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| www..com 1.2 V Ultralow Power High PSRR Voltage Reference ADR280 FEATURES 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 A Maximum Temperature Coefficient, 40 ppm/oC 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 APPLICATIONS GSM, GPRS, 3G Mobile Stations Portable Battery-Operated Electronics Low Voltage Converter References Wireless Devices PIN CONFIGURATIONS 3-Lead SOT-23 (RT Suffix) V+ 1 ADR280 VOUT 2 3 V- 3-Lead SC70 (KS Suffix) VOUT 1 GENERAL DESCRIPTION ADR280 V+ 2 3 V- LINE REGULATION (ppm/V) 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, which has an analog baseband IC with on-board baseband and audio codecs, voltage regulators, and battery charger, rely on the ADR280's ability to reject input battery voltage variations during RF power amplifier activity. 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. 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 -40C to +85C. 15 10 5 3V TO 5V 0 -5 -10 -15 -40 -20 0 20 40 TEMPERATURE (C) 60 80 100 Figure 1. Line Regulation vs. Temperature REV. A 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. Trademarks and registered trademarks are the property of their respective companies. One Technology Way, P Box 9106, Norwood, MA 02062-9106, U.S.A. .O. Tel: 781/329-4700 www.analog.com Fax: 781/326-8703 (c) 2003 Analog Devices, Inc. All rights reserved. www..com ADR280-SPECIFICATIONS ELECTRICAL CHARACTERISTICS (V Parameter Output Voltage Temperature Coefficient Line Regulation Supply Current Ground Current Input Voltage Range Operating Temperature Range Nominal Load Capacitance Output Noise Voltage Output Noise Density Power Supply Ripple Rejection3 Start-Up Time 2 IN = 2.55 V to 5.5 V, TA = 25C, unless otherwise noted.) Min 1.195 Typ1 1.200 5 10 2 10 12 Max 1.205 20 40 12 16 20 5.5 +85 Unit V ppm/oC ppm/oC ppm/V A A V C F Vrms nV//Hz dB ms Symbol VOUT TCVo VOUT/VIN IIN IGND VIN TA COUT VN eN PSRR tON Conditions 0C < TA < 50C -40C < TA < +85C 2.55 V < VIN < 5.5 V, No Load 2.4 V < VIN < 5.5 V, No Load V- Grounded, ILOAD = 10 A 2.4 -40 1 f = 10 Hz to 10 kHz f = 400 kHz ILOAD = 10 A 12.5 12.5 -80 2 NOTES 1Typical values represent average readings taken at room temperature. 2Conditions: 2.4 V < V IN < 5.5 V, 0 A < IOUT < 10 A, -40C < TA < +85C. 3Power supply ripple rejection measurement applies to a changing input voltage (V ) waveform with a nominal 3.6 V baseline that drops to a 3 V value for IN 380 s at a 4.6 ms repetition rate. Specifications subject to change without notice. ABSOLUTE MAXIMUM RATINGS1, 2 Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 V Storage Temperature Range . . . . . . . . . . . . . . -65C to +150C Operating Temperature Range . . . . . . . . . . . . . -40C to +85C Junction Temperature Range . . . . . . . . . . . . . . -65C to +150C Lead Temperature Range (Soldering, 60 Sec) . . . . . . . . . .300C NOTES 1 Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only and 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. 2 Absolute Maximum Ratings apply at 25C, unless otherwise noted. THERMAL RESISTANCE Package Type SOT-23 SC70 JA* 230 376 JC 146 102 Unit C/W C/W * JA is specified for the worst-case conditions, i.e., JA is specified for device soldered in circuit board for surface-mount packages. ORDERING GUIDE Model ADR280ART-R2 ADR280ART-REEL7 ADR280ART-REEL ADR280AKS-R2 ADR280AKS-REEL7 ADR280AKS-REEL Temperature Range -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C Package Description SOT-23 SOT-23 SOT-23 SC70 SC70 SC70 Package Option RT-3 RT-3 RT-3 KS-3 KS-3 KS-3 Top Mark RBA RBA RBA RBA RBA RBA Output Voltage (V) 1.200 1.200 1.200 1.200 1.200 1.200 Number of Parts per Reel 250 3,000 10,000 250 3,000 10,000 PIN FUNCTION DESCRIPTIONS Mnemonic Pin No. 1 2 3 SOT-23 V+ VOUT V- SC70 VOUT V+ V- Description High Supply Voltage Input Output Voltage Low Supply Voltage Input VOUT 2 V+ 1 PIN CONFIGURATIONS SOT-23 SC70 VOUT 1 ADR280 3 V- ADR280 V+ 2 3 V- 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 ADR280 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. -2- REV. A www..com Typical Performance Characteristics-ADR280 1.20225 1.20200 1.20175 VOUT (V) 1.20150 1.20125 1.20100 1.20075 1.20050 1.20025 1.20000 -40 -20 0 20 40 TEMPERATURE (C) 60 80 100 Ch1 50.0V M 1.00 s 1 NO LOAD TPC 1. VOUT vs. Temperature TPC 4. Noise Voltage Peak-to-Peak 10 Hz to 10 kHz 15 -40 NOISE POWER DENSITY (dBm) 60 80 100 14 13 IIN (A) -60 VIN = 5V 12 VIN = 3V -80 11 -100 10 9 -40 -20 0 20 40 TEMPERATURE (C) 0 2.5 5.0 FREQUENCY (kHz) 7.5 10.0 TPC 2. Supply Current vs. Temperature TPC 5. Output Noise Density Plot (VIN = 3.6 V, COUT = 1 F CIN = 1 F) , 15 -40dB 10 LINE REGULATION (ppm/V) 5 3V TO 5V 0 10dB/DIV -5 -10 -15 -40 -20 0 20 40 TEMPERATURE (C) 60 80 100 0Hz 100kHz TPC 3. Line Regulation vs. Temperature TPC 6. Voltage Noise Density 0 Hz to 100 kHz REV. A -3- www..com ADR280 1.2 tS 1.0 0.8 VOLTAGE (V) 0.6 0.4 0.2 0 0 2 4 6 8 10 12 14 16 18 20 TIME (ms) TPC 7. Settling Time THEORY OF OPERATION APPLICATIONS 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 their Vbes produces a PTAT (proportional to absolute temperature) voltage that cancels the CTAT (complementary to absolute temperature) 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 2). 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. V+ R1 I1 Q1 R3 R4 R13 PNP3 Q3 Q17 Q18 Q9 Q5 R6 R8 R11 Q6 R10 C1 R2 R12 Q2 Q10 The ADR280 should be decoupled with a 0.1 F ceramic cap at the output for optimum stability. It is also good practice to include 0.1 F ceramic caps at the IC supply pin. These capacitors should be mounted close to their respective pins (see Figure 3). V+ 0.1F ADR280 V- VOUT 0.1F Q7 Figure 3. Basic Configuration 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 4). 5V 0.1F VOUT V+ ADR280 V- 2.5V VOUT R7 R5 0.1F 1.2V V- R9 Figure 4. Floating References Figure 2. Simplified Architecture -4- REV. A www..com ADR280 The ADR280 provides the core 1.2 V band gap voltage and is able to drive a maximum load of only 100 A. Users can simply buffer the output for high current or sink/source current applications, such as ADC or LCD driver references (see Figure 5). U1 V+ 0.1F Precision Low Power Current Source By adding a buffer to redirect the IGND in Figure 8, a current can be precisely set by RSET with the equation IL = 1.2 V/RSET. U1 5V V+ ADR280 ADR280 V- VOUT V- VOUT U2 0.1F VOUT C2 U2 = AD8541, SC70 AD8601, SOT-23-5 RSET 12k 0.1F 5V U2 Figure 5. Buffered Output V+ AD8541 V- IL 100A Users can also tailor any specific need for voltage and dynamics with an external op amp and discrete components (see Figure 5). 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 pF. U1 5V V+ RL 1k IL = 1.2V/RSET Figure 8. Precision Low Power Current Source 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 9). U1 5V V+ 5V ADR280 V- 1.2V C1 0.1F VO 1.8V R2 60k 0.1% C2 U2 V+ AD8541 V- VOUT 5V U2 V+ V- C1 RSET 230 RL 500 + 1.2V - IL 5mA ADR280 V- 2.2pF VOUT R1 120k 0.1% 0.1F 5V U3 Figure 6. 1.8 V Reference LOW COST, LOW POWER CURRENT SOURCE V+ V- 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 7 produces 100 A with 2 V compliance at 5 V supply. The load current is the sum of ISET and IGND. IGND will increase slightly with load; an RSET of 13.6 k yields 100 A of load current. U1 5V V+ IL = 1.2V/RSET U2 = U3 = AD8542, AD822 Figure 9. Precision Current Source ADR280 V- ISET C1 + RSET 1.2V 0.1F - 13.6k RL 1k IL 100A VOUT IGND IL = ISET + IGND Figure 7. Low Cost Current Source REV. A -5- www..com ADR280 Negative Reference A negative reference can be precisely configured without using any expensive tight tolerance resistors, as shown in Figure 10. The voltage difference between VOUT and V- is 1.2 V. Since VOUT is at virtual ground, U2 will close the loop by forcing the V- pin to be the negative reference output. U1 +5V V+ VO 2.5V/100mA 5V U1 V+ RL 25 M1 ADR280 V- R2 10.8k 0.1% U2 C2 1pF 1.2V V+ AD8541 V- C1 VOUT 0.1F ADR280 V- VOUT C1 0.1F -VREF -1.2V R1 10k 0.1% M1 = FDB301N, 2N7000, 2N7002, OR EQUIVALENT U2 V+ AD8541 V- Figure 11. 2.5 V Boosted Reference GSM and 3G Mobile Station Applications -2.7V Figure 10. Negative Reference Boosted Reference with Scalable Output A precision user defined output with boosted current capability can be implemented with the circuit shown in Figure 11. 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 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. The ADR280 voltage reference is ideal for use with analog baseband ICs in GSM and 3G mobile station applications. Figure 12 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 and audio codecs, voltage regulators, and a battery charger. Besides low current consumption and a small footprint, the ADR280 is optimized for excellent power supply rejection ratio (PSRR) necessary for optimum AD6535 device performance when the main battery voltage fluctuates during RF power amplifier activity. DIGITAL BASEBAND AD6535 ANALOG BASEBAND BASEBAND CODEC RADIO AUDIO CODEC POWER MANAGEMENT ADR280 VOLTAGE REFERENCE Figure 12. GSM Mobile Station Application -6- REV. A www..com ADR280 OUTLINE DIMENSIONS 3-Lead Small Outline Transistor Package [SOT-23] (RT-3) Dimensions shown in millimeters 3.04 2.90 2.80 1.40 1.30 1.20 1 3 2 2.64 2.10 PIN 1 0.95 BSC 1.90 BSC 1.12 0.89 0.10 0.01 SEATING PLANE 0.50 0.30 0.60 0.50 0.40 0.20 0.08 COMPLIANT TO JEDEC STANDARDS TO-236AB Tape and Reel Dimensions (RT-3) Dimensions shown in millimeters 4.10 4.00 3.90 1.10 1.00 0.90 1.85 1.75 1.65 7" REEL 100.00 OR 13" REEL 330.00 0.35 0.30 0.25 20.20 MIN 1.55 1.50 1.50 14.40 MAX 2.05 2.00 1.95 8.30 8.00 7.70 2.80 2.70 2.60 1.50 MIN 3.55 3.50 3.45 3.20 3.10 2.90 1.00 MIN 0.75 MIN 13.20 13.00 12.80 7" REEL 50.00 MIN OR 13" REEL 100.00 MIN DIRECTION OF UNREELING 9.90 8.40 8.40 3-Lead Thin Shrink Small Outline Transistor Package [SC70] (KS-3) Dimensions shown in millimeters 2.20 1.80 1.35 1.15 1 3 2 2.40 1.80 PIN 1 1.00 0.80 0.65 BSC 1.10 MAX 0.18 0.10 0.10 MAX 0.40 0.25 0.10 COPLANARITY SEATING PLANE 0.30 0.10 REV. A -7- www..com ADR280 Revision History Location 6/03--Data Sheet changed from REV. 0 to REV. A. Page Added SC70 package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Universal 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 C03065-0-6/03(A) Changes to FEATURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 -8- REV. 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