TMP421_12 Datasheet, PDF (15/34 Pages) Texas Instruments – ±1°C Remote and Local TEMPERATURE SENSOR

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TMP421
TMP422
TMP423
SBOS398C – JULY 2007 – REVISED MAY 2012
The RC bit (bit 2) enables the resistance correction
feature for the external temperature channels. If RC =
'1', series resistance correction is enabled; if RC = '0',
resistance correction is disabled. Resistance
correction should be enabled for most applications.
However, disabling the resistance correction may
yield slightly improved temperature measurement
noise performance, and reduce conversion time by
about 50%, which could lower power consumption
when conversion rates of two per second or less are
selected.
The LEN bit (bit 3) enables the local temperature
measurement channel. If LEN = '1', the local channel
is enabled; if LEN = '0', the local channel is disabled.
The REN bit (bit 4) enables external temperature
measurement for channel 1. If REN = '1', the first
external channel is enabled; if REN = '0', the external
channel is disabled.
For the TMP422 and TMP423 only, the REN2 bit (bit
5) enables the second external measurement
channel. If REN2 = '1', the second external channel is
enabled; if REN2 = '0', the second external channel is
disabled.
For the TMP423 only, the REN3 bit (bit 6) enables
the third external measurement channel. If REN3 =
'1', the third external channel is enabled; if REN3 =
'0', the third external channel is disabled.
The temperature measurement sequence is: local
channel, external channel 1, external channel 2,
external channel 3, shutdown, and delay (to set
conversion rate, if necessary). The sequence starts
over with the local channel. If any of the channels are
disabled, they are bypassed in the sequence.
CONVERSION RATE REGISTER
The Conversion Rate Register (pointer address 0Bh)
controls the rate at which temperature conversions
are performed. This register adjusts the idle time
between conversions but not the conversion timing
itself, thereby allowing the TMP421/22/23 power
dissipation to be balanced with the temperature
register update rate. Table 7 describes the
conversion rate options and corresponding current
consumption. A one-shot command can be used
during the idle time between conversions to
immediately start temperature conversions on all
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)
BIT
NAME
FUNCTION
POWER-ON RESET
VALUE
7
Reserved
—
0
6
REN3
0 = External Channel 3 Disabled
1 = External Channel 3 Enabled
1 (TMP423)
0 (TMP421, TMP422)
5
REN2
0 = External Channel 2 Disabled
1 = External Channel 2 Enabled
1 (TMP422, TMP423)
0 (TMP421)
4
REN
0 = External Channel 1 Disabled
1 = External Channel 1 Enabled
1
3
LEN
0 = Local Channel Disabled
1 = Local Channel Enabled
1
2
RC
0 = Resistance Correction Disabled
1 = Resistance Correction Enabled
1
1, 0
Reserved
—
0
Copyright © 2007–2012, Texas Instruments Incorporated
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