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CONVERSION RATE REGISTER

TMP421

TMP422

TMP423

SBOS398B – JULY 2007 – REVISED MARCH 2008

The RC bit (bit 2) enables the resistance correction

For the TMP423 only, the REN3 bit (bit 6) enables

feature for the external temperature channels. If RC =

the third external measurement channel. If REN3 =

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

'1', the third external channel is enabled; if REN3 =

resistance

correction

is

disabled.

Resistance

'0', the third external channel is disabled.

correction should be enabled for most applications.

The temperature measurement sequence is: local

However, disabling the resistance correction may

channel, external channel 1, external channel 2,

yield slightly improved temperature measurement

external channel 3, shutdown, and delay (to set

noise performance, and reduce conversion time by

conversion rate, if necessary). The sequence starts

about 50%, which could lower power consumption

over with the local channel. If any of the channels are

when conversion rates of two per second or less are

disabled, they are bypassed in the sequence.

selected.

The LEN bit (bit 3) enables the local temperature

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

The Conversion Rate Register (pointer address 0Bh)

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

controls the rate at which temperature conversions

The REN bit (bit 4) enables external temperature

are performed. This register adjusts the idle time

measurement for channel 1. If REN = '1', the first

between conversions but not the conversion timing

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

itself, thereby allowing the TMP421/22/23 power

channel is disabled.

dissipation to be balanced with the temperature

register

update

rate.

Table

7

describes

the

For the TMP422 and TMP423 only, the REN2 bit (bit

conversion rate options and corresponding current

5)

enables

the

second

external

measurement

consumption. A one-shot command can be used

channel. If REN2 = '1', the second external channel is

during

the

idle

time

between

conversions

to

enabled; if REN2 = '0', the second external channel is

immediately start temperature conversions on all

disabled.

enabled channels.

Table 6. Configuration Register 2 Bit Descriptions

CONFIGURATION REGISTER 2 (Read/Write = 0Ah, POR = 1Ch for TMP421; 3Ch for TMP422; 7Ch for TMP423)

POWER-ON RESET

BIT

NAME

FUNCTION

VALUE

7

Reserved

—

0

0 = External Channel 3 Disabled

1 (TMP423)

6

REN3

1 = External Channel 3 Enabled

0 (TMP421, TMP422)

0 = External Channel 2 Disabled

1 (TMP422, TMP423)

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

14

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