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FEATURES Voltage Output 5.0 V 6.0 V to 15 V Supply Range Supply Current 15 A Max Initial Accuracy 3 mV Max Temperature Coefficient 8 ppm/ C Max Low Noise 15 V p-p Typ (0.1 Hz to 10 Hz) High Output Current 5 mA Min Temperature Range 40 C to 125 C REF02/REF19x Pinout APPLICATIONS Portable Instrumentation Precision Reference for 5 V Systems A/D and D/A Converter Reference Solar Powered Applications Loop-Current Powered Instruments GENERAL DESCRIPTION
Low Noise Micropower Precision Voltage Reference ADR293
PIN CONFIGURATIONS 8-Lead Narrow Body SO (R Suffix)
NC 1 VIN 2 8 NC
7 NC TOP VIEW NC 3 (Not to Scale) 6 VOUT 5 NC
ADR293
GND 4
NC = NO CONNECT
8-Lead TSSOP (RU Suffix)
NC 1 VIN 2 8 NC
7 NC TOP VIEW 3 (Not to Scale) 6 VOUT NC 5 NC
ADR293
The ADR293 is a low noise, micropower precision voltage reference that utilizes an XFETTM (eXtra implanted junction FET) reference circuit. The new XFET architecture offers significant performance improvements over traditional bandgap and Zener-based references. Improvements include: one quarter the voltage noise output of bandgap references operating at the same current, very low and ultralinear temperature drift, low thermal hysteresis and excellent long-term stability. The ADR293 is a series voltage reference providing stable and accurate output voltage from a 6.0 V supply. Quiescent current is only 15 A max, making this device ideal for battery powered instrumentation. Three electrical grades are available offering initial output accuracy of 3 mV, 6 mV, and 10 mV. Temperature coefficients for the three grades are 8 ppm/C, 15 ppm/C and 25 ppm/C max. Line regulation and load regulation are typically 30 ppm/V and 30 ppm/mA, maintaining the reference's overall high performance. The ADR293 is specified over the extended industrial temperature range of -40C to +125C. This device is available in the 8-lead SOIC, 8-lead TSSOP and the TO-92 package.
GND 4
NC = NO CONNECT
3-Lead TO-92 (T9 Suffix)
PIN 1 VIN PIN 2 GND PIN 3 VOUT
BOTTOM VIEW
Part Number ADR290 ADR291 ADR292 ADR293
Nominal Output Voltage (V) 2.048 2.500 4.096 5.000
XFET is a trademark of Analog Devices, Inc.
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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 which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781/329-4700 World Wide Web Site: http://www.analog.com Fax: 781/326-8703 (c) Analog Devices, Inc., 1998
ADR293-SPECIFICATIONS
ELECTRICAL SPECIFICATIONS (V =
S
6.0 V, TA =
25 C unless otherwise noted)
Min 4.997 4.994 4.990 Typ Max Units V V V ppm/V ppm/V ppm/mA ppm/mA ppm V p-p nV/Hz
Parameter INITIAL ACCURACY "E" Grade "F" Grade "G" Grade LINE REGULATION "E/F" Grades "G" Grade LOAD REGULATION "E/F" Grades "G" Grade LONG TERM STABILITY NOISE VOLTAGE WIDEBAND NOISE DENSITY
Symbol VO
Conditions IOUT = 0 mA
5.000 5.003 5.006 5.010 30 40 30 40 0.2 15 640 100 150 100 150
VO/VIN
6.0 V to 15 V, IOUT = 0 mA
VO/ILOAD VO eN eN
S
VS = 6.0 V, 0 mA to 5 mA 1000 hrs @ +25C, VS = +15 V 0.1 Hz to 10 Hz at 1 kHz
ELECTRICAL SPECIFICATIONS (V =
Parameter TEMPERATURE COEFFICIENT "E" Grade "F" Grade "G" Grade LINE REGULATION "E/F" Grades "G" Grade LOAD REGULATION "E/F" Grades "G" Grade Symbol TCVO/C
6.0 V, TA =
25 C TA
85 C unless otherwise noted)
Min Typ 3 5 10 35 50 20 30 Max 8 15 25 150 200 150 200 Units ppm/C ppm/C ppm/C ppm/V ppm/V ppm/mA ppm/mA
Conditions IOUT = 0 mA
VO/VIN
6.0 V to 15 V, IOUT = 0 mA
VO/ILOAD
VS = 6.0 V, 0 mA to 5 mA
ELECTRICAL SPECIFICATIONS (V =
S
6.0 V, TA =
40 C TA
125 C unless otherwise noted)
Min Typ 3 5 10 40 70 20 30 11 15 160 72 157 Max 10 20 30 200 250 200 300 15 20 Units ppm/C ppm/C ppm/C ppm/V ppm/V ppm/mA ppm/mA A A ppm ppm ppm
Parameter TEMPERATURE COEFFICIENT "E" Grade "F" Grade "G" Grade LINE REGULATION "E/F" Grades "G" Grade LOAD REGULATION "E/F" Grades "G" Grade SUPPLY CURRENT THERMAL HYSTERESIS
Symbol TCVO/C
Conditions IOUT = 0 mA
VO/VIN
6.0 V to 15 V, IOUT = 0 mA
VO/ILOAD
VS = 6.0 V, 0 mA to 5 mA @ +25C TO-92 SO-8 TSSOP-8
Specifications subject to change without notice.
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ADR293 WAFER TEST LIMITS (V =
S
6.0 V, TA =
Symbol VO VO/VIN VO/ILOAD
25 C unless otherwise noted)
Conditions IOUT = 0 mA 6.0 V < VIN < 15 V, IOUT = 0 mA 0 mA to 5 mA No load Limits 4.990/5.010 150 150 15 Units V ppm/V ppm/mA A
Parameter INITIAL ACCURACY LINE REGULATION LOAD REGULATION SUPPLY CURRENT
NOTES Electrical tests are performed as wafer probe to the limits shown. Due to variations in assembly methods and normal yield loss, yield after packaging is not guaranteed for standard product dice. Consult factory to negotiate specifications based on dice lot qualification through sample lot assembly and testing. Specifications subject to change without notice.
DICE CHARACTERISTICS
Die Size 0.074 0.052 inch, 3848 sq. mils (1.88 1.32 mm, 2.48 sq. mm) Transistor Count: 52
VIN
1
4
VOUT(SENSE)
3
VOUT(FORCE)
GND
2
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ADR293
ABSOLUTE MAXIMUM RATINGS 1
Supply Voltage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 V Output Short-Circuit Duration . . . . . . . . . . . . . . . . . Indefinite Storage Temperature Range T9, R, RU Package . . . . . . . . . . . . . . . . . 65C to 150C Operating Temperature Range . . . . . . . . . . 40C to 125C Junction Temperature Range T9, R, RU Package . . . . . . . . . . . . . . . . . 65C to 125C Lead Temperature (Soldering, 60 sec) . . . . . . . . . . . . 300C
NOTE 1 Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only; functional operation of the device at these or any other conditions above those listed in the operational sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
Package Type 8-Lead SOIC (R) 3-Lead TO-92 (T9) 8-Lead TSSOP (RU)
1 JA
JC
Units C/W C/W C/W
158 162 240
43 120 43
NOTE 1 JA is specified for worst case conditions, i.e., JA is specified for device in socket for PDIP, and JA is specified for a device soldered in circuit board for SOIC packages.
ORDERING GUIDE
Model ADR293ER, ADR293FR, ADR293GR ADR293ER-REEL, ADR293FR-REEL, ADR293GR-REEL ADR293ER-REEL7, ADR293FR-REEL7, ADR293GR-REEL7 ADR293GT9 ADR293GT9-REEL ADR293GRU-REEL ADR293GRU-REEL7 ADR293GBC
Temperature Range 40C to 40C to 40C to 40C to 40C to 40C to 40C to 25C 125C 125C 125C 125C 125C 125C 125C
Package Type 8-Lead SOIC 8-Lead SOIC 8-Lead SOIC 3-Lead TO-92 3-Lead TO-92 8-Lead TSSOP 8-Lead TSSOP DICE
Package Options R-8 R-8 R-8 T9 T9 RU-8 RU-8
CAUTION ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the human body and test equipment and can discharge without detection. Although the ADR293 features proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of functionality.
WARNING!
ESD SENSITIVE DEVICE
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Typical Performance Characteristics- ADR293
5.006 VS = 6.0V 5.004 3 TYPICAL PARTS
100 VS = 6.0V TO 15V LINE REGULATION - ppm/V 80 IOUT = 0mA
OUTPUT VOLTAGE - V
5.002
60
5.000
40
4.998
4.996
20
4.994
50
25
0
25
50
75
100
125
0
50
25
0
25
50
75
100
125
TEMPERATURE - C
TEMPERATURE - C
Figure 1. VOUT vs. Temperature
Figure 4. Line Regulation vs. Temperature
16 14 12
100 VS = 6.0V TO 9.0V LINE REGULATION - ppm/V
TA = +125 C TA = +25 C TA = 40 C
IOUT = 0mA
80
SUPPLY CURRENT - A
10 8 6 4 2 0
60
40
20
0
2
4
6 8 10 INPUT VOLTAGE - V
12
14
16
0
50
25
0
25
50
75
100
125
TEMPERATURE - C
Figure 2. Supply Current vs. Input Voltage
Figure 5. Line Regulation vs. Temperature
16 VS = 6.0V
0.7 0.6
DIFFERENTIAL VOLTAGE - V
14 SUPPLY CURRENT - A
0.5
TA = +125 C
12
0.4 0.3 0.2 TA = 0.1
TA = +25 C
10
8
40 C
6
50
25
0
25
50
75
100
125
0 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 LOAD CURRENT - mA 4.0 4.5 5.0
TEMPERATURE - C
Figure 3. Supply Current vs. Temperature
Figure 6. Minimum Input-Output Voltage Differential vs. Load Current
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ADR293
200 VS = 6.0V
100 120 VS = 6.0V
LOAD REGULATION - ppm/mA
160
RIPPLE REJECTION - dB
80
120 IOUT = 5mA 80 IOUT = 1mA 40
60
40
20
0
50
25
0
25
50
75
100
125
0 10
TEMPERATURE - C
100 FREQUENCY - Hz
1000
Figure 7. Load Regulation vs. Temperature
Figure 10. Ripple Rejection vs. Frequency
2
50 VS = 6.0V IL = 0mA 40
1
VOUT FROM NOMINAL - mV
0 TA = +25 C 1 TA = 2 40 C TA = +125 C
OUTPUT IMPEDANCE -
10
30
20
3
10
4
0
1 SOURCING LOAD CURRENT - mA
0 10
100 1k FREQUENCY - Hz
10k
Figure 8. VOUT from Nominal vs. Load Current
Figure 11. Output Impedance vs. Frequency
1200 VIN = 15V TA = 25 C
VOLTAGE NOISE DENSITY - nV/ Hz
1000
800
600
10 V p-p
400
200
1s
0 10
100 FREQUENCY - Hz
1000
Figure 9. Voltage Noise Density
Figure 12. 0.1 Hz to 10 Hz Noise
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ADR293
IL = 5mA 5V/DIV IL = 5mA CL = 1nF
2V/DIV
50 s
1ms
Figure 13. Turn-On Time
Figure 16. Load Transient
IL = 5mA
IL = 5mA CL = 100nF
5V/DIV
2V/DIV
50 s
1ms
Figure 14. Turn-Off Time
Figure 17. Load Transient
IL = 5mA
1ms
Figure 15. Load Transient
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ADR293
THEORY OF OPERATION Device Power Dissipation Considerations
The ADR293 uses a new reference generation technique known as XFET, which yields a reference with low noise, low supply current and very low thermal hysteresis. The core of the XFET reference consists of two junction fieldeffect transistors one of which has an extra channel implant to raise its pinch-off voltage. By running the two JFETS at the same drain current, the difference in pinch-off voltage can be amplified and used to form a highly stable voltage reference. The intrinsic reference voltage is around 0.5 V with a negative temperature coefficient of about -120 ppm/K. This slope is essentially locked to the dielectric constant of silicon and can be closely compensated by adding a correction term generated in the same fashion as the proportional-to-temperature (PTAT) term used to compensate bandgap references. The big advantage over a bandgap reference is that the intrinsic temperature coefficient is some thirty times lower (therefore less correction is needed) and this results in much lower noise since most of the noise of a bandgap reference comes from the temperature compensation circuitry. The simplified schematic below shows the basic topology of the ADR293. The temperature correction term is provided by a current source with value designed to be proportional to absolute temperature. The general equation is:
VOUT R1 + R2 + R3 = VP + I PTAT R3 R1
The ADR293 is guaranteed to deliver load currents to 5 mA with an input voltage that ranges from 5.5 V to 15 V. When this device is used in applications with large input voltages, care should be exercised to avoid exceeding the published specifications for maximum power dissipation or junction temperature that could result in premature device failure. The following formula should be used to calculate a device's maximum junction temperature or dissipation:
PD =
T J -TA JA
In this equation, TJ and TA are the junction and ambient temperatures, respectively, PD is the device power dissipation, and JA is the device package thermal resistance.
Basic Voltage Reference Connections
References, in general, require a bypass capacitor connected from the VOUT pin to the GND pin. The circuit in Figure 19 illustrates the basic configuration for the ADR293. Note that the decoupling capacitors are not required for circuit stability.
NC INPUT 2 7 NC OUTPUT + 10 F NC 0.1 F 4 5 NC = NO CONNECT NC 3 6 0.1 F 1 8 NC
(
)( )
ADR293
where VP is the difference in pinch-off voltage between the two FETs and IPTAT is the positive temperature coefficient correction current. The process used for the XFET reference also features vertical NPN and PNP transistors, the latter of which are used as output devices to provide a very low drop-out voltage.
VIN I1 I1
Figure 19. Basic Voltage Reference Configuration
Noise Performance
The noise generated by the ADR293 is typically less than 15 Vp-p over the 0.1 Hz to 10 Hz band. The noise measurement is made with a bandpass filter made of a 2-pole high-pass filter with a corner frequency at 0.1 Hz and a 2-pole low-pass filter with a corner frequency at 10 Hz.
Turn-On Time
*
VP R1
VOUT
IPTAT R2
Upon application of power (cold start), the time required for the output voltage to reach its final value within a specified error band is defined as the turn-on settling time. Two components normally associated with this are; the time for the active circuits to settle, and the time for the thermal gradients on the chip to stabilize. Figure 13 shows the typical turn-on time for the ADR293.
R3 GND R3
*EXTRA CHANNEL IMPLANT
VOUT R1 R2 R3 R1 VP I PTAT
Figure 18. Simplified Schematic
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ADR293
APPLICATIONS A Negative Precision Reference without Precision Resistors A Precision Current Source
In many current-output CMOS DAC applications where the output signal voltage must be of the same polarity as the reference voltage, it is often required to reconfigure a currentswitching DAC into a voltage-switching DAC through the use of a 1.25 V reference, an op amp and a pair of resistors. Using a current-switching DAC directly requires the need for an additional operational amplifier at the output to reinvert the signal. A negative voltage reference is then desirable from the point that an additional operational amplifier is not required for either reinversion (current-switching mode) or amplification (voltage-switching mode) of the DAC output voltage. In general, any positive voltage reference can be converted into a negative voltage reference through the use of an operational amplifier and a pair of matched resistors in an inverting configuration. The disadvantage to that approach is that the largest single source of error in the circuit is the relative matching of the resistors used. The circuit illustrated in Figure 20 avoids the need for tightly matched resistors with the use of an active integrator circuit. In this circuit, the output of the voltage reference provides the input drive for the integrator. The integrator, to maintain circuit equilibrium, adjusts its output to establish the proper relationship between the reference's VOUT and GND. One caveat with this approach should be mentioned: although rail-to-rail output amplifiers work best in the application, these operational amplifiers require a finite amount (mV) of headroom when required to provide any load current. The choice for the circuit's negative supply should take this issue into account.
VIN
Many times in low power applications, the need arises for a precision current source that can operate on low supply voltages. As shown in Figure 21, the ADR293 is configured as a precision current source. The circuit configuration illustrated is a floating current source with a grounded load. The reference's output voltage is bootstrapped across RSET, which sets the output current into the load. With this configuration, circuit precision is maintained for load currents in the range from the reference's supply current, typically 15 A to approximately 5 mA.
VIN
2
ADR293
6 VOUT R1 1F ISY ADJUST P1 IOUT RL RSET
GND 4
Figure 21. A Precision Current Source
2
ADR293
1k 6
1F +5V 100
VOUT GND 4 100k 1F
A1 -VREF -5V A1 = 1/2 OP291, 1/2 OP295
Figure 20. A Negative Precision Voltage Reference Uses No Precision Resistors
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ADR293
Kelvin Connections Voltage Regulator For Portable Equipment
In many portable instrumentation applications where PC board cost and area go hand-in-hand, circuit interconnects are very often of dimensionally minimum width. These narrow lines can cause large voltage drops if the voltage reference is required to provide load currents to various functions. In fact, a circuit's interconnects can exhibit a typical line resistance of 0.45 mW/square (1 oz. Cu, for example). Force and sense connections also referred to as Kelvin connections, offer a convenient method of eliminating the effects of voltage drops in circuit wires. Load currents flowing through wiring resistance produce an error (VERROR = R IL ) at the load. However, the Kelvin connection of Figure 22 overcomes the problem by including the wiring resistance within the forcing loop of the op amp. Since the op amp senses the load voltage, op amp loop control forces the output to compensate for the wiring error and to produce the correct voltage at the load.
VIN RLW 2 VIN RLW +VOUT FORCE RL 1F 100k +VOUT SENSE
The ADR293 is ideal for providing a stable, low cost and low power reference voltage in portable equipment power supplies. Figure 23 shows how the ADR293 can be used in a voltage regulator that not only has low output noise (as compared to switch mode design) and low power, but also a very fast recovery after current surges. Some precautions should be taken in the selection of the output capacitors. Too high an ESR (effective series resistance) could endanger the stability of the circuit. A solid tantalum capacitor, 16 V or higher, and an aluminum electrolytic capacitor, 10 V or higher, are recommended for C1 and C2, respectively. Also, the path from the ground side of C1 and C2 to the ground side of R1 should be kept as short as possible.
CHARGER INPUT
0.1 F 2 VIN 6V V OUT 6 + 2 7 6 3 GND 4 R1 402k 1% R2 402k 1% C1 68 F TANT + + C2 1000 F ELECT 4 OP-20 +5V, 100mA IRF9530 R3 510k
LEAD-ACID BATTERY
ADR293
ADR293
A1 6
VOUT GND 4
Figure 23. Voltage Regulator for Portable Equipment
A1 = 1/2 OP295
Figure 22. Advantage of Kelvin Connection
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ADR293
OUTLINE DIMENSIONS
Dimensions shown in inches and (mm).
0.1968 (5.00) 0.1890 (4.80)
8 5
0.122 (3.10) 0.114 (2.90)
0.177 (4.50) 0.169 (4.30)
1
4
PIN 1
0.102 (2.59) 0.094 (2.39)
0.0196 (0.50) x 45 0.0099 (0.25)
PIN 1
1
4
0.0098 (0.25) 0.0040 (0.10) 0.0500 0.0192 (0.49) SEATING (1.27) 0.0138 (0.35) 0.0098 (0.25) PLANE BSC 0.0075 (0.19)
8 0
0.0500 (1.27) 0.0160 (0.41)
0.006 (0.15) 0.002 (0.05)
0.0256 (0.65) BSC 0.0433 (1.10) MAX 0.0118 (0.30) 0.0075 (0.19) 0.0079 (0.20) 0.0035 (0.090)
0.256 (6.50) 0.246 (6.25)
0.2440 (6.20) 0.2284 (5.80)
0.1574 (4.00) 0.1497 (3.80)
8
5
SEATING PLANE
8 0
0.028 (0.70) 0.020 (0.50)
3-Lead TO-92 (T9 Suffix)
0.135 (3.43) MIN 0.205 (5.20) 0.175 (4.96)
0.210 (5.33) 0.170 (4.38) SEATING PLANE 0.050 (1.27) MAX
0.500 (12.70) MIN
0.019 (0.482) 0.016 (0.407) SQUARE
0.105 (2.66) 0.095 (2.42) 0.105 (2.66) 0.080 (2.42)
0.055 (1.39) 0.045 (1.15)
0.105 (2.66) 0.080 (2.42)
1
2
3
0.165 (4.19) 0.125 (3.94)
BOTTOM VIEW
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PRINTED IN U.S.A.
C3347-8-6/98
8-Lead Narrow Body SO (R-8)
8-Lead TSSOP (RU-8)

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