Final Electrical Specifications LT1790-2.5 2.5V Micropower SOT-23 Low Dropout Reference March 2000 U FEATURES ■ ■ ■ ■ ■ ■ ■ DESCRIPTIO The LT®1790-2.5 is a SOT-23 micropower low dropout series reference that combines high accuracy and low drift with low power dissipation and small package size. This micropower reference uses curvature compensation to obtain a low temperature coefficient and trimmed precision thin-film resistors to achieve high output accuracy. In addition, the LT1790-2.5 uses post-package trimming to greatly reduce the temperature coefficient and increase the output accuracy. Output accuracy is further assured by excellent line and load regulation. Special care has been taken to minimize thermally induced hysteresis. High Accuracy: A Grade—0.05% Max B Grade—0.1% Max Low Drift: A Grade—10ppm/°C Max B Grade—25ppm/°C Max Low Supply Current: 60µA Max Sinks and Sources: 5mA Min Low Dropout Voltage Guaranteed Operational –40°C to 125°C Wide Supply Range: 2.6V to 18V The LT1790-2.5 is ideally suited for battery-operated systems because of its small size, low supply current and reduced dropout voltage. This reference provides supply current and power dissipation advantages over shunt references that must idle the entire load current to operate. However, since the LT1790-2.5 can also sink current, it can operate as a micropower negative voltage reference with the same performance as a positive reference. U APPLICATIO S ■ ■ ■ ■ ■ Handheld Instruments Negative Voltage References Industrial Control Systems Data Acquisition Systems Battery-Operated Equipment , LTC and LT are registered trademarks of Linear Technology Corporation. U TYPICAL APPLICATIO Typical VOUT Distribution 50 167 UNITS 45 2.6V ≤ VIN ≤ 18V 0.1µF 4 LT1790-2.5 1, 2 6 VOUT = 2.5V 1µF 1790 TA01 NUMBER OF UNITS 40 Positive Connection LT1790BC LIMITS 35 LT1790AC LIMITS 30 25 20 15 10 5 0 2.498 2.499 2.500 2.501 OUTPUT VOLTAGE (V) 2.502 1790 TA02 Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights. 1 LT1790-2.5 W U U U W W W ABSOLUTE MAXIMUM RATINGS PACKAGE/ORDER INFORMATION (Note 1) Input Voltage .......................................................... 20V Specified Temperature Range ..................... 0°C to 70°C Operating Temperature Range (Note 2) ........................................... – 40°C to 125°C Storage Temperature Range (Note 3) ........................................... – 65°C to 150°C Lead Temperature (Soldering, 10 sec)................. 300°C ORDER PART NUMBER TOP VIEW GND 1 6 VOUT GND 2 5 DNC* DNC* 3 LT1790ACS6-2.5 LT1790BCS6-2.5 4 VIN S6 PART MARKING S6 PACKAGE 6-LEAD PLASTIC SOT-23 TJMAX = 150°C, θJA = 230°C/W LTMX LTMZ *DNC: DO NOT CONNECT Consult factory for Industrial and Military grade parts. ELECTRICAL CHARACTERISTICS The ● denotes specifications that apply over the specified temperature range, otherwise specifications are at TA = 25°C. VIN = 3V, CL = 1µF unless otherwise specified. PARAMETER CONDITIONS MIN TYP MAX Output Voltage (Notes 3, 4) LT1790ACS6-2.5 2.49875 –0.05 2.50 2.50125 0.05 V % LT1790BCS6-2.5 2.4975 –0.1 2.50 2.5025 0.1 V % 5 12 10 25 ppm/°C ppm/°C 50 170 220 ppm/V ppm/V 80 70 160 250 110 ppm/mA ppm/mA ppm/mA 60 300 40 100 400 250 mV mV mV 35 60 75 µA µA 125 µA Output Voltage Temperature Coefficient (Note 5) LT1790ACS6-2.5 LT1790BCS6-2.5 Line Regulation 3V ≤ VIN ≤ 18V ● ● ● Load Regulation (Note 6) Dropout Voltage (Note 7) Supply Current IOUT Source = 5mA IOUT Source = 5mA IOUT Sink = 5mA ● VIN – VOUT, ∆VOUT ≤ 0.1% IOUT = 0mA IOUT Source = 5mA IOUT Sink = 5mA ● ● VOUT = 2.5V ● UNITS Minimum Current VOUT = – 2.5V 100 Turn-On Time CLOAD = 1µF 700 µs Output Noise (Note 8) 0.1Hz ≤ f ≤ 10Hz 10Hz ≤ f ≤ 1kHz 12 33 µVP-P µVRMS 50 ppm/√kHr 40 60 ppm ppm Long-Term Drift of Output Voltage (Note 9) Hysteresis (Note 10) ∆T = 0°C to 70°C ∆T = – 40°C to 85°C Note 1: Absolute Maximum Ratings are those values beyond which the life of the device may be impaired. Note 2: The LT1790S6 is guaranteed functional over the operating temperature range of – 40°C to 125°C. Note 3: If the part is stored outside of the specified temperature range, the output voltage may shift due to hysteresis. 2 ● ● Note 4: ESD (Electrostatic Discharge) sensitive device. Extensive use of ESD protection devices are used internal to the LT1790, however, high electrostatic discharge can damage or degrade the device. Use proper ESD handling precautions. LT1790-2.5 ELECTRICAL CHARACTERISTICS Note 5: Temperature coefficient is measured by dividing the change in output voltage by the specified temperature range. Incremental slope is also measured at 25°C. Note 6: Load regulation is measured on a pulse basis from no load to the specified load current. Output changes due to die temperature change must be taken into account separately. Note 7: Excludes load regulation errors. Note 8: Peak-to-peak noise is measured with a single pole highpass filter at 0.1Hz and a 2-pole lowpass filter at 10Hz. The unit is enclosed in a still air environment to eliminate thermocouple effects on the leads. The test time is 10 seconds. RMS noise is measured with a single pole highpass filter at 10Hz and a 2-pole lowpass filter at 1kHz. The resulting output is full-wave rectified and then integrated for a fixed period, making the final reading an average as opposed to RMS. A correction factor of 1.1 is used to convert from average to RMS and a second correction of 0.88 is used to correct for the nonideal bandpass of the filters. Note 9: Long-term drift typically has a logarithmic characteristic and therefore changes after 1000 hours tend to be smaller than before that time. Total drift in the second thousand hours is normally less than one third that to the first thousand hours with a continuing trend toward reduced drift with time. Long-term drift is affected by differential stress between the IC and the board material created during board assembly. See Applications Information. Note 10: Hysteresis in the output voltage is created by package stress that differs depending on whether the IC was previously at a higher or lower temperature. Output voltage is always measured at 25°C, but the IC is cycled to 85°C or – 40°C before a successive measurements. Hysteresis is roughly proportional to the square of the temperature change. Hysteresis is not normally a problem for operational temperature excursions where the instrument might be stored at high or low temperature. See Applications Information. U W TYPICAL PERFOR A CE CHARACTERISTICS Minimum Input-Output Voltage Differential (Sourcing) Series Mode Output Voltage Temperature Drift 2.508 Minimum Input-Output Voltage Differential (Sinking) Series Mode 10 FOUR TYPICAL PARTS 90 2.504 2.502 2.500 2.498 TA = –55°C VOLTAGE DIFFERENTIAL (mV) OUTPUT CURRENT (mA) OUTPUT VOLTAGE (V) 2.506 TA = 125°C TA = 25°C 1 2.496 0.1 2.494 –50 –30 –10 10 30 50 70 90 110 130 TEMPERATURE (°C) 0 0.1 0.2 0.3 0.4 0.5 INPUT-OUTPUT VOLTAGE (V) TA = 125°C –3 –4 1 OUTPUT CURRENT (mA) –10 80 70 10 1790 616 TA = –55°C 4 3 TA = –55°C 2 TA = 125°C 1 0 0.1 1mA 5mA Supply Current vs Input Voltage 0.1 1 OUTPUT CURRENT (mA) 60 50 TA = 25°C 40 30 TA = 125°C 20 10 TA = 25°C –5 10 1790 G15 SUPPLY CURRENT (µA) OUTPUT VOLTAGE CHANGE (mV) OUTPUT VOLTAGE CHANGE (mV) TA = 25°C 100µA –30 –50 –30 –10 10 30 50 70 90 110 130 TEMPERATURE (°C) 0.6 5 TA = –55°C –2 30 Load Regulation (Sinking) Load Regulation (Sourcing) –1 50 1790 G14 1790 G13 0 70 10 0 0 5 10 15 20 INPUT VOLTAGE (V) 1790 617 1790 G18 3 LT1790-2.5 U W TYPICAL PERFOR A CE CHARACTERISTICS Power Supply Rejection Ratio vs Frequency Line Regulation 2.515 TA = 125°C OUTPUT VOLTAGE (V) 2.510 2.505 TA = 25°C 2.500 TA = –55°C 2.495 2.490 2.489 0 2 4 10 CL = 1µF CL = 0.47µF 0 –10 –20 –30 –40 –50 CL = 4.7µF 10 –70 1k 10k 100k FREQUENCY (Hz) 1M 1 100 1k 10k FREQUENCY (Hz) Long-Term Drift (Data Points Reduced After 500 Hr) – 2.5V Characteristics 140 0.30 TA = 30°C 120 2 TYPICAL PARTS SOLDERED TO PCB R1 10k 3V 4 0.25 LT1790-2.5 0.20 80 VOUT RL 5k 1µF 60 ppm 0.15 100 6 1, 2 –VEE 40 20 0.10 0 TA = 25°C TA = 125°C TA = –55°C 0.05 –20 –40 0 –4.0 –3.5 –3.0 –2.5 –2.0 –1.5 –1.0 –0.5 OUTPUT TO GROUND VOLTAGE (V) –60 0 0 200 600 400 HOURS 1790 G22 800 1000 1790 G23 Output Noise 0.1Hz to 10Hz Output Voltage Noise Spectrum OUTPUT NOISE (5µV/DIV) NOISE VOLTAGE (µV/√Hz) 10 CL = 1µF 8 6 IO = 0µA IO = 100µA 4 IO = 250µA 2 IO = 1mA 0 0 1 2 3 4 5 6 TIME (SEC) 7 8 9 10 1790 G24 4 10 100k 1790 G21 1790 G20 1790 G19 CURRENT IN RL (mA) CL = 1µF 100 –60 –80 100 6 8 10 12 14 16 18 20 INPUT VOLTAGE (V) Output Impedance vs Frequency 1000 OUTPUT IMPEDANCE (Ω) POWER SUPPLY REJECTION RATIO (dB) 20 100 1k FREQUENCY (Hz) 10k 1790 G25 LT1790-2.5 U W U U APPLICATIONS INFORMATION Bypass and Load Capacitors The LT1790-2.5 voltage reference should have an input bypass capacitor of 0.1µF or larger, however the bypassing of other local devices may serve as the required component. This reference also requires an output capacitor for stability. The optimum output capacitance for most applications is 1µF, although larger values work as well. This capacitor affects the turn-on and settling time for the output to reach its final value. The test circuit of Figure 3 is used to measure the stability of various load currents. With RL = 1k, the 1V step produces a current step of 1mA. Figure 4 shows the response to a ±0.5mA load. Figure 5 is the output response to a sourcing step from 4mA to 5mA, and Figure 6 is the output response of a sinking step from – 4mA to – 5mA. 4 VIN 3V CIN 0.1µF Figure 1 shows the turn-on time for the LT1790-2.5 with a 1µF input bypass and 1µF load capacitor. Figure 2 shows the output response to a 0.5V transient on VIN with the same capacitors. VIN 3V VOUT 2V LT1790-2.5 1, 2 1k 6 CL 1µF VGEN 1V 1790 F03 Figure 3. Response Time Test Circuit VGEN 3V 2V 1V 0V VOUT 1790 F04 1790 F01 Figure 1. Turn-On Characteristics of LT1790-2.5 Figure 4. LT1790-2.5 Sourcing and Sinking 0.5mA VIN 3V VOUT 2V 1V 0V VOUT VGEN –2V –3V 1790 F02 Figure 2. Output Response to 0.5V Ripple on VIN 1790 F05 Figure 5. LT1790-2.5 Sourcing 4mA to 5mA 5 LT1790-2.5 U W U U APPLICATIONS INFORMATION transistor from turning on and driving the grounded output. C1 provides stability during load transients. This connection maintains the accuracy and temperature coefficient of the positive connected LT1790-2.5. VGEN 8V 6V 4V Long-Term Drift VOUT 2V 0V 1790 F06 Figure 6. LT1790-2.5 Sinking – 4mA to – 5mA Positive or Negative Operation Series operation is ideal for extending battery life. If the LT1790-2.5 is operated in series mode it does not require an external current setting resistor. The specifications guarantee the LT1790-2.5 operates from 2.6V to 18V. When the circuitry being regulated does not demand current, the series connected LT1790-2.5 consumes only a few hundred µW, yet the same connection can sink or source 5mA of load current when demanded. A typical series connection is shown on the front page of this data sheet. The circuit in Figure 7 shows the connection for a – 2.5V reference. The LT1790-2.5 can be used as a very stable negative reference, however, it requires a positive voltage applied to Pin 4 to bias internal circuitry. This voltage must be current limited with R1 to keep the output PNP Long-term drift cannot be extrapolated from accelerated high temperature testing. This erroneous technique gives drift numbers that are widely optimistic. The only way long-term drift can be determined is to measure it over the time interval of interest. The LT1790S6 drift data was taken on over 100 parts that were soldered into PC boards similar to a “real world” application. The boards were then placed into a constant temperature oven with TA = 30°C, their outputs scanned regularly and measured with an 8.5 digit DVM. Long-term drift curves are shown in the Typical Performance Characteristics. Hysteresis Hysteresis data shown in Figures 8 and 9 represent the worst-case data taken on parts from 0°C to 70°C and from – 40°C to 85°C. Units were cycled several times over these temperature ranges and the largest change is shown. As expected, the parts cycled over the higher temperature range have higher hysteresis than those cycled over the lower range. When the LT1790-2.5 is IR reflow soldered onto a PC board, the output shift is typically just 150ppm (0.015%). R1 10k 3V 4 6 LT1790-2.5 C1 0.1µF 1, 2 VOUT = –2.5V V – 2.5V RL = EE 125µA CL 1µF VEE 1790 F07 Figure 7. Using the LT1790-2.5 to Build a –2.5V Reference 6 LT1790-2.5 U W U U APPLICATIONS INFORMATION 12 16 11 14 10 9 10 70°C TO 25°C NUMBER OF UNITS NUMBER OF UNITS 12 0°C TO 25°C 8 6 4 85°C TO 25°C –40°C TO 25°C 6 5 4 3 2 2 0 8 7 1 –50 –30 –10 10 30 50 70 HYSTERESIS (ppm) 90 110 130 0 –100 –80 –60 –40 –20 20 40 0 HYSTERESIS (ppm) 1790 F08 Figure 8. Worst-Case 0°C to 70°C Hysteresis on 44 Units 60 80 100 120 1790 F09 Figure 9. Worst-Case –40°C to 85°C Hysteresis on 44 Units W W SI PLIFIED SCHEMATIC 4 VIN 6 VOUT 1, 2 GND 1790 SS 7 LT1790-2.5 U TYPICAL APPLICATION – 2.5V Negative 50mA Series Reference No Load Supply Current ICC = 1.6mA IEE = 440µA VCC = 5V 2k 4 LT1790-2.5 VZ = 5.1V 6 1, 2 5.1k –2.5V 50mA VEE = –5V MPS2907A 1µF 1790 TA03 U PACKAGE DESCRIPTION Dimensions in inches (millimeters) unless otherwise noted. S6 Package 6-Lead Plastic SOT-23 (LTC DWG # 05-08-1634) 2.6 – 3.0 (0.110 – 0.118) 1.50 – 1.75 (0.059 – 0.069) 0.35 – 0.55 (0.014 – 0.022) 0.00 – 0.15 (0.00 – 0.006) 0.90 – 1.45 (0.035 – 0.057) 2.80 – 3.00 (0.110 – 0.118) (NOTE 3) PIN 1 0.09 – 0.20 (0.004 – 0.008) (NOTE 2) 0.35 – 0.50 0.90 – 1.30 (0.014 – 0.020) (0.035 – 0.051) SIX PLACES (NOTE 2) NOTE: 1. DIMENSIONS ARE IN MILLIMETERS 2. DIMENSIONS ARE INCLUSIVE OF PLATING 3. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR 4. MOLD FLASH SHALL NOT EXCEED 0.254mm 5. PACKAGE EIAJ REFERENCE IS SC-74A (EIAJ) 1.90 (0.074) REF 0.95 (0.037) REF S6 SOT-23 0898 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LT1019 Precision Reference Bandgap, 0.05%, 5ppm/°C LT1027 Precision 5V Reference Lowest TC, High Accuracy, Low Noise, Zener Based LT1236 Precision Reference 5V and 10V Zener-Based 5ppm/°C, SO-8 Package LTC®1798 Micropower Low Dropout Reference 0.15% Max, 6.5µA Supply Current LT1460 Micropower Precison Series Reference Bandgap, 130µA Supply Current, 10ppm/°C, Available in SOT-23 LT1461 Micropower Precision Low Dropout Reference Bandgap 0.04%, 3ppm/°C, 50µA Max Supply Current LT1634 Micropower Precision Shunt Voltage Reference Bandgap, 0.05%, 10ppm/°C, 10µA Supply Current 8 Linear Technology Corporation 179025i LT/TP 0300 4K • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408)432-1900 ● FAX: (408) 434-0507 ● www.linear-tech.com LINEAR TECHNOLOGY CORPORATION 2000