MIC184YM データシートの表示（PDF） - Micrel

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MIC184YM

Local/Remote Thermal Supervisor

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MIC184

Interrupt Polarity Selection

The INT output can be programmed to behave as an active-

low signal or an active-high signal. The default is active-low.

INT polarity is selected by programming the appropriate value

into the polarity bit (POL) in the CONFIG register. Clearing

POL selects active-low interrupts; setting POL selects ac-

tive-high interrupts. INT is an open-drain digital output and

may be wire-ORed with other open-drain logic signals. Most

applications will require a pull-up resistor on this pin.

Whether the CONFIG register’s POL bit is set to provide a

current-sinking (low) or high-Z (high) state at the INT pin when

STS is high, writing a one to IM will put the INT pin into a high-

Z state. This meets the requirement of an active-low interrupt

for the SMBus, while making IM available as an INT-forcing

bit for those applications which employ an active-high INT

output (for example, software fan-control routines).

LM75 Compatibility

The MIC184 can be used interchangeably with the LM75 in

existing applications. The MIC184 offers several advantages

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over the LM75:

• Ability to monitor a second, remote temperature

• Interrupt masking capability

• Status bit for software polling routines

• Lower quiescent current

• Supports single-byte reads from 16-bit registers

• No “inadvertent 8-bit read” bus lock-up issues

The three MSB’s of the configuration register (which power

up as zeroes) are used to access the MIC184’s additional

functions. These are reserved bits according to the LM75

specification and, for the LM75, must always be written as

zeroes. The MSB of the MIC184’s status register is a status

flag that does not exist in the LM75. This bit will be set to one

whenever an overtemperature event occurs. This bit would

never be set by an LM75. Software should not depend on this

bit being zero when using the MIC184 as an LM75 upgrade. If

at power-up the measured temperature is higher than T_SET,

the status bit will be set following the first conversion by the

A/D. See “Applications Information” for a method by which

host software can use this fact to differentiate between an

MIC184 and an LM75.

MIC184

12

May 2006

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