TMP451-Q1 datasheet(20/42 Pages) TI2

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TMP451

SBOS686A – JUNE 2013 – REVISED DECEMBER 2014

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caused the setting of the flags is not present anymore (that is, the value of the corresponding result register is

within the limits, or the remote sensor is connected properly and functional). The ALERT interrupt latch (and the

ALERT pin correspondingly) is not reset by reading the status register. The reset is done by the master reading

the temperature sensor device address to service the interrupt, and only if the flags have been reset and the

condition that caused them to be set is not present.

The RTHRM and LTHRM flags are set when the corresponding temperature exceeds the programmed THERM

limit. They are reset automatically when the temperature returns to within the limits. The THERM output goes low

in the case of overtemperature on either the local or the remote channel, and goes high as soon as the

measurements are within the limits again. The THERM hysteresis register (21h) allows hysteresis to be added so

that the flag resets and the output goes high when the temperature returns to or goes below the limit value minus

the hysteresis value.

When pin 6 is configured as THERM2, only the high limits matter. The LHIGH and RHIGH flags are set if the

respective temperatures exceed the limit values, and the pin goes low to indicate the event. The LLOW and

RLOW flags have no effect on THERM2, and the output behaves the same way when configured as THERM.

7.6.1.6 Configuration Register (offset: Read = 03h; Write = 09h) [reset = 00h]

Figure 21. Configuration Register

MASK1

ALERT/THERM

RESERVED

RANGE

RESERVED

R/W-0h

LEGEND: R/W = Read/Write; R = Read only; -n = value after reset

Table 7. Configuration Register Field Descriptions

Bit

Field

Type

Reset

Description

MASK1

R/W

This bit masks the ALERT output

1 = ALERT is disabled.

0 = ALERT is enabled.

R/W

Device shutdown control

1 = Places the device is in shutdown mode.

0 = Places the device in continuous conversion mode.

ALERT/THERM2

R/W

ALERT or THERM2 mode select

1 = THERM2 mode

0 = ALERT mode

RANGE

R/W

This bit configures the range of the temperature measurement

1 = –64 °C to 191°C

0 = 0 °C to 127°C

MASK1 of the configuration register masks the ALERT output. If MASK1 is 0 (default), the ALERT output is

enabled. If MASK1 is set to 1, the ALERT output is disabled. This configuration applies only if the value of

ALERT/THERM2 bit is 0 (that is, pin 6 is configured as the ALERT output). If pin 6 is configured as the THERM2

output, the value of the MASK1 bit has no effect.

The shutdown bit, SD, enables or disables the temperature-measurement circuitry. If SD = 0 (default), the

TMP451 device converts continuously at the rate set in the conversion rate register. When SD is set to 1, the

TMP451 device stops converting when the current conversion sequence is complete and enters a shutdown

mode. When SD is set to 0 again, the TMP451 resumes continuous conversions. When SD = 1, a single

conversion can be started by writing to the one-shot start register. See the One-shot Mode section for more

information.

ALERT/THERM2 (bit 5) sets the configuration of pin 6. If the ALERT/THERM2 bit is 0 (default), then pin 6 is

configured as the ALERT output; if it is set to 1, then pin 6 is configured as the THERM2 output.

The temperature range is set by configuring RANGE (bit 2) of the configuration register. Setting this bit low

(default) configures the TMP451 device for the standard measurement range (0°C to 127°C); temperature

conversions are stored in the standard binary format. Setting bit 2 high configures the TMP451 device for the

extended measurement range (–64°C to 191°C); temperature conversions are stored in the extended binary

format (see Table 1).

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