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CONFIGURATION REGISTER 2

TMP421

TMP422

SBOS398A – JULY 2007 – REVISED SEPTEMBER 2007

The remaining bits of the Configuration Register are

The

LEN

bit

enables

the

local

temperature

reserved and must always be set to '0'. The power-on

measurement channel. If LEN = '1', the local channel

reset

value

for

this

register

is

00h.

Table

5

is enabled; if LEN = '0', the local channel is disabled.

summarizes the bits of the Configuration Register.

The

REN

bit

enables

external

temperature

measurement channel 1 (connected to pins 1 and 2.)

If REN = '1', the external channel is enabled; if REN =

'0', the external channel is disabled.

Configuration

Register

2

(pointer

address

0Ah)

controls which temperature measurement channels

For the TMP422 only, the REN2 bit enables the

are enabled and whether the external channels have

second external measurement channel (connected to

the resistance correction feature enabled or not.

pins 3 and 4.) If REN2 = '1', the second external

channel is enabled; if REN = '0', the second external

The RC bit enables the resistance correction feature

channel is disabled.

for the external temperature channels. If RC = '1',

series resistance correction is enabled; if RC = '0',

The temperature measurement sequence is local

resistance

correction

is

disabled.

Resistance

channel, external channel 1, external channel 2,

correction should be enabled for most applications.

shutdown, and delay (to set conversion rate, if

However, disabling the resistance correction may

necessary). The sequence starts over with local

yield slightly improved temperature measurement

channel. If any of the channels are disabled, they are

noise performance, and reduce conversion time by

skipped in the sequence.

about 50%, which could lower power consumption

when conversion rates of two per second or less are

selected.

Table 5. Configuration Register 1 Bit Descriptions

CONFIGURATION REGISTER 1 (Read/Write = 09h, POR = 00h)

BIT

NAME

FUNCTION

POWER-ON RESET VALUE

7

Reserved

—

0

0 = Run

6

SD

0

1 = Shut Down

5, 4, 3

Reserved

—

0

0 = –55

°C to +127°C

2

Temperature Range

0

1 = –55

°C to +150°C

1, 0

Reserved

—

0

Table 6. Configuration Register 2 Bit Descriptions

CONFIGURATION REGISTER 2 (Read/Write = 0Ah, POR = 1Ch for TMP421; 3Ch for TMP422)

BIT

NAME

FUNCTION

POWER-ON RESET VALUE

7, 6

Reserved

—

0

0 = External Channel 2 Disabled

1 (TMP422)

5

REN2

1 = External Channel 2 Enabled

0 (TMP421)

0 = External Channel 1 Disabled

4

REN

1

1 = External Channel 1 Enabled

0 = Local Channel Disabled

3

LEN

1

1 = Local Channel Enabled

0 = Resistance Correction Disabled

2

RC

1

1 = Resistance Correction Enabled

1, 0

Reserved

—

0

Copyright © 2007, Texas Instruments Incorporated

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