ADR292ER

a FEATURES Supply Range 2.35 V to 15 V, ADR290 2.8 V to 15 V, ADR291 4.4 V to 15 V, ADR292 Supply Current 12 A Max Low-Noise 6 V, 8 V, 12 V p-p (0.1 Hz–10 Hz) High Output Current 5 mA Temperature Range 40 C to 125 C Pin Compatible with REF02/REF19x APPLICATIONS Portable Instrumentation Precision Reference for 3 V and 5 V Systems A/D and D/A Converter Reference Solar-Powered Applications Loop-Current-Powered Instruments Low Noise Micropower 2.048 V, 2.5 V, and 4.096 V Precision Voltage References ADR290/ADR291/ADR292 PIN CONFIGURATIONS 8-Lead Narrow Body SO (SO Suffix) NC 1 VIN 2 8 NC 7 NC TOP VIEW NC 3 (Not to Scale) 6 VOUT 5 NC ADR29x GND 4 NC = NO CONNECT 8-Lead TSSOP (RU Suffix) NC 1 VIN 2 8 NC 7 NC TOP VIEW NC 3 (Not to Scale) 6 VOUT 5 NC ADR29x GND 4 NC = NO CONNECT GENERAL DESCRIPTION The ADR290, ADR291 and ADR292 are low noise, micropower precision voltage references that use an XFET® reference circuit. The new XFET architecture offers significant performance improvements over traditional bandgap and Buried 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 ADR29x family are series voltage references providing stable and accurate output voltages from supplies as low as 2.35 V for the ADR290. Output voltage options are 2.048 V, 2.5 V, and 4.096 V for the ADR290, ADR291, and ADR292 respectively. Quiescent current is only 12 µA, making these devices ideal for batterypowered instrumentation. Three electrical grades are available offering initial output accuracies of ± 2 mV, ± 3 mV and ± 6 mV max for the ADR290 and ADR291, and ± 3 mV, ± 4 mV and ± 6 mV max for the ADR292. Temperature coefficients for the three grades are 8 ppm/°C, 15 ppm/°C, and 25 ppm/°C max, respectively. Line regulation and load regulation are typically 30 ppm/V and 30 ppm/mA, maintaining the reference’s overall high performance. For a device with 5.0 V output, refer to the ADR293 data sheet. The ADR290, ADR291, and ADR292 references are specified over the extended industrial temperature range of –40°C to +125°C. Devices are available in the 8-lead SOIC and 8-lead TSSOP packages. ADR29x Product Part Number ADR290 ADR291 ADR292 ADR293 Output Voltage (V) 2.048 2.500 4.096 5.000 Initial Accuracy (%) Temperature Coefficient (ppm/ C) Max 0.10, 0.15, 0.29 8, 15, 25 0.08, 0.12, 0.24 8, 15, 25 0.07, 0.10, 0.15 8, 15, 25 (See ADR293 Data Sheet) XFET is a registered trademark of Analog Devices, Inc. REV. B 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 © Analog Devices, Inc., 2001 ADR290/ADR291/ADR292 ADR290–SPECIFICATIONS ELECTRICAL SPECIFICATIONS Parameter E GRADE Output Voltage Initial Accuracy F GRADE Output Voltage Initial Accuracy G GRADE Output Voltage Initial Accuracy LINE REGULATION “E/F” Grades “G” Grade LOAD REGULATION “E/F” Grades “G” Grade LONG-TERM STABILITY NOISE VOLTAGE WIDEBAND NOISE DENSITY (VS = 2.7 V, TA = +25 C unless otherwise noted) Conditions IOUT = 0 mA Min 2.046 –2 –0.10 2.045 –3 –0.15 2.042 –6 –0.29 Typ Max Unit V mV % V mV % V mV % ppm/V ppm/V ppm/mA ppm/mA ppm µV p-p nV/√Hz Symbol VO VOERR 2.048 2.050 +2 +0.10 2.048 2.051 +3 +0.15 2.048 2.054 +6 +0.29 30 40 30 40 50 6 420 100 125 100 125 VO VOERR IOUT = 0 mA VO VOERR ∆VO/∆VIN ∆VO/∆ ILOAD ∆VO eN eN IOUT = 0 mA 2.7 V to 15 V, IOUT = 0 mA VS = 5.0 V, 0 mA to 5 mA After 1000 hrs of Operation @ 125°C 0.1 Hz to 10 Hz @ 1 kHz ELECTRICAL SPECIFICATIONS (V = 2.7 V, T = –25 C ≤ T ≤ +85 C unless otherwise noted) S A A 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 Conditions IOUT = 0 mA Min Typ 3 6 10 35 50 20 30 Max 8 15 25 125 150 125 150 Unit ppm/°C ppm/°C ppm/°C ppm/V ppm/V ppm/mA ppm/mA ∆VO/∆VIN ∆VO/∆ ILOAD 2.7 V to 15 V, IOUT = 0 mA VS = 5.0 V, 0 mA to 5 mA ELECTRICAL SPECIFICATIONS (V = 2.7 V, T = S A 40 C ≤ TA ≤ +125 C unless otherwise noted) Min Typ 3 5 10 40 70 20 30 8 12 50 Max 10 20 30 200 250 200 300 12 15 Unit ppm/°C ppm/°C ppm/°C ppm/V ppm/V ppm/mA ppm/mA µA µA ppm REV. B 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 Specifications subject to change without notice. Symbol TCVO Conditions IOUT = 0 mA ∆VO/∆VIN ∆VO/∆ ILOAD IS VO–HYS 2.7 V to 15 V, IOUT = 0 mA VS = 5.0 V, 0 mA to 5 mA TA = +25°C –40°C ≤ TA ≤ +125°C SO-8, TSSOP-8 –2– ADR291–SPECIFICATIONS ELECTRICAL SPECIFICATIONS (V = 3.0 V, T = +25 C unless otherwise noted) S ADR290/ADR291/ADR292 A Parameter E GRADE Output Voltage Initial Accuracy F GRADE Output Voltage Initial Accuracy G GRADE Output Voltage Initial Accuracy LINE REGULATION “E/F” Grades “G” Grade LOAD REGULATION “E/F“ Grades “G“ Grade LONG-TERM STABILITY NOISE VOLTAGE WIDEBAND NOISE DENSITY Symbol VO VOERR Conditions IOUT = 0 mA Min 2.498 –2 –0.08 2.497 –3 –0.12 2.494 –6 –0.24 Typ Max Unit V mV % V mV % V mV % ppm/V ppm/V ppm/mA ppm/mA ppm µV p-p nV/√Hz 2.500 2.502 +2 +0.08 2.500 2.503 +3 +0.12 2.500 2.506 +6 +0.24 30 40 30 40 50 8 480 100 125 100 125 VO VOERR IOUT = 0 mA VO VOERR ∆VO/∆VIN ∆VO/∆ ILOAD ∆VO eN eN IOUT = 0 mA 3.0 V to 15 V, IOUT = 0 mA VS = 5.0 V, 0 mA to 5 mA After 1000 hrs of Operation @ 125°C 0.1 Hz to 10 Hz @ 1 kHz ELECTRICAL SPECIFICATIONS Parameter TEMPERATURE COEFFICIENT “E” Grade “F” Grade “G” Grade LINE REGULATION “E/F” Grades “G” Grade LOAD REGULATION “E/F” Grades “G” Grade (VS = 3.0 V, TA = –25 C ≤ TA ≤ +85 C unless otherwise noted) Conditions IOUT = 0 mA Min Typ 3 5 10 35 50 20 30 Max 8 15 25 125 150 125 150 Unit ppm/°C ppm/°C ppm/°C ppm/V ppm/V ppm/mA ppm/mA Symbol TCVO ∆VO/∆VIN ∆VO/∆ ILOAD 3.0 V to 15 V, IOUT = 0 mA VS = 5.0 V, 0 mA to 5 mA ELECTRICAL SPECIFICATIONS (V = 3.0 V, T = –40 C ≤ T ≤ +125 C unless otherwise noted) S A A 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 Specifications subject to change without notice. Symbol TCVO Conditions IOUT = 0 mA Min Typ 3 5 10 40 70 20 30 9 12 50 Max 10 20 30 200 250 200 300 12 15 Unit ppm/°C ppm/°C ppm/°C ppm/V ppm/V ppm/mA ppm/mA µA µA ppm ∆VO/∆VIN ∆VO/∆ ILOAD IS VO–HYS 3.0 V to 15 V, IOUT = 0 mA VS = 5.0 V, 0 mA to 5 mA TA = +25°C –40°C ≤ TA ≤ +125°C SO-8, TSSOP-8 REV. B –3– ADR290/ADR291/ADR292 ADR292–SPECIFICATIONS ELECTRICAL SPECIFICATIONS Parameter E GRADE Output Voltage Initial Accuracy F GRADE Output Voltage Initial Accuracy G GRADE Output Voltage Initial Accuracy LINE REGULATION “E/F” Grades “G” Grade LOAD REGULATION “E/F” Grades “G” Grade LONG-TERM STABILITY NOISE VOLTAGE WIDEBAND NOISE DENSITY (VS = 5 V, TA = +25 C unless otherwise noted) Conditions IOUT = 0 mA Min 4.093 –3 –0.07 4.092 –4 –0.10 4.090 –6 –0.15 Typ Max Unit V mV % V mV % V mV % ppm/V ppm/V ppm/mA ppm/mA ppm µV p-p nV/√Hz Symbol VO VOERR 4.096 4.099 +3 +0.07 4.096 4.1 +4 +0.10 4.096 4.102 +6 +0.15 30 40 30 40 50 12 640 100 125 100 125 VO VOERR IOUT = 0 mA VO VOERR ∆VO/∆VIN ∆VO/∆ ILOAD ∆VO eN eN IOUT = 0 mA 4.5 V to 15 V, IOUT = 0 mA VS = 5.0 V, 0 mA to 5 mA After 1000 hrs of Operation @ 125°C 0.1 Hz to 10 Hz @ 1 kHz ELECTRICAL SPECIFICATIONS (V = 5 V, T = –25 C ≤ T ≤ +85 C unless otherwise noted) S A A 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 Conditions IOUT = 0 mA Min Typ 3 5 10 35 50 20 30 Max 8 15 25 125 150 125 150 Unit ppm/°C ppm/°C ppm/°C ppm/V ppm/V ppm/mA ppm/mA ∆VO/∆VIN ∆VO/∆ ILOAD 4.5 V to 15 V, IOUT = 0 mA VS = 5.0 V, 0 mA to 5 mA ELECTRICAL SPECIFICATIONS (V = 5 V, T = –40 C ≤ T ≤ +125 C unless otherwise noted) S A A 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 Specifications subject to change without notice. Symbol TCVO Conditions IOUT = 0 mA Min Typ 3 5 10 40 70 20 30 10 12 50 Max 10 20 30 200 250 200 300 15 18 Unit ppm/°C ppm/°C ppm/°C ppm/V ppm/V ppm/mA ppm/mA µA µA ppm REV. B ∆VO/∆VIN ∆VO/∆ ILOAD IS VO–HYS 4.5 V to 15 V, IOUT = 0 mA VS = 5.0 V, 0 mA to 5 mA TA = +25°C –40°C ≤ TA ≤ +125°C SO-8, TSSOP-8 –4– ADR290/ADR291/ADR292 ABSOLUTE MAXIMUM RATINGS Package Type 8-Lead SOIC (SO) 8-Lead TSSOP (RU) Supply Voltage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 V Output Short-Circuit Duration to GND . . . . . . . . . . Indefinite Storage Temperature Range SO, RU Package . . . . . . . . . . . . . . . . . . . 65°C to 150°C Operating Temperature Range ADR290/ADR291/ADR292 . . . . . . . . . . . 40°C to 125°C Junction Temperature Range SO, RU Package . . . . . . . . . . . . . . . . . . . 65°C to 125°C Lead Temperature (Soldering, 60 sec) . . . . . . . . . . . . . 300°C NOTES 1. Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only; functional operation at or above this specification is not implied. Exposure to the above maximum rating conditions for extended periods may affect device reliability. 2. Remove power before inserting or removing units from their sockets. JA* JC Unit °C/W °C/W 158 240 43 43 *θJA is specified for worst-case conditions, i.e., θJA is specified for device in socket testing. In practice, θJA is specified for a device soldered in the circuit board. 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 ADR290/ADR291/ADR292 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 ORDERING GUIDE Model ADR290 ER, ER-REEL7, ER-REEL FR, FR-REEL7, FR-REEL GR, GR-REEL7, GR-REEL GRU-REEL7, GRU-REEL ADR291 ER, ER-REEL7, ER-REEL FR, FR-REEL7, FR-REEL GR, GR-REEL7, GR-REEL GRU-REEL7, GRU-REEL ADR292 ER, ER-REEL7, ER-REEL FR, FR-REEL7, FR-REEL GR, GR-REEL7, GR-REEL GRU-REEL7, GRU-REEL Output Voltage 2.048 2.048 2.048 2.048 2.50 2.50 2.50 2.50 4.096 4.096 4.096 4.096 Initial Accuracy (%) 0.10 0.15 0.29 0.29 0.08 0.12 0.24 0.24 0.07 0.10 0.15 0.15 Temperature Coefficient Max (ppm/ C) 8 15 25 25 8 15 25 25 8 15 25 25 Package Description SOIC SOIC SOIC TSSOP SOIC SOIC SOIC TSSOP SOIC SOIC SOIC TSSOP Package Option SO-8 SO-8 SO-8 RU-8 SO-8 SO-8 SO-8 RU-8 SO-8 SO-8 SO-8 RU-8 Number of Parts per Package 98, 1000, 2500 98, 1000, 2500 98, 1000, 2500 1000, 2500 98, 1000, 2500 98, 1000, 2500 98, 1000, 2500 1000, 2500 98, 1000, 2500 98, 1000, 2500 98, 1000, 2500 1000, 2500 See ADR293 data sheet for ordering guide. OTHER XFET PRODUCTS Part Number ADR420 ADR421 Nominal Output Voltage (V) 2.048 2.50 Package Type 8-Lead_µSOIC/SOIC 8-Lead_µSOIC/SOIC REV. B –5– ADR290/ADR291/ADR292 PARAMETER DEFINITION Line Regulation Thermal Hysteresis 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-pervolt, or microvolts-per-volt change in input voltage. Load Regulation Thermal hysteresis is defined as the change of output voltage after the device is cycled through temperature from +25°C to –40°C to +85°C and back to +25°C. This is a typical value from a sample of parts put through such a cycle. VO – HYS = VO (25°C ) – VO _ TC VO – HYS [ ppm] = VO (25°C ) – VO _ TC × 106 VO (25°C ) 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-permillion-per-milliampere, or ohms of dc output resistance. Long-Term Stability Where VO (25°C) = VO at 25°C VO–TC = VO at 25°C after temperature cycle at +25°C to –40°C to +85°C and back to +25°C Typical shift of output voltage at 25°C on a sample of parts subjected to high-temperature operating life test of 1000 hours at 125°C. ∆VO = VO (t0 ) – VO (t1 ) V (t ) – VO (t1 ) ∆VO [ ppm] = O 0 × 106 VO (t0 ) Where VO (t0 ) = VO at 25°C at time 0 VO (t1 ) = VO at 25°C after 1000 hours operation at 125°C Temperature Coefficient The change of output voltage over the operating temperature change and normalized by the output voltage at 25°C, expressed in ppm/°C. The equation follows: TCVO [ ppm / °C ] = Where VO (25°C) = VO at 25°C VO (T2 ) – VO (T1 ) × 106 VO (25°C ) × (T2 – T1 ) VO(T1 ) = VO at Temperature 1 VO(T2 ) = VO at Temperature 2 NC = No Connect (There are in fact internal connections at NC pins which are reserved for manufacturing purposes. Users should not connect anything at NC pins.) –6– REV. B Typical Performance Characteristic – ADR290/ADR291/ADR292 2.054 VS = 5V 2.052 3 TYPICAL PARTS 12 14 A OUTPUT VOLTAGE – V 10 TA = +125 C 2.050 QUIESCENT CURRENT – 8 6 4 TA = +25 C TA = –40 C 2.048 2.046 2.044 2 0 2.042 –50 –25 0 25 50 75 100 125 0 2 4 TEMPERATURE – C 6 8 10 INPUT VOLTAGE – V 12 14 16 TPC 1. ADR290 VOUT vs. Temperature TPC 4. ADR290 Quiescent Current vs. Input Voltage 2.506 VS = 5V 2.504 3 TYPICAL PARTS 14 12 A TA = +125 C 10 OUTPUT VOLTAGE – V 2.502 QUIESCENT CURRENT – 8 6 4 TA = +25 C TA = –40 C 2.500 2.498 2.496 2 0 2.494 –50 –25 0 25 50 75 100 125 0 2 4 TEMPERATURE – C 6 8 10 INPUT VOLTAGE – V 12 14 16 TPC 2. ADR291 VOUT vs. Temperature TPC 5. ADR291 Quiescent Current vs. Input Voltage 4.102 VS = 5V 4.100 3 TYPICAL PARTS 16 14 12 10 8 6 4 2 0 OUTPUT VOLTAGE – V 4.098 QUIESCENT CURRENT – A TA = +125 C TA = +25 C TA = –40 C 4.096 4.094 4.092 4.090 –50 –25 0 25 50 75 100 125 0 2 4 TEMPERATURE – C 6 8 10 INPUT VOLTAGE – V 12 14 16 TPC 3. ADR292 VOUT vs. Temperature TPC 6. ADR292 Quiescent Current vs. Input Voltage REV. B –7– ADR290/ADR291/ADR292 14 VS = 5V 0.6 0.7 DIFFERENTIAL VOLTAGE – V 12 ADR292 ADR291 0.5 TA = +125 C 0.4 0.3 0.2 SUPPLY CURRENT – A TA = –40 C 10 8 ADR290 TA = +25 C 6 0.1 4 –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 TPC 7. ADR290/ADR291/ADR292 Supply Current vs. Temperature TPC 10. ADR290 Minimum Input-Output Voltage Differential vs. Load Current 100 ADR290: VS = 2.7V TO 15V ADR291: VS = 3.0V TO 15V ADR292: VS = 4.5V TO 15V IOUT = 0mA 0.7 0.6 DIFFERENTIAL VOLTAGE – V LINE REGULATION – ppm/V 80 TA = +125 C 0.5 TA = +25 C 0.4 0.3 TA = –40 C 0.2 60 ADR292 40 20 ADR290 ADR291 0 –50 –25 0 25 50 75 100 125 0.1 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 TPC 8. ADR290/ADR291/ADR292 Line Regulation vs. Temperature TPC 11. ADR291 Minimum Input-Output Voltage Differential vs. Load Current 100 ADR290: VS = 2.7V TO 7.0V ADR291: VS = 3.0V TO 7.0V ADR292: VS = 4.5V TO 9.0V IOUT = 0mA 0.7 0.6 DIFFERENTIAL VOLTAGE – V LINE REGULATION – ppm/V 80 TA = +125 C 0.5 TA = +25 C 0.4 0.3 0.2 60 ADR291 40 ADR290 TA = –40 C 20 ADR292 0.1 0 –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 TPC 9. ADR290/ADR291/ADR292 Line Regulation vs. Temperature TPC 12. ADR292 Minimum Input-Output Voltage Differential vs. Load Current –8– REV. B ADR290/ADR291/ADR292 200 VS = 5V 500 250 LINE REGULATION – ppm/mA VOUT FROM NOMINAL – V 0 160 120 IOUT = 1mA TA = +25 C –250 TA = +125 C –500 TA = –40 C 80 40 IOUT = 5mA 0 –50 –750 –25 0 25 50 75 100 125 –1000 0.1 TEMPERATURE – C 1 SOURCING LOAD CURRENT – mA 10 TPC 13. ADR290 Line Regulation vs. Temperature TPC 16. ADR290 ∆VOUT from Nominal vs. Load Current 200 VS = 5V 0 –250 V LOAD REGULATION – ppm/mA 160 IOUT = 1mA 120 IOUT = 5mA 80 TA = +25 C –500 –750 TA = –40 C –1000 –1250 –1500 –1750 TA = +125 C 40 0 –50 VOUT FROM NOMINAL – –25 0 25 50 75 100 125 –2000 0.1 TEMPERATURE – C 1 SOURCING LOAD CURRENT – mA 10 TPC 14. ADR291 Load Regulation vs. Temperature TPC 17. ADR291 ∆VOUT from Nominal vs. Load Current 200 VS = 5V 0 –500 V LOAD REGULATION – ppm/mA 160 –1000 VOUT FROM NOMINAL – 120 IOUT = 1mA IOUT = 5mA 80 –1500 –2000 –2500 –3000 –3500 TA = –40 C TA = +25 C TA = +125 C 40 0 –50 –25 0 25 50 75 100 125 –4000 0.1 TEMPERATURE – C 1 SOURCING LOAD CURRENT – mA 10 TPC 15. ADR292 Load Regulation vs. Temperature TPC 18. ADR292 ∆VOUT from Nominal vs. Load Current REV. B –9– ADR290/ADR291/ADR292 1000 900 ADR292 VIN = 15V TA = 25 C 50 VS = 5V IL = 0 mA 40 OUTPUT IMPEDANCE – 1000 VOLTAGE NOISE DENSITY – nV/ Hz 800 700 ADR291 600 500 400 300 200 100 0 10 100 FREQUENCY – Hz ADR290 30 20 10 0 0 10 100 FREQUENCY – Hz 1k 10k TPC 19. Voltage Noise Density vs. Frequency TPC 22. ADR290 Output Impedance vs. Frequency 120 VS = 5V 100 50 VS = 5V IL = 0 mA 40 OUTPUT IMPEDANCE – RIPPLE REJECTION – dB 80 30 60 20 40 20 10 0 10 100 FREQUENCY – Hz 1000 0 0 10 100 FREQUENCY – Hz 1k 10k TPC 20. ADR290/ADR291/ADR292 Ripple Rejection vs. Frequency TPC 23. ADR291 Output Impedance vs. Frequency 50 1s 100 90 VS = 5V IL = 0 mA 40 OUTPUT IMPEDANCE – 30 2 V p-p 20 10 0% 10 0 0 10 100 FREQUENCY – Hz 1k 10k TPC 21. ADR290 0.1 Hz to 10 Hz Noise TPC 24. ADR292 Output Impedance vs. Frequency –10– REV. B ADR290/ADR291/ADR292 IL = 5mA OFF 100 100 90 1ms IL = 5mA 500 s ON 90 10 0% 10 0% 1V 1V TPC 25. ADR291 Load Transient TPC 28. ADR291 Turn-On Time IL = 5mA CL = 1nF 100 1ms 100 90 IL = 0mA 10ms OFF ON 90 10 0% 10 0% 1V 1V TPC 26. ADR291 Load Transient TPC 29. ADR291 Turn-Off Time 18 IL = 5mA CL = 100nF 100 5ms 16 14 12 TEMPERATURE +25 C – 40 C 85 C +25 C OFF ON 90 FREQUENCY 10 0% 10 8 6 4 1V 2 0 TPC 27. ADR291 Load Transient TPC 30. Typical Hysteresis for the ADR291 Product REV. B –11– –200 –180 –160 –140 –120 –100 –80 –60 –40 –20 0 20 40 60 80 100 120 140 160 180 200 MORE VOUT DEVIATION – ppm ADR290/ADR291/ADR292 THEORY OF OPERATION Device Power Dissipation Considerations The ADR29x series of references uses a new reference generation technique known as XFET (eXtra implanted junction FET). This technique 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 ADR29x series. 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 ADR29x family of references is guaranteed to deliver load currents to 5 mA with an input voltage that ranges from 2.7 V to 15 V (minimum supply voltage depends on output voltage option). When these devices are 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 = TJ – T A θ JA In this equation, TJ and TA are the junction and ambient temperatures, respectively, PD is the device power dissipation, and θJA 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 2 illustrates the basic configuration for the ADR29x family of references. Note that the decoupling capacitors are not required for circuit stability. NC 1 2 8 NC ADR29x 7 NC 6 OUTPUT 0.1 F ( )( ) + 10 F NC 3 0.1 F 4 5 NC where ∆VP is the difference in pinch-off voltage between the two FETs, and IPTAT is the positive temperature coefficient correction current. The various versions of the ADR29x family are created by on-chip adjustment of R1 and R3 to achieve 2.048 V, 2.500 V or 4.096 V at the reference output. 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 NC = NO CONNECT Figure 2. Basic Voltage Reference Configuration Noise Performance The noise generated by the ADR29x family of references is typically less than 12 µV p-p over the 0.1 Hz to 10 Hz band. TPC 21 shows the 0.1 Hz to 10 Hz noise of the ADR290 which is only 6 µV p-p. 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 R3 GND 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. TPC 28 shows the turn-on settling time for the ADR291. * EXTRA CHANNEL IMPLANT R1 + R2 + R3 VOUT = VP + IPTAT R1 R3 Figure 1. ADR290/ADR291/ADR292 Simplified Schematic –12– REV. B ADR290/ADR291/ADR292 APPLICATIONS SECTION A Negative Precision Reference without Precision Resistors VIN 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 current-switching 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 currentswitching 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 (voltageswitching 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 3 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. Thus, any negative output voltage desired can be chosen by simply substituting for the appropriate reference IC. 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 ADR29x VOUT R1 GND 1F ISY ADJUST P1 IOUT RL RSET Figure 4. A Precision Current Source High Voltage Floating Current Source The circuit of Figure 5 can be used to generate a floating current source with minimal self heating. This particular configuration can operate on high supply voltages determined by the breakdown voltage of the N-channel JFET. +VS E231 SILICONIX VIN ADR29X GND OP90 2N3904 2.10k ADR29x VOUT 1k 1F +5V GND 100 A1 –VS Figure 5. High Voltage Floating Current Source Kelvin Connections 100k 1F –VREF –5V A1 = 1/2 OP291, 1/2 OP295 Figure 3. A Negative Precision Voltage Reference Uses No Precision Resistors A Precision Current Source 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 4, any one of the devices in the ADR29x family of references 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 12 µA to approximately 5 mA. 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 mΩ/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 6, 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. REV. B –13– ADR290/ADR291/ADR292 VIN RLW VIN +VOUT SENSE RLW A1 VOUT 1F GND A1 = 1/2 OP295 100k Voltage Regulator For Portable Equipment ADR29x +VOUT FORCE RL Figure 6. Advantage of Kelvin Connection Low Power, Low Voltage Reference For Data Converters The ADR29x family of references is ideal for providing a stable, low cost and low power reference voltage in portable equipment power supplies. Figure 8 shows how the ADR290/ADR291/ ADR292 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 The ADR29x family has a number of features that makes it ideally suited for use with A/D and D/A converters. The low supply voltage required makes it possible to use the ADR290 and ADR291 with today’s converters that run on 3 V supplies without having to add a higher supply voltage for the reference. The low quiescent current (12 µA max) and low noise, tight temperature coefficient, combined with the high accuracy of the ADR29x makes it ideal for low power applications such as hand-held, battery operated equipment. One such ADC for which the ADR291 is well suited is the AD7701. Figure 7 shows the ADR291 used as the reference for this converter. The AD7701 is a 16-bit A/D converter with onchip digital filtering intended for the measurement of wide dynamic range, low frequency signals such as those representing chemical, physical or biological processes. It contains a charge balancing (sigma-delta) ADC, calibration microcontroller with on-chip static RAM, a clock oscillator and a serial communications port. This entire circuit runs on ± 5 V supplies. The power dissipation of the AD7701 is typically 25 mW and, when combined with the power dissipation of the ADR291 (60 µW), the entire circuit still consumes about 25 mW. +5V ANALOG SUPPLY 0.1 F R3 510k VIN ADR29x 6V LEAD-ACID BATTERY + VOUT TEMP GND OP20 IRF9530 5V, 100mA R1 402k 1% R2 402k 1% C1 68 F TANT + + C2 1000 F ELECT Figure 8. Voltage Regulator for Portable Equipment 0.1 F 10 F AVDD VIN VOUT DVDD VREF SLEEP MODE DRDY DATA READY READ (TRANSMIT) SERIAL CLOCK SERIAL CLOCK 0.1 F 0.1 F ADR291 GND AD7701 RANGES SELECT CALIBRATE ANALOG INPUT ANALOG GROUND 0.1 F AVSS –5V ANALOG SUPPLY BP/UP CAL CS SCLK SDATA CLKIN AIN AGND CLKOUT SC1 SC2 DGND 0.1 F DVSS 0.1 F 10 F Figure 7. Low Power, Low Voltage Supply Reference for the AD7701 –14– REV. B ADR290/ADR291/ADR292 OUTLINE DIMENSIONS Dimensions shown in inches and (mm). 8-Lead Narrow Body SO (SO Suffix) 0.1968 (5.00) 0.1890 (4.80) 8 5 4 0.1574 (4.00) 0.1497 (3.80) PIN 1 1 0.2440 (6.20) 0.2284 (5.80) 0.0500 (1.27) BSC 0.0098 (0.25) 0.0040 (0.10) SEATING PLANE 0.0688 (1.75) 0.0532 (1.35) 0.0192 (0.49) 0.0138 (0.35) 8 0.0098 (0.25) 0 0.0075 (0.19) 0.0196 (0.50) 0.0099 (0.25) 45 0.0500 (1.27) 0.0160 (0.41) 8-Lead TSSOP (RU Suffix) 0.122 (3.10) 0.114 (2.90) 8 5 0.177 (4.50) 0.169 (4.30) 0.256 (6.50) 0.246 (6.25) 1 4 PIN 1 0.0256 (0.65) BSC 0.006 (0.15) 0.002 (0.05) SEATING PLANE 0.0118 (0.30) 0.0075 (0.19) 0.0433 (1.10) MAX 0.0079 (0.20) 0.0035 (0.090) 8 0 0.028 (0.70) 0.020 (0.50) REV. B –15– PRINTED IN U.S.A. C00163–0–3/01 (B)