EMC2101-R-ACZL-TR datasheet(21/55 Pages) SMSC

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SMBus Fan Control with 1°C Accurate Temperature Monitoring

Datasheet

SMSC EMC2101

Revision 2.53 (03-13-07)

DATASHEET

5.4.2

ALERT / TACH as an Interrupt

When the ALERT / TACH pin is used as an interrupt signal the pin is asserted whenever an out-of-

limit condition is detected. The ALERT / TACH pin will remain asserted until it is cleared even if the

error condition is removed.

5.4.3

Mask Bit

The MASK bit behaves differently depending on which mode the ALERT / TACH pin is configured to

operate in.

If the EMC2101 is configured with the ALERT / TACH pin operating in Interrupt Mode, the MASK bit

will be set in the following cases:

1. Automatically after the Status Register has been read if any bits in the Status Register have been

set (except BUSY and FAULT) (See Table 6.3).

2. Automatically when the EMC2101 responds to an Alert Response Address (ARA) command on an

SMBus and the ALERT / TACH pin is asserted. The ARA command does not clear the Status

ALERT / TACH pin will be asserted.

3. Directly via the SMBus.

In Interrupt Mode, the MASK bit will block the ALERT / TACH pin from being asserted in response to

an error condition.

If the EMC2101 is configured with the ALERT / TACH pin operating in Comparator Mode, the MASK

bit can only be set via the SMBus. In this mode, setting the MASK bit willl not affect the ALERT / TACH

pin.

In either mode, setting the individual channel mask bits will block the appropriate channel from

asserting the ALERT / TACH pin.

5.5

Temperature Monitors

In general, thermal diode temperature measurements are based on the change in forward bias voltage

of a diode when operated at two different currents. The change in forward bias voltage is proportional

to absolute temperature (T).

Where:

Eq: [1]

k = Boltzmann’s constant

T = Absolute Temperature in Kelvin

q = electron charge

η = Diode Ideality Factor

⎟⎟

⎠

⎞

⎜⎜

⎝

⎛

−

LOW

HIGH

LOW

HIGH

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