Datasheet

300 1.000´
h
eff
N
ADJUST
=300 -
1.000 300
300 N
´
-
ADJUST
h
eff
=
300 1.008´
h
eff
N
ADJUST
=300 -
1.008 300
300 N
´
-
ADJUST
h
eff
=
V V =-
BE2 BE1
ln
hkT
q
()
I
I
2
1
TMP431
TMP432
www.ti.com SBOS441F –SEPTEMBER 2009–REVISED AUGUST 2013
η-Factor Correction Register
correction value may be written to and read from
pointer address 27h. The η-correction value for the
The TMP431/32 allow for a different η-factor value to
second remote channel is read to and written from
be used for converting remote channel
pointer address 28h. The register power-on reset
measurements to temperature. The remote channel
value is 00h, thus having no effect unless written to.
uses sequential current excitation to extract a
differential V
BE
voltage measurement to determine
Table 11. η-Factor Range
the temperature of the remote transistor. Equation 1
N
ADJUST
relates this voltage and temperature.
BINARY HEX DECIMAL η
01111111 7F 127 1.747977
(1)
00001010 0A 10 1.042759
The value η in Equation 1 is a characteristic of the
00001000 08 8 1.035616
particular transistor used for the remote channel.
00000110 06 6 1.028571
When the beta compensation configuration is set to
00000100 04 4 1.021622
'0111' (beta compensation disabled) or the sensor is
diode-connected (base shorted to collector), the η-
00000010 02 2 1.014765
factor used by the TMP431/32 is 1.008. When the
00000001 01 1 1.011371
beta compensation configuration is set to '1000' (beta
00000000 00 0 1.008
compensation enabled) and the sensor is GND
11111111 FF –1 1.004651
collector-connected (PNP collector to ground), the η-
11111110 FE –2 1.001325
factor used by the TMP431/32 is 1.000. If the η-factor
used for the temperature conversion does not match
11111100 FC –4 0.994737
the characteristic of the sensor, then temperature
11111010 FA –6 0.988235
offset is observed. The value in the η-Factor
11111000 F8 –8 0.981818
Correction Register may be used to adjust the
11110110 F6 –10 0.975484
effective η-factor according to Equation 2 and
10000000 80 –128 0.706542
Equation 3 for disabled beta compensation or a
diode-connected sensor. Equation 4 and Equation 5
space
may be used for enabled beta compensation and a
GND collector-connected sensor.
Software Reset
The TMP431/32 may be reset by writing any value to
(2)
Pointer Register FCh. This action restores the power-
on reset state to all of the TMP431/32 registers as
(3)
well as abort any conversion in process and clear the
ALERT and THERM pins.
(4)
The TMP431/32 also support reset via the two-wire
general call address (00000000). The TMP431/32
acknowledge the general call address and respond to
(5)
the second byte. If the second byte is 00000110, the
TMP431/32 execute a software reset. The
The η-correction value must be stored in twos-
TMP431/32 do not respond to other values in the
complement format, yielding an effective data range
second byte.
from –128 to +127. Table 11 shows the η-factor
range for both 1.008 and 1.000. For the TMP431, the
η-correction value may be written to and read from
pointer address 18h. For the TMP432, the η-
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