Datasheet
TMP421
TMP422
TMP423
www.ti.com
SBOS398C –JULY 2007–REVISED MAY 2012
Table 3. Register Map
BIT DESCRIPTION
POINTER
(HEX) POR (HEX) 7 6 5 4 3 2 1 0 REGISTER DESCRIPTION
00 00 LT11 LT10 LT9 LT8 LT7 LT6 LT5 LT4 Local Temperature (High Byte)
(1)
Remote Temperature 1
01 00 RT11 RT10 RT9 RT8 RT7 RT6 RT5 RT4
(High Byte)
(1)
Remote Temperature 2
02 00 RT11 RT10 RT9 RT8 RT7 RT6 RT5 RT4
(High Byte)
(1) (2) (3)
Remote Temperature 3
03 00 RT11 RT10 RT9 RT8 RT7 RT6 RT5 RT4
(High Byte)
(1) (3)
08 BUSY 0 0 0 0 0 0 0 Status Register
09 00 0 SD 0 0 0 RANGE 0 0 Configuration Register 1
1C/3C
(2)
/
0A 0 REN3
(3)
REN2
(2) (3)
REN LEN RC 0 0 Configuration Register 2
7C
(3)
0B 07 0 0 0 0 0 R2 R1 R0 Conversion Rate Register
0F X X X X X X X X One-Shot Start
(4)
10 00 LT3 LT2 LT1 LT0 0 0 PVLD 0 Local Temperature (Low Byte)
11 00 RT3 RT2 RT1 RT0 0 0 PVLD OPEN Remote Temperature 1 (Low Byte)
Remote Temperature 2
12 00 RT3 RT2 RT1 RT0 0 0 PVLD OPEN
(Low Byte)
(2) (3)
13 00 RT3 RT2 RT1 RT0 0 0 PLVD OPEN Remote Temperature 3 (Low Byte)
(3)
21 00 NC7 NC6 NC5 NC4 NC3 NC2 NC1 NC0 N Correction 1
22 00 NC7 NC6 NC5 NC4 NC3 NC2 NC1 NC0 N Correction 2
(2) (3)
23 00 NC7 NC6 NC5 NC4 NC3 NC2 NC1 NC0 N Correction 3
(3)
FC X X X X X X X X Software Reset
(5)
FE 55 0 1 0 1 0 1 0 1 Manufacturer ID
0 0 1 0 0 0 0 1 TMP421 Device ID
FF 21 0 0 1 0 0 0 1 0 TMP422 Device ID
0 0 1 0 0 0 1 1 TMP423 Device ID
(1) Compatible with Two-Byte Read; see Figure 19.
(2) TMP422.
(3) TMP423.
(4) X = undefined. Writing any value to this register initiates a one-shot start; see the One-Shot Conversion section.
(5) X = undefined. Writing any value to this register initiates a software reset; see the Software Reset section.
The TMP421/22/23 contain circuitry to assure that a
TEMPERATURE REGISTERS
low byte register read command returns data from the
same ADC conversion as the immediately preceding
The TMP421/22/23 have multiple 8-bit registers that
high byte read command. This assurance remains
hold temperature measurement results. The local
valid only until another register is read. For proper
channel and each of the remote channels have a high
operation, the high byte of a temperature register
byte register that contains the most significant bits
should be read first. The low byte register should be
(MSBs) of the temperature analog-to-digital converter
read in the next read command. The low byte register
(ADC) result and a low byte register that contains the
may be left unread if the LSBs are not needed.
least significant bits (LSBs) of the temperature ADC
Alternatively, the temperature registers may be read
result. The local channel high byte address is 00h;
as a 16-bit register by using a single two-byte read
the local channel low byte address is 10h. The
command from address 00h for the local channel
remote channel high byte is at address 01h; the
result, or from address 01h for the remote channel
remote channel low byte address is 11h. For the
result (02h for the second remote channel result, and
TMP422, the second remote channel high byte
03h for the third remote channel). The high byte is
address is 02h; the second remote channel low byte
output first, followed by the low byte. Both bytes of
is 12h. The TMP 423 uses the same local and remote
this read operation are from the same ADC
address as the TMP421 and TMP422, with the third
conversion. The power-on reset value of all
remote channel high byte of 03h; the third remote
temperature registers is 00h.
channel low byte is 13h. These registers are read-
only and are updated by the ADC each time a
temperature measurement is completed.
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