LM134 Series
APPLICATIO S I FOR ATIO
The two trims shown in Figure 3 are still intended to be a
“one point” temperature calibration, where the zero and
the slope are trimmed at a single temperature. The LT1009
reference is adjusted to give 2.700V at node “a” at T
SENSOR
= 25°C. The 1k trimmer then adjusts the output for 0.25V,
completing the calibration. If the calibration is to be done
at a temperature other than 25°C , trim the LT1009 for
2.7025—(1µA)[T
SENSOR
(°C)](100Ω) at node “a”, then
adjust the 1k trimmer for proper output.
V
S
≥
4V
V
+
LM134-3
R
OUTPUT
10mV/°C
R
SET
226Ω
9.53k
1%
1k
SLOPE
ADJ
“a”
100Ω
10k
10k
ZERO
ADJ
V
–
LT1009
134 F03
–15V
Figure 3. Centigrade Temperature Sensor
TYPICAL APPLICATIO S
Basic 2-Terminal
Current Source
V
IN
V
+
I
SET
LM334
V
–
R
R
SET
Low Output Impedance
Thermometer (Kelvin Output)
V
IN
≥
4.8V
V
+
R
R3*
600Ω
R1
230Ω
1%
R2
10k
1%
134 TA03
LM334
C1
0.1µF
134 TA02
–V
IN
*OUTPUT IMPEDANCE OF THE LM134 AT THE “R” PIN IS
–R
O
APPROXIMATELY
Ω,
WHERE R
O
IS THE EQUIVALENT
16
EXTERNAL RESISTANCE CONNECTED TO THE V
–
PIN. THIS
NEGATIVE RESISTANCE CAN BE REDUCED BY A FACTOR OF
5 OR MORE BY INSERTING AN EQUIVALENT RESISTOR IN
SERIES WITH THE OUTPUT.
U
If higher accuracy is required, a two point calibration
technique can be used. In Figure 4, separate zero and slope
trims are provided. Residual nonlinearity is now the limi-
tation on accuracy. Nonlinearity of the LM134 in a 100°C
span is typically less than 0.5°C. This particular method of
trimming has the advantage that the slope trim does not
interact with the zero trim. Trim procedure is to adjust for
zero output with T
SENSOR
= 0°C, then trim slope for proper
output at some convenient second temperature. No fur-
ther trimming is required.
V
+
≥
5V
V
+
LM134-3
R
226Ω*
OUTPUT
10mV/°C
50k
*LOW TC, STABLE RESISTOR
SLOPE
TRIM
500k
332k
1%
15k
LT1009
11k*
1%
ZERO
TRIM
10k
V
–
–15V
134 F04
W
U
U
U
Figure 4. Centigrade Temperature Sensor with 2 Point Trim
Zero Temperature
Coefficient Current Source
V
IN
V
+
I
+
V
OUT
= 10mV/°K
Z
OUT
≤
100Ω
LM334
D1
1N457
R
V
–
V
–
R
SET
R1*
≈10
R
SET
–V
IN
134 TA04
*SELECT RATIO OF R1 TO R
SET
TO
OBTAIN ZERO DRIFT. I
+
≈2
I
SET
.
7
LINER [ LINEAR TECHNOLOGY ]
