Datasheet
REF02
Rev. I | Page 11 of 16
TEMPERATURE MONITORING
The REF02 provides a TEMP output (Pin 3) that varies linearly
with temperature. This output can be used to monitor the
temperature change in the system. The voltage at V
TEMP
is
approximately 550 mV at 25°C, and the temperature coefficient
is approximately 1.96 mV/°C (see Figure 18).
850
800
750
700
650
600
550
500
450
400
–50 –25 0 25 50 75 100 125
00375-F-017
TEMPERATURE (°C)
TEMP PIN OUTPUT (mV)
∆
V
TEMP
/
∆
T = 1.96mV/°C
V
IN
= 9V
SAMPLE SIZE = 6
J, S, AND P PACKAGES
Z PACKAGE AND 833 PRODUCT
∆
V
TEMP
/
∆
T = 2.1mV/°C
Figure 18. Voltage at TEMP Pin vs. Temperature
A voltage change of 39.2 mV at the TEMP pin corresponds to a
20°C change in temperature.
The TEMP function is provided as a convenience rather than a
precise feature. Since the voltage at the TEMP node is acquired
from the band gap core, current pulling from this pin has a
significant effect on V
OUT
. Care must be taken to buffer the
TEMP output with a suitable low bias current op amp, such as
the AD8601, AD820, or OP1177. Using any of these three op
amps results in less than a 100 µV change in ΔV
OUT
(see
Figure 19). Without buffering, even tens of microamps drawn
from the TEMP pin can cause V
OUT
to fall out of specification.
00375-F-018
TEMP
TRIM
GND
U1
OP1177
V+
V–
15V
U2
V
O
V
OUT
V
IN
V
TEMP
1.9mV/°C
V
IN
REF02
Figure 19. Temperature Monitoring
00375-F-019
GND
REF02
4
6
2
TEMP
3
CMP02
2
3
8
4
R6
1
7
R7
27kΩ
R1
(9.2kΩ)
R3
(1.3kΩ)
R2
1.5kΩ
R4
2.7kΩ
R5
2.2kΩ
V+
V–
–
+
HEATING
ELEMENT
V+ (12V TO 32V)
V
IN
V
O
(SEE NOTE 1)
NOTES
1. REF02 SHOULD BE THERMALLY CONNECTED
TO SUBSTANCE BEING HEATED.
2. NUMBERS IN PARENTHESES ARE FOR A
SETPOINT TEMPERATURE OF 60°C.
3. R3 = R1
||
R2
||
R6
Figure 20. Temperature Controller
REFERENCE STACK WITH EXCELLENT LINE
REGULATION
Two REF01s and one REF02 can be stacked to yield 5.00 V,
15.00 V, and 25.00 V outputs. An additional advantage is near-
perfect line regulation of the 5.0 V and 15.0 V output. A 27 V to
55 V input change produces an output change that is less than
the noise voltage of the devices. A load bypass resistor (R
B
)
provides a path for the supply current (I
SY
) of the 15.00 V
regulator.
In general, any number of REF01s and REF02s can be stacked
this way. For example, 10 devices yield 10 outputs in 5 V or 10 V
steps. The line voltage can change from 100 V to 130 V. Care
must be taken, however, to ensure that the total load currents
do not exceed the maximum usable current (typically 21 mA).
00375-F-020
GND
REF02
GND
REF02
GND
REF02
TRIM
TRIM
10kΩ
10kΩ
R
B
6.8kΩ
10kΩ
2
6
5
4
2
6
5
4
2
6
5
4
15V
10V
5V
TRIM
27V TO 55V
V
IN
V
O
V
IN
V
O
V
IN
V
O
Figure 21. Reference Stack