November 2004

1

MIC280

MIC280

Micrel

MIC280

Precision IttyBitty™ Thermal Supervisor

REV. 11/04

General Description

TheMIC280isadigitalthermalsupervisorcapableofmeasur-

ing its own internal temperature and that of a remote PN junc-

tion. The remote junction may be an inexpensive commodity

transistor, e.g., 2N3906, or an embedded thermal diode such

as found in Intel Pentium* II/III/IV CPUs, AMD Athlon* CPUs,

and Xilinx Virtex* FPGA's. A 2-wire SMBus* 2.0 compatible

serial interface is provided for host communication. Remote

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

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

over-temperature thresholds are provided for each zone.

The advanced integratingA/D converter and analog front-end

reduce errors due to noise for maximum accuracy and mini-

mum guardbanding.The interrupt output signals temperature

events to the host, including data-ready and diode faults.

Critical device settings can be locked to prevent changes and

insure failsafe operation. The clock, data, and interrupt pins

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.

Typical Application

DATA

5

4

6

2

3

1

TO

SERIAL BUS

HOST

2N3906/�

CPU DIODE

1800pF

MIC280

CLK

/INT

3V to 3.6V

3 ×

10k

VDD

T1

GND

0.1µF

ceramic

MIC280 Typical Application

Features

• Measures local and remote temperature

• Highly accurate remote sensing

±1°C max., 60°C to 100°C

• Superior noise immunity for reduced temperature guard-

bands

• 9-bit to 12-bit temperature resolution for remote zone

• Fault queues to further reduce nuisance tripping

• Programmable high, low, and over-temperature thresh-

olds for each zone

• SMBus 2 compatible serial interface including device

timeout to prevent bus lockup

• Voltage tolerant I/O’s

• Open-drain interrupt output pin - supports SMBus Alert

Response Address protocol

• Low power shutdown mode

• Locking of critical functions to insure failsafe operation

• Failsafe response to diode faults

• Enables ACPI compliant thermal management

• 3.0V to 3.6V power supply range

• IttyBitty™ SOT23-6 package

Applications

• Desktop, server and notebook computers

• Printers and copiers

• Test and measurement equipment

• Thermal supervision of Xilinx Virtex FPGA's

• Wireless/RF systems

• Intelligent power supplies

• Datacom/telecom cards

Micrel, Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com

IttyBiity is a trademark of Micrel, Inc.

*All trademarks are the property of their respective owners.