Datasheet
η -FACTOR CORRECTION REGISTER
hkT
q
V =-
BE2 BE1
V
ln
I
2
I
1
()
(1)
SOFTWARE RESET
1.008 300
300 N
´
-
ADJUST
h
eff
=
(2)
IDENTIFICATION REGISTERS
300 1.008´
h
eff
N
ADJUST
=300 -
(3)
1.000 300
300 N
´
-
ADJUST
h
eff
=
(4)
300 1.000´
h
eff
N
ADJUST
=300 -
(5)
TMP441
TMP442
www.ti.com
.............................................................................................................................................. SBOS425A – DECEMBER 2008 – REVISED MARCH 2009
Table 9. η -Factor Range
N
ADJUST
The TMP441/42 allow for a different η -factor value to
η -FACTOR η -FACTOR
BINARY HEX DECIMAL = 1.008 = 1.000
be used for converting remote channel
0111 1111 7F 127 1.747977 1.734104
measurements to temperature. The remote channel
uses sequential current excitation to extract a
0000 1010 0A 10 1.042759 1.034482
differential V
BE
voltage measurement to determine
0000 1000 08 8 1.035616 1.027397
the temperature of the remote transistor. Equation 1
0000 0110 06 6 1.028571 1.020408
relates this voltage and temperature.
0000 0100 04 4 1.021622 1.013513
0000 0010 02 2 1.014765 1.006711
0000 0001 01 1 1.011371 1.003344
0000 0000 00 0 1.008 1.000
The value η in Equation 1 is a characteristic of the
1111 1111 FF – 1 1.004651 0.996677
particular transistor used for the remote channel.
1111 1110 FE – 2 1.001325 0.993377
When the beta compensation configuration is set to
1111 1100 FC – 4 0.994737 0.986842
'0111' (beta compensation disabled) or the sensor is
1111 1010 FA – 6 0.988235 0.980392
diode-connected (base shorted to collector), the
1111 1000 F8 – 8 0.981818 0.974025
η -factor used by the TMP441/42 is 1.008. When the
1111 0110 F6 – 10 0.975484 0.967741
beta compensation configuration is set to '1000' (beta
1000 0000 80 – 128 0.706542 0.700934
compensation enabled) and the sensor is GND
collector-connected (PNP collector to ground), the
η -factor used by the TMP441/42 is 1.000. If the
η -factor used for the temperature conversion does
The TMP441/42 may be reset by writing any value to
not match the characteristic of the sensor, then
the Software Reset Register (pointer address FCh).
temperature offset is observed. The value in the
This action restores the power-on reset state to all of
η -Factor Correction Register may be used to adjust
the TMP441/42 registers as well as aborts any
the effective η -factor according to Equation 2 and
conversion in process. The TMP441/42 also support
Equation 3 for disabled beta compensation or a
reset via the Two-Wire general call address (0000
diode-connected sensor. Equation 4 and Equation 5
0000). The TMP441/42 acknowledge the general call
may be used for enabled beta compensation and a
address and respond to the second byte. If the
GND collector-connected sensor.
second byte is 0000 0110, the TMP441/42 execute a
software reset. The TMP441/42 do not respond to
other values in the second byte.
The TMP441/42 allow for the Two-Wire bus controller
to query the device for manufacturer and device IDs
to enable software identification of the device at the
particular Two-Wire bus address. The manufacturer
ID is obtained by reading from pointer address FEh.
The device ID is obtained by reading from pointer
The η -correction value must be stored in twos
address FFh. The TMP441/42 both return 55h for the
complement format, yielding an effective data range
manufacturer code. The TMP441 returns 41h for the
from – 128 to +127. Table 9 shows the η -factor range
device ID and the TMP442 returns 42h for the device
for both 1.008 and 1.000. The η -correction value may
ID. These registers are read-only.
be written to and read from pointer address 21h. (The
η -correction value for the second remote channel is
read to/written from pointer address 22h.) The
register power-on reset value is 00h, thus having no
effect unless the register is written to.
space
space
Copyright © 2008 – 2009, Texas Instruments Incorporated Submit Documentation Feedback 15
Product Folder Link(s): TMP441 TMP442