1.2 V Ultralow Power High PSRR Voltage Reference ADR280 FEATURES PIN CONFIGURATIONS 1.2 V precision output Excellent line regulation: 2 ppm/V typical High power supply ripple rejection: –80 dB at 220 Hz Ultralow power supply current: 16 μA maximum Temperature coefficient: 40 ppm/°C maximum Low noise, 12.5 nV/√Hz typical Operating supply range, 2.4 V to 5.5 V Compact 3-lead SOT-23 and SC70 packages VOUT 2 APPLICATIONS VOUT 1 V+ 1 ADR280 3 V– 03065-002 V+ 2 Figure 2. 3-Lead SC70 (KS Suffix) GENERAL DESCRIPTION 15 10 LINE REGULATION (ppm/V) 5 3V TO 5V 0 –5 –10 –15 –40 –20 0 20 40 TEMPERATURE (°C) 60 80 100 03065-003 In addition to mobile stations, the ADR280 is suitable for a variety of general-purpose applications. Most band gap references include internal gain for specific outputs, which simplifies the user’s design, but compromises on the cost, form factor, and flexibility. The ADR280, on the other hand, optimizes the band gap core voltage and allows users to tailor the voltage, current, or transient response by simply adding their preferred op amps. V– Figure 1. 3-Lead SOT-23 (RT Suffix) List GSM, GPRS, 3G mobile stations Portable battery-operated electronics Low voltage converter references Wireless devices The ADR280 is a 1.2 V band gap core reference with excellent line regulation and power supply rejection designed specifically for applications experiencing heavy dynamic supply variations, such as data converter references in GSM, GPRS, and 3G mobile station applications. Devices such as the AD6535 that have an analog baseband IC with on-board baseband, audio codecs, voltage regulators, and battery chargers rely on the ability of the ADR280 to reject input battery voltage variations during RF power amplifier activity. 3 03065-001 ADR280 Figure 3. Line Regulation vs. Temperature The ADR280 operates on a wide supply voltage range from 2.4 V to 5.5 V. It is available in compact 3-lead SOT-23 and SC70 packages. The device is specified over the extended industrial temperature range of −40°C to +85°C. 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. 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 ©2002–2007 Analog Devices, Inc. All rights reserved. ADR280 TABLE OF CONTENTS Features .............................................................................................. 1 Thermal Resistance .......................................................................4 Applications....................................................................................... 1 ESD Caution...................................................................................4 General Description ......................................................................... 1 Typical Performance Characteristics ..............................................5 Pin Configurations ........................................................................... 1 Theory of Operation .........................................................................7 Revision History ............................................................................... 2 Applications Information .................................................................8 Specifications..................................................................................... 3 Low Cost, Low Power Current Source .......................................8 Electrical Characteristics............................................................. 3 Outline Dimensions ....................................................................... 10 Absolute Maximum Ratings............................................................ 4 Ordering Guide .......................................................................... 11 REVISION HISTORY 4/07—Rev. B to Rev. C 6/03—Rev. 0 to Rev. A Updated Format..................................................................Universal Changes to Figure 1, Figure 2.......................................................... 1 Deleted Pin Function Descriptions Section and Pin Configurations Section .................................................................... 2 Changes to Figure 20 and Figure 21............................................... 9 Updated Outline Dimensions ....................................................... 10 Added SC70 package..........................................................Universal Changes to Features ..........................................................................1 Changes to General Description .....................................................1 Changes to Specifications.................................................................2 Changes to Ordering Guide .............................................................2 Changes to TPCs 4, 6, and 7 ............................................................3 Updated SOT-23 Outline Dimensions ...........................................7 10/04—Rev. A to Rev. B Changes to Pin Configurations.........................................Universal Changes to Ordering Guide ............................................................ 2 Changes to Outline Dimensions..................................................... 7 11/02—Revision 0: Initial Version Rev. C | Page 2 of 12 ADR280 SPECIFICATIONS ELECTRICAL CHARACTERISTICS VIN = 2.55 V to 5.5 V, TA = 25°C, unless otherwise noted. Table 1. Parameter Output Voltage Temperature Coefficient Symbol VOUT TCVO Line Regulation Supply Current Ground Current Input Voltage Range Operating Temperature Range Nominal Load Capacitance Output Noise Voltage Voltage Noise Density Power Supply Ripple Rejection 2 Start-Up Time ΔVOUT/ΔVIN IIN IGND VIN TA COUT VN rms eN PSRR tON 1 2 Conditions 2.4 V < VIN < 5.5 V, 0 μA < IOUT < 10 μA, −40°C < TA < +85°C 0°C < TA < 50°C –40°C < TA < +85°C 2.55 V < VIN < 5.5 V, no load 2.4 V < VIN < 5.5 V, no load V– grounded, ILOAD = 10 μA Min 1.195 Typ 1 1.200 5 10 2 10 12 2.4 −40 1 f = 10 Hz to 10 kHz f = 400 kHz ILOAD = 10 μA 12.5 12.5 −80 2 Max 1.205 20 40 12 16 20 5.5 +85 Unit V ppm/°C ppm/°C ppm/V μA μA V °C μF μV rms nV/√Hz dB ms Typical values represent average readings taken at room temperature. Power supply ripple rejection measurement applies to a changing input voltage (VIN) waveform with a nominal 3.6 V baseline that drops to a 3 V value for 380 μs at a 4.6 ms repetition rate. Rev. C | Page 3 of 12 ADR280 ABSOLUTE MAXIMUM RATINGS TA = 25°C, unless otherwise noted. THERMAL RESISTANCE Table 2. θJA is specified for the worst-case conditions, that is, θJA is specified for a device soldered in circuit board for surfacemount packages. Parameter Supply Voltage Storage Temperature Range Operating Temperature Range Junction Temperature Range Lead Temperature Range (Soldering, 60 Sec) Rating 6V −65°C to +150°C −40°C to +85°C −65°C to +150°C 300°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. Table 3. Package Type SOT-23 SC70 ESD CAUTION Rev. C | Page 4 of 12 θJA 230 376 θJC 146 102 Unit °C/W °C/W ADR280 TYPICAL PERFORMANCE CHARACTERISTICS 15 1.20225 10 1.20200 LINE REGULATION (ppm/V) NO LOAD VOUT (V) 1.20175 1.20150 1.20125 1.20100 1.20075 1.20050 5 3V TO 5V 0 –5 –10 –20 0 20 40 60 TEMPERATURE (°C) 80 100 –15 –40 Figure 4. VOUT vs. Temperature –20 0 20 40 TEMPERATURE (°C) 60 80 100 Figure 6. Line Regulation vs. Temperature 15 14 13 12 1 VIN = 3V 11 9 –40 –20 0 20 40 60 TEMPERATURE (°C) 80 100 CH1 50.0µV M 1.00s Figure 7. Noise Voltage Peak-to-Peak, 10 Hz to 10 kHz Figure 5. Supply Current vs. Temperature Rev. C | Page 5 of 12 03065-009 10 03065-007 IIN (µA) VIN = 5V 03065-008 1.20000 –40 03065-006 1.20025 ADR280 T 1.2 tS 1.0 VOLTAGE (V) –60 –80 –100 0.8 0.6 0.4 0.2 0 2.5 5.0 7.5 10.0 FREQUENCY (kHz) 0 6 8 10 12 Figure 10. Settling Time –40dB 03065-011 10dB/DIV 100kHz 4 TIME (ms) Figure 8. Output Noise Density Plot (V+ = 3.6 V, COUT = 1 μF, CIN = 1 μF) 0Hz 2 Figure 9. Voltage Noise Density, 0 Hz to 100 kHz Rev. C | Page 6 of 12 14 16 18 20 03065-012 0 03065-010 NOISE POWER DENSITY (dBm) –40 ADR280 THEORY OF OPERATION V+ R2 R1 I1 R12 Q2 Q7 Q1 R3 Q10 R4 R13 C1 PNP3 Q3 Q17 R10 Q18 Q9 Q6 VOUT R7 R5 Q5 R6 R11 R8 R9 V– Figure 11. Simplified Architecture Rev. C | Page 7 of 12 03065-013 The ADR280 provides the basic core 1.2 V band gap reference. It contains two NPN transistors, Q9 and Q17, with their emitter areas scaled in a fixed ratio. The difference in the VBE produces a proportional to absolute temperature (PTAT) voltage that cancels the complementary to absolute temperature (CTAT) Q9 VBE voltage. As a result, a core band gap voltage that is almost a constant 1.2 V over temperature is generated (see Figure 11). Precision laser trimming of the internal resistors and other proprietary circuit techniques are used to enhance the initial accuracy, temperature curvature, and temperature drift performance. ADR280 APPLICATIONS INFORMATION U1 The ADR280 should be decoupled with a 0.1 μF ceramic capacitor at the output for optimum stability. It is also good practice to include 0.1 μF ceramic capacitors at the IC supply pin. These capacitors should be mounted close to their respective pins (see Figure 12). ADR280 5V V+ 1.8V ADR280 R2 60kΩ ± 0.1% V– U2 VO C2 2.2pF 03065-014 0.1µF LOW COST, LOW POWER CURRENT SOURCE The low supply voltage input pin V− can be elevated above ground; a 1.2 V differential voltage can therefore be established above V− (see Figure 13). V+ ADR280 V– 2.5V Because of its low power characteristics, the ADR280 can be converted to a current source with just a setting resistor. In addition to the ADR280 current capability, the supply voltage and the load limit the maximum current. The circuit in Figure 16 produces 100 μA with 2 V compliance at a 5 V supply. The load current is the sum of ISET and IGND. IGND increases slightly with load; a RSET of 13.6 kΩ yields 100 μA of load current. U1 VOUT 03065-015 0.1µF 5V V+ ADR280 V– Figure 13. Floating References ISET VOUT C1 RSET + 0.1µF 1.2V – 13.6kΩ RL 1kΩ U1 IL 100µA IGND IL = ISET + IGND V+ 0.1µF Figure 16. Low Cost Current Source ADR280 Precision Low Power Current Source V– U1 0.1µF U2 = AD8541, SC70 AD8601, SOT-23-5 03065-016 VOUT By adding a buffer to redirect the IGND in Figure 17, a current can be precisely set by RSET with the equation IL = 1.2 V/RSET. VOUT U2 03065-018 The ADR280 provides the core 1.2 V band gap voltage and is able to drive a maximum load of only 100 μA. Users can simply buffer the output for high current or sink/source current applications, such as ADC or LCD driver references (see Figure 14). 5V V+ ADR280 Figure 14. Buffered Output V– Users can also tailor any specific need for voltage and dynamics with an external op amp and discrete components (see Figure 14 and Figure 15). Depending on the specific op amp and PCB layout, it may be necessary to add a compensation capacitor, C2, to prevent gain peaking and oscillation. The exact value of C2 needed requires some trial and error but usually falls in the range of a few picofarads. VOUT C2 0.1µF RSET 12kΩ RL 1kΩ 5V U2 V+ AD8541 V– + – IL 100µA IL = 1.2V/RSET 03065-019 1.2V + V– VOUT C1 0.1µF Figure 15. 1.8 V Reference Figure 12. Basic Configuration 0.1µF 1.2V + V+ AD8541 V– – R1 120kΩ ± 0.1% VOUT 5V V– 03065-017 0.1µF V+ 5V Figure 17. Precision Low Power Current Source Rev. C | Page 8 of 12 ADR280 Boosted Current Source Adding one more buffer to the previous circuit boosts the current to the level that is limited only by the buffer U2 current handling capability (see Figure 18). U1 100 mA load is achievable at a 5 V supply. The higher the supply voltage, the lower the current handling is because of the heat generated on the MOSFET. For heavy capacitive loads, additional buffering is needed at the output to enhance the transient response. V+ VO ADR280 V+ RL 25Ω V– ADR280 M1* 5V + U2 VOUT V+ R2 10.8kΩ ± 0.1% C1 V– – C2 1pF 0.1µF RL 500Ω + 1.2V – – + IL 5mA V+ R1 10kΩ ± 0.1% V– IL = 1.2V/RSET U2 = U3 = AD8542, AD822 + V+ AD8541 V– – VOUT C1 0.1µF GSM and 3G Mobile Station Applications Negative Reference A negative reference can be precisely configured without using any expensive tight tolerance resistors, as shown in Figure 19. The voltage difference between VOUT and V− is 1.2 V. Since VOUT is at virtual ground, U2 closes the loop by forcing the V− pin to be the negative reference output. U1 V+ ADR280 V– *M1 = FDB301N, 2N7000, 2N7002, OR EQUIVALENT. Figure 20. 2.5 V Boosted Reference Figure 18. Precision Current Source +5V U2 V– VREF 1.2V 5V U3 03065-020 RSET 230Ω U1 5V 2.5V/100mA 03065-022 5V The ADR280 voltage reference is ideal for use with analog baseband ICs in GSM and 3G mobile station applications. Figure 21 illustrates the use of the ADR280 with the AD6535 GSM analog baseband. The AD6535 provides all of the data converters and power management functions needed to implement a GSM mobile station, including baseband codecs, audio codecs, voltage regulators, and a battery charger. Besides low current consumption and a small footprint, the ADR280 is optimized for excellent PSRR, which is necessary for optimum AD6535 device performance when the main battery voltage fluctuates during RF power amplifier activity. –VREF –1.2V DIGITAL BASEBAND AD6535 ANALOG BASEBAND RADIO VOUT BASEBAND CODEC C1 0.1µF U2 – V+ AD8541 V– + 03065-021 –2.7V AUDIO CODEC POWER MANAGEMENT Figure 19. Negative Reference A precision user defined output with boosted current capability can be implemented with the circuit shown in Figure 20. In this circuit, U2 forces VO to be equal to VREF × (1 + R2/R1) by regulating the turn-on of M1; the load current is therefore furnished by the 5 V supply. For higher output voltage, U2 must be changed and the supply voltage of M1 and U2 must also be elevated and separated from the U1 input voltage. In this configuration, a Rev. C | Page 9 of 12 ADR280 VOLTAGE REFERENCE Figure 21. GSM Mobile Station Application 03065-023 Boosted Reference with Scalable Output ADR280 OUTLINE DIMENSIONS 3.04 2.90 2.80 1.40 1.30 1.20 3 2.64 2.10 1 2 PIN 1 0.95 BSC 1.90 BSC 1.12 0.89 0.10 0.01 0.50 0.30 SEATING PLANE 0.20 0.08 0.60 0.50 0.40 COMPLIANT TO JEDEC STANDARDS TO-236-AB Figure 22. 3-Lead Small Outline Transistor Package [SOT-23-3] (RT-3) Dimensions shown in millimeters 1.55 1.50 1.45 1.10 1.00 0.90 2.05 2.00 1.95 8.30 8.00 7.70 0.35 0.30 0.25 1.50 MIN 2.80 2.70 2.60 3.55 3.50 3.45 3.20 3.10 2.90 7” REEL 100.00 OR 13” REEL 330.00 1.10 1.00 0.90 20.20 MIN 14.40 MIN 7” REEL 50.00 MIN OR 13” REEL 100.00 MIN 13.20 13.00 12.80 0.75 MIN 1.00 MIN 9.90 8.40 6.90 DIRECTION OF UNREELING Figure 23. Tape and Reel Dimensions (RT-3) Dimensions shown in millimeters 2.20 2.00 1.80 3 1 2 PIN 1 0.65 BSC 1.10 0.80 1.00 0.80 0.10 MAX 2.40 2.10 1.80 0.40 0.25 0.10 COPLANARITY SEATING PLANE 0.40 0.10 0.26 0.10 0.30 0.20 0.10 ALL DIMENSIONS COMPLIANT WITH EIAJ SC70 Figure 24. 3-Lead Thin Shrink Small Outline Transistor Package [SC70] (KS-3) Dimensions shown in millimeters Rev. C | Page 10 of 12 111505-0 1.35 1.25 1.15 053006-0 4.10 4.00 3.90 ADR280 ORDERING GUIDE Model ADR280AKS-R2 ADR280AKS-REEL ADR280AKS-REEL7 ADR280AKSZ-R21 ADR280AKSZ-REEL71 ADR280ART-R2 ADR280ART-REEL ADR280ART-REEL7 ADR280ARTZ-R21 ADR280ARTZ-REEL71 1 Temperature Range −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C Package Description 3-Lead SC70 3-Lead SC70 3-Lead SC70 3-Lead SC70 3-Lead SC70 3-Lead SOT-23 3-Lead SOT-23 3-Lead SOT-23 3-Lead SOT-23 3-Lead SOT-23 Package Option KS-3 KS-3 KS-3 KS-3 KS-3 RT-3 RT-3 RT-3 RT-3 RT-3 Z = RoHS Compliant Part. Rev. C | Page 11 of 12 Branding RBA RBA RBA L25 L25 RBA RBA RBA L25 L25 Output Voltage (V) 1.200 1.200 1.200 1.200 1.200 1.200 1.200 1.200 1.200 1.200 Ordering Quantity 250 10,000 3,000 250 3,000 250 10,000 3,000 250 3,000 ADR280 NOTES ©2002–2007 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. C03065-0-4/07(C) Rev. C | Page 12 of 12