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| Precision Low Power 2.048 V SOT-23 Voltage Reference ADR370* FEATURES Initial Accuracy: 4 mV Max Initial Accuracy Error: 0.2% Low TCVO: 50 ppm/ C Max from -40 C to +125 C, 630 ppm/ C Max from +25 C to +70 C Load Regulation: 200 V/mA, 100 ppm/mA Line Regulation: 25 V/V, 20 ppm/V Wide Operating Range: VIN = 2.3 V to 12 V Low Power: 72 A Max High Output Sink/Source Current: 5 mA Min Wide Temperature Range: -40 C to +125 C Tiny 3-Lead SOT-23 Package with Standard Pinout APPLICATIONS Battery Powered Instrumentation Portable Medical Instruments Data Acquisition Systems Industrial Process Control Systems Automotive PIN CONFIGURATION 3-Lead SOT-23 VIN 1 ADR370 VOUT 2 3 GND Table I. ADR370 Products GENERAL DESCRIPTION The ADR370 is a low cost, 3-terminal (series) band-gap voltage reference featuring high accuracy, high stability, and low power consumption packaged in a tiny 3-lead SOT-23 package. Precise matching and thermal tracking of on-chip components as well as patented temperature drift curvature correction design techniques have been employed to ensure that the ADR370 provides an accurate 2.048 V output. This micro-powered, low dropout voltage device will source or sink up to 5 mA of load current while providing a stable 2.048 V output. The compact footprint, high accuracy, and an operating range of 2.3 V to 12 V make the ADR370 ideal for use in 3 V and 5 V systems where there may be wide variations in supply voltage and a need to minimize power dissipation. The ADR370 is offered in A and B grades; all devices are specified over the extended industrial range of -40C to +125C. Products ADR370BRT-REEL7 ADR370ART-REEL7 Output Voltage (VO) 2.048 2.048 Initial Accuracy (mV) (%) 4 10 0.2 0.5 Tempco (ppm/C) 50 100 *Protected by U.S.Patent No. 5,969,657; other patents pending. 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. 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.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781/329-4700 www.analog.com Fax: 781/326-8703 (c) 2003 Analog Devices, Inc. All rights reserved. ADR370-SPECIFICATIONS ELECTRICAL CHARACTERISTICS (T = T A MIN to TMAX, VIN = 5 V, unless otherwise noted.) Min 2.044 -10 -0.5 -4 -0.2 Typ Max Unit V mV % mV % ppm/C ppm/C mV mV/mA mV/mA mV/mA ppm/V dB A A V p-p V rms s ppm/1,000 hrs ppm C Parameter Output Voltage (@25C) Initial Accuracy Error A Grade B Grade Output Voltage Temperature Drift Supply Headroom Load Regulation Symbol VO VOERR VOERR VOERR VOERR Conditions 2.048 2.052 +10 +0.5 +4 +0.2 50 30 -40C to +125C 25C to 70C VIN - VOUT 0 mA < IOUT < 5 mA @ 25C -3 mA < IOUT < 0 mA @ 25C -0.1 mA < IOUT < +0.1 mA VOUT 200 mV < VIN < 12 V IOUT = 0 mA VIN = 5 V 100 mV (f = 120 Hz) 0.1 Hz to 10 Hz 10 Hz to 10 kHz CL = 0.2 F 1,000 Hours @ 25C 115 -40 200 -0.200 -0.480 -0.425 Line Regulation Ripple Rejection Quiescent Current Short Circuit Current to Ground Noise Voltage (@25C) Turn-On Settling Time Long Term Stability Output Voltage Hysteresis Temperature Range Specifications subject to change without notice. +0.200 +0.480 +0.425 20 VOUT/VIN 80 72 15 70 50 100 100 +125 -2- REV. 0 ADR370 ABSOLUTE MAXIMUM RATINGS* Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 V Storage Temperature Range RT Package . . . . . . . . . . . . . . . . . . . . . . . . -65C to +125C Operating Temperature Range . . . . . . . . . . . -40C to +125C Lead Temperature Range Soldering, 60 sec . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215C Infrared, 15 sec . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220C *Absolute maximum ratings apply at 25C, unless otherwise noted. Package Type 3-SOT-23 (RT) JA JC Unit C/W 220 102 ORDERING GUIDE Model Output Voltage (VO) Initial Accuracy (mV) (%) 4 10 0.2 0.5 Temperature Number Coefficient Package Package of Parts (ppm/C) Description Option Branding per Reel 50 100 SOT-23 SOT-23 3-Lead 3-Lead RPB RPA 3,000 3,000 Temperature Range -40C to +125C -40C to +125C ADR370BRT-REEL7 2.048 ADR370ART-REEL7 2.048 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 ADR370 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 -3- ADR370-Typical Performance Characteristics 12 10 LINE REGULATION - ppm/V 6 VIN 5V TO 15V 4 2 0 -2 -4 -6 -8 -10 -40 8 -40 C 6 VO - mV 4 +125 C 2 0 -2 -4 +25 C -4 -3 -2 -1 0 1 LOAD - mA 2 3 4 5 45 TEMPERATURE - C 125 TPC 1. Load Regulation vs. Load Current TPC 4. Line Regulation vs. Temperature 2.048 0 0 2.046 VIN = 5V OUTPUT VOLTAGE - V VIN = 15V 2.044 VOLTAGE - 10 V/DIV 0 0 0 0 0 2.042 2.040 2.038 0 2.036 -40 45 TEMPERATURE - C 125 0 0 0 0 0 0 0 0 TIME - 0.1s/DIV 0 0 0 0 TPC 2. Output Voltage vs. Temperature TPC 5. Voltage Noise 0.1 Hz to 10 Hz 80 0 0 70 A VIN = 15V 60 VIN = 5V VOLTAGE - 200 V/DIV 0 0 0 0 0 SUPPLY CURRENT - 50 40 30 0 20 -40 45 TEMPERATURE - C 125 0 0 0 0 0 0 0 0 TIME - 0.1s/DIV 0 0 0 0 TPC 3. Supply Current vs. Temperature TPC 6. Voltage Noise 10 Hz to 100 kHz -4- REV. 0 ADR370 0 0 0 VOLTAGE - V VOLTAGE - V 0 CBY = 0.1 F CLOAD = 0.22 F VOUT = 1V/DIV 0 VIN = 1V/DIV 0 0 0 VOUT = 1V/DIV 0 0 0 0 0 0 0 0 0 0 TIME - 100 s/DIV 0 0 0 0 0 0 0 0 0 0 0 TIME - 100 s/DIV 0 0 0 0 CL = 0.1 F 0 0 0 0 VIN = 5V/DIV 0 0 0 TPC 7. Turn-On Response TPC 9. Line Transient Response 0 RLOAD = 1k 0 0 VOUT = 1V/DIV VOLTAGE - V VOLTAGE - V 0 0 0 0 0 VIN = 2V/DIV 0 0 0 0 CBY = 0.1 F CLOAD = 0.1 F VOUT = 20mV/DIV 0 0 0 VIN = 5V/DIV 0 0 0 0 0 0 0 0 0 0 TIME - 100 s/DIV 0 0 0 0 0 0 0 0 0 0 0 TIME - 100ms/DIV 0 0 0 0 TPC 8. Turn-Off Response TPC 10. Load Transient Response REV. 0 -5- ADR370 PARAMETER DEFINITIONS Temperature Coefficient THEORY OF OPERATION Temperature coefficient is the change of output voltage with respect to operating temperature changes, normalized by the output voltage at 25C. This parameter is expressed in ppm/C, and can be determined with the following equation: VO (T2 ) - VO (T1) ppm 6 TCVO ppm = V (25C ) x (T - T ) x 10 C 2 1 O (1) Where: VO(25C) = VO at 25C VO(T1) = VO at temperature 1 VO(T2) = VO at temperature 2 Line Regulation Line regulation is the change in output voltage 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, parts-per-million per volt, or microvolts per volt change in input voltage. Load Regulation The ADR370 uses the band gap concept to produce a stable, low temperature coefficient voltage reference suitable for high accuracy data acquisition components and systems. This device makes use of underlying temperature characteristics of a silicon transistor's base-emitter voltage (VBE) in the forward biased operating region. Under this condition, all such transistors have a -2 mV/C temperature coefficient (TC) and a VBE that, when extrapolated to absolute zero, 0 K, (with collector current proportional to absolute temperature) approximates the silicon band-gap voltage. By summing a voltage that has an equal and opposite temperature coefficient of 2 mV/C with a VBE of a forward biased transistor, an almost zero TC reference can be developed. The simplified circuit diagram in Figure 1 shows how a compensating voltage, V1, is achieved by driving two transistors at different current densities and amplifying the resultant VBE difference (VBE, which has a positive TC). The sum (VBG) of VBE and V1 is then buffered and amplified to produce a stable reference voltage of 2.048 V at the output. VIN R4 R3 VOUT R5 VDS R2 R6 R1 V1 GND Load regulation is 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. Long Term Stability Long term stability is the typical shift of output voltage at 25C on a sample of parts subjected to a test of 1,000 hours at 25C: VO = VO (t0 ) - VO (t1) VO [ ppm ] = Where: VO(T1) = VO at 25C at time 0 VO(T2) = VO at 25C after 1,000 hours operation at 25C Thermal Hysteresis VO (t0 ) - VO (t1) VO (t0 ) x 10 6 (2) Figure 1. Simplified Schematic Applying the ADR370 Thermal hysteresis is defined as the change of output voltage after the device is cycled through temperature from +25C to -40C to +125C and back to +25C. This is a typical value from a sample of parts put through such a cycle. VO _ HYS = VO (25C ) -VO _ TC VO _ HYS [ ppm ] = Where: VO(25C) = VO at 25C VO_TC = VO at 25C after temperature cycle at +25C to -40C to +125C and back to +25C. VO (25C ) -VO _ TC VO (25C ) In order to achieve the specified performance, two external components should be used in conjunction with the ADR370, a 4.7 F capacitor and a 1 F capacitor should be applied to the input and output, respectively. Figure 2 shows the ADR370 with both the input and output capacitors attached. For further transient response optimization, an additional 0.1 F capacitor in parallel with the 4.7 F input capacitor can be used. A 1 F output capacitor will provide stable performance for all loading conditions. The ADR370 can, however, operate under low (-100 A < IOUT < +100 A) current conditions with just a 0.2 F output capacitor and a 1 F input capacitor. VIN CIN 4.7 F x 106 (3) ADR370 GND VOUT COUT 1F Figure 2. Typical Connection Diagram -6- REV. 0 ADR370 APPLICATIONS Low Cost Negative Reference VL + 2.5V < VDD < VL + 12V ADR370 VIN VOUT RSET ISET = VL Iq = 65 A RL IL 2.048V RSET A low cost negative reference can be obtained by leveraging the current sinking capability of the ADR370. Simply tying the VOUT terminal to ground and adding a bias resistor, RSET, to the GND pin of the device, a negative voltage reference can be obtained as shown in Figure 3. RSET should be chosen such that ISET remains between 1 mA to 5 mA. GND VDD ADR370 VIN VOUT Figure 5. Low Cost Current Source Precision Current Source with Adjustable Output GND -VREF RSET ISET A precision current source can be implemented with the circuit shown in Figure 6. By adding a mechanical or digital potentiometer, this circuit becomes an adjustable current source. If a digital potentiometer like the AD5201 is used, the load current is simply the voltage across terminals B-to-W of the digital potentiometer divided by RSET: IL = VREF x D RSET x 256 (5) VSS Figure 3. Low Cost Negative Reference Precision Negative Reference Without using any matching resistors, a precision negative reference can be obtained using the configuration shown in Figure 4. The voltage difference between VOUT and GND of the ADR370 is 2.048 V. Since VOUT is at virtual ground, U2 will close the loop by forcing the GND pin to be the negative reference node. U2 should be a low offset voltage precision op amp, such as the OP1177. U1 2.3V TO 12V where D is the decimal equivalent of the digital potentiometer input code. 12V ADR370 0V TO (2.048V + VL) VIN VOUT B GND W AD5201 A ADR370 VIN VOUT +15V GND -VREF U2 -2.048V TO VL RSET +12V OP1177 -12V RL IL VL OP1177 -15V Figure 4. Precision Negative Reference Low Cost Current Source Figure 6. Programmable 0 mA to 5 mA Current Source Figure 5 illustrates how a simple, low cost current source can be configured using the ADR370. The load current, IL, is simply the sum of ISET and the quiescent current, Iq. ISET is simply the reference voltage generated by the ADR370 divided by RSET. I SET 2.048V = RSET To optimize the resolution of this circuit, dual supply op amps should be used because the ground potential of ADR370 can swing from -2.048 V at zero scale to VL at full scale of the potentiometer setting. 12-Bit Precision Programmable Current Source (4) The quiescent current, Iq, varies slightly with load. The variation in Iq limits the use of this circuit to general-purpose applications. By replacing the potentiometer in Figure 6 with a 12-bit precision DAC like the AD5322, a higher precision programmable current source can be achieved. Figure 7 illustrates the implementation of this circuit. The load current can be determined with the following equation: IL = RSET x 4096 VREF (1 - D) (6) The compliance voltage should be kept low so that the supply voltage to U2, between VDD and GND, does not fall below 2.5 V. REV. 0 -7- ADR370 U1 +5V VDD 4V TO 12V ADR370 VIN VOUT U2 GND +5V VDD GND 1 U3 V+ V- 11 -5V RL IL VIN VO +5V 2 3 TOL 0.05% VREF (1 - D2/N) R1 10k 2N3906 Q1 ADR370 RSET VIN VOUT GND VL RL IL OP1177 Figure 8. Precision Boosted Output Regulator Figure 7. 12-Bit Programmable Current Source Precision Boosted Output Regulator A precision voltage output with boosted current can be realized with the circuit shown in Figure 8. In this circuit, VO is maintained by the ADR370 at 2.048 V. The ADR370 sources a maximum of 5 mA if the load current, IL, is more than 5 mA, current is furnished by the transistor, Q1, and the input voltage supply VDD. Q1 will be turned on to regulate current as needed. R1 is required to bias the base of the Q1, and must be large enough to comply with the supply current requirements of the ADR370. The supply voltage can be as low as 4 V. The maximum current output of this circuit is limited by the power dissipation of the bipolar transistor, Q1. PDISS = ( DD - 2.048) x I L V (7) Using the 2N3906 PNP transistor shown in Figure 8 and a 4 V power supply, RL should be chosen so that a maximum of 100 mA is drawn from the circuit, which limits the power dissipation of Q1 to ~200 mW. TAPE AND REEL DIMENSIONS Dimensions shown in millimeters. 4.10 4.00 3.90 2.05 2.00 1.95 1.85 1.75 1.65 OUTLINE DIMENSIONS 3-Lead Plastic Surface-Mount Package [SOT-23] (RT-3) Dimensions shown in millimeters. 0.35 0.30 0.25 1.55 1.50 1.50 1.10 1.00 0.90 8.30 8.00 7.70 2.80 2.70 2.60 3.04 2.90 2.80 1.40 1.30 1.20 1 3.55 3.50 3.45 3.20 3.10 2.90 1.00 MIN 0.75 MIN 3 2.64 2.10 2 PIN 1 0.95 BSC 1.90 BSC 1.12 0.89 14.40 MAX DIRECTION OF UNREELING 7" REEL 100.00 OR 13" REEL 330.00 0.10 0.01 SEATING PLANE 0.50 0.30 0.60 0.50 0.40 0.20 0.08 0.69 REF 1.50 MIN 20.20 MIN 13.20 13.00 12.80 7" REEL 50.00 MIN OR 13" REEL 100.00 MIN COMPLIANT TO JEDEC STANDARDS TO-236AB 9.90 8.40 8.40 -8- REV. 0 PRINTED IN U.S.A. C03432-0-1/03(0) AD8532 |
Price & Availability of ADR370
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