSB represents one-sixteenth degree centigrade. The values are in a binary format such that 1/16th°C (0.0625°C) is

reported as 0001 0000b. See Temperature Data Format 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.

Note:

20. 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 significat bits. Reserved always reads zero.

Bit

Function

Operation

D[7:4]

High temperature limit for the remote zone, least significant bits.

Read/write

D[3:0]

Reserved

Always reads as zero

Power-up default value: 0000 0000b = 00h (0°C)

Read/write command byte: 0001 0011b = 13h

Each LSB represents one-sixteenth degree centigrade. The values are in a binary format such that 1/16th°C (0.0625°C) is

reported as 0001 0000b. See Temperature Data Format for more details.

Any writes to a temperature limit register will result in the corresponding fault queue being purged and reset.

Micrel, Inc.

MIC280

May 5, 2014

Revision 2.0

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 significat bits. Reserved always reads zero.

Bit

Function

Operation

D[7:4]

Low temperature limit for the remote zone, least significant bits.

Read/write

D[3:0]

Reserved

Always reads as zero

Power-up default value: 0000 0000b = 00h (0°C)

Read/write command byte: 0001 0100b = 14h

Each LSB represents one-sixteenth degree centigrade. The values are in a binary format such that 1/16th°C (0.0625°C) is

reported as 0001 0000b. See Temperature Data Format for more details.

Any writes to a temperature limit register will result in the corresponding fault queue being purged and reset.

Remote Overtemperature Limit Register (CRIT1) 8-bits, Read/Write

Remote Overtemperature 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

Overtemperature limit for remote zone.

Bit

Function

Operation

D[7:0]

Overtemperature limit for the remote zone.

Read/write

Power-up default value: 0110 0100b = 64h (100°C)

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 0°C is

reported as 0000 0000b. See Temperature Data Format for more details.

Any writes to a temperature limit register will result in the corresponding fault queue being purged and reset.

Micrel, Inc.

MIC280

May 5, 2014

Revision 2.0

Local Overtemperature Limit Register (CRIT0) 8-bits, Read/Write

Local Overtemperature 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

Overtemperature limit for local zone.

Bit

Function

Operation

D[7:0]

Overtemperature limit for the local zone.

Read/write

Power-up default value: 0100 0110b = 46h (70°C)

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 0°C is

reported as 0000 0000b. See Temperature Data Format 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

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

Bit

Function

Operation

D[7:0]

Identifies Micrel, Inc. as the manufacturer of the device

Read only. Always returns 2Ah

Power-up default value: 0010 1010b = 2Ah

Read command byte: 1111 1110b = FEh

Die Revision Register (DIE_REV) 8-bits, Read only

Die Revision 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

MIC280 die revision number

Bit

Function

Operation

D[7:0]

Identifies the device revision number.

Read only

Power-up default value: [device revision number]h

Read command byte: 1111 1111b = FFh

Micrel, Inc.

MIC280

May 5, 2014

Revision 2.0

Application Information

Remote Diode Section

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.

Table 8. Transistors suitable for use as remote diodes

Vendor

Part

Number

Package

Fairchild Semiconductor

MMBT3906

SOT-23

On Semiconductor

MMBT3906L

SOT-23

Philips Semiconductor

PMBT3906

SOT-23

Samsung Semiconductor

KST3906-TF

SOT-23

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 × IDD) + (VOL × 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 worst-case 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 ×VDD)+(IOL(DATA)×VOL(DATA))+(IOL(/INT)×VOL(/INT)]

PD = [(0.4mA× 3.6V)+(6mA× 0.5V)+(6mA× 0.5V)]

PD = 7.44mW

Rθ(J-A) of the SOT23-6 package is 230°C/W Theoretical

Maximum ∆TJ due to self-heating is:

7.44mW × 230°C/W = 1.7112°C

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) × 3.3V) + (25% × 1.5mA IOL(DATA) × 0.15V)

+ (1% × 1.5mA IOL(/INT) × 0.15V) = 0.817mW

∆TJ = (0.8175mW × 230°C/W) = 0.188°C

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

tem- perature data may be poorly deﬁned or unobtainable

except by empirical means.

Series Resistance

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. Because 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 that for

each ohm in series with the external transistor, there will

be a 0.8°C error in the MIC280’s temperature

measurement. It is not 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 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 recom- mended 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 six-to-twelve inches 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. Because 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

Micrel, Inc.

MIC280

May 5, 2014

Revision 2.0

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 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 10mm 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.

6. Always place a good quality power supply bypass

capacitor directly adjacent to, or underneath, the

MIC280. This should be a 0.1 µF 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 100Ω

resistor in series with the part’s VDD pin, and a 4.7µF,

6.3V electrolytic capacitor from VDD to GND. See

Figure 7.

Figure 6. Guard Traces/Kelvin Ground Returns

Figure 7. VDD Decoupling for Very Noisy Supplies

Micrel, Inc.

MIC280

May 5, 2014

Revision 2.0

Package Information(21)

6-Pin SOT23 (M6)

Note:

21. Package information is correct as of the publication date. For updates and most current information, go to www.micrel.com.

Micrel, Inc.

MIC280

May 5, 2014

Revision 2.0

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Micrel makes no representations or warranties with respect to the accuracy or completeness of the information furnished in this data sheet. This

information is not intended as a warranty and Micrel does not assume responsibility for its use. Micrel reserves the right to change circuitry,

specifications and descriptions at any time without notice. No license, whether express, implied, arising by estoppel or otherwise, to any intellectual

property rights is granted by this document. Except as provided in Micrel’s terms and conditions of sale for such products, Micrel assumes no liability

whatsoever, and Micrel disclaims any express or implied warranty relating to the sale and/or use of Micrel products including liability or warranties

relating to fitness for a particular purpose, merchantability, or infringement of any patent, copyright or other intellectual property right.

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

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