Datasheet
"#$%
SBOS371A − AUGUST 2006 − REVISED OCTOBER 2007
www.ti.com
13
RESOLUTION REGISTER
The RES1 and RES0 bits (resolution bits 1 and 0) of the
Resolution Register set the resolution of the local
temperature measurement channel. Remote temperature
measurement channel resolution is not affected.
Changing the local channel resolution also affects the
conversion time and rate of the TMP401. The Resolution
Register is set by writing to pointer address 1Ah and is
read by reading from pointer address 1Ah. Table 6 shows
the resolution bits for the Resolution Register.
Table 6. Resolution Register:
Local Channel Programmable Resolution
RESOLUTION REGISTER (Read = 1Ah, Write = 1Ah, POR = 1Ch)
RES1 RES0 RESOLUTION
CONVERSION TIME
(Typical)
0 0 9 Bits (0.5°C) 12.5ms
0 1 10 Bits (0.25°C) 25ms
1 0 11 Bits (0.125°C) 50ms
1 1 12 Bits (0.0625°C) 100ms
Bits 2 through 4 of the Resolution Register must always be
set to ‘1’. Bits 5 through 7 of the Resolution Register must
always be set to ‘0’. The power-on reset value of this
register is 1Ch.
CONVERSION RATE REGISTER
The Conversion Rate Register 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 TMP401
power dissipation to be balanced with the temperature
register update rate. Table 7 shows the conversion rate
options and corresponding current consumption.
ONE-SHOT CONVERSION
When the TMP401 is in shutdown mode (SD = 1 in the
Configuration Register), a single conversion on both
channels is started by writing any value to the One-Shot
Start Register, pointer address 0Fh. This write operation
starts one conversion; the TMP401 returns to shutdown
mode when that conversion completes. The value of the
data sent in the write command is irrelevant and is not
stored by the TMP401. When the TMP401 has been set to
shutdown mode, an initial 200µs is required before a
one-shot command can be given. This wait time only
applies to the 200µs immediately following shutdown.
One-shot commands can be issued without delay
thereafter.
Table 7. Conversion Rate Register
CONVERSION RATE REGISTER
AVERAGE I
Q
(typ)
(µA)
R7 R6 R5 R4 R3 R2 R1 R0 CONVERSION/SEC
V
S
= 3V V
S
= 5V
0 0 0 0 0 0 0 0 0.0625 8 29
0 0 0 0 0 0 0 1 0.125 11 31
0 0 0 0 0 0 1 0 0.25 15 36
0 0 0 0 0 0 1 1 0.5 24 45
0 0 0 0 0 1 0 0 1 41 63
0 0 0 0 0 1 0 1 2 69 92
0 0 0 0 0 1 1 0 4 111 136
07h to 0Fh 8 320 355