a FEATURES Initial Accuracy: ⴞ5 mV Max, ⴞ0.27% Max Low Temperature Coefficient: 25 ppm/ⴗC Max Load Regulation: 100 ppm/mA Line Regulation: 25 ppm/V Low Supply Headroom: 0.6 V Wide Operating Range: (VOUT + 0.6 V) to 15 V Low Power: 120 A Max Shutdown to Less than 3 A Max Output Current: 5 mA Wide Temperature Range: 0ⴗC to 70ⴗC Tiny 5-Lead SOT-23 Package Precision Low Drift SOT-23 Voltage Reference with Shutdown ADR318* PIN CONFIGURATION 5-Lead SOT-23 SHDN 1 5 GND VIN 2 ADR318 VOUT (SENSE) 3 4 –VOUT (FORCE) APPLICATIONS Battery Powered Instrumentation Portable Medical Instruments Data Acquisition Systems Industrial Process Control Systems Fault Protection Critical Systems GENERAL DESCRIPTION The ADR318 is a precision 1.8 V band gap voltage reference featuring high accuracy, high stability, and low power consumption in a tiny footprint. Patented temperature drift curvature correction techniques minimize nonlinearity of the voltage change with temperature. The wide operating range and low power consumption with additional shutdown capability make the part ideal for battery powered applications. The VOUT (SENSE) pin enables greater accuracy by supporting full Kelvin operation in PCBs employing thin or long traces. The ADR318 is a low dropout voltage (LDV) device that provides a stable output voltage from supplies as low as 600 mV above the output voltage. This device is specified over the industrial operating range of 0°C to 70°C, and is available in the tiny 5-lead SOT-23 package. The combination of VOUT (SENSE) and shutdown functions also enables a number of unique applications, combining precision reference/regulation with fault decision and overcurrent protection. Details are provided in the Applications section. *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 © 2003 Analog Devices, Inc. All rights reserved. ADR318–SPECIFICATIONS ELECTRICAL CHARACTERISTICS (T = T A MIN Parameter Symbol Initial Accuracy Initial Accuracy Error Temperature Coefficient Minimum Supply Voltage Headroom Line Regulation VO VOERR TCVO VIN – VOUT ∆VOUT/∆VIN Load Regulation ∆VOUT/∆ILOAD Quiescent Current ISY Voltage Noise Turn-On Settling Time Long Term Stability2 Output Voltage Hysteresis Ripple Rejection Ratio Short Circuit to Ground eN tR ∆VOUT VO_HYS RRR ISC Shutdown Supply Current Shutdown Logic Input Current Shutdown Logic Low Shutdown Logic High ISHDN ILOGIC VINL VINH to TMAX,1 VIN = 5 V, unless otherwise noted.) Conditions Min Typ Max Unit 1.795 –0.27 1.8 5 1.802 +0.27 25 10 25 V % ppm/°C mV ppm/V 100 ppm/mA 120 140 µA µA µV p-p µs ppm/1,000 hrs ppm dB mA mA µA nA V V 0°C to 70°C 600 VIN = 2.5 V to 15 V 0°C < TA < 70°C VIN = 3 V, ILOAD = 0 mA to 5 mA 0°C < TA < 70°C No load 0°C < TA < 70°C 0.1 Hz to 10 Hz 100 5 20 50 40 85 25 30 fIN = 60 Hz VIN = 5.0 V VIN = 15.0 V 3 500 0.8 2.4 NOTES 1 TMIN = 0°C, TMAX = 70°C 2 The long-term stability specification is noncumulative. The drift in subsequent 1,000 hour periods is significantly lower than in the first 1,000 hour period. Specifications subject to change without notice. –2– REV. 0 ADR318 ABSOLUTE MAXIMUM RATINGS 1, 2 Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 V Output Short-Circuit Duration to GND . . . . . . . . . . . . . . . . . . . . . Observe Derating Curves Storage Temperature Range RJ Package . . . . . . . . . . . . . . . . . . . . . . . . . –65°C to +125°C Operating Temperature Range . . . . . . . . . . . . . . . 0°C to 70°C Junction Temperature Range RJ Package . . . . . . . . . . . . . . . . . . . . . . . . . –65°C to +150°C Lead Temperature Range Soldering, 60 sec . . . . . . . . . . . . . . . . . . . . . . . . . . . . 300°C Package Type JA JC Unit 5-Lead SOT-23 (RJ) 230 146 °C/W NOTES 1 Absolute maximum ratings apply at 25°C, unless otherwise noted. 2 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 listed in the operational sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ORDERING GUIDE Model Temperature Range Package Description Package Option Branding Information Output Voltage Devices per Reel ADR318ARJ-REEL7 0ºC to 70ºC 5-Lead SOT-23 RJ-5 R0A 1.800 V 3,000 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 ADR318 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– ADR318–Typical Performance Characteristics 110 1.802 –30 1.800 1.799 1.798 0 10 20 30 40 50 TEMPERATURE – ⴗC 60 100 90 0ⴗC 80 70 2.5 70 5.0 7.5 10.0 12.5 INPUT VOLTAGE – V 0 10V –50 –60 2.5V –70 –80 15.0 TPC 2. Supply Current vs. Input Voltage TPC 1. Typical Output Voltage vs. Temperature 0 10 20 30 40 50 TEMPERATURE – ⴗC 60 70 TPC 3. Load Regulation vs. Temperature 2.5 –5 –10 –15 25ⴗC 2.1 1.9 –20 –25 0ⴗC VOLTAGE – 2mV/DIV 2.3 VIN_MIN – V LINE REGULATION – ppm/mV 25ⴗC –40 70ⴗC 0 10 20 30 40 50 TEMPERATURE – ⴗC 60 1.7 70 0 1 2 3 4 TPC 4. Line Regulation vs. Temperature TPC 7. Typical Output Voltage Noise 10 Hz to 10 kHz TIME – 400ms/DIV TPC 6. Typical Output Voltage Noise 0.1 Hz to 10 Hz TPC 5. Minimum Input Voltage vs. Load Current VOLTAGE – 50mV/DIV VOLTAGE – 10mV/DIV TIME – 10ms/DIV 5 LOAD CURRENT – mA VOLTAGE – 50mV/DIV VOUT – V 1.801 LOAD REGULATION – ppm/mA SUPPLY CURRENT – A 70ⴗC TIME – 40s/DIV TPC 8. Line Transient Response, CBYPASS = 0 µ F –4– TIME – 40s/DIV TPC 9. Line Transient Response, CBYPASS = 0.1 µ F REV. 0 TIME – 200s/DIV TPC 10. Load Transient Response, CL = 0 nF TPC 11. Load Transient Response, CL = 1 nF TPC 13. Turn On/Turn Off Response at 5 V, RLOAD = 1.8 kΩ REV. 0 LOAD OFF LOAD ON TIME – 200s/DIV TPC 12. Load Transient Response, CL = 100 nF VOUT VIN VOLTAGE – 2V/DIV VOLTAGE – 50mV/DIV TIME – 40s/DIV LOAD ON TIME – 200s/DIV VIN VOUT LOAD OFF VOLTAGE – 200mV/DIV LOAD ON VOUT TIME – 100s/DIV TPC 14. Turn On/Turn Off Response at 5 V, RLOAD = 1.8 kΩ, CBYPASS = 0.1 µ F –5– VOLTAGE – 1V/DIV LOAD OFF VOLTAGE – 200mV/DIV VOLTAGE – 200mV/DIV ADR318 SHUTDOWN PIN TIME – 4s/DIV TPC 15. Shutdown Pin Response ADR318 PARAMETER DEFINITIONS Temperature Coefficient THEORY OF OPERATION Band gap references are the high performance solution for low supply voltage and low power voltage reference applications, and the ADR318 is no exception. The uniqueness of this product lies in its architecture. By observing Figure 1, the ideal zero TC band gap voltage is referenced to the output, not to ground. Therefore, if noise exists on the ground line, it will be greatly attenuated on VOUT. The band gap cell consists of the PNP pair Q51 and Q52, running at unequal current densities. The difference in VBE results in a voltage with a positive TC that is amplified by the ratio of 2 ⫻ R58/R54. This PTAT voltage, combined with the VBEs of Q51 and Q52, produces the stable band gap voltage. Temperature coefficient is the change of output voltage with respect to operating temperature changes, normalized by the output voltage at 25°C. This parameter is expressed in ppm/°C, and can be determined with the following equation: VO (T2 ) – VO (T1 ) ppm TCVO × 106 = – C V C T T ° 25 ° × ( ) ( ) 2 1 O (1) where: VO(25°C) = VO at 25°C VO(T1) = VO at temperature 1 Reduction in band gap curvature is performed by the ratio of the resistors R44 and R59, one of which is linearly temperature dependent. Precision laser trimming and other patented circuit techniques are used to further enhance the drift performance. VO(T2) = VO at temperature 2 Long Term Stability Long term stability is the typical shift of output voltage at 25°C on a sample of parts subjected to a test of 1,000 hours at 25°C: VIN ∆VO = VO (t0 ) −VO (t1) ∆VO [ ppm ] = VO (t0 ) −VO (t1) VO (t0 ) Q1 VOUT(FORCE) (2) × 106 VOUT(SENSE) R59 where: R44 R58 R49 VO(t0) = VO at 25°C at time 0 R54 VO(t1) = VO at 25°C after 1,000 hours operation at 25°C Thermal Hysteresis R53 Thermal hystereses is defined as the change of output voltage after the device is cycled through temperature 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. Q51 Q52 SHDN R48 R60 VO _ HYS = VO (25°C ) −VO _ TC VO _ HYS [ ppm ] = VO (25°C ) −VO _ TC VO (25°C ) R61 GND × 106 Figure 1. Simplified Schematic (3) Device Power Dissipation Considerations The ADR318 is capable of delivering load currents up to 5 mA with an input voltage that ranges from 2.4 V to 15 V. When this device is used in applications with high input voltages, care should be taken to avoid exceeding the specified maximum power dissipation or junction temperature that could result in premature device failure. The following formula should be used to calculate the device’s maximum junction temperature or dissipation: where: VO(25°C) = VO at 25°C VO_TC = VO at 25°C after temperature cycle at +25°C to –40°C to +125°C and back to +25°C PD = TJ − TA θ JA (4) In Equation 4, TJ and TA are, respectively, the junction and ambient temperatures, PD is the device power dissipation, and θJA is the device package thermal resistance. Shutdown Mode Operation The ADR318 includes a shutdown feature that is TTL/CMOS compatible. A logic LOW or a 0 V condition on the SHDN pin is required to turn the device off. During shutdown, the output of the reference becomes a high impedance state where its potential would then be determined by external circuitry. If the shutdown feature is not used, the SHDN pin should be connected to VIN (Pin 2). –6– REV. 0 ADR318 APPLICATIONS Basic Voltage Reference Connection General-Purpose 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, the ADR318 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 R1, 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 90 mA to approximately 5 mA. The supply current is a function of ISET and will increase slightly at a given ISET. The circuit in Figure 2 illustrates the basic configuration for the ADR318. Decoupling capacitors are not required for circuit stability. The ADR318 is capable of driving capacitative loads from 0 µF to 10 µF. However, a 0.1 µF ceramic output capacitor is recommended to absorb and deliver the charge as is required by a dynamic load. GND SHDN SHUTDOWN ADR318 INPUT VIN CI 0.1F VOUT(S) +VDD VOUT(F) ADR318 U1 OUTPUT CO VIN 0.1F VOUT(F) SHDN VOUT(S) Figure 2. Voltage Reference Connection GND Precision Negative Voltage Reference without Precision Resistors ISET 0.1F A negative reference can be easily generated by combining the ADR318 with an op amp. Figure 3 shows this simple negative reference configuration. VOUT(F) and VOUT(S) are at virtual ground and therefore the negative reference can be taken directly from the output of the op amp. The op amp should be a dual-supply, low offset, rail-to-rail amplifier, such as the OP1177. ISY ADJ ISY (ISET) RL IOUT = ISET + ISV (ISET) Figure 4. General-Purpose Current Source +VDD ADR318 VIN VOUT(F) SHDN VOUT(S) GND –VREF OP1177 –VSS Figure 3. Negative Reference REV. 0 R1 –7– ADR318 A similar circuit function can also be achieved using the Darlington transistor configuration, as shown in Figure 6. High Power Performance with Current Limit In some cases, the user may want higher output current delivered to a load and still achieve better than 0.5% accuracy out of the ADR318. The accuracy for a reference is normally specified on the data sheet with no load. However, the output voltage changes with load current. VIN ADR318 R1 4.7k⍀ SHDN VOUT(S) GND Q1 VOUT(F) Q2 The transistor Q2 protects Q1 during short circuit limit faults by robbing its base drive. The maximum current is IL, MAX = 0.6 V/RS. RS RL VIN ADR318 R1 C03431–0–1/03(0) VIN The circuit in Figure 5 provides high current without compromising the accuracy of the ADR318. The power BJT Q1 provides the required current, up to a 1 A. The ADR318 delivers the base drive to Q1 through the force pin. The sense pin of the ADR318 is a regulated output and is connected to the load. Figure 6. High Output Current with Darlington Drive Configuration 4.7k⍀ VIN SHDN VOUT(S) GND Q1 VOUT(F) Q2 RS RL Figure 5. High Power Performance with Current Limit OUTLINE DIMENSIONS 5-Lead Plastic Surface-Mount Package [SOT-23] (RJ-5) Dimensions shown in millimeters 2.90 BSC 5 4 2.80 BSC 1.60 BSC 2 3 PRINTED IN U.S.A. 1 PIN 1 0.95 BSC 1.30 1.15 0.90 1.90 BSC 1.45 MAX 0.15 MAX 0.50 0.30 SEATING PLANE 0.22 0.08 10ⴗ 0ⴗ 0.60 0.45 0.30 COMPLIANT TO JEDEC STANDARDS MO-178AA –8– REV. 0