LT1461-2.5 Micropower Precision Low Dropout Series Voltage Reference U FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ DESCRIPTIO Trimmed to High Accuracy: 0.04% Max Low Drift: 3ppm/°C Max Low Supply Current: 50µA Max Temperature Coefficient Guaranteed to 125°C High Output Current: 50mA Min Low Dropout Voltage: 300mV Max Excellent Thermal Regulation Power Shutdown Thermal Limiting Operating Temperature Range: – 40°C to 125°C Available in SO-8 Package U APPLICATIO S ■ ■ ■ ■ A/D and D/A Converters Precision Regulators Handheld Instruments Power Supplies The LT ®1461 is a low dropout micropower bandgap reference that combines very high accuracy and low drift with low supply current and high output drive. This series reference uses advanced curvature compensation techniques to obtain low temperature coefficient and trimmed precision thin-film resistors to achieve high output accuracy. The LT1461 draws only 35µA of supply current, making it ideal for low power and portable applications, however its high 50mA output drive makes it suitable for higher power requirements, such as precision regulators. In low power applications, a dropout voltage of less than 300mV ensures maximum battery life while maintaining full reference performance. Line regulation is nearly immeasurable, while the exceedingly good load and thermal regulation will not add significantly to system error budgets. The shutdown feature can be used to switch full load currents and can be used for system power down. Thermal shutdown protects the part from overload conditions. , LTC and LT are registered trademarks of Linear Technology Corporation. U TYPICAL APPLICATIO Load Regulation, PDISS = 200mW Basic Connection VIN ≥ 2.8V 2.5V LT1461-2.5 CIN 1µF CL 2µF 1461 TA01 0mA IOUT 20mA VOUT LOAD REG 1mV/DIV 10ms/DIV 1461 TA02 1 LT1461-2.5 U W U U W W W ABSOLUTE MAXIMUM RATINGS PACKAGE/ORDER INFORMATION (Note 1) Input Voltage ........................................................... 20V Output Short-Circuit Duration ......................... Indefinite Operating Temperature Range (Note 2) ........................................... – 40°C to 125°C Specified Temperature Range Commercial ............................................ 0°C to 70°C Industrial ........................................... – 40°C to 85°C High ................................................. – 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 LT1461ACS8-2.5 LT1461BCS8-2.5 LT1461CCS8-2.5 LT1461AIS8-2.5 LT1461BIS8-2.5 LT1461CIS8-2.5 LT1461DHS8-2.5 TOP VIEW DNC* 1 8 DNC* VIN 2 7 DNC* SHDN 3 6 VOUT GND 4 5 DNC* S8 PACKAGE 8-LEAD PLASTIC SO *DNC: DO NOT CONNECT TJMAX = 130°C, θJA = 190°C/ W S8 PART MARKING 461A25 61BI25 461B25 61CI25 461C25 61DH25 61AI25 Consult factory for Military grade parts. U AVAILABLE OPTIO S INITIAL ACCURACY (%) MAXIMUM TEMPERATURE COEFFICIENT (ppm/°C) LT1461ACS8-2.5/LT1461AIS8-2.5 0.04% 3 LT1461BCS8-2.5/LT1461BIS8-2.5 0.06% 7 GRADE LT1461CCS8-2.5/LT1461CIS8-2.5 0.08% 12 LT1461DHS8-2.5, – 40°C to 125°C 0.15% 20 ELECTRICAL CHARACTERISTICS The ● denotes specifications which apply over the specified temperature range, otherwise specifications are at TA = 25°C. VIN – VOUT = 0.5V, Pin 3 = 2.4V, CL = 2µF, unless otherwise specified. PARAMETER CONDITIONS MIN TYP MAX UNITS Output Voltage (Note 4) LT1461ACS8-2.5/LT1461AIS8-2.5 2.499 – 0.04 2.500 2.501 0.04 V % LT1461BCS8-2.5/LT1461BIS8-2.5 2.4985 – 0.06 2.500 2.5015 0.06 V % LT1461CCS8-2.5/LT1461CIS8-2.5 2.498 – 0.08 2.500 2.502 0.08 V % 2.49625 – 0.15 2.500 2.50375 0.15 V % 1 3 5 7 3 7 12 20 LT1461DHS8-2.5 Output Voltage Temperature Coefficient (Note 5) 2 LT1461ACS8-2.5/LT1461AIS8-2.5 LT1461BCS8-2.5/LT1461BIS8-2.5 LT1461CCS8-2.5/LT1461CIS8-2.5 LT1461DHS8-2.5 ● ● ● ● ppm/°C ppm/°C ppm/°C ppm/°C LT1461-2.5 ELECTRICAL CHARACTERISTICS The ● denotes specifications which apply over the specified temperature range, otherwise specifications are at TA = 25°C. VIN – VOUT = 0.5V, Pin 3 = 2.4V, CL = 2µF, unless otherwise specified. PARAMETER CONDITIONS MIN TYP MAX UNITS Line Regulation (VOUT + 0.5V) ≤ VIN ≤ 20V 2 8 12 ppm/V ppm/V 15 50 ppm/V 12 ● 30 40 ppm/mA ppm/mA LT1461DHS8, 0 ≤ IOUT ≤ 10mA ● 50 ppm/mA VIN – VOUT, VOUT Error = 0.1% IOUT = 0mA IOUT = 1mA IOUT = 10mA IOUT = 50mA, I and C Grades Only ● ● ● 0.3 0.4 2.0 V V V V ● LT1461DHS8 Load Regulation Sourcing (Note 6) Dropout Voltage ● VIN = VOUT + 2.5V 0 ≤ IOUT ≤ 50mA Output Current Short VOUT to GND Shutdown Pin Logic High Input Voltage Logic High Input Current, Pin 3 = 2.4V ● ● Logic Low Input Voltage Logic Low Input Current, Pin 3 = 0.8V ● ● Supply Current 0.06 0.13 0.20 1.50 100 No Load 2 15 V µA 0.5 0.8 4 V µA 35 50 70 µA µA 25 35 55 µA µA ● Shutdown Current RL = 1k, Pin 3 = 0.8V ● Output Voltage Noise (Note 7) mA 2.4 0.1Hz ≤ f ≤ 10Hz 20 8 µVP-P ppmP-P 10Hz ≤ f ≤ 1kHz 24 9.6 µVRMS ppmRMS Long-Term Drift of Output Voltage, SO-8 Package (Note 8) See Applications Information 60 ppm/√kHr Thermal Hysteresis (Note 9) ∆T = 0°C to 70°C ∆T = – 40°C to 85°C ∆T = – 40°C to 125°C 40 70 120 ppm ppm ppm Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: The LT1461 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 may shift due to hysteresis. Note 4: ESD (Electrostatic Discharge) sensitive device. Extensive use of ESD protection devices are used internal to the LT1461, however, high electrostatic discharge can damage or degrade the device. Use proper ESD handling precautions. Note 5: Temperature coefficient is calculated from the minimum and maximum output voltage measured at TMIN, Room and TMAX as follows: TC = (VOMAX – VOMIN)/(TMAX – TMIN) 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: 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 stillair environment to eliminate thermocouple effects on the leads. The test time is 10 sec. 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 8: Long-term drift typically has a logarithmic characteristic and therefore, changes after 1000 hours tend to be much smaller than before that time. Total drift in the second thousand hours is normally less than one third that of the first thousand hours with a continuing trend toward reduced drift with time. Long-term drift will also be affected by differential stresses between the IC and the board material created during board assembly. See the Applications Information section. Note 9: Hysteresis in output voltage is created by package stress that depends 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 hot or cold before 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. 3 LT1461-2.5 U W TYPICAL PERFORMANCE CHARACTERISTICS Reference Voltage vs Temperature Load Regulation 2.5020 4 TEMPCO –60°C TO 120°C 3 TYPICAL PARTS 2.5005 2.5000 2.4995 2.4990 LINE REGULATION (ppm/V) 2.5010 0 –1 OUTPUT VOLTAGE CHANGE (mV) REFERENCE VOLTAGE (V) 2.5015 Line Regulation vs Temperature 3 125°C 25°C 2 1 –2 –3 –4 –5 –6 – 55°C SUPPLY ∆ = 15V 5V – 20V –7 2.4985 2.4980 – 60 – 40 – 20 0 0.1 0 20 40 60 80 100 120 TEMPERATURE (°C) 1 10 OUTPUT CURRENT (mA) –8 –40 – 20 100 0 20 40 60 80 TEMPERATURE (°C) 1461 G02 1461 G01 Minimum Input/Output Voltage Differential vs Load Current 1461 G03 Supply Current vs Input Voltage 10 100 120 Supply Current vs Temperature 1000 50 IS 1 125°C SUPPLY CURRENT (µA) 40 SUPPLY CURRENT (µA) INPUT/OUTPUT VOLTAGE (V) VIN = 5V 100 125°C 25°C – 55°C 25°C IS(SHDN) 30 20 10 – 55°C 0.1 1 10 OUTPUT CURRENT (mA) 10 100 0 5 10 15 20 INPUT VOLTAGE (V) 1461 G04 140 SHDN PIN CURRENT (µA) CURRENT LIMIT (mA) 100 80 60 200 100 180 90 160 140 125°C 120 25°C – 55°C 100 80 60 20 125 1461 G07 4 80 70 60 50 40 30 20 10 0 100 100 120 Ripple Rejection Ratio vs Frequency 40 50 25 0 75 TEMPERATURE (°C) 20 40 60 80 TEMPERATURE (°C) 1461 G06 SHDN Pin Current vs SHDN Input Voltage 120 0 1461 G05 Current Limit vs Temperature 40 –50 –25 0 – 40 –20 25 RIPPLE REJECTION RATIO (dB) 0.1 0 15 10 5 SHDN PIN INPUT VOLTAGE (V) 20 1461 G08 0 0.01 0.1 1 10 FREQUENCY (kHz) 100 1000 1641 G01 LT1461-2.5 U W TYPICAL PERFORMANCE CHARACTERISTICS Output Impedance vs Frequency Turn-On Time Turn-On Time 1000 10 10 0 0 2 10 VIN 20 VOLTAGE (V) COUT = 1µF 100 VIN 20 VOLTAGE (V) OUTPUT IMPEDANCE (Ω) COUT = 2µF 2 VOUT VOUT 1 1 CIN = 1µF CL = 2µF RL = ∞ 0 1 0.01 0.1 1 FREQUENCY (kHz) 10 CIN = 1µF CL = 2µF RL = 50Ω 0 TIME (100µs/DIV) TIME (100µs/DIV) 1461 G11 1461 G12 1461 G10 Transient Response to 10mA Load Step Output Noise 0.1Hz ≤ f ≤ 10Hz Line Transient Response VIN VOUT 50mV/DIV 5V OUTPUT NOISE (20µV/DIV) IOUT 0mA 10mA/DIV 4V VOUT 50mV/DIV 1461 G13 CL = 2µF 1461 G14 CIN = 0.1µF TIME (2SEC/DIV) 1461 G18 Long-Term Drift (Number of Data Points Reduced at 650 Hours)* 250 LT1461S8-2.5 3 TYPICAL PARTS SOLDERED ONTO PCB TA = 30°C 200 ppm 150 100 50 0 –50 0 200 400 600 800 1000 HOURS 1200 1400 1600 1800 2000 1461 G15 *SEE APPLICATIONS INFORMATION FOR DETAILED EXPLANATION OF LONG-TERM DRIFT 5 LT1461-2.5 U W TYPICAL PERFORMANCE CHARACTERISTICS 0°C to 70°C Hysteresis 20 18 WORST-CASE HYSTERESIS ON 35 UNITS NUMBER OF UNITS 16 14 70°C TO 25°C 0°C TO 25°C 12 10 8 6 4 2 0 –100 – 80 – 60 – 40 – 20 0 20 HYSTERESIS (ppm) 40 60 80 100 1461 G16 – 40°C to 85°C Hysteresis 20 18 WORST-CASE HYSTERESIS ON 35 UNITS NUMBER OF UNITS 16 14 85°C TO 25°C 12 – 40°C TO 25°C 10 8 6 4 2 0 –100 – 80 – 60 – 40 – 20 0 20 HYSTERESIS (ppm) 40 60 80 100 1461 G17 – 40°C to 125°C Hysteresis 16 14 NUMBER OF UNITS 12 WORST-CASE HYSTERESIS ON 35 UNITS 125°C TO 25°C – 40°C TO 25°C 10 8 6 4 2 0 –200 –160 –120 –80 –40 0 40 HYSTERESIS (ppm) 80 120 160 200 1461 G19 6 LT1461-2.5 U W U U APPLICATIONS INFORMATION Bypass and Load Capacitors The LT1461 requires a capacitor on the input and on the output for stability. The capacitor on the input is a supply bypass capacitor and if the bypass capacitors from other components are close (within 2 inches) they should be sufficient. The output capacitor acts as frequency compensation for the reference and cannot be omitted. For light loads ≤ 1mA, a 1µF nonpolar output capacitor is usually adequate, but for higher loads (up to 75mA), the output capacitor should be 2µF or greater. Figures 1 and 2 show the transient response to a 1mA load step with a 1µF output capacitor and a 50mA load step with a 2µF output capacitor. IOUT 0mA 1mA/DIV 1mA load current or input voltage changes, is not measurable. This often overlooked parameter must be added to normal line and load regulation errors. The load regulation photo, on the first page of this data sheet, shows the output response to 200mW of instantaneous power dissipation and the reference shows no sign of thermal errors. The reference has thermal shutdown and will turn off if the junction temperature exceeds 150°C. Shutdown The shutdown (Pin 3 low) serves to shut off load current when the LT1461 is used as a regulator. The LT1461 operates normally with Pin 3 open or greater than or equal to 2.4V. In shutdown, the reference draws a maximum supply current of 35µA. Figure 3 shows the transient response of shutdown while the part is delivering 25mA. After shutdown, the reference powers up in about 200µs. 5V VOUT 20mV/DIV PIN 3 0V 1461 F01 Figure 1. 1mA Load Step with CL = 1µF VOUT 0V 1461 F03 Figure 3. Shutdown While Delivering 25mA, RL = 100Ω PC Board Layout IOUT 50mA/DIV VOUT 200mV/DIV 1461 F02 Figure 2. 50mA Load Step with CL = 2µF Precision Regulator The LT1461 will deliver 50mA with VIN = VOUT + 2.5V and higher load current with higher VIN. Load regulation is typically 12ppm/mA, which means for a 50mA load step, the output will change by only 1.5mV. Thermal regulation, caused by die temperature gradients and created from In 13- to 16-bit systems where initial accuracy and temperature coefficient calibrations have been done, the mechanical and thermal stress on a PC board (in a card cage for instance) can shift the output voltage and mask the true temperature coefficient of a reference. In addition, the mechanical stress of being soldered into a PC board can cause the output voltage to shift from its ideal value. Surface mount voltage references are the most susceptible to PC board stress because of the small amount of plastic used to hold the lead frame. A simple way to improve the stress-related shifts is to mount the reference near the short edge of the PC board, or in a corner. The board edge acts as a stress boundary, 7 LT1461-2.5 U U W U APPLICATIONS INFORMATION or a region where the flexure of the board is minimum. The package should always be mounted so that the leads absorb the stress and not the package. The package is generally aligned with the leads parallel to the long side of the PC board as shown in Figure 5a. A qualitative technique to evaluate the effect of stress on voltage references is to solder the part into a PC board and deform the board a fixed amount as shown in Figure 4. The flexure #1 represents no displacement, flexure #2 is concave movement, flexure #3 is relaxation to no displacement and finally, flexure #4 is a convex movement. 1 This motion is repeated for a number of cycles and the relative output deviation is noted. The result shown in Figure 5a is for two LT1461S8-2.5s mounted vertically and Figure 5b is for two LT1461S8-2.5s mounted horizontally. The parts oriented in Figure 5a impart less stress into the package because stress is absorbed in the leads. Figures 5a and 5b show the deviation to be between 125µV and 250µV and implies a 50ppm and 100ppm change respectively. This corresponds to a 13- to 14-bit system and is not a problem for most 10- to 12-bit systems unless the system has a calibration. In this case, as with temperature hysteresis, this low level can be important and even more careful techniques are required. The most effective technique to improve PC board stress is to cut slots in the board around the reference to serve as a strain relief. These slots can be cut on three sides of the reference and the leads can exit on the fourth side. This “tongue” of PC board material can be oriented in the long direction of the board to further reduce stress transferred to the reference. 2 3 4 1461 F04 Figure 4. Flexure Numbers 2 OUTPUT DEVIATION (mV) OUTPUT DEVIATION (mV) 2 1 LONG DIMENSION 0 1 0 SLOT –1 0 10 20 30 40 –1 0 FLEXURE NUMBER 10 20 30 40 1461 F05a FLEXURE NUMBER Figure 5a. Two Typical LT1461S8-2.5s, Vertical Orientation Without Slots 1461 F06a Figure 6a. Same Two LT1461S8-2.5s in Figure 5a, but with Slots 2 OUTPUT DEVIATION (mV) OUTPUT DEVIATION (mV) 2 1 LONG DIMENSION 0 1 0 SLOT –1 0 10 20 30 FLEXURE NUMBER Figure 5b. Two Typical LT1461S8-2.5s, Horizontal Orientation Without Slots 8 40 1461 F05b –1 0 10 20 FLEXURE NUMBER 30 40 1461 F06b Figure 6b. Same Two LT1461S8-2.5s in Figure 5b, but with Slots LT1461-2.5 U U W U APPLICATIONS INFORMATION The results of slotting the PC boards of Figures 5a and 5b are shown in Figures 6a and 6b. In this example the slots can improve the output shift from about 100ppm to nearly zero. Long-Term Drift Long-term drift cannot be extrapolated from accelerated high temperature testing. This erroneous technique gives drift numbers that are wildly optimistic. The only way long-term drift can be determined is to measure it over the time interval of interest. The erroneous technique uses the Arrhenius Equation to derive an acceleration factor from elevated temperature readings. The equation is: AF EA 1 1 – = e K T 1 T 2 The LT1461 long-term drift data was taken with parts that were soldered onto PC boards similar to a “real world” application. The boards were then placed into a constant temperature oven with TA = 30°C, their outputs were scanned regularly and measured with an 8.5 digit DVM. As an additional accuracy check on the DVM, a Fluke 732A laboratory reference was also scanned. Figure 7 shows the long-term drift measurement system. The long-term drift is the trend line that asymptotes to a value beyond 2000 hours. Note the slope in output shift between 0 hours and 1000 hours compared to the slope between 1000 hours and 2000 hours. Long-term drift is affected by differential stresses between the IC and the board material created during board assembly. PCB3 PCB2 PCB1 SCANNER where: EA = Activation Energy (Assume 0.7) K = Boltzmann’s Constant T2 = Test Condition in °Kelvin T1 = Use Condition Temperature in °Kelvin To show how absurd this technique is, compare the LT1461 data. Typical 1000 hour long-term drift at 30°C = 60ppm. The typical 1000 hour long-term drift at 130°C = 120ppm. From the Arrhenius Equation the acceleration factor is: AF 1 0.7 1 – . 0 0000863 303 403 =e = 767 The erroneous projected long-term drift is: 120ppm/767 = 0.156ppm/1000 hr For a 2.5V reference, this corresponds to a 0.39µV shift after 1000 hours. This is pretty hard to determine (read impossible) if the peak-to-peak output noise is larger than this number. As a practical matter, one of the best laboratory references available is the Fluke 732A and its longterm drift is 1.5µV/mo. This performance is only available from the best subsurface zener references utilizing specialized heater techniques. 8.5 DIGIT DVM COMPUTER 1461 F07 FLUKE 732A LABORATORY REFERENCE Figure 7. Long-Term Drift Measurement Setup Hysteresis The hysteresis curves found in the Typical Performance Characteristics represent the worst-case data taken on 35 typical parts after multiple temperature cycles. As expected, the parts that are cycled over the wider – 40°C to 125°C temperature range have more hysteresis than those cycled over lower ranges. Note that the hysteresis coming from 125°C to 25°C has an influence on the – 40°C to 25°C hysteresis. The – 40°C to 25°C hysteresis is different depending on the part’s previous temperature. This is because not all of the high temperature stress is relieved during the 25°C measurement. 9 LT1461-2.5 U U W U APPLICATIONS INFORMATION The typical performance hysteresis curves are for parts mounted in a socket and represents the performance of the parts alone. What is more interesting are parts IR soldered onto a PC board. If the PC board is then temperature cycled several times from – 40°C to 85°C, the resulting hysteresis curve is shown in Figure 8. This graph shows the influence of the PC board stress on the reference. When the LT1461 is soldered onto a PC board, the output shifts due to thermal hysteresis. Figure 9 shows the effect of soldering 40 pieces onto a PC board using standard IR reflow techniques. The average output voltage shift is –110ppm. Remeasurement of these parts after 12 days shows the outputs typically shift back 45ppm toward their initial value. This second shift is due to the relaxation of stress incurred during soldering. The LT1461 is capable of dissipating high power, i.e., 17.5V • 50mA = 875mW. The SO-8 package has a thermal resistance of 190°C/W and this dissipation causes a 166°C internal rise producing a junction temperature of TJ = 25°C + 166°C = 191°C. What will actually occur is the thermal shutdown will limit the junction temperature to around 150°C. This high temperature excursion will cause the output to shift due to thermal hysteresis. Under these conditions, a typical output shift is –135ppm, although this number can be higher. This high dissipation can cause the 25°C output accuracy to exceed its specified limit. For best accuracy and precision, the LT1461 junction temperature should not exceed 125°C. 12 11 WORST-CASE HYSTERESIS ON 35 UNITS 10 85°C TO 25°C NUMBER OF UNITS 9 – 40°C TO 25°C 8 7 6 5 4 3 2 1 0 – 200 –160 –120 – 80 – 40 0 40 HYSTERESIS (ppm) 80 120 160 200 1461 F08 Figure 8. – 40°C to 85°C Hysteresis of 35 Parts Soldered Onto a PC Board 12 NUMBER OF UNITS 10 8 6 4 2 0 –300 200 0 100 –200 –100 OUTPUT VOLTAGE SHIFT (ppm) 300 1461 F09 Figure 9. Typical Distribution of Output Voltage Shift After Soldering Onto PC Board 10 LT1461-2.5 W W SI PLIFIED SCHE ATIC 2 VIN 6 VOUT SHDN 3 4 GND 1461 SS U PACKAGE DESCRIPTION Dimensions in inches (millimeters) unless otherwise noted. S8 Package 8-Lead Plastic Small Outline (Narrow 0.150) (LTC DWG # 05-08-1610) 0.189 – 0.197* (4.801 – 5.004) 8 7 6 5 0.150 – 0.157** (3.810 – 3.988) 0.228 – 0.244 (5.791 – 6.197) 1 0.010 – 0.020 × 45° (0.254 – 0.508) 0.008 – 0.010 (0.203 – 0.254) 0.053 – 0.069 (1.346 – 1.752) 0°– 8° TYP 0.016 – 0.050 (0.406 – 1.270) 0.014 – 0.019 (0.355 – 0.483) TYP *DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE **DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE 2 3 4 0.004 – 0.010 (0.101 – 0.254) 0.050 (1.270) BSC 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. SO8 1298 11 LT1461-2.5 U TYPICAL APPLICATION Low Power 16-Bit A/D VCC 35µA 200µA VCC 1µF VCC FO LTC2400 VREF SCK SD0 CS VIN LT1461-2.5 VOUT 1µF INPUT 0.1µF GND GND SPI INTERFACE 1461 TA03 NOISE PERFORMANCE* VIN = 0V, VNOISE = 1.1ppmRMS = 2.25µVRMS = 16µVP-P VIN = VREF/2, VNOISE = 1.6ppmRMS = 4µVRMS = 24µVP-P VIN = VREF, VNOISE = 2.5ppmRMS = 6.25µVRMS = 36µVP-P *FOR 24-BIT PERFORMANCE USE LT1236 REFERENCE 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 Precision Series Reference Bandgap, 130µA Supply Current 10ppm/°C, Available in SOT-23 LT1634 Micropower Precision Shunt Voltage Reference Bandgap 0.05%, 10ppm/°C, 10µA Supply Current ® 12 Linear Technology Corporation 146125f LT/TP 0100 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 1999