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Precision Low Drift 2.048 V/2.5 V/4.096 V/ 5.0 V SOT-23 Reference with Shutdown ADR390/ADR391/ADR392/ADR395
PIN CONFIGURATION 5-Lead SOT-23 (RT Suffix)
FEATURES Initial Accuracy: 6 mV Max Low TCVO: 25 ppm/ C Max Load Regulation: 60 ppm/mA Line Regulation: 25 ppm/V Low Supply Headroom: 0.3 V Wide Operating Range: (VOUT + 0.3 V) to 15 V Low Power: 120 A Max Shutdown to Less Than 3 A Max Output Current: 5 mA Wide Temperature Range: -40 C to +85 C for ADR390, ADR391 -40 C to +125 C for ADR392, ADR395 Tiny 5-Lead SOT-23 Package APPLICATIONS Battery-Powered Instrumentation Portable Medical Instruments Data Acquisition Systems Industrial Process Control Systems Fault Protection Critical Systems Automotive GENERAL DESCRIPTION
SHDN 1 VIN 2
VOUT (SENSE) 3 (Not to Scale) 4 VOUT (FORCE)
ADR390/ ADR391/ ADR392/ ADR395
5
GND
Table I. ADR39x Products
Part Number ADR390 ADR391 ADR392 ADR395
Nominal Output Voltage (V) 2.048 2.500 4.096 5.000
The ADR390, ADR391, ADR392, and ADR395 are precision 2.048 V, 2.5 V, 4.096 V, and 5 V band gap voltage references featuring high accuracy and stability and low power consumption in a tiny footprint. Patented temperature drift curvature correction techniques minimize nonlinearity of the voltage change with temperature. The wide operating range and low power consumption with additional shutdown capability make them ideal for battery-powered applications. The VOUT Sense Pin enables greater accuracy by supporting full Kelvin operation in PCBs employing thin or long traces. The ADR390, ADR391, ADR392, and ADR395 are micropower, low dropout voltage (LDV) devices that provide a stable output voltage from supplies as low as 300 mV above the output voltage. ADR390 and ADR391 are specified over the industrial range (-40C to +85C), while ADR392 and ADR395 are specified over the extended industrial range (-40C to +125C). Each is available in the tiny 5-lead SOT-23 package. The combination of VOUT sense and shutdown functions also enables a number of unique applications combining precision reference/regulation with fault decision and overcurrent protection. Details are provided in the Applications section.
REV. C
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. 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 www.analog.com Fax: 781/326-8703 (c) Analog Devices, Inc., 2002
ADR390/ADR391/ADR392/ADR395
ADR390 SPECIFICATIONS
ELECTRICAL CHARACTERISTICS
Parameter Initial Accuracy Initial Accuracy Error Temperature Coefficient Minimum Supply Voltage Headroom Line Regulation Load Regulation Quiescent Current Voltage Noise Turn-On Settling Time Long-Term Stability* Output Voltage Hysteresis Ripple Rejection Ratio Short Circuit to GND Shutdown Supply Current Shutdown Logic Input Current Shutdown Logic Low Shutdown Logic High Symbol VO VOERR TCVO VIN - VO VO/ VIN VO/ ILOAD ISY eN tR VO VO_HYS RRR ISC ISHDN ILOGIC VINL VINH
(@ VS = 5.0 V to 15 V, TA = 25 C, unless otherwise noted.)
Conditions Min 2.042 0.29 -40C < TA < +85C 300 VIN = 2.5 V to 15 V -40C < TA < +85C VIN = 3 V, ILOAD = 0 mA to 5 mA -40C < TA < +85C No Load -40C < TA < +85C 0.1 Hz to 10 Hz 10 25 60 120 140 Typ 2.048 5 Max 2.054 0.29 25 Unit V % ppm/C mV ppm/V ppm/mA A A V p-p s ppm/1000 hrs ppm dB mA mA A nA V V
100 5 20 50 40 85 25 30
fIN = 60 Hz VIN = 5.0 V VIN = 15.0 V
3 500 0.8 2.4
*The long-term stability specification is noncumulative. The drift in subsequent 1000 hour periods is significantly lower than in the first 1000 hour period. Specifications subject to change without notice.
ADR391 SPECIFICATIONS
ELECTRICAL CHARACTERISTICS
Parameter Initial Accuracy Initial Accuracy Error Temperature Coefficient Minimum Supply Voltage Headroom Line Regulation Load Regulation Symbol VO VOERR TCVO VIN - VO VO/ VIN VO/ ILOAD ISY eN tR VO VO_HYS RRR ISC ILOGIC VINL VINH
(@ VS = 5.0 V to 15 V, TA = 25 C, unless otherwise noted.)
Conditions Min 2.494 0.24 -40C < TA < +85C 300 VIN = 2.8 V to 15 V -40C < TA < +85C VSY = 3.5 V, ILOAD = 0 mA to 5 mA -40C < TA < +85C No Load -40C < TA < +85C 0.1 Hz to 10 Hz 10 25 Typ 2.5 5 Max 2.506 0.24 25 Unit V % ppm/C mV ppm/V
Quiescent Current Voltage Noise Turn-On Settling Time Long-Term Stability* Output Voltage Hysteresis Ripple Rejection Ratio Short Circuit to GND Shutdown Supply Current Shutdown Logic Input Current Shutdown Logic Low Shutdown Logic High
100 5 20 50 75 85 25 30
60 120 140
fIN = 60 Hz VIN = 5.0 V VIN = 15.0 V
3 500 0.8 2.4
ppm/mA A A V p-p s ppm/1000 hrs ppm dB mA mA A nA V V
*The long-term stability specification is noncumulative. The drift in subsequent 1000 hour periods is significantly lower than in the first 1000 hour period. Specifications subject to change without notice.
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ADR390/ADR391/ADR392/ADR395
ADR392 SPECIFICATIONS
ELECTRICAL CHARACTERISTICS
Parameter Initial Accuracy Initial Accuracy Error Temperature Coefficient Minimum Supply Voltage Headroom Line Regulation Load Regulation Symbol VO VOERR TCVO VS - VO VO/ VIN VO/ ILOAD ISY eN tR VO VO_HYS RRR ISC ILOGIC VINL VINH
(@ VS = 5.0 V to 15 V, TA = 25 C, unless otherwise noted.)
Conditions Min 4.090 0.15 -40C < TA < +125C 300 VIN = 4.4 V to 15 V -40C < TA < +125C VSY = 5 V, ILOAD = 0 mA to 5 mA -40C < TA < +125C No Load -40C < TA < +125C 0.1 Hz to 10 Hz 10 25 Typ 4.096 5 Max 4.912 0.15 25 Unit V % ppm/C mV ppm/V
Quiescent Current Voltage Noise Turn-On Settling Time Long-Term Stability* Output Voltage Hysteresis Ripple Rejection Short Circuit to GND Shutdown Supply Current Shutdown Logic Input Current Shutdown Logic Low Shutdown Logic High
100 5 20 50 75 85 25 30
140 120 140
fIN = 60 Hz VIN = 5.0 V VIN = 15.0 V
3 500 0.8 2.4
ppm/mA A A V p-p s ppm/1000 hrs ppm dB mA mA A nA V V
*The long-term stability specification is noncumulative. The drift in subsequent 1000 hour periods is significantly lower than in the first 1000 hour period. Specifications subject to change without notice.
ADR395 SPECIFICATIONS
ELECTRICAL CHARACTERISTICS
Parameter Initial Accuracy Initial Accuracy Error Temperature Coefficient Minimum Supply Voltage Headroom Line Regulation Load Regulation Symbol VO VOERR TCVO VS - VO VO/ VIN VO/ ILOAD ISY eN tR VO VO_HYS RRR ISC ILOGIC VINL VINH
(@ VS = 6.0 V to 15 V, TA = 25 C, unless otherwise noted.)
Conditions Min 4.994 0.12 -40C < TA < +125C 300 VIN = 5.3 V to 15 V -40C < TA < +125C VSY = 6 V, ILOAD = 0 mA to 5 mA -40C < TA < +125C No Load -40C < TA < +125C 0.1 Hz to 10 Hz 10 30 Typ 5.000 5 Max 5.006 0.12 25 Unit V % ppm/C mV ppm/V
Quiescent Current Voltage Noise Turn-On Settling Time Long-Term Stability* Output Voltage Hysteresis Ripple Rejection Short Circuit to GND Shutdown Supply Current Shutdown Logic Input Current Shutdown Logic Low Shutdown Logic High
100 5 20 50 75 85 25 30
140 120 140
fIN = 60 Hz VIN = 5.0 V VIN = 15.0 V
3 500 0.8 2.4
ppm/mA A A V p-p s ppm/1000 hrs ppm dB mA mA A nA V V
*The long-term stability specification is noncumulative. The drift in subsequent 1000 hour periods is significantly lower than in the first 1000 hour period. Specifications subject to change without notice.
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ADR390/ADR391/ADR392/ADR395
ABSOLUTE MAXIMUM RATINGS 1, 2
Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 V Output Short-Circuit Duration to GND . . . . . . . . . . . . . . . . . . . . . Observe Derating Curves Storage Temperature Range RT Package . . . . . . . . . . . . . . . . . . . . . . . -65C to +150C Operating Temperature Range ADR390/ADR391 . . . . . . . . . . . . . . . . . . . -40C to +85C ADR392/ADR395 . . . . . . . . . . . . . . . . . . -40C to +125C Junction Temperature Range RT Package . . . . . . . . . . . . . . . . . . . . . . . -65C to +150C Lead Temperature Range (Soldering, 60 Sec) . . . . . . . . 300C
Package Type 5-Lead SOT-23 (RT)
JA
JC
Unit C/W
230
NOTES 1 Absolute Maximum Ratings apply at 25C, unless otherwise noted. 2 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.
ORDERING GUIDE
Model ADR390ART-RL7 ADR390ART-RL ADR391ART-RL7 ADR391ART-RL ADR392ART-RL7 ADR392ART-RL ADR395ART-RL7
Temperature Range -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +125C -40C to +125C -40C to +125C
Package Description 5-Lead SOT-23 5-Lead SOT-23 5-Lead SOT-23 5-Lead SOT-23 5-Lead SOT-23 5-Lead SOT-23 5-Lead SOT-23
Package Option RT-5 RT-5 RT-5 RT-5 RT-5 RT-5 RT-5
Top Mark R0A R0A R1A R1A RCA RCA RDA
Output Voltage 2.048 2.048 2.500 2.500 4.096 4.096 5.000
Number of Parts Per Reel 3,000 10,000 3,000 10,000 3,000 10,000 3,000
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 ADR390/ADR391/ADR392/ADR395 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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REV. C
ADR390/ADR391/ADR392/ADR395
PARAMETER DEFINITION Temperature Coefficient (TCV O)
The change of output voltage over the operating temperature change and normalized by the output voltage at 25C, expressed in ppm/C. The equation follows:
TCVO ppm C =
where: VO(25C) = VO at 25C
[
]
VO T2 - VO T1 VO
2
( ) ( ) 10 (25C ) (T - T )
1
response can be improved with an additional 1 mF to 10 mF output capacitor in parallel. A capacitor here will act as a source of stored energy for a sudden increase in load current. The only parameter that will degrade, by adding an output capacitor, is turn-on time and it depends on the size of the capacitor chosen.
Long-Term Stability
6
Typical shift in output voltage over 1000 hours at a controlled temperature. Figure 1 shows a sample of parts measured at different intervals in a controlled environment of 50C for 1000 hours.
VO(T1) = VO at temperature1 VO(T2) = VO at temperature2
Line Regulation ( VO/ VIN)
DVO = VO (t0 ) - VO (t1 ) DVO ppm =
where: VO(t0) = VO at time 0
[
]
VO (t0 ) - VO (t1 ) VO (t0 )
106
The change in output voltage due to a specified change in input voltage. It includes the effects of self-heating. Line regulation is expressed in either percent per volt, parts per million per volt, or microvolts per volt change in input voltage.
Load Regulation ( VO/ ILOAD)
VO(t1) = VO after 1000 hours operation at a controlled temperature
Thermal Hysteresis (VO_HYS)
The change in output voltage due to a specified change in load current. It includes the effects of self-heating. Load regulation is expressed in either microvolts per milliampere, parts per million per milliampere, or W of dc output resistance.
Input Capacitor
The change of output voltage after the device is cycled through temperature from +25C to -40C to +85C and back to +25C. This is a typical value from a sample of parts put through such a cycle. VO
_ HYS
Input capacitors are not required on the ADR39x. There is no limit for the value of the capacitor used on the input, but a 1 mF to 10 mF capacitor on the input will improve transient response in applications where the supply suddenly changes. An additional 0.1 mF in parallel will also help in reducing noise from the supply.
Output Capacitor
= VO (25C ) - VO
_ TC
VO
_ HYS
[ ppm ] =
VO (25C ) - VO VO (25C )
_ TC
106
where: VO(25C) = VO at 25C
The ADR39x does not need output capacitors for stability under any load condition. An output capacitor, typically 0.1 mF, will filter out any low level noise voltage and will not affect the operation of the part. On the other hand, the load transient
VO_TC = VO at 25C after temperature cycle at +25C to -40C to +85C and back to +25C
200 DATA TAKEN IN CONTROLLED ENVIRONMENT @ 50 C 1 C 150 100
DRIFT - ppm
50
0 50 100 150
0
86
176
250 324 440 TIME - Hours
640
840
1040
Figure 1. ADR391 Typical Long-Term Drift over 1000 Hours
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ADR390/ADR391/ADR392/ADR395 -Typical Performance Characteristics
2.054 SAMPLE 1 2.052
5.004 SAMPLE 3 5.006
2.050
VOUT - V
5.002
2.048
SAMPLE 2
VOUT - V
SAMPLE 2 5.000 SAMPLE 1 4.998
2.046
2.044
SAMPLE 3
4.996
2.042 40 15 10 35 TEMPERATURE - C 60 85
4.994 -40
-5
30 65 TEMPERATURE - C
100
125
TPC 1. ADR390 Output Voltage vs. Temperature
TPC 4. ADR395 Output Voltage vs. Temperature
2.506
140
2.504
A
SAMPLE 1 2.502
VOUT - V
120 +85 C
SUPPLY CURRENT -
100 +25 C 40 C
SAMPLE 2 2.500
80
2.498 SAMPLE 3 2.496
60
2.494 40 15 10 35 TEMPERATURE - C 60 85
40 2.5
5.0
7.5 10.0 INPUT VOLTAGE - V
12.5
15.0
TPC 2. ADR391 Output Voltage vs. Temperature
TPC 5. ADR390 Supply Current vs. Input Voltage
4.100
140
4.098
A
120
SAMPLE 3 4.096 SAMPLE 2 VOUT - V 4.094 SAMPLE 1 4.092
SUPPLY CURRENT -
+85 C 100 +25 C 40 C 80
4.090
60
4.088 -40
0
40 TEMPERATURE - C
80
125
40 2.5
5.0
7.5 10.0 INPUT VOLTAGE - V
12.5
15.0
TPC 3. ADR392 Output Voltage vs. Temperature
TPC 6. ADR391 Supply Current vs. Input Voltage
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ADR390/ADR391/ADR392/ADR395
140
40 IL= 0mA TO 5mA
LOAD REGULATION - ppm/mA
120 A
+125 C
35
SUPPLY CURRENT -
30 VIN = 3.5V 25 VIN = 5.0V 20
100
+25 C
-40 C 80
60
15
40 5 7 9 11 INPUT VOLTAGE - V 13 15
10 40 15 10 35 TEMPERATURE - C 60 85
TPC 7. ADR392 Supply Current vs. Input Voltage
TPC 10. ADR391 Load Regulation vs. Temperature
140
90
LINE REGULATION - ppm/mA
120 A
+125 C 80 VIN = 7.5V 70 VIN = 5V 60
SUPPLY CURRENT -
100
+25 C
-40 C 80
60
50
40 5.5
7.0
8.5
10.0 11.5 INPUT VOLTAGE - V
13.0
14.5
40 -40
-5
30 65 TEMPERATURE - C
100
125
TPC 8. ADR395 Supply Current vs. Input Voltage
TPC 11. ADR392 Load Regulation vs. Temperature
40 IL= 0mA TO 5mA
LOAD REGULATION - ppm/mA
80
35
LOAD REGULATION - ppm/mA
70 VIN = 7.5V VIN = 5V 60
30 VIN = 3.0V 25 VIN = 5.0V
50
20
15
40
10 40 15 10 35 TEMPERATURE - C 60 85
30 -40
-5
30 65 TEMPERATURE - C
100
125
TPC 9. ADR390 Load Regulation vs. Temperature
TPC 12. ADR395 Load Regulation vs. Temperature
REV. C
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ADR390/ADR391/ADR392/ADR395
5 VIN = 2.5V TO 15V
12
LINE REGULATION - ppm/V
14
4
LINE REGULATION - ppm/V 10 VIN = 5.3V TO 15V 8
3
2
6
4
1
2
0 40 15 10 35 TEMPERATURE - C 60 85
0 -40
-5
30 65 TEMPERATURE - C
100
125
TPC 13. ADR390 Line Regulation vs. Temperature
TPC 16. ADR395 Line Regulation vs. Temperature
5 VIN = 2.8V TO 15V
LINE REGULATION - ppm/V
2.848
4
2.648 VIN_MIN - V
3
40 C 2.448 +85 C +25 C 2.248
2
1
0 40 15 10 35 TEMPERATURE - C 60 85
2.048
0
1
2 3 LOAD CURRENT - mA
4
5
TPC 14. ADR391 Line Regulation vs. Temperature
TPC 17. ADR390 Minimum Input Voltage vs. Load Current
14
3.30
12 LINE REGULATION - ppm/V 3.10
10
8 VIN = 4.4V TO 15V
VIN_MIN - V
+85 C +25 C 2.90 40 C
6
4 2.70 2
0 -40
2.50 -5 30 65 TEMPERATURE - C 100 125
0
1
2 3 LOAD CURRENT - mA
4
5
TPC 15. ADR392 Line Regulation vs. Temperature
TPC 18. ADR391 Minimum Input Voltage vs. Load Current
-8-
REV. C
ADR390/ADR391/ADR392/ADR395
4.8 70 60 TEMPERATURE: +25 C 40 C +85 C +25 C +125 C 4.6 50 VIN_MIN - V
FREQUENCY
4.4
+25 C
40 30 20
-40 C 4.2
4.0 10 3.8 0 1 2 3 LOAD CURRENT - mA 4 5
0 0.56
0.41
0.11 0.26 0.04 VOUT DEVIATION - mV
0.19
0.34
TPC 19. ADR392 Minimum Input Voltage vs. Load Current
TPC 22. ADR391 VOUT Hysteresis Distribution
6.0
1k
VIN = 5V
+125 C 5.6 VIN_MIN - V +25 C
5.4
VOLTAGE NOISE DENSITY - nV/ Hz
5.8
ADR391
5.2
-40 C
5.0
ADR390
4.8
4.6 0 1 2 3 LOAD CURRENT - mA 4 5
100
10
100 1k FREQUENCY - Hz
10k
TPC 20. ADR395 Minimum Input Voltage vs. Load Current
TPC 23. Voltage Noise Density vs. Frequency
60 TEMPERATURE: +25 C 50 40 C +85 C +25 C
0 0 0
40
VOLTAGE - 2 V/DIV
FREQUENCY
0 0 0 0
30
20
10
0
0 0.24
0.18
0.12
0.06 0 0.06 0.12 VOUT DEVIATION - mV
0.18
0.24
0.30
0 TIME - 1 Sec/DIV
TPC 21. ADR390 VOUT Hysteresis Distribution
TPC 24. ADR391 Typical Voltage Noise 0.1 Hz to 10 Hz
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ADR390/ADR391/ADR392/ADR395
0 0 0 0 0 0 0 0 0 TIME - 10ms/DIV
0 CL = 0nF 0 0 VOUT
VOLTAGE - 100 V/DIV
VOLTAGE - 1V/DIV
0 0 VLOAD ON 0 0 0 0 TIME - 200 s/DIV LOAD OFF
TPC 25. ADR391 Voltage Noise 10 Hz to 10 kHz
TPC 28. ADR391 Load Transient Response
0 CBYPASS = 0 F 0 0 0 0
0 CL = 1nF 0 0
VOLTAGE - 1V/DIV
VOUT
LINE INTERRUPTION
0.5V/DIV
VOLTAGE
0 0 LOAD OFF 0 VLOAD ON 0 0 0
VOUT 0 0 0 TIME - 10 s/DIV
1V/DIV
TIME - 200 s/DIV
TPC 26. ADR391 Line Transient Response
TPC 29. ADR391 Load Transient Response
0 CBYPASS = 0.1 F 0 0 0 0 0 VOUT 0 0 0 TIME - 10 s/DIV 1V/DIV LINE INTERRUPTION
0 CL = 100nF 0 0 VOUT
VOLTAGE - 1V/DIV
0.5V/DIV
VOLTAGE
0 0 LOAD OFF 0 VLOAD ON 0 0 0 TIME - 200 s/DIV
TPC 27. ADR391 Line Transient Response
TPC 30. ADR391 Load Transient Response
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ADR390/ADR391/ADR392/ADR395
0 VIN = 15V 0 5V/DIV 0 0 VIN 0 0 VOUT 0 0 0 TIME - 20 s/DIV 2V/DIV 0 VOUT
VOLTAGE VOLTAGE
0 RL = 500 0 2V/DIV
0 0 0 VIN 0 0 0 TIME - 200 s/DIV 5V/DIV
TPC 31. ADR391 Turn-On Response Time at 15 V
TPC 34. ADR391 Turn-On/Turn-Off Response at 5 V
0 VIN = 15V 0 VIN 0
VOLTAGE - 5V/DIV
0 0 RL = 500 CL = 100nF 2V/DIV VOUT 0 0 0 VIN 0 0 0 5V/DIV
5V/DIV
0
VOLTAGE
0 0 0 0 0 0 TIME - 40 s/DIV VOUT 2V/DIV
TIME - 200 s/DIV
TPC 32. ADR391 Turn-Off Response at 15 V
TPC 35. ADR391 Turn-On/Turn-Off Response at 5 V
0 CBYPASS = 0.1 F 0 2V/DIV VOUT
80 60 40
RIPPLE REJECTION - dB
0 0 0 0 VIN 0 0 0
20 0 20 40 60 80 100 120 10 100 1k 10k FREQUENCY - Hz 100k 1M
VOLTAGE
5V/DIV
TIME - 200 s/DIV
TPC 33. ADR391 Turn-On/Turn-Off Response at 5 V
TPC 36. Ripple Rejection vs. Frequency
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ADR390/ADR391/ADR392/ADR395
100 90 80
OUTPUT IMPEDANCE -
Device Power Dissipation Considerations
70 60 CL = 0 F 50 40 30 20 10 0 10 100 CL = 1 F CL = 0.1 F
The ADR390/ADR391/ADR392/ADR395 is capable of delivering load currents to 5 mA with an input voltage that ranges from 2.8 V (ADR391 only) to 15 V. When this device is used in applications with large input voltages, care should be taken to avoid exceeding the specified 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 = TJ - TA JA
1k 10k FREQUENCY - Hz
100k
1M
TPC 37. Output Impedance vs. Frequency
THEORY OF OPERATION
In this equation, TJ and TA are, respectively, the junction and ambient temperatures, PD is the device power dissipation, and JA is the device package thermal resistance.
Shutdown Mode Operation
Band gap references are the high performance solution for low supply voltage and low power voltage reference applications, and the ADR390/ADR391/ADR392/ADR395 is no exception. The uniqueness of this product lies in its architecture. By observing Figure 2, the ideal zero TC band gap voltage is referenced to the output, not to ground. Therefore, if noise exists on the ground line, it will be greatly attenuated on VOUT. The band gap cell consists of the pnp pair Q51 and Q52, running at unequal current densities. The difference in VBE results in a voltage with a positive TC, which is amplified by the ratio of 2 x R58 . This R54 PTAT voltage, combined with VBEs of Q51 and Q52, produces the stable band gap voltage. Reduction in the band gap curvature is performed by the ratio of the resistors R44 and R59, one of which is linearly temperature dependent. Precision laser trimming and other patented circuit techniques are used to further enhance the drift performance.
VIN
The ADR390/ADR391/ADR392/ADR395 includes a shutdown feature that is TTL/CMOS level compatible. A logic LOW or a zero volt condition on the SHDN Pin is required to turn the device off. During shutdown, the output of the reference becomes a high impedance state where its potential would then be determined by external circuitry. If the shutdown feature is not used, the SHDN Pin should be connected to VIN (Pin 2).
APPLICATIONS BASIC VOLTAGE REFERENCE CONNECTION
The circuit in Figure 3 illustrates the basic configuration for the ADR39x family. Decoupling capacitors are not required for circuit stability. The ADR39x family is capable of driving capacitive loads from 0 F to 10 F. However, a 0.1 F ceramic output capacitor is recommended to absorb and deliver the charge as is required by a dynamic load.
SHUTDOWN INPUT CB SHDN VIN VOUT(S) VOUT(F) GND
ADR39x
* 0.1 F
Q1
VOUT (FORCE) VOUT (SENSE)
R59
R44
* * NOT REQUIRED CB
OUTPUT 0.1 F
R58
R49
Figure 3. Basic Configuration for the ADR39x Family
Stacking Reference ICs for Arbitrary Outputs
R54
SHDN
Q51
R53 Q52
R48
Some applications may require two reference voltage sources, which are a combined sum of standard outputs. Figure 4 circuit shows how this "stacked output" reference can be implemented:
R60
R61
GND
Figure 2. Simplified Schematic
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ADR390/ADR391/ADR392/ADR395
OUTPUT TABLE U1/U2 ADR390/ADR390 ADR391/ADR391 ADR392/ADR392 ADR395/ADR395 VOUT1 (V) VOUT2 (V) 2.048 2.5 4.096 5 4.096 5.0 8.192 10
2 VIN 4V OUT(F) 3V OUT(S) SHDN
1
+VDD
VIN 2 VIN 1 C2 0.1 F SHDN VOUT(F) VOUT(S) GND 5
-VDD
U2
GND 5
4 3
VOUT2
A1 -VREF
Figure 5. Negative Reference
U1 2 VIN 1 C2 0.1 F SHDN VOUT(F) VOUT(S) GND 5 4 3 VOUT1
General-Purpose Current Source
Figure 4. Stacking Voltage References with the ADR390/ADR391/ADR392/ADR395
Two reference ICs are used, fed from an unregulated input, VIN. The outputs of the individual ICs are simply connected in series, which provides two output voltages VOUT1 and VOUT2. VOUT1 is the terminal voltage of U1, while VOUT2 is the sum of this voltage and the terminal voltage of U2. U1 and U2 are simply chosen for the two voltages that supply the required outputs (see Output Table). For example, if both U1 and U2 are ADR391s, VOUT1 is 2.5 V and VOUT2 is 5.0 V. While this concept is simple, a precaution is in order. Since the lower reference circuit must sink a small bias current from U2, plus the base current from the series PNP output transistor in U2, either the external load of U1 or R1 must provide a path for this current. If the U1 minimum load is not well defined, the resistor R1 should be used, set to a value that will conservatively pass 600 A of current with the applicable VOUT1 across it. Note that the two U1 and U2 reference circuits are locally treated as macrocells, each having its own bypasses at input and output for best stability. Both U1 and U2 in this circuit can source dc currents up to their full rating. The minimum input voltage, VIN, is determined by the sum of the outputs, VOUT2, plus the dropout voltage of U2.
A Negative Precision Reference without Precision Resistors
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 6, the ADR390/ADR391/ADR392/ADR395 can be 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 90 A to approximately 5 mA.
VIN
SHDN VOUT
ADR39x
VIN VOUT ISET R1 0.1 F R1
GND
ISY ADJUST P1
ISY (ISET)
}
RSET
IOUT = ISET + ISY (ISET) RL
Figure 6. A General-Purpose Current Source
High Power Performance with Current Limit
A negative reference can be easily generated by adding an op amp, A1, and configured as shown in Figure 5. VOUTF and VOUTS are at virtual ground and therefore the negative reference can be taken directly from the output of the op amp. The op amp must be dual supply, low offset, and rail-to-rail if the negative supply voltage is close to the reference output.
In some cases, the user may want higher output current delivered to a load and still achieve better than 0.5% accuracy out of the ADR39x. The accuracy for a reference is normally specified on the data sheet with no load. However, the output voltage changes with load current. The circuit in Figure 7 provides high current without compromising the accuracy of the ADR39x. The series pass transistor Q1 provides up to 1 A load current. The ADR39x delivers only the base drive to Q1 through the force pin. The sense pin of the ADR39x is a regulated output and is connected to the load. The transistor Q2 protects Q1 during short circuit limit faults by robbing its base drive. The maximum current is ILMAX 0.6 V/RS.
REV. C
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ADR390/ADR391/ADR392/ADR395
VIN R1 4.7k SHDN VIN VOUT (FORCE) VOUT (SENSE) Q2 Q2N2222 Q1 Q2N4921 U1 GND
VIN R1 4.7k SHDN VIN VOUT (FORCE) VOUT (SENSE) U1 GND Q2N2222 Q1 Q2 Q2N4921 RS
ADR39x
RS IL
ADR39x
RL
RL
Figure 7. ADR39x for High Power Performance with Current Limit
Figure 8. ADR39x High Output Current with Darlington Drive Configuration
A similar circuit function can also be achieved with the Darlington transistor configuration (see Figure 8).
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REV. C
ADR390/ADR391/ADR392/ADR395
OUTLINE DIMENSIONS
5-Lead Plastic Surface-Mount Package [SOT-23] (RT-5)
Dimensions shown in millimeters
2.90
5
4
1.60 BSC
1 2 3
2.80 BSC
PIN 1 0.95 BSC 1.30 1.15 0.90 1.90 BSC
1.45 MAX 10 0
0.15 MAX
0.50 0.30
SEATING PLANE
0.22 0.08
0.60 0.45 0.30
COMPLIANT TO JEDEC STANDARDS MO-178AA
REV. C
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ADR390/ADR391/ADR392/ADR395 Revision History
Location 10/02--Data Sheet changed from REV. B to REV. C. Page
Add parts ADR392 and ADR395 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Universal Changes to GENERAL DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Additions to Table I . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Changes to SPECIFICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Changes to ORDERING GUIDE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Changes to ABSOLUTE MAXIMUM RATINGS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 New TPCs 3, 4, 7, 8, 11, 12, 15, 16, 19, and 20 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 New Figures 4 and 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Deleted A Negative Precision Reference without Precision Resistors section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Edits to General-Purpose Current Source section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Updated OUTLINE DIMENSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
5/02--Data Sheet changed from REV. A to REV. B.
C00419-0-10/02(C) PRINTED IN U.S.A.
Changes to FEATURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Change to Figure 6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Edits to layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Universal
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REV. C

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