LT1236 Precision Reference U DESCRIPTIO FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ The LT®1236 is a precision reference that combines ultralow drift and noise with excellent long-term stability and high output accuracy. The reference output will both source and sink up to 10mA and is almost totally immune to input voltage variations. Two voltages are available: 5V and 10V. The 10V version can be used as a shunt regulator (two-terminal zener) with the same precision characteristics as the three-terminal connection. Special care has been taken to minimize thermal regulation effects and temperature induced hysteresis. Ultra-Low Drift: 5ppm/°C Max Trimmed to High Accuracy: 0.05% Max Industrial Temperature Range SO Package Operates in Series or Shunt Mode Pin Compatible with AD586, AD587 Output Sinks and Sources in Series Mode Very Low Noise < 1ppm P-P (0.1Hz to 10Hz) 100% Noise Tested > 100dB Ripple Rejection Minimum Input/Output Differential of 1V The LT1236 combines both superior accuracy and temperature coefficient specifications without the use of high power, on-chip heaters. The LT1236 references are based on a buried zener diode structure which eliminates noise and stability problems with surface breakdown devices. Further, a subsurface zener exhibits better temperature drift and time stability than even the best band-gap references. UO APPLICATI ■ ■ ■ ■ ■ S A/D and D/A Converters Precision Regulators Precision Scales Inertial Navigation Systems Digital Voltmeters , LTC and LT are registered trademarks of Linear Technology Corporation. UO TYPICAL APPLICATI Typical Distribution of Temperature Drift Basic Positive and Negative Connections 24 LT1236 IN OUT VOUT NC IN GND OUT 18 GND 16 –VOUT V – (V – ) R1 = OUT ILOAD + 1.5mA R1 UNITS (%) VIN DISTRIBUTION 22 OF THREE RUNS 20 LT1236-10 14 12 10 8 –15V (V – ) 6 4 LT1236 TA01 2 0 –3 –2 –1 0 1 OUTPUT DRIFT (ppm/°C) 2 3 LT1236 TA02 1 LT1236 W W W AXI U U ABSOLUTE RATI GS Input Voltage .......................................................... 40V Input/Output Voltage Differential ............................ 35V Output-to-Ground Voltage (Shunt Mode Current Limit) LT1236-5 ............................................................. 10V LT1236-10 ........................................................... 16V Trim Pin-to-Ground Voltage Positive................................................ Equal to VOUT Negative ........................................................... – 20V Output Short-Circuit Duration VIN = 35V ......................................................... 10 sec VIN ≤ 20V ................................................... Indefinite Operating Temperature Range LT1236AC, BC, CC .................................. 0°C to 70°C LT1236AI, BI, CI ................................ – 40°C to 85°C Storage Temperature Range ................ – 65°C to 150°C Lead Temperature (Soldering, 10 sec)................ 300°C U W U PACKAGE/ORDER I FOR ATIO ORDER PART NUMBER TOP VIEW NC* 1 8 NC* VIN 2 7 NC* NC* 3 6 V0UT GND 4 5 TRIM** N8 PACKAGE 8-LEAD PDIP *CONNECTED INTERNALLY. D0 NOT CONNECT EXTERNAL CIRCUITRY TO THESE PINS **SEE APPLICATIONS INFORMATION SECTION TJMAX = 125°C, θJA = 130°C/W ORDER PART NUMBER TOP VIEW LT1236ACN8-5 LT1236BCN8-5 LT1236CCN8-5 LT1236ACN8-10 LT1236BCN8-10 LT1236CCN8-10 LT1236AIN8-5 LT1236BIN8-5 LT1236CIN8-5 LT1236AIN8-10 LT1236BIN8-10 LT1236CIN8-10 NC* 1 8 NC* VIN 2 7 NC* NC* 3 6 V0UT GND 4 5 TRIM** S8 PACKAGE 8-LEAD PLASTIC SO LT1236ACS8-5 LT1236BCS8-5 LT1236CCS8-5 LT1236ACS8-10 LT1236BCS8-10 LT1236CCS8-10 LT1236AIS8-5 LT1236BIS8-5 LT1236CIS8-5 LT1236AIS8-10 LT1236BIS8-10 LT1236CIS8-10 S8 PART MARKING *CONNECTED INTERNALLY. D0 NOT CONNECT EXTERNAL CIRCUITRY TO THESE PINS 236AC5 236BC5 236CC5 236AC1 236BC1 236CC1 **SEE APPLICATIONS INFORMATION SECTION TJMAX = 125°C, θJA = 190°C/W 236AI5 236BI5 236CI5 236AI1 236BI1 236CI1 Consult factory for Military grade parts. ELECTRICAL CHARACTERISTICS VIN = 10V, IOUT = 0, TA = 25°C, unless otherwise noted. PARAMETER CONDITIONS Output Voltage (Note 1) LT1236A-5 LT1236B-5/LT1236C-5 Output Voltage Temperature Coefficient (Note 2) TMIN ≤ TJ ≤ TMAX LT1236A-5 LT1236B-5 LT1236C-5 Line Regulation (Note 3) 7.2V ≤ VIN ≤ 10V MIN LT1236-5 TYP MAX 4.9975 4.9950 5.000 5.000 5.0025 5.0050 2 5 10 5 10 15 ppm/°C ppm/°C ppm/°C 4 12 20 6 10 ppm/V ppm/V ppm/V ppm/V 20 35 ppm/mA ppm/mA ● 10V ≤ VIN ≤ 40V 2 ● Load Regulation (Sourcing Current) (Note 3) 2 0 ≤ IOUT ≤ 10mA 10 ● UNITS V V LT1236 ELECTRICAL CHARACTERISTICS VIN = 10V, IOUT = 0, TA = 25°C, unless otherwise noted. PARAMETER CONDITIONS Load Regulation (Sinking Current) (Note 3) 0 ≤ IOUT ≤ 10mA MIN LT1236-5 TYP MAX UNITS 60 100 150 ppm/mA ppm/mA 0.8 1.2 1.5 mA mA 3.5 µVP-P µVRMS ● Supply Current ● Output Voltage Noise (Note 5) 0.1Hz ≤ f ≤ 10Hz 10Hz ≤ f ≤ 1kHz 3.0 2.2 Long-Term Stability of Output Voltage (Note 6) ∆t = 1000Hrs Non-Cumulative 20 ppm Temperature Hysteresis of Output (Note 7) ∆T = ±25°C 10 ppm VIN = 15V, IOUT = 0, TA= 25°C, unless otherwise noted. PARAMETER CONDITIONS MIN LT1236-10 TYP MAX Output Voltage (Note 1) LT1236A-10 LT1236B-10/LT1236C-10 9.995 9.990 10.000 10.000 10.005 10.010 Output Voltage Temperature Coefficient (Note 2) TMIN ≤ TJ ≤ TMAX LT1236A-10 LT1236B-10 LT1236C-10 2 5 10 5 10 15 ppm/°C ppm/°C ppm/°C 1.0 4 6 2 4 ppm/V ppm/V ppm/V ppm/V 12 25 40 ppm/mA ppm/mA 50 100 150 ppm/mA ppm/mA 1.2 1.7 2.0 mA mA 1.1 1.5 1.7 mA mA Line Regulation (Note 3) 11.5V ≤ VIN ≤ 14.5V ● 14.5V ≤ VIN ≤ 40V 0.5 ● Load Regulation (Sourcing Current) (Note 3) 0 ≤ IOUT ≤ 10mA Load Regulation (Shunt Mode) (Notes 3, 4) 1.7mA ≤ ISHUNT ≤ 10mA ● ● Series Mode Supply Current ● Shunt Mode Minimum Current VIN is Open ● UNITS V V 0.1Hz ≤ f ≤ 10Hz 10Hz ≤ f ≤ 1kHz 6.0 3.5 Long-Term Stablility of Output Voltage (Note 6) ∆t = 1000Hrs Non-Cumulative 30 ppm Temperature Hysteresis of Output (Note 7) ∆T = ±25°C 5 ppm Output Voltage Noise (Note 5) The ● denotes specifications which apply over the specified temperature range. Note 1: Output voltage is measured immediately after turn-on. Changes due to chip warm-up are typically less than 0.005%. Note 2: Temperature coefficient is measured by dividing the change in output voltage over the temperature range by the change in temperature. Incremental slope is also measured at 25°C. Note 3: Line and load regulation are measured on a pulse basis. Output changes due to die temperature change must be taken into account separately. Note 4: Shunt mode regulation is measured with the input open. With the input connected, shunt mode current can be reduced to 0mA. Load regulation will remain the same. 6 µVP-P µVRMS Note 5: RMS noise is measured with a 2-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. Correction factors are used to convert from average to RMS, and 0.88 is used to correct for the non-ideal bandbass of the filters. Peak-to-peak noise is measured with a single 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. Test time is 10 seconds. Note 6: Long-term stability 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. Significant improvement in long-term drift can be 3 LT1236 ELECTRICAL CHARACTERISTICS VIN = 15V, IOUT = 0, TA = 25°C, unless otherwise noted. temperature. Output voltage is always measured at 25°C, but the IC is cycled to 50°C or 0°C before successive measurements. Hysteresis is roughly proportional to the square of temperature change. Hysteresis is not normally a problem for operational temperature excursions, but can be significant in critical narrow temperature range applications where the instrument might be stored at high or low temperatures. realized by preconditioning the IC with a 100-200 hour, 125°C burn in. Long term stability will also be affected by differential stresses between the IC and the board material created during board assembly. Temperature cycling and baking of completed boards is often used to reduce these stresses in critical applications. Note 7: Hysteresis in output voltage is created by package stress that differs depending on whether the IC was previously at a higher or lower U W TYPICAL PERFOR A CE CHARACTERISTICS Ripple Rejection 130 120 100 LT1236-5 95 LT1236-10 100 90 80 LT1236-5 70 90 60 5 10 15 20 25 30 INPUT VOLTAGE (V) 35 100 1k FREQUENCY (Hz) 10 40 Start-Up (Series Mode) OUTPUT VOLTAGE (V) OUTPUT VOLTAGE (V) 9 8 7 6 LT1236-5 9 VOUT + 2V 0V 8 NC 1k VOUT OUT IN GND 7 6 8 TIME (µs) 10 12 14 LT1236 G04 4 300 250 200 150 LT1236-10 100 LT1236-5 0 5 4 6 8 10 12 14 16 18 20 OUTPUT CURRENT (mA) 50 4 2 4 350 6 3 2 Output Voltage Noise Spectrum LT1236-10 LT1236-10 0 400 10 11 0 0.4 LT1236 G03 11 VIN = 0V TO 12V 5 0.6 Start-Up (Shunt Mode), LT1236-10 13 10 0.8 LT1236 G02 LT1236 G01 12 TJ = 25 °C 1.0 0 10k NOISE VOLTAGE (nV/√Hz) 0 TJ = –55 °C 1.2 0.2 50 85 TJ = 125 °C 1.4 110 LT1236-10 REJECTION (dB) REJECTION (dB) 110 1.6 VIN = 15V COUT = 0 f = 150Hz INPUT/OUTPUT VOLTAGE (V) 115 105 Minimum Input/Output Differential, LT1236-10 Ripple Rejection 0 2 6 4 TIME (µs) 8 10 12 LT1236 G05 10 1k 100 FREQUENCY (Hz) 1M LT1236 G06 LT1236 U W TYPICAL PERFOR A CE CHARACTERISTICS Output Voltage Temperature Drift LT1236-5 Output Voltage Noise COUT = 0 FILTER = 1 POLE fLOW = 0.1Hz 14 5.004 OUTPUT VOLTAGE (V) 10 8 LT1236-10 4 3 5.003 5.002 5.001 100 1k BANDWIDTH (Hz) 5.000 –40 –20 10k 40 20 0 60 TEMPERATURE (°C) Sink Mode* Current Limit, LT1236-5 60 CURRENT INTO OUTPUT (mA) 1.4 1.2 TJ = – 55°C 1.0 TJ = 25°C TJ = 125°C 0.6 0.4 2 4 6 8 SINKING 10 LT1236 G09 Thermal Regulation, LT1236-5 VIN = 8V VIN = 25V ∆POWER = 200mW 50 OUTPUT CHANGE (mV) IOUT = 0 1.6 0 OUTPUT CURRENT (mA) LT1236 G08 Quiescent Current, LT1236-5 40 30 20 LOAD REGULATION 0 – 0.5 THERMAL REGULATION* – 1.0 ILOAD = 10mA 10 0.2 0 0 0 5 10 15 20 25 30 INPUT VOLTAGE (V) 35 40 0 2 4 6 8 10 12 14 OUTPUT VOLTAGE (V) Load Transient Response, LT1236-5, CLOAD = 0 OUTPUT CHANGE (20mV/DIV) ISINK = 0 50mV 50mV ISINK = 0.2mA ISOURCE = 0.5mA ISINK = 2-10mA ISOURCE = 2-10mA ISINK = 0 20mV 20mV ISINK = 0.2mA ISOURCE = 0.2mA ISINK = 2-10mA 0 1 2 ∆ISOURCE = 100µAP-P ∆ISINK = 100µAP-P 3 4 0 TIME (µs) 1 2 3 4 LT1236 G13 0 5 20 40 60 80 TIME (ms) 100 120 140 *INDEPENDENT OF TEMPERATURE COEFFICIENT LT1236 G12 Output Noise 0.1Hz to 10Hz, LT1236-5 ISOURCE = 2-10mA ∆ISOURCE = 100µAP-P 0 18 Load Transient Response, LT1236-5, CLOAD = 1000pF ISOURCE = 0 ISOURCE = 0 16 *NOTE THAT AN INPUT VOLTAGE IS REQUIRED FOR 5V UNITS. LT1236 G11 LT1236 G10 OUTPUT CHANGE (50mV/DIV) INPUT CURRENT (mA) –1 –2 –5 –10 – 8 – 6 – 4 – 2 SOURCING 100 80 LT1236 G07 0.8 1 0 –4 LT1236-5 0 1.8 2 –3 2 10 VIN = 8V FILTERING = 1 ZERO AT 0.1Hz 2 POLES AT 10Hz OUTPUT VOLTAGE NOISE (5µV/DIV) RMS NOISE (µV) 5 4 12 6 Load Regulation LT1236-5 5.005 OUTPUT CHANGE (mV) 16 5µV (1ppm) ∆ISINK = 100µAP-P 10 15 20 0 TIME (µs) 5 10 15 20 LT1236 G14 0 1 4 3 2 TIME (MINUTES) 5 6 LT1236 G15 5 LT1236 U W TYPICAL PERFOR A CE CHARACTERISTICS Load Regulation, LT1236-10 10.0020 5 10.0015 4 VIN = 12V 10.0000 9.9995 9.9990 9.9985 9.9980 –40 –20 0 20 60 40 TEMPERATURE (˚C) 80 INPUT CURRENT (mA) 10.0005 2 1 0 –1 –2 2 4 6 8 SINKING TJ = 125°C 1.0 0.8 0.6 0 10 1.4 1.2 TJ = – 55°C 0.8 TJ = 25°C 0.4 TJ = 125°C 0 2 4 6 10 8 OUTPUT TO GROUND VOLTAGE (V) 35 40 Thermal Regulation, LT1236-10 INPUT PIN OPEN VIN = 30V ∆POWER = 200mW 50 40 30 20 LOAD REGULATION 0 – 0.5 –1.0 THERMAL REGULATION* –1.5 ILOAD = 10mA 10 0 12 15 20 25 30 INPUT VOLTAGE (V) LT1236 G18 0 0 10 LT1236 G17 OUTPUT CHANGE (mV) INPUT PIN OPEN 5 0 Shunt Mode Current Limit, LT1236-10 CURRENT INTO OUTPUT (mA) CURRENT INTO OUTPUT (mA) 0 OUTPUT CURRENT (mA) 1.6 0.2 TJ = 25°C 1.2 0.2 60 0.6 1.4 –4 Shunt Characteristics, LT1236-10 1.0 TJ = – 55°C 0.4 –5 –10 – 8 – 6 – 4 – 2 SOURCING 100 IOUT = 0 1.6 –3 LT1236 G16 1.8 Input Supply Current, LT1236-10 1.8 3 10.0010 OUTPUT CHANGE (mV) OUTPUT VOLTAGE (V) Output Voltage Temperature Drift, LT1236-10 2 4 6 8 10 12 14 OUTPUT VOLTAGE (V) 16 LT1236 G20 LT1236 G19 0 18 20 40 60 80 TIME (ms) 100 120 140 *INDEPENDENT OF TEMPERATURE COEFFICIENT LT1236 G21 Load Transient Response, LT1236-10, CLOAD = 0 OUTPUT VOLTAGE CHANGE OUTPUT VOLTAGE CHANGE ISOURCE = 0 50mV 10mV ISINK = 0.8mA ISOURCE = 0.2mA ISINK = 1.0mA 1 2 3 4 0 TIME (µs) 1 3 2 ISINK = 1.2mA ISOURCE = 0.5mA ISOURCE = 2-10mA ∆ISOURCE = 100µAP-P ∆ISINK = 100µAP-P 4 NOTE VERTICAL SCALE CHANGE BETWEEN SOURCING AND SINKING LT1236 G22 6 5mV ISINK = 2-10mA ISOURCE = 2-10mA ∆ISOURCE = 100µAP-P 20mV 0 1 2 ISINK = 1.4mA ISINK = 2-10mA ∆ISINK = 100µAP-P 3 4 0 TIME (µs) 1 3 2 4 NOTE VERTICAL SCALE CHANGE BETWEEN SOURCING AND SINKING LT1236 G23 FILTERING = 1 ZERO AT 0.1Hz 2 POLES AT 10Hz OUTPUT VOLTAGE NOISE (10µV/DIV) ISINK = 0.8mA ISINK = 0.6mA ISOURCE = 0 0 Output Noise 0.1Hz to 10Hz, LT1236-10 Load Transient Response, LT1236-10, CLOAD = 1000pF 10µV (1ppm) 0 1 4 3 2 TIME (MINUTES) 5 6 LT1236 G24 LT1236 U U W U APPLICATIONS INFORMATION Effect of Reference Drift on System Accuracy A large portion of the temperature drift error budget in many systems is the system reference voltage. This graph indicates the maximum temperature coefficient allowable if the reference is to contribute no more than 0.5LSB error to the overall system performance. The example shown is a 12-bit system designed to operate over a temperature range from 25°C to 65°C. Assuming the system calibration is performed at 25°C, the temperature span is 40°C. It can be seen from the graph that the temperature coefficient of the reference must be no worse than 3ppm/°C if it is to contribute less than 0.5LBS error. For this reason, the LT1236 family has been optimized for low drift. MAXIMUM TEMPERATURE COEFFICIENT FOR 0.5LSB ERROR (ppm/°C) Maximum Allowable Reference Drift 100 in series with a 20kΩ potentiometer will give ±10mV trim range. Effect on the output TC will be only 1ppm/°C for the ± 5mV trim needed to set the “A” device to 10.000V. LT1236-5 The LT1236-5 does have an output voltage trim pin, but the TC of the nominal 4V open circuit voltage at pin 5 is about –1.7mV/°C. For the voltage trimming not to affect reference output TC, the external trim voltage must track the voltage on the trim pin. Input impedance of the trim pin is about 100kΩ and attenuation to the output is 13:1. The technique shown below is suggested for trimming the output of the LT1236-5 while maintaining minimum shift in output temperature coefficient. The R1/R2 ratio is chosen to minimize interaction of trimming and TC shifts, so the exact values shown should be used. 8-BIT LT1236-5 IN 10-BIT 10 GND VOUT OUT TRIM R1 27k R2 50k 12-BIT 1N4148 14-BIT 1.0 LT1236 AI02 10 20 30 40 50 60 70 80 90 100 TEMPERATURE SPAN (°C) LT1236 AI01 Trimming Output Voltage The LT1236-10 has a trim pin for adjusting output voltage. The impedance of the trim pin is about 12kΩ with a nominal open circuit voltage of 5V. It is designed to be driven from a source impedance of 3kΩ or less to minimize changes in the LT1236 TC with output trimming. Attenuation between the trim pin and the output is 70:1. This allows ±70mV trim range when the trim pin is tied to the wiper of a potentiometer connected between the output and ground. A 10kΩ potentiometer is recommended, preferably a 20 turn cermet type with stable characteristics over time and temperature. The LT1236-10 “A” version is pre-trimmed to ±5mV and therefore can utilize a restricted trim range. A 75k resistor Capacitive Loading and Transient Response The LT1236 is stable with all capacitive loads, but for optimum settling with load transients, output capacitance should be under 1000pF. The output stage of the reference is class AB with a fairly low idling current. This makes transient response worse-case at light load currents. Because of internal current drain on the output, actual worst-case occurs at ILOAD = 0 on LT1236-5 and ILOAD = 1.4mA (sinking) on LT1236-10. Significantly better load transient response is obtained by moving slightly away from these points. See Load Transient Response curves for details. In general, best transient response is obtained when the output is sourcing current. In critical applications, a 10µF solid tantalum capacitor with several ohms in series provides optimum output bypass. 7 LT1236 U W U U APPLICATIONS INFORMATION Kelvin Connections Although the LT1236 does not have true force/sense capability at its outputs, significant improvements in ground loop and line loss problems can be achieved with proper hook-up. In series mode operation, the ground pin of the LT1236 carries only ≈ 1mA and can be used as a sense line, greatly reducing ground loop and loss problems on the low side of the reference. The high side supplies load current so line resistance must be kept low. Twelve feet of #22 gauge hook-up wire or 1 foot of 0.025 inch printed circuit trace will create 2mV loss at 10mA output current. This is equivalent to 1LSB in a 10V, 12-bit system. The following circuits show proper hook-up to minimize errors due to ground loops and line losses. Losses in the output lead can be greatly reduced by adding a PNP boost transistor if load currents are 5mA or higher. R2 can be added to further reduce current in the output sense lead. temperature gradients in the package leads. Variations in thermal resistance, caused by uneven air flow, create differential lead temperatures, thereby causing thermoelectric voltage noise at the output of the reference. Standard Series Mode LT1236 INPUT IN KEEP THIS LINE RESISTANCE LOW OUT + GND LOAD GROUND RETURN LT1236 AI03 Series Mode with Boost Transistor INPUT R1 220Ω 2N3906 Effects of Air Movement on Low Frequency Noise The LT1236 has very low noise because of the buried zener used in its design. In the 0.1Hz to 10Hz band, peak-to-peak noise is about 0.5ppm of the DC output. To achieve this low noise, however, care must be taken to shield the reference from ambient air turbulence. Air movement can create noise because of thermoelectric differences between IC package leads and printed circuit board materials and/or sockets. Power dissipation in the reference, even though it rarely exceeds 20mW, is enough to cause small IN LT1236 OUT GND LOAD R2* GROUND RETURN *OPTIONAL—REDUCES CURRENT IN OUTPUT SENSE LEAD: R2 = 2.4k (LT1236-5), 5.6k (LT1236-10) LT1236 AI04 U TYPICAL APPLICATIONS Restricted Trim Range for Improved Resolution, 10V, “A” Version Only LT1236-10 Full Trim Range (±0.7%) Negative Series Reference 15V LT1236-10 LT1236A-10 VIN IN GND 10.000V OUT TRIM R1 75k R2 50k VIN IN GND R1 4.7k VOUT OUT IN TRIM R2 4.7k R1* 10k –15V LT1236 TA03 TRIM RANGE ≈ ±10mV 8 LT1236 TA10 LT1236-10 *CAN BE RAISED TO 20k FOR LESS CRITICAL APPLICATIONS D1 15V Q1 2N2905 OUT GND –10V AT 50mA LT1236 TA04 LT1236 U TYPICAL APPLICATIONS Boosted Output Current with No Current Limit Boosted Output Current with Current Limit ±10V Output Reference V+ ≥ VOUT + 2.8V V + ≥ (VOUT + 1.8V) D1* LED R1 220Ω R1 220Ω LT1236-10 8.2Ω 15V VOUT VIN 2N2905 2N2905 +10V GND IN IN LT1236 10V AT 100mA OUT GND + COM LT1236 10V AT 100mA OUT 2µF SOLID TANT GND + LT1236-10 VOUT V IN 2µF SOLID TANT GND –10V LT1236 TA05 *GLOWS IN CURRENT LIMIT, DO NOT OMIT –15V –10V R1 = ILOAD + 1.5mA LT1236 TA06 ILOAD R1 –15V Handling Higher Load Currents 15V LT1236 TA17 Operating 5V Reference from 5V Supply 5V LOGIC SUPPLY 30mA 1N914 CMOS LOGIC GATE** R1* 169Ω IN LT1236-10 fIN ≥ 2kHz* VOUT 10V OUT TYPICAL LOAD CURRENT = 30mA LT1236-5 1N914 ≈8.5V + C2* C1* 5µF GND RL + IN OUT 5V REFERENCE GND 5µF *FOR HIGHER FREQUENCIES C1 AND C2 MAY BE DECREASED **PARALLEL GATES FOR HIGHER REFERENCE CURRENT LOADING LT1236 TA15 *SELECT R1 TO DELIVER TYPICAL LOAD CURRENT. LT1236 WILL THEN SOURCE OR SINK AS NECESSARY TO MAINTAIN PROPER OUTPUT. DO NOT REMOVE LOAD AS OUTPUT WILL BE DRIVEN UNREGULATED HIGH. LINE REGULATION IS DEGRADED IN THIS APPLICATION LT1236 TA07 Trimming 10V Units to 10.24V CMOS DAC with Low Drift Full-Scale Trimming** LT1236-10 R3 4.02K 1% OUT LT1236-10 TRIM GND FB R1 4.99k 1% REF CMOS DAC LTC7543 30pF IOUT R2 40.2Ω 1% 1.2k –15V *TC LESS THAN 200ppm/°C **NO ZERO ADJUST REQUIRED WITH LT1007 (V0S ≤ 60µV) VIN R4* 100Ω FULL-SCALE ADJUST TRIM OUT VOUT = 10.24V GND 4.32k – LT1007C + IN 10V F.S. 5k V – = –15V* LT1236 TA14 *MUST BE WELL REGULATED dVOUT 15mV = V dV – LT1236 TA11 9 LT1236 U TYPICAL APPLICATIONS Negative Shunt Reference Driven by Current Source Strain Gauge Conditioner for 350Ω Bridge R1 357Ω 1/2W LT1236-10 28mA LT1236-10 15V IN OUT 28.5mA GND OUT 5V 350Ω STRAIN GAUGE BRIDGE** GND + 6 – 100pF 2 R4 20k LM301A† 1 2.5mA R2 20k 3 2 –10V (ILOAD ≤ 1mA) R3 2M – LT1012C 3 6 LM334 VOUT X100 + R5 2M 8 27Ω R6* 2M –11V TO – 40V –5V LT1236 TA13 357Ω 1/2W –15V *THIS RESISTOR PROVIDES POSITIVE FEEDBACK TO THE BRIDGE TO ELIMINATE LOADING EFFECT OF THE AMPLIFIER. EFFECTIVE ZIN OF AMPLIFIER STAGE IS ≥ 1MΩ. IF R2 TO R5 ARE CHANGED, SET R6 = R3 **BRIDGE IS ULTRA-LINEAR WHEN ALL LEGS ARE ACTIVE, TWO IN COMPRESSION AND TWO IN TENSION, OR WHEN ONE SIDE IS ACTIVE WITH ONE COMPRESSED AND ONE TENSIONED LEG † OFFSET AND DRIFT OF LM301A ARE VIRTUALLY ELIMINATED BY DIFFERENTIAL CONNECTION OF LT1012C LT1236 TA08 2-Pole Lowpass Filtered Reference Precision DAC Reference with System TC Trim 1µF MYLAR LT1236-10 15V IN – OUT GND VIN 8.87k 1% VIN D1 1N457 1.24k 1% LT1001 LT1236 50k TC TRIM* 10k 1% 10k 1% D2 1N457 50k ROOM TEMP TRIM IN GND R1 36k R2 36k f = 10Hz 10.36k 1% 200k 1% VREF + OUT 0.5µF MYLAR TOTAL NOISE ≤2µVRMS 1Hz ≤ f ≤ 10kHz –VREF LT1236 TA12 50k *TRIMS 1mA REFERENCE CURRENT TC BY ±40ppm/°C. THIS TRIM SCHEME HAS VERY LITTLE EFFECT ON ROOM TEMPERATURE CURRENT TO MINIMIZE ITERATIVE TRIMMING 10 8.45k 1mA DAC LT1236 TA16 LT1236 U TYPICAL APPLICATIONS Ultra-Linear Platinum Temperature Sensor* LT1236-10 IN OUT 20V GND R2* 5k R10 182k 1% R14 5k R1** 253k R9 100k R11 6.65M 1% R8 10M R15 10k Rf** 654k R12 1k R13 24.3k 20V R4 4.75k 1% R3** 5k RS† 100Ω AT 0°C 2 R5 200k 1% LT1001 3 R6 619k 1% R7 392k 1% –15V 7 – + 6 VOUT =100mV/°C –50°C ≤ T ≤ 150°C 4 –15V † STANDARD INDUSTRIAL 100Ω PLATINUM 4-WIRE SENSOR, ROSEMOUNT 78S OR EQUIVALENT. α = 0.00385 TRIM R9 FOR VOUT = 0V AT 0°C TRIM R12 FOR VOUT = 10V AT 100°C TRIM R14 FOR VOUT = 5V AT 50°C USE TRIM SEQUENCE AS SHOWN. TRIMS ARE NONINTERACTIVE SO THAT ONLY ONE TRIM SEQUENCE IS NORMALLY REQUIRED. *FEEDBACK LINEARIZES OUTPUT TO ± 0.005°C FROM – 50°C TO 150°C LT1236 TA09 **WIREWOUND RESISTORS WITH LOW TC U W EQUIVALE T SCHE ATIC INPUT Q3 D1 D2 OUTPUT D3 R1 Q1 + – A1 R2 D4 6.3V Q2 GND LT1236 ES 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. 11 LT1236 U PACKAGE DESCRIPTION Dimensions in inches (millimeters) unless otherwise noted. N8 Package 8-Lead Plastic DIP 0.300 – 0.325 (7.620 – 8.255) 0.045 – 0.065 (1.143 – 1.651) ( 0.130 ± 0.005 (3.302 ± 0.127) 0.065 (1.651) TYP 0.009 – 0.015 (0.229 – 0.381) +0.025 0.325 –0.015 +0.635 8.255 –0.381 0.400* (10.160) MAX 7 6 5 1 2 3 4 0.255 ± 0.015* (6.477 ± 0.381) 0.125 (3.175) MIN 0.045 ± 0.015 (1.143 ± 0.381) ) 8 0.015 (0.380) MIN 0.018 ± 0.003 (0.457 ± 0.076) 0.100 ± 0.010 (2.540 ± 0.254) N8 0395 *THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.010 INCH (0.254mm). S8 Package 8-Lead Plastic SOIC 0.189 – 0.197* (4.801 – 5.004) 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) 0.004 – 0.010 (0.101 – 0.254) 8 7 6 5 0°– 8° TYP 0.016 – 0.050 0.406 – 1.270 0.014 – 0.019 (0.355 – 0.483) 0.050 (1.270) BSC 0.150 – 0.157* (3.810 – 3.988) 0.228 – 0.244 (5.791 – 6.197) *THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.006 INCH (0.15mm). 1 2 3 4 SO8 0294 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LT1019 Precision Bandgap Reference 0.05%, 5ppm/°C LT1027 Precision 5V Reference 0.02%, 2ppm/°C 12 Linear Technology Corporation LT/GP 0695 10K • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7487 (408) 432-1900 ● FAX: (408) 434-0507 ● TELEX: 499-3977 LINEAR TECHNOLOGY CORPORATION 1995