Precision, Micropower LDO Voltage References in TSOT ADR121/ADR125/ADR127 Initial accuracy A grade: ±0.24% B grade: ±0.12% Maximum tempco A grade: 25 ppm/°C B grade: 9 ppm/°C Low dropout: 300 mV for ADR121, ADR125 High output current: +5 mA/−2 mA Low typical operating current: 85 μA Input range: 2.7 V to 18 V Temperature range: −40°C to +125°C Tiny TSOT (UJ-6) package PIN CONFIGURATION NC1 1 6 NC1 ADR12x 5 NC1 TOP VIEW (Not to Scale) VIN 3 4 VOUT GND 2 NC = NO CONNECT 1 MUST BE LEFT FLOATING 05725-001 FEATURES Figure 1. APPLICATIONS Battery-powered instrumentation Portable medical equipment Data acquisition systems Automotive GENERAL DESCRIPTION The ADR121/ADR125/ADR127 are a family of micropower, high precision, series mode, band gap references with sink and source capability. The parts feature high accuracy and low power consumption in a tiny package. The ADR12x design includes a patented temperature drift curvature correction technique that minimizes the nonlinearities in the output voltage vs. temperature characteristics. The ADR12x is a low dropout voltage reference, requiring only 300 mV for ADR121/ADR125 and 1.45 V for ADR127 above the nominal output voltage on the input to provide a stable output voltage. This low dropout performance coupled with the low 85 μA operating current makes the ADR12x ideal for battery-powered applications. Available in an extended industrial temperature range of −40°C to +125°C, the ADR12x is housed in the tiny TSOT (UJ-6) package. Rev. 0 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. Trademarks and registered trademarks are the property of their respective owners. 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 ©2006 Analog Devices, Inc. All rights reserved. ADR121/ADR125/ADR127 TABLE OF CONTENTS Features .............................................................................................. 1 Terminology .......................................................................................7 Applications....................................................................................... 1 Typical Performance Characteristics ..............................................8 Pin Configuration............................................................................. 1 Theory of Operation ...................................................................... 16 General Description ......................................................................... 1 Power Dissipation Considerations........................................... 16 Revision History ............................................................................... 2 Notes ............................................................................................ 16 Specifications..................................................................................... 3 Applications..................................................................................... 17 ADR121 Electrical Characteristics............................................. 3 Basic Voltage Reference Connection ....................................... 17 ADR125 Electrical Characteristics............................................. 4 Stacking Reference ICs for Arbitrary Outputs ....................... 17 ADR127 Electrical Characteristics............................................. 5 Negative Precision Reference Without Precision Resistors.. 17 Absolute Maximum Ratings............................................................ 6 General-Purpose Current Source ............................................ 17 Thermal Resistance ...................................................................... 6 Outline Dimensions ....................................................................... 18 ESD Caution.................................................................................. 6 Ordering Guide .......................................................................... 18 REVISION HISTORY 6/06—Revision 0: Initial Version Rev. 0 | Page 2 of 20 ADR121/ADR125/ADR127 SPECIFICATIONS ADR121 ELECTRICAL CHARACTERISTICS @ TA = 25°C, VIN = 2.8 V to 18 V, IOUT = 0 mA, unless otherwise noted. Table 1. Parameter OUTPUT VOLTAGE B Grade A Grade INITIAL ACCURACY ERROR B Grade A Grade TEMPERATURE COEFFICIENT B Grade A Grade DROPOUT (VOUT − VIN) LOAD REGULATION Symbol VO VOERR TCVO VDO PSRR RIPPLE REJECTION ΔVOUT/ΔVIN QUIESCENT CURRENT IQ VOLTAGE NOISE TURN-ON SETTLING TIME LONG-TERM STABILITY OUTPUT VOLTAGE HYSTERESIS Min Typ Max Unit 2.497 2.494 2.5 2.5 2.503 2.506 V V +0.12 +0.24 % % 3 15 9 25 ppm/°C ppm/°C mV 80 300 ppm/mA 50 300 ppm/mA +3 −90 60 +50 ppm/V dB dB 95 80 18 40 125 95 μA μA mA mA @ 25°C −0.12 −0.24 LINE REGULATION SHORT-CIRCUIT CURRENT TO GROUND Conditions/Comments @ 25°C −40°C < TA < +125°C IOUT = 0 mA −40°C < TA < +125°C; VIN = 3.0 V, 0 mA < IOUT < 5 mA −40°C < TA < +125°C; VIN = 3.0 V, −2 mA < IOUT < 0 mA 2.8 V to 18 V IOUT = 0 mA f = 1 Khz f = 60 Hz −40°C < TA < +125°C, no load VIN = 18 V VIN = 2.8 V VIN = 2.8 V VIN = 18 V @ 25°C f = 10 KHz 0.1 Hz to 10 Hz To 0.1%, CL = 0.2 μF 1000 hours @ 25°C See the Terminology section Rev. 0 | Page 3 of 20 300 −50 500 10 100 150 300 nV/√Hz μV p-p μs ppm/1000 hrs ppm ADR121/ADR125/ADR127 ADR125 ELECTRICAL CHARACTERISTICS @ TA = 25°C, VIN = 5.3 V to 18 V, IOUT = 0 mA, unless otherwise noted. Table 2. Parameter OUTPUT VOLTAGE B Grade A Grade INITIAL ACCURACY ERROR B Grade A Grade TEMPERATURE COEFFICIENT B Grade A Grade DROPOUT (VOUT − VIN) LOAD REGULATION Symbol VO Condition @ 25°C VOERR 2.497 @ 25°C TCVO VDO PSRR IOUT = 5 mA −40°C < TA < +125°C; VIN = 3.0 V, 0 mA < IOUT < 5 mA −40°C < TA < +125°C; VIN = 3.0 V, −2 mA < IOUT < 0 mA 5.3 V < VIN < 18 V IOUT = 0 mA f = 60 Hz ΔVOUT/ΔVIN f = 60 Hz QUIESCENT CURRENT IQ −40°C < TA < +125°C, no load VIN = 18 V VIN = 3.0 V VIN = 5.3 V VIN = 18 V @ 25°C f = 10 Khz 0.1 Hz to 10 Hz To 0.1%, CL = 0.2 μF 1000 hours @ 25°C See the Terminology section TURN-ON SETTLING TIME LONG-TERM STABILITY OUTPUT VOLTAGE HYSTERESIS Max Unit 4.994 4.988 5.0 5.0 5.006 5.012 V V +0.12 +0.24 % % 3 15 9 25 ppm/°C ppm/°C mV 35 200 ppm/mA 35 200 ppm/mA 30 −90 ppm/V dB 60 dB −40°C < TA < +125°C RIPPLE REJECTION VOLTAGE NOISE Typ −0.12 −0.24 LINE REGULATION SHORT-CIRCUIT CURRENT TO GROUND Min Rev. 0 | Page 4 of 20 300 95 80 25 40 900 20 100 150 300 125 95 μA μA mA mA nV/√Hz μV p-p μs ppm/1000 hrs ppm ADR121/ADR125/ADR127 ADR127 ELECTRICAL CHARACTERISTICS @ TA = 25°C, 2.7 V to 18 V, IOUT = 0 mA, unless otherwise noted. Table 3. Parameter OUTPUT VOLTAGE B Grade A Grade INITIAL ACCURACY ERROR B Grade A Grade TEMPERATURE COEFFICIENT B Grade A Grade DROPOUT (VOUT − VIN) LOAD REGULATION Symbol VO VOERR Condition @ 25°C TCVO VDO PSRR Unit 1.2485 1.2470 1.25 1.25 1.2515 1.2530 V V +0.12 +0.24 % % 3 15 9 25 ppm/°C ppm/°C V 85 400 ppm/mA 65 400 ppm/mA 30 −90 90 ppm/V dB −40°C < TA < +125°C IOUT = 0 mA −40°C < TA < +125°C; VIN = 3.0 V, 0 mA < IOUT < 5 mA −40°C < TA < +125°C; VIN = 3.0 V, −2 mA < IOUT < 0 mA 2.7 V to 18 V IOUT = 0 mA F = 60 Hz ΔVOUT/ΔVIN f = 60 Hz QUIENSCENT CURRENT IQ −40°C < TA < +125°C, no load VIN = 18 V VIN = 2.7 V VIN = 2.7 V VIN = 18 V @ 25°C f = 10 kHz 0.1 Hz to 10 Hz To 0.1%, CL = 0.2 μF 1000 hours @ 25°C See the Terminology section TURN-ON SETTLING TIME LONG-TERM STABILITY OUTPUT VOLTAGE HYSTERESIS Max @ 25°C RIPPLE REJECTION VOLTAGE NOISE Noise Density Typ −0.12 −0.24 LINE REGULATION SHORT-CIRCUIT CURRENT TO GROUND Min Rev. 0 | Page 5 of 20 1.45 60 95 80 15 30 300 5 80 150 300 dB 125 95 μA μA mA mA nV/√Hz μV p-p μs ppm/1000 hrs ppm ADR121/ADR125/ADR127 ABSOLUTE MAXIMUM RATINGS Table 4. Parameter VIN to GND Internal Power Dissipation TSOT (UJ-6) Storage Temperature Range Specified Temperature Range Lead Temperature, Soldering Vapor Phase (60 sec) Infrared (15 sec) Ratings 20 V 40 mW −65°C to +150°C −40°C to +125°C 215°C 220°C 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 indicated in the operational section of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. THERMAL RESISTANCE θJA is specified for the worst-case conditions, that is, a device soldered in a circuit board for surface-mount packages. Table 5. Thermal Resistance Package Type TSOT (UJ-6) θJA 230 ESD 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 this product 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. Rev. 0 | Page 6 of 20 θJC 146 Unit °C/W ADR121/ADR125/ADR127 TERMINOLOGY Temperature Coefficient The change of output voltage with respect to operating temperature change normalized by the output voltage at 25°C. This parameter is expressed in ppm/°C and can be determined by TCVO [ppm/°C ] = VO (T2 ) − VO (T1 ) VO (25°C ) × (T2 − T1 ) × 10 Long-Term Stability Typical shift of output voltage at 25°C on a sample of parts subjected to a test of 1000 hours at 25°C. ΔVO = VO (t O ) − VO (t1 ) ΔVO [ppm ] = 6 VO (t O ) − VO (t1 ) VO (t O ) × 10 6 where: where: VO(t0) = VO at 25°C at Time 0. VO(t1) = VO at 25°C after 1000 hours operating at 25°C. VO(25°C) = VO at 25°C. VO(T1) = VO at Temperature 1. VO(T2) = VO at Temperature 2. Line Regulation The change in the output due to a specified change in input voltage. This parameter accounts for the effects of self-heating. Line regulation is expressed in either percent per volt, partsper-million per volt, or microvolts per voltage changes in input voltage. Load Regulation The change in output voltage due to a specified change in load current. This parameter accounts for the effects of self-heating. Load regulation is expressed in either microvolts per milliampere, parts-per-million per milliampere, or ohms of dc output resistance. Thermal Hysteresis The change of output voltage after the device is cycled through temperatures from +25°C to −40°C to +125°C and back to +25°C. This is a typical value from a sample of parts put through such a cycle. where: VO (25°C) = VO at 25°C. VOTC = VO at 25°C after temperature cycle at +25°C to −40°C to +125°C and back to +25°C. Rev. 0 | Page 7 of 20 ADR121/ADR125/ADR127 TYPICAL PERFORMANCE CHARACTERISTICS 1.256 5 1.254 NUMBER OF PARTS 4 1.250 1.248 2 5 20 35 50 65 80 95 110 125 TEMPERATURE (°C) 0 –50 –40 –30 –20 –10 0 10 20 30 40 50 40 50 05725-010 –10 05725-006 –25 40 50 TEMPERATURE COEFFICIENT (ppm/°C) Figure 2. ADR127 VOUT vs. Temperature 05725-009 1 1.246 1.244 –40 3 05725-011 VOUT (V) 1.252 Figure 5. ADR127 Temperature Coefficient 2.510 5 2.508 2.506 4 NUMBER OF PARTS VOUT (V) 2.504 2.502 2.500 2.498 2.496 2.494 3 2 1 2.492 –25 –10 5 20 35 50 65 80 95 110 125 TEMPERATURE (°C) 0 –50 05725-007 2.490 –40 –40 –30 –20 –10 0 10 20 30 TEMPERATURE COEFFICIENT (ppm/°C) Figure 3. ADR121 VOUT vs. Temperature Figure 6. ADR125 Temperature Coefficient 5.020 5 5.015 4 NUMBER OF PARTS 5.010 5.000 4.995 3 2 4.990 1 4.985 4.980 –40 –25 –10 5 20 35 50 65 80 TEMPERATURE (°C) 95 110 125 05725-008 VOUT (V) 5.005 Figure 4. ADR125 VOUT vs. Temperature 0 –50 –40 –30 –20 –10 0 10 20 30 TEMPERATURE COEFFICIENT (ppm/°C) Figure 7. ADR121 Temperature Coefficient Rev. 0 | Page 8 of 20 ADR121/ADR125/ADR127 3.0 120 100 SUPPLY CURRENT (µA) 2.8 2.6 +25°C 2.4 +125°C 2.2 +125°C –40°C 60 40 –1 0 1 2 3 4 5 LOAD CURRENT (mA) 0 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 INPUT VOLTAGE (V) Figure 8. ADR127 Minimum Input Voltage vs. Load Current 05725-015 2.0 –2 +25°C 80 20 05725-012 VIN_MIN (V) –40°C Figure 11. ADR127 Supply Current vs. Input Voltage 120 3.5 3.4 SUPPLY CURRENT (µA) 3.2 VIN_MIN (V) +125°C 100 3.3 +125°C 3.1 +25°C 3.0 –40°C 2.9 2.8 2.7 +25°C 80 –40°C 60 40 20 –1 0 1 2 3 4 5 LOAD CURRENT (mA) 0 05725-013 2 6.0 100 SUPPLY CURRENT (µA) 120 +125°C 5.8 +25°C –40°C 5.4 6 7 8 9 10 11 12 13 14 15 16 17 18 +25°C 80 +125°C –40°C 60 40 20 5.2 –1 0 1 2 3 4 5 LOAD CURRENT (mA) 0 05725-014 VIN_MIN (V) 5 Figure 12. ADR121 Supply Current vs. Input Voltage 6.2 5.0 –2 4 INPUT VOLTAGE (V) Figure 9. ADR121 Minimum Input Voltage vs. Load Current 5.6 3 5 6 7 8 9 10 11 12 13 14 15 16 17 INPUT VOLTAGE (V) Figure 13. ADR125 Supply Current vs. Input Voltage Figure 10. ADR125 Minimum Input Voltage vs. Load Current Rev. 0 | Page 9 of 20 18 05725-017 2.5 –2 05725-016 2.6 ADR121/ADR125/ADR127 6 0 — +125°C — +25°C — –40°C LINE REGULATION (ppm/V) 4 3 2 –10 –20 VIN = 2.7V TO 18V –30 0 1 2 3 4 5 LOAD CURRENT (mA) –50 –40 LINE REGULATION (ppm/V) SUPPLY CURRENT (mA) 35 50 65 80 95 110 125 125 125 2 3 2 1 1 0 VIN = 2.8V TO 18V –1 –2 –1 0 1 2 3 4 5 LOAD CURRENT (mA) –3 –40 05725-019 0 –2 –25 –10 5 20 35 50 65 80 95 110 TEMPERATURE (°C) Figure 15. ADR121 Supply Current vs. Load Current Figure 18. ADR121 Line Regulation vs. Temperature 6 — +125°C — +25°C — –40°C 5 LINE REGULATION (ppm/V) 4 4 3 2 1 2 VIN = 5.3V TO 18V 0 –2 –4 –1 0 1 2 3 4 LOAD CURRENT (mA) 5 05725-020 SUPPLY CURRENT (mA) 20 3 — +125°C — +25°C — –40°C 4 0 –2 5 Figure 17. ADR127 Line Regulation vs. Temperature 5 6 -10 TEMPERATURE (°C) Figure 14. ADR127 Supply Current vs. Load Current 6 -25 05725-021 –1 05725-018 0 –2 05725-022 –40 1 05725-023 SUPPLY CURRENT (mA) 5 Figure 16. ADR125 Supply Current vs. Load Current –6 –40 –25 –10 5 20 35 50 65 80 95 110 TEMPERATURE (°C) Figure 19. ADR125 Line Regulation vs. Temperature Rev. 0 | Page 10 of 20 ADR121/ADR125/ADR127 200 LOAD REGULATION (ppm/mA) 150 CIN = COUT = 0.1µF 2mA SINKING, VIN = 3V 100 50 CH1 p-p 5.76µV 0 1 –50 –100 CH1 rms 0.862µV 5mA SOURCING, VIN = 3V –150 2µV/DIV –10 5 20 35 50 65 80 95 110 125 TEMPERATURE (°C) TIME (1s/DIV) 05725-027 –25 05725-024 –200 –40 Figure 20. ADR127 Load Regulation vs. Temperature Figure 23. ADR127 0.1 Hz to 10 Hz Noise 100 LOAD REGULATION (ppm/mA) 80 CIN = COUT = 0.1µF 60 2mA SINKING, VIN = 5V 40 20 CH1 p-p 10.8µV 0 –20 1 5mA SOURCING, VIN = 5V –40 CH1 rms 1.75µV –60 –80 –10 5 20 35 50 65 80 95 110 125 TEMPERATURE (°C) TIME (1s/DIV) 05725-025 –25 05725-028 5µV/DIV –100 –40 Figure 24. ADR121 0.1 Hz to 10 Hz Noise Figure 21. ADR121 Load Regulation vs. Temperature 50 CIN = COUT = 0.1µF 30 2mA SINKING, VIN = 6V 20 10 CH1 p-p 20.6µV 0 –10 1 CH1 rms 3.34µV 5mA SOURCING, VIN = 6V –20 –30 –40 –25 –10 5 20 35 50 65 80 95 110 TEMPERATURE (°C) 125 TIME (1s/DIV) 05725-029 10µV/DIV –50 –40 05725-026 LOAD REGULATION (ppm/mA) 40 Figure 22. ADR125 Load Regulation vs. Temperature Figure 25. ADR125 0.1 Hz to 10 Hz Noise Rev. 0 | Page 11 of 20 ADR121/ADR125/ADR127 CIN = COUT = 0.1µF VIN 1V/DIV CIN = COUT = 0.1µF CH1 p-p 287µV CH1 rms 38.8µV TIME (1s/DIV) 2 05725-030 50µV/DIV 1 Figure 26. ADR127 10 Hz to 10 KHz Noise VOUT 500mV/DIV TIME (200µs/DIV) 05725-033 1 Figure 29. ADR127 Turn-On Response CIN = COUT = 0.1µF VIN 1V/DIV CIN = COUT = 0.1µF CH1 p-p 450µV 1 CH1 rms 58.1µV 1 VOUT 500mV/DIV TIME (40µs/DIV) TIME (1s/DIV) Figure 27. ADR121 10 Hz to 10 KHz Noise 05725-034 2 05725-031 100µV/DIV Figure 30. ADR127 Turn-On Response CIN = COUT = 0.1µF VIN 1V/DIV CIN = COUT = 0.1µF 1 1 2 TIME (1s/DIV) Figure 28. ADR125 10 Hz to 10 KHz Noise VOUT 500mV/DIV TIME (100µs/DIV) Figure 31. ADR127 Turn-Off Response Rev. 0 | Page 12 of 20 05725-035 200µV/DIV CH1 rms 115µV 05725-032 CH1 p-p 788µV ADR121/ADR125/ADR127 CIN = COUT = 0.1µF VIN 1V/DIV CIN = COUT = 0.1µF VIN 2V/DIV 1 1 2 05725-036 TIME (100µs/DIV) 2 TIME (100µs/DIV) Figure 32. ADR121 Turn-On Response 05725-039 VOUT 2V/DIV VOUT 1V/DIV Figure 35. ADR125 Turn-On Response CIN = COUT = 0.1µF VIN 1V/DIV CIN = COUT = 0.1µF VIN 2V/DIV 1 1 VOUT 2V/DIV TIME (40µs/DIV) TIME (20µs/DIV) 2 05725-037 2 Figure 33. ADR121 Turn-On Response 05725-040 VOUT 1V/DIV Figure 36. ADR125 Turn-On Response CIN = COUT = 0.1µF VIN 1V/DIV VIN 2V/DIV 1 1 VOUT 1V/DIV 2 TIME (20µs/DIV) Figure 34. ADR121 Turn-Off Response Figure 37. ADR125 Turn-Off Response Rev. 0 | Page 13 of 20 05725-041 TIME (200µs/DIV) 05725-038 2 VOUT 2V/DIV ADR121/ADR125/ADR127 CIN = COUT = 0.1µF 2.50V 1 VIN 1V/DIV LINE INTERRUPTION VIN 500mV/DIV CIN = COUT = 0.1µF 625Ω LOAD 2mA SINKING 1.25V 2 1 TIME (200µs/DIV) VOUT 20mV/DIV TIME (40µs/DIV) 05725-045 VOUT 500mV/DIV 05725-042 2 Figure 38. ADR127 Line Transient Response Figure 41. ADR127 Load Transient Response (Sinking) CIN = COUT = 0.1µF 1 LINE INTERRUPTION 1V/DIV 1.25V VIN 500mV/DIV CIN = COUT = 0.1µF 250Ω LOAD 5mA SOURCING 0V 1 TIME (400µs/DIV) 2 VOUT 100mV/DIV 05725-043 VOUT 500mV/DIV Figure 39. ADR121 Line Transient Response TIME (40µs/DIV) Figure 42. ADR127 Load Transient Response (Sourcing) CIN = COUT = 0.1µF 1 05725-046 2 5V VIN 1V/DIV CIN = COUT = 0.1µF 1250Ω LOAD 2mA SINKING VIN 1V/DIV 2.5V 1 TIME (400µs/DIV) VOUT 10mV/DIV 05725-044 VOUT 500mV/DIV Figure 40. ADR125 Line Transient Response TIME (40µs/DIV) Figure 43. ADR121 Load Transient Response (Sinking) Rev. 0 | Page 14 of 20 05725-047 2 2 ADR121/ADR125/ADR127 0 –20 2.5V VIN 1V/DIV CIN = COUT = 0.1µF 500Ω LOAD 5mA SOURCING –60 0V –80 (dB) 1 –40 1 –100 –120 –140 2 –160 –180 –200 10 100 1k 10k 100k 1M 10M 100M 05725-051 TIME (40µs/DIV) 05725-048 VOUT 100mV/DIV Figure 47. ADR121/ADR125/ADR127 PSRR Figure 44. ADR121 Load Transient Response (Sourcing) 50 45 10V VIN 2V/DIV CIN = COUT = 0.1µF 2.5kΩ LOAD 2mA SINKING 5V OUTPUT IMPEDANCE (Ω) 40 1 35 30 ADR127 25 20 ADR121 15 ADR125 10 2 5 10 5V 1 0V TIME (40µs/DIV) 05725-050 2 VOUT 100mV/DIV 100 1k FREQUENCY (Hz) 10k 100k Figure 48. ADR121/ADR125/ADR127 Output Impedance vs. Frequency Figure 45. ADR125 Load Transient Response (Sinking) VIN 2V/DIV CIN = COUT = 0.1µF 1kΩ LOAD 5mA SOURCING 1 0 05725-054 TIME (40µs/DIV) 05725-049 VOUT 20mV/DIV Figure 46. ADR125 Load Transient Response (Sourcing) Rev. 0 | Page 15 of 20 ADR121/ADR125/ADR127 THEORY OF OPERATION The ADR12x band gap references are the high performance solution for low supply voltage and low power applications. The uniqueness of these products lies in their architecture. POWER DISSIPATION CONSIDERATIONS The ADR12x family is capable of delivering load currents to 5 mA with an input range from 3.0 V to 18 V. When this device is used in applications with large input voltages, care must be taken to avoid exceeding the specified maximum power dissipation or junction temperature, because this could result in premature device failure. Use the following formula to calculate a device’s maximum junction temperature or dissipation: PD = TJ − TA NOTES Input Capacitor Input capacitors are not required on the ADR12x. There is no limit for the value of the capacitor used on the input, but a 1 μF to 10 μF capacitor on the input improved transient response in the applications where there is a sudden supply change. An additional 0.1 μF capacitor in parallel also helps reduce noise from the supply. Output Capacitor The ADR12x requires a small 0.1 μF capacitor for stability. Additional 0.1 μF to 10 μF capacitance in parallel can improve load transient response. This acts as a source of stored energy for a sudden increase in load current. The only parameter affected with the additional capacitance is turn-on time. θ JA where: TJ is the junction temperature. TA is the ambient temperature. PD is the device power dissipation. θJA is the device package thermal resistance. Rev. 0 | Page 16 of 20 ADR121/ADR125/ADR127 APPLICATIONS BASIC VOLTAGE REFERENCE CONNECTION Table 6. Required Outputs The circuit in Figure 4 illustrates the basic configuration for the ADR12x family voltage reference. U1/U2 ADR127/ADR121 ADR127/ADR125 ADR121/ADR125 NC NC 6 ADR12x + GND 3 VIN NEGATIVE PRECISION REFERENCE WITHOUT PRECISION RESISTORS NC 5 OUTPUT VOUT 4 + 0.1µF 0.1µF A negative reference is easily generated by adding an op amp, A1, and is configured as shown in Figure 51. VOUT1 is 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. 05725-002 INPUT 2 Figure 49. Basic Configuration for the ADR12x Family STACKING REFERENCE ICs FOR ARBITRARY OUTPUTS 1 NC Some applications may require two reference voltage sources that are a combined sum of the standard outputs. Figure 50 shows how this stacked output reference can be implemented. NC 6 ADR127 2 GND NC 5 3 VIN +VDD 1 NC VOUT 4 NC 6 ADR12x 2 GND 0.1µF NC 5 + + 0.1µF AD8603 –VREF OUTPUT1 VOUT 4 1kΩ 2 – V+ 3 VIN VOUT1 3.75 V 6.25 V 7.5 V V– + 3 0.1µF 05725-055 1 VOUT2 1.25 V 1.25 V 2.5 V –VDD Figure 51. Negative Reference NC 6 GENERAL-PURPOSE CURRENT SOURCE ADR12x 2 GND 3 VIN + 0.1µF OUTPUT2 NC 5 VOUT 4 + 0.1µF Figure 50. Stacking References with ADR12x Two reference ICs are used and fed from an unregulated input, VIN. The outputs of the individual ICs are connected in series, which provide two output voltages, VOUT1 and VOUT2. VOUT1 is the terminal voltage of U1, while VOUT2 is the sum of this voltage and the terminal of U2. U1 and U2 are chosen for the two voltages that supply the required outputs (see Table 6). For example, if U1 and U2 are ADR127 and VIN ≥ 3.95 V, VOUT1 is 1.25 V and VOUT2 is 2.5 V. In low power applications, the need can arise for a precision current source that can operate on low supply voltages. The ADR12x can be configured as a precision current source (see Figure 52). The circuit configuration shown 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 ranging from the reference’s supply current, typically 85 μA, to approximately 5 mA. 1 NC NC 6 ADR12x NC 5 2 GND +VDD 3 VIN VOUT 4 ISY R1 ISET P1 RL Figure 52. ADR12x Trim Configuration Rev. 0 | Page 17 of 20 05725-005 1 NC 05725-003 INPUT ADR121/ADR125/ADR127 OUTLINE DIMENSIONS 2.90 BSC 6 5 4 1 2 3 2.80 BSC 1.60 BSC PIN 1 INDICATOR 0.95 BSC 1.90 BSC *0.90 0.87 0.84 *1.00 MAX 0.50 0.30 0.10 MAX 0.20 0.08 SEATING PLANE 8° 4° 0° 0.60 0.45 0.30 *COMPLIANT TO JEDEC STANDARDS MO-193-AA WITH THE EXCEPTION OF PACKAGE HEIGHT AND THICKNESS. Figure 53. 6-Lead Thin Small Outline Transistor Package [TSOT] (UJ-6) Dimensions shown in millimeters ORDERING GUIDE Model ADR121AUJZREEL7 1 ADR121AUJZR21 ADR121BUJZREEL71 ADR125AUJZREEL71 ADR125AUJZR21 ADR125BUJZREEL71 ADR127AUJZREEL71 ADR127AUJZR21 ADR127BUJZREEL71 1 Output Voltage (VO) Initial Accuracy (mV/%) Temperature Coefficient (ppm/°C) Package Description Package Option Temperature Range (°C) 2.5 2.5 0.24 25 6-Lead TSOT UJ-6 2.5 2.5 0.24 25 6-Lead TSOT UJ-6 2.5 2.5 0.12 9 6-Lead TSOT UJ-6 5.0 5.0 0.24 25 6-Lead TSOT UJ-6 5.0 5.0 0.24 25 6-Lead TSOT UJ-6 5.0 5.0 0.12 9 6-Lead TSOT UJ-6 1.25 3 0.24 25 6-Lead TSOT UJ-6 1.25 3 0.24 25 6-Lead TSOT UJ-6 1.25 1.5 0.12 9 6-Lead TSOT UJ-6 −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C Z = Pb-free part. Rev. 0 | Page 18 of 20 Ordering Quantity 3000 Branding 250 R0N 3000 R0P 3000 R0Q 250 R0Q 3000 R0R 3000 R0S 250 R0S 3000 R0T R0N ADR121/ADR125/ADR127 NOTES Rev. 0 | Page 19 of 20 ADR121/ADR125/ADR127 NOTES ©2006 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D05725-0-6/06(0) Rev. 0 | Page 20 of 20