NVT210DMTR2G【PDF 15/20 页】IC TEMP SENSOR DGTL 8-WDFN

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NVT210

http://onsemi.com

The NVT210 Interrupt System

The NVT210 has two interrupt outputs, ALERT

and

THERM

. Both have different functions and behavior.

ALERT

is maskable and responds to violations of software

programmed temperature limits or an open-circuit fault on

the external diode. THERM

is intended as a fail-safe

interrupt output that cannot be masked.

If the external or local temperature exceeds the

programmed high temperature limits, or equals or exceeds

the low temperature limits, the ALERT

output is asserted

low. An open-circuit fault on the external diode also causes

ALERT

to assert. ALERT

is reset when serviced by a master

reading its device address, provided the error condition has

gone away and the status register has been reset.

The THERM

output asserts low if the external or local

temperature exceeds the programmed THERM

limits.

THERM

temperature limits should normally be equal to or

greater than the high temperature limits. THERM

is reset

automatically when the temperature falls back within the

THERM

limit. A hysteresis value can be programmed; in

which case, THERM

resets when the temperature falls to the

limit value minus the hysteresis value. This applies to both

local and remote measurement channels. The power-on

hysteresis default value is 10癈, but this can be

reprogrammed to any value after powerup.

The hysteresis loop on the THERM

outputs is useful when

THERM

is used, for example, as an on/off controller for a

fan. The users system can be set up so that when THERM

asserts, a fan is switched on to cool the system. When

THERM

goes high again, the fan can be switched off.

Programming a hysteresis value protects from fan jitter,

where the temperature hovers around the THERM

limit, and

the fan is constantly switched.

Table 14. THERM

HYSTERESIS

THERM

Hysteresis

Binary Representation

0癈

0 000 0000

1癈

0 000 0001

10癈

0 000 1010

Figure 19 shows how the THERM

and ALERT

outputs

operate. The ALERT

output can be used as a SMBALERT

to signal to the host via the SMBus/I

C that the temperature

has risen. The user can use the THERM

output to turn on a

fan to cool the system, if the temperature continues to

increase. This method ensures that there is a fail-safe

mechanism to cool the system, without the need for host

intervention.

Figure 19. Operation of the ALERT

and THERM

Interrupts

1005C

THERM

LIMIT

905C

805C

705C

605C

505C

405C

THERM

LIMIT HYSTERESIS

HIGH TEMP LIMIT

RESET BY MASTER

TEMPERATURE

ALERT

THERM

?SPAN class="pst NVT210DMTR2G_2295433_3"> If the measured temperature exceeds the high

temperature limit, the ALERT

output asserts low.

?SPAN class="pst NVT210DMTR2G_2295433_3"> If the temperature continues to increase and exceeds the

THERM

limit, the THERM

output asserts low.

?SPAN class="pst NVT210DMTR2G_2295433_3"> The THERM

output deasserts (goes high) when the

temperature falls to THERM

limit minus hysteresis. In ,

the default hysteresis value of 10癈 is shown.

?SPAN class="pst NVT210DMTR2G_2295433_3"> The ALERT

output deasserts only when the

temperature has fallen below the high temperature

limit, and the master has read the device address and

cleared the status register.

?SPAN class="pst NVT210DMTR2G_2295433_3"> Pin 6 on the NVT210 can be configured as either an

ALERT

output or as an additional THERM

output.

?SPAN class="pst NVT210DMTR2G_2295433_3"> THERM2

asserts low when the temperature exceeds the

programmed local and/or remote high temperature

limits. It is reset in the same manner as THERM

and is

not maskable.

?SPAN class="pst NVT210DMTR2G_2295433_3"> The programmed hysteresis value also applies to

THERM2

Figure 20 shows how THERM

and THERM2

operate

together to implement two methods of cooling the system.

In this example, the THERM2

limits are set lower than the

THERM

limits. The THERM2

output is used to turn on a

fan.

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