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5 V Precision Voltage
Reference/Temperature Transducer
REF02
FEATURES
5 V output: ±0.3% maximum
Temperature voltage output: 1.96 mV/°C
Adjustment range: ±3% minimum
Excellent temperature stability: 8.5 ppm/°C maximum
Low noise: 15 µV p-p maximum
Low supply current: 1.4 mA maximum
Wide input voltage range: 7 V to 40 V
High load-driving capability: 10 mA
No external components
Short-circuit proof
GENERAL DESCRIPTION
The REF02 precision voltage reference provides a stable 5 V
output that can be adjusted over a ±6% range with minimal
effect on temperature stability. Single-supply operation over an
input voltage range of 7 V to 40 V, low current drain of 1 mA,
and excellent temperature stability are achieved with an
improved band gap design. Low cost, low noise, and low power
make the REF02 an excellent choice whenever a stable voltage
reference is required. Applications include DACs and ADCs,
portable instrumentation, and digital voltmeters. The versatility
of the REF02 is enhanced by its use as a monolithic temperature
transducer. For new designs, refer to the ADR02.
PIN CONFIGURATIONS
NC
8
NC 1
7 NC
VIN 2
6 VOUT
NC 3
5 TRIM
4
GROUND
(CASE)
NC = NO CONNECT. DO NOT CONNECT ANYTHING
ON THESE PINS. SOME OF THEM ARE RESERVED
FOR FACTORY TESTING PURPOSES.
Figure 1. 8-Lead TO-99 (J-Suffix)
NC 1
8 NC
VIN 2 REF02 7 NC
TEMP
3
TOP VIEW
(Not to Scale)
6 VOUT
GND 4
5 TRIM
NC = NO CONNECT. DO NOT CONNECT ANYTHING
ON THESE PINS. SOME OF THEM ARE RESERVED
FOR FACTORY TESTING PURPOSES.
Figure 2. 8-Lead PDIP (P-Suffix), 8-Lead CERDIP (Z-Suffix)
and 8-Lead SOIC (S-Suffix)
NC 4
VIN 5
NC 6
TEMP 7
NC 8
3 2 1 20 19
REF02
TOP VIEW
(Not to Scale)
18 NC
17 NC
16 NC
15 VOUT
14 NC
9 10 11 12 13
NC = NO CONNECT. DO NOT CONNECT ANYTHING
ON THESE PINS. SOME OF THEM ARE RESERVED
FOR FACTORY TESTING PURPOSES.
Figure 3. 20-Terminal LCC (RC-Suffix)
OUTPUT RESISTORS
REF02 OPTION
R9 R11
883C PRODUCT
18kΩ 2kΩ
P, S, J, Z PACKAGES 18kΩ 4.5kΩ
R12
6.1kΩ
15kΩ
R8
Q8
R7 R14
Q7 Q14
Q13
Q15
INPUT
2
R15
Q9
Q12
C1
R6
Q6 Q5
Q11
Q10
Q21
Q17
R3 R4
R13
R5
Q1
Q4
Q2
Q3
Q20
≈1.23V
3 R1
TEMP
R2
R10
*SEE OUTPUT RESISTORS
Figure 4. Simplified Schematic
Q18
Q16
Q19
OUTPUT
6
R12*
R9*
TRIM
5
R11*
GROUND
4
Rev. I
Information furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other
rights of third parties that may result from its use. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
Trademarksandregisteredtrademarksarethepropertyoftheirrespectiveowners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
www.analog.com
Fax: 781.461.3113
© 2005 Analog Devices, Inc. All rights reserved.
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 VTEMP is
approximately 550 mV at 25°C, and the temperature coefficient
is approximately 1.96 mV/°C (see Figure 18).
850
VIN = 9V
800 SAMPLE SIZE = 6
750
Z PACKAGE AND 833 PRODUCT
700
∆VTEMP/∆T = 2.1mV/°C
650
600
∆VTEMP/∆T = 1.96mV/°C
550
J, S, AND P PACKAGES
500
450
400
–50
–25
0 25 50 75
TEMPERATURE (°C)
100
Figure 18. Voltage at TEMP Pin vs. Temperature
125
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 VOUT. 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 ΔVOUT (see
Figure 19). Without buffering, even tens of microamps drawn
from the TEMP pin can cause VOUT to fall out of specification.
U1
15V REF02
VIN VIN
VOUT
VO
VTEMP
1.9mV/°C
V+
OP1177
U2 V–
TEMP TRIM
GND
Figure 19. Temperature Monitoring
REF02
V+ (12V TO 32V)
HEATING
ELEMENT
2
VIN VO 6
REF02
TEMP 3
GND
(SEE NOTE 1) 4
R7
27kΩ
R1
(9.2kΩ)
R6
R3
(1.3kΩ)
R2
1.5kΩ
2
3
+
8
V+
CMP02V–
–4
7
1
R5
2.2kΩ
R4
2.7kΩ
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 (RB)
provides a path for the supply current (ISY) 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).
27V TO 55V
2
VIN 6
VO
REF02
5
TRIM
GND
4
2
VIN VO
6
15V
10kΩ
10V
2
VIN
VO
6
REF02
5
TRIM
GND
4
REF02
5
TRIM
GND
4
10kΩ
10kΩ
5V
RB
6.8kΩ
Figure 21. Reference Stack
Rev. I | Page 11 of 16