Datasheet

TMP421
TMP422
TMP423
SBOS398C –JULY 2007–REVISED MAY 2012 www.ti.com
STATUS REGISTER shutdown mode. When SD is set to '0' again, the
TMP421/22/23 resume continuous conversions.
The Status Register reports the state of the
When SD = '1', a single conversion can be started by
temperature ADCs. Table 4 summarizes the Status
writing to the One-Shot Register. See the One-Shot
Register bits. The Status Register is read-only, and is
Conversion section for more information.
read by accessing pointer address 08h.
The temperature range is set by configuring the
The BUSY bit = '1' if the ADC is making a conversion;
RANGE bit (bit 2) of the Configuration Register.
it is set to '0' if the ADC is not converting.
Setting this bit low configures the TMP421/22/23 for
the standard measurement range (–40°C to +127°C);
CONFIGURATION REGISTER 1
temperature conversions will be stored in the
standard binary format. Setting bit 2 high configures
Configuration Register 1 (pointer address 09h) sets
the TMP421/22/23 for the extended measurement
the temperature range and controls the shutdown
range (–55°C to +150°C); temperature conversions
mode. The Configuration Register is set by writing to
will be stored in the extended binary format (see
pointer address 09h and read by reading from pointer
Table 1).
address 09h. Table 5 summarizes the bits of
Configuration Register 1.
The remaining bits of the Configuration Register are
reserved and must always be set to '0'. The power-on
The shutdown (SD) bit (bit 6) enables or disables the
reset value for this register is 00h.
temperature measurement circuitry. If SD = '0', the
TMP421/22/23 convert continuously at the rate set in
CONFIGURATION REGISTER 2
the conversion rate register. When SD is set to '1',
the TMP421/22/23 stop converting when the current
Configuration Register 2 (pointer address 0Ah)
conversion sequence is complete and enter a
controls which temperature measurement channels
are enabled and whether the external channels have
the resistance correction feature enabled or not.
Table 6 summarizes the bits of Configuration
Register 2.
Table 4. Status Register Format
STATUS REGISTER (Read = 08h, Write = NA)
BIT # D7 D6 D5 D4 D3 D2 D1 D0
BIT NAME BUSY 0 0 0 0 0 0 0
POR VALUE 0
(1)
0 0 0 0 0 0 0
(1) FOR TMP421/TMP423: The BUSY changes to '1' almost immediately (< 100μs) following power-up, as the TMP421/TMP423 begin the
first temperature conversion. It is high whenever the TMP421/TMP423 convert a temperature reading.
FOR TMP422: The BUSY bit changes to '1' approximately 1ms following power-up. It is high whenever the TMP422 converts a
temperature reading.
Table 5. Configuration Register 1 Bit Descriptions
CONFIGURATION REGISTER 1 (Read/Write = 09h, POR = 00h)
POWER-ON RESET
BIT NAME FUNCTION VALUE
7 Reserved — 0
0 = Run
6 SD 0
1 = Shut Down
5, 4, 3 Reserved — 0
0 = –40°C to +127°C
2 Temperature Range 0
1 = –55°C to +150°C
1, 0 Reserved — 0
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