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

0

0

0

0

0

0

(1)

FOR TMP421/TMP423: The BUSY changes to '1' almost immediately (< 100

μs) 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

14

Submit Documentation Feedback

Copyright © 2007–2012, Texas Instruments Incorporated

Product Folder Link(s): TMP421 TMP422 TMP423