LT1021

LT1021 Precision Reference FEATURES s DESCRIPTIO s s s s s s s s Pin Compatible with Most Bandgap Reference Applications, Including Ref 01, Ref 02, LM368, MC1400 and MC1404 with Greatly Improved Stability, Noise and Drift Ultralow Drift: 5ppm/°C Max Slope Trimmed Output Voltage Operates in Series or Shunt Mode Output Sinks and Sources in Series Mode Very Low Noise: 100dB Ripple Rejection Minimum Input/Output Differential of 1V 100% Noise Tested The LT®1021 is a precision reference with ultralow drift and noise, extremely good long term stability and almost total immunity to input voltage variations. The reference output will both source and sink up to 10mA. Three voltages are available: 5V, 7V and 10V. The 7V and 10V units can be used as shunt regulators (two-terminal zeners) with the same precision characteristics as the threeterminal connection. Special care has been taken to minimize thermal regulation effects and temperature induced hysteresis. The LT1021 references are based on a buried zener diode structure that eliminates noise and stability problems associated with surface breakdown devices. Further, a subsurface zener exhibits better temperature drift and time stability than even the best bandgap references. Unique circuit design makes the LT1021 the first IC reference to offer ultralow drift without the use of high power on-chip heaters. The LT1021-7 uses no resistive divider to set output voltage, and therefore exhibits the best long term stability and temperature hysteresis. The LT1021-5 and LT102110 are intended for systems requiring a precise 5V or 10V reference with an initial tolerance as low as ± 0.05%. , LTC and LT are registered trademarks of Linear Technology Corporation. APPLICATI s s s s s s S A/D and D/A Converters Precision Regulators Digital Voltmeters Inertial Navigation Systems Precision Scales Portable Reference Standard TYPICAL APPLICATI Typical Distribution of Temperature Drift Basic Positive and Negative Connections LT1021 VIN IN GND OUT VOUT NC LT1021 (7 AND 10 ONLY) OUT GND –VOUT V – (V – ) R1 = OUT ILOAD + 1.5mA R1 –15V (V – ) 24 21 18 UNITS (%) IN 15 12 9 6 3 1021 TA01 –0 – 5 – 4 – 3 – 2 –1 0 1 2 3 OUTPUT DRIFT (ppm/°C) 4 5 U DISTRIBUTION OF THREE RUNS 1021 TA01 UO UO 1 LT1021 ABSOLUTE AXI U RATI GS Input Voltage .......................................................... 40V Input/Output Voltage Differential ............................ 35V Output-to-Ground Voltage (Shunt Mode Current Limit) LT1021-5 ............................................................. 10V LT1021-7 ............................................................. 10V LT1021-10 ........................................................... 16V Trim Pin-to-Ground Voltage Positive ............................................... Equal to VOUT Negative ........................................................... – 20V PACKAGE/ORDER I FOR ATIO ORDER PART NUMBER LT1021BCH-5 LT1021BMH-5 LT1021CCH-5 LT1021CMH-5 LT1021DCH-5 LT1021DMH-5 LT1021BCH-7 LT1021BMH-7 LT1021DCH-7 LT1021DMH-7 LT1021BCH-10 LT1021BMH-10 LT1021CCH-10 LT1021CMH-10 LT1021DCH-10 LT1021DMH-10 TOP VIEW NC* 8 NC* 1 VIN 2 NC* 3 7 NC* 6 VOUT 5 TRIM** 4 GND H PACKAGE 8-LEAD TO-5 METAL CAN *CONNECTED INTERNALLY. D0 NOT CONNECT EXTERNAL CIRCUITRY TO THESE PINS **NO TRIM PIN ON LT1021-7. DO NOT CONNECT EXTERNAL CIRCUITRY TO PIN 5 ON LT1021-7 TJMAX = 150°C, θJA = 150°C/W,θJC = 45°C/W 2 U U W WW U W (Note 1) Output Short-Circuit Duration VIN = 35V ......................................................... 10 sec VIN ≤ 20V ................................................... Indefinite Operating Temperature Range Commercial ............................................ 0°C to 70°C Industrial ........................................... – 40°C to 85°C Military ............................................ – 55°C to 125°C Storage Temperature Range ................ – 65°C to 150°C Lead Temperature (Soldering, 10 sec)................ 300°C ORDER PART NUMBER LT1021BCN8-5 LT1021CCN8-5 LT1021CIN8-5 LT1021DCN8-5 LT1021DIN8-5 LT1021DCS8-5 LT1021BCN8-7 LT1021DCN8-7 LT1021DCS8-7 LT1021BCN8-10 LT1021CCN8-10 LT1021CIN8-10 LT1021DCN8-10 LT1021DCS8-10 LT1021DIN8-10 TOP VIEW DNC* 1 VIN 2 DNC* 3 GND 4 N8 PACKAGE 8-LEAD PDIP 8 7 6 5 DNC* DNC* V0UT TRIM** S8 PACKAGE 8-LEAD PLASTIC SO *CONNECTED INTERNALLY. D0 NOT CONNECT EXTERNAL CIRCUITRY TO THESE PINS **NO TRIM PIN ON LT1021-7. DO NOT CONNECT EXTERNAL CIRCUITRY TO PIN 5 ON LT1021-7 TJMAX = 130°C, θJA = 130°C/W (N) TJMAX = 130°C, θJA = 150°C/W (S) S8 PART MARKING 021DC5 021DC7 021DC1 LT1021 The q denotes specifications that apply over the full operating temperature range, otherwise specifications are TA = 25°C. VIN = 10V, IOUT = 0, unless otherwise noted. PARAMETER Output Voltage (Note 2) Output Voltage Temperature Coefficient (Note 3) CONDITIONS LT1021C-5 LT1021B-5/LT1021D-5 TMIN ≤ TJ ≤ TMAX LT1021B-5 LT1021C-5/LT1021D-5 7.2V ≤ VIN ≤ 10V q q q ELECTRICAL CHARACTERISTICS MIN 4.9975 4.9500 LT1021-5 TYP 5.000 5.000 2 3 4 2 MAX 5.0025 5.0500 5 20 12 20 6 10 20 35 100 150 1.2 1.5 3.5 UNITS V V ppm/°C ppm/°C ppm/V ppm/V ppm/V ppm/V ppm/mA ppm/mA ppm/mA ppm/mA mA mA µVP-P µVRMS ppm ppm Line Regulation (Note 4) 10V ≤ VIN ≤ 40V q Load Regulation (Sourcing Current) Load Regulation (Sinking Current) Supply Current 0 ≤ IOUT ≤ 10mA (Note 4) 0 ≤ IOUT ≤ 10mA (Note 4) 10 q 60 q 0.8 q Output Voltage Noise (Note 6) Long Term Stability of Output Voltage (Note 7) Temperature Hysteresis of Output 0.1Hz ≤ f ≤ 10Hz 10Hz ≤ f ≤ 1kHz ∆t = 1000Hrs Noncumulative ∆T = ± 25°C 3.0 2.2 15 10 The q denotes specifications that apply over the full operating temperature range, otherwise specifications are TA = 25°C. VIN = 12V, IOUT = 0, unless otherwise noted. PARAMETER Output Voltage (Note 2) Output Voltage Temperature Coefficient (Note 3) TMIN ≤ TJ ≤ TMAX LT1021B-7 LT1021D-7 8.5V ≤ VIN ≤ 12V q q q CONDITIONS MIN 6.95 LT1021-7 TYP 7.00 2 3 1.0 2.0 0.5 1.0 12 MAX 7.05 5 20 4 8 2 4 25 40 100 150 1.2 1.5 1.0 1.2 4.0 UNITS V ppm/°C ppm/°C ppm/V ppm/V ppm/V ppm/V ppm/mA ppm/mA ppm/mA ppm/mA mA mA mA mA µVP-P µVRMS ppm ppm Line Regulation (Note 4) 12V ≤ VIN ≤ 40V q Load Regulation (Sourcing Current) Load Regulation (Shunt Mode) Supply Current (Series Mode) 0 ≤ IOUT ≤ 10mA (Note 4) 1.2mA ≤ ISHUNT ≤ 10mA (Notes 4, 5) q 50 q 0.75 q Minimum Current (Shunt Mode) Output Voltage Noise (Note 6) Long Term Stability of Output Voltage (Note 7) Temperature Hysteresis of Output VIN is Open q 0.7 4.0 2.5 7 3 0.1Hz ≤ f ≤ 10Hz 10Hz ≤ f ≤ 1kHz ∆t = 1000Hrs Noncumulative ∆T = ± 25°C 3 LT1021 The q denotes specifications that apply over the full operating temperature range, otherwise specifications are TA = 25°C. VIN = 15V, IOUT = 0, unless otherwise noted. PARAMETER Output Voltage (Note 2) Output Voltage Temperature Coefficient (Note 3) CONDITIONS LT1021C-10 LT1021B-10/LT1021D-10 TMIN ≤ TJ ≤ TMAX LT1021B-10 LT1021C-10/LT1021D-10 11.5V ≤ VIN ≤ 14.5V q q q ELECTRICAL CHARACTERISTICS MIN 9.995 9.950 LT1021-10 TYP 10.00 10.00 2 5 1.0 0.5 MAX 10.005 10.050 5 20 4 6 2 4 25 40 100 150 1.7 2.0 1.5 1.7 6 UNITS V V ppm/°C ppm/°C ppm/V ppm/V ppm/V ppm/V ppm/mA ppm/mA ppm/mA ppm/mA mA mA mA mA µVP-P µVRMS ppm ppm Line Regulation (Note 4) 14.5V ≤ VIN ≤ 40V q Load Regulation (Sourcing Current) Load Regulation (Shunt Mode) Supply Current (Series Mode) 0 ≤ IOUT ≤ 10mA (Note 4) 1.7mA ≤ ISHUNT ≤ 10mA (Notes 4, 5) 12 q 50 q 1.2 q Minimum Current (Shunt Mode) Output Voltage Noise (Note 6) Long Term Stability of Output Voltage (Note 7) Temperature Hysteresis of Output VIN is Open q 1.1 6.0 3.5 15 5 0.1Hz ≤ f ≤ 10Hz 10Hz ≤ f ≤ 1kHz ∆t = 1000Hrs Noncumulative ∆T = ± 25°C Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: Output voltage is measured immediately after turn-on. Changes due to chip warm-up are typically less than 0.005%. Note 3: Temperature coefficient is measured by dividing the change in output voltage over the temperature range by the change in temperature. Separate tests are done for hot and cold; TMIN to 25°C and 25°C to TMAX. Incremental slope is also measured at 25°C. Note 4: Line and load regulation are measured on a pulse basis. Output changes due to die temperature change must be taken into account separately. Package thermal resistance is 150°C/W for TO-5 (H), 130°C/W for N and 150°C/W for the SO-8. Note 5: 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. Note 6: 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 correct for the non-ideal bandpass 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 7: Consult factory for units with long term stability data. 4 LT1021 TYPICAL PERFOR A CE CHARACTERISTICS Ripple Rejection 115 110 REJECTION (dB) f = 150Hz LT1021-7 120 LT1021-10 110 LT1021-7 INPUT/OUTPUT VOLTAGE (V) REJECTION (dB) 105 100 LT1021-5 95 90 85 0 5 10 15 20 25 30 INPUT VOLTAGE (V) Start-Up (Series Mode) 13 12 11 OUTPUT VOLTAGE (V) OUTPUT VOLTAGE (V) VIN = 0V TO 12V 10 9 8 7 6 5 4 3 0 2 4 LT1021-10 VOUT + 2V 1k VOUT OUT IN GND NOISE VOLTAGE (nV/√Hz) LT1021-7 LT1021-5 6 8 TIME (µs) 10 Output Voltage Noise 16 14 12 RMS NOISE (µV) COUT = 0 FILTER = 1 POLE fLOW = 0.1Hz OUTPUT CHANGE (mV) OUTPUT VOLTAGE (V) 10 8 LT1021-7 6 4 LT1021-5 2 0 10 100 1k BANDWIDTH (Hz) 10k LT1021 G07 LT1021-10 UW 35 40 LT1021 G01 Ripple Rejection 130 Minimum Input/Output Differential LT1021-7, LT1021-10 1.6 TJ = 125 °C TJ = – 55 °C TJ = 25 °C 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 VIN = 15V COUT = 0 100 LT1021-10 90 LT1021-5 80 70 60 50 10 100 1k FREQUENCY (Hz) 10k LT1021 G02 0 2 4 6 8 10 12 14 16 18 20 OUTPUT CURRENT (mA) 1021 G03 Start-Up (Shunt Mode) LT1021-7, LT1021-10 11 LT1021-10 10 9 8 7 6 5 12 14 0V NC Output Voltage Noise Spectrum 400 350 300 250 200 150 100 50 0 LT1021-10 LT1021-7 LT1021-5 LT1021-7 0 2 6 4 TIME (µs) 8 10 12 10 100 1k FREQUENCY (Hz) 10k LT1021 G06 LT1021 G04 LT1021 G05 Output Voltage Temperature Drift LT1021-5 5.006 5.004 5.002 5.000 4.998 4.996 4.994 – 50 –25 Load Regulation LT1021-5 5 4 3 2 1 0 –1 –2 –3 –4 VIN = 8V 50 0 75 25 TEMPERATURE (°C) 100 125 –5 –10 – 8 – 6 – 4 – 2 SOURCING 0 2 468 SINKING 10 LT1021 G08 OUTPUT CURRENT (mA) LT1021 G09 5 LT1021 TYPICAL PERFOR A CE CHARACTERISTICS Quiescent Current LT1021-5 1.8 1.6 1.4 INPUT CURRENT (mA) IOUT = 0 CURRENT INTO OUTPUT (mA) 1.2 1.0 0.8 0.6 0.4 0.2 0 0 5 10 TJ = – 55°C TJ = 25°C TJ = 125°C 40 30 20 10 0 OUTPUT CHANGE (mV) 15 20 25 30 INPUT VOLTAGE (V) Load Transient Response LT1021-5, CLOAD = 0 ISOURCE = 0 ISINK = 0 OUTPUT VOLTAGE NOISE (5µV/DIV) OUTPUT CHANGE (50mV/DIV) OUTPUT CHANGE (20mV/DIV) 50mV 50mV ISOURCE = 0.5mA ISOURCE = 2-10mA ISINK = 0.2mA ISINK = 2-10mA ∆ISOURCE = 100µAP-P 0 1 2 ∆ISINK = 100µAP-P 1 2 3 4 340 TIME (µs) Output Voltage Temperature Drift LT1021-7 7.003 7.002 OUTPUT CHANGE (mV) OUTPUT VOLTAGE (V) 7.001 7.000 6.999 6.998 6.997 – 50 –25 2 1 0 –1 –2 –3 –4 INPUT CURRENT (mA) 50 0 75 25 TEMPERATURE (°C) 6 UW 35 40 LT1021 G10 LT1021 G13 Sink Mode* Current Limit LT1021-5 60 50 VIN = 8V Thermal Regulation LT1021-5 VIN = 25V ∆POWER = 200mW 0 – 0.5 – 1.0 LOAD REGULATION THERMAL REGULATION ILOAD = 10mA 0 2 4 6 8 10 12 14 OUTPUT VOLTAGE (V) 16 18 0 20 40 60 80 TIME (ms) 100 120 140 LT1021 G12 *NOTE THAT AN INPUT VOLTAGE IS REQUIRED FOR 5V UNITS. LT1021 G11 Load Transient Response LT1021-5, CLOAD = 1000pF ISOURCE = 0 ISINK = 0 Output Noise 0.1Hz to 10Hz LT1021-5 FILTERING = 1 ZERO AT 0.1Hz 2 POLES AT 10Hz 5µV (1ppm) 20mV 20mV ISOURCE = 0.2mA ISOURCE = 2-10mA ISINK = 0.2mA ISINK = 2-10mA ∆ISOURCE = 100µAP-P 0 5 ∆ISINK = 100µAP-P 5 10 15 20 LT1021 G14 10 15 20 0 TIME (µs) 0 1 4 3 2 TIME (MINUTES) 5 6 LT1021 G15 Load Regulation LT1021-7, LT1021-10 5 4 3 VIN = 12V 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 Quiescent Current LT1021-7 IOUT = 0 TJ = – 55°C TJ = 25°C TJ = 125°C 100 125 –5 –10 – 8 – 6 – 4 – 2 SOURCING 0 2 468 SINKING 10 0 0 5 10 15 20 25 30 INPUT VOLTAGE (V) 35 40 LT1021 G16 OUTPUT CURRENT (mA) LT1021 G17 LT1021 G18 LT1021 TYPICAL PERFOR A CE CHARACTERISTICS Shunt Characteristics LT1021-7 1.2 1.0 0.8 0.6 0.4 0.2 0 0 7 1 3 8 2 5 6 4 OUTPUT TO GROUND VOLTAGE (V) 9 TJ = 125°C INPUT PIN OPEN CURRENT INTO OUTPUT (mA) 60 50 40 30 20 10 0 0 2 4 6 8 10 12 14 OUTPUT VOLTAGE (V) 16 18 CURRENT INTO OUTPUT (mA) TJ = – 55°C TJ = 25°C OUTPUT CHANGE (mV) Load Transient Response LT1021-7, CLOAD = 0 ISINK = 0.8mA ISOURCE = 0 ISINK = 1.2mA 5mV 50mV ISOURCE = 0.5mA ISINK = 1.4mA ISOURCE = 2-10mA ∆ISOURCE = 100µAP-P 0 1 2 ISINK = 2-10mA ∆ISINK = 100µAP-P 1 2 3 4 5mV 20mV OUTPUT VOLTAGE NOISE (5µV/DIV) OUTPUT VOLTAGE CHANGE OUTPUT VOLTAGE CHANGE 340 TIME (µs) NOTE VERTICAL SCALE CHANGE BETWEEN SOURCING AND SINKING LT1021 G22 Output Voltage Temperature Drift LT1021-10 10.006 10.004 OUTPUT CHANGE (mV) OUTPUT VOLTAGE (V) 10.002 10.000 9.998 9.996 9.994 – 50 –25 2 1 0 –1 –2 –3 –4 INPUT CURRENT (mA) 50 0 75 25 TEMPERATURE (°C) UW 1021 G19 Shunt Mode Current Limit LT1021-7 INPUT PIN OPEN Thermal Regulation LT1021-7 VIN = 27V ∆POWER = 200mW 0 – 0.5 –1.0 –1.5 ILOAD = 10mA THERMAL REGULATION* LOAD REGULATION 0 20 40 60 80 TIME (ms) 100 120 140 LT1021 G20 *INDEPENDENT OF TEMPERATURE COEFFICIENT LT1021 G21 Load Transient Response LT1021-7, CLOAD = 1000pF ISOURCE = 0 ISINK = 0.6mA Output Noise 0.1Hz to 10Hz LT1021-7 FILTERING = 1 ZERO AT 0.1Hz 2 POLES AT 10Hz 5µV (0.7ppm) ISINK = 0.8mA ISOURCE = 0.5mA ISINK = 1mA ISOURCE = 2-10mA ∆ISOURCE = 100µAP-P 0 5 ISINK = 2-10mA ∆ISINK = 100µAP-P 5 10 15 20 10 15 20 0 5µs/DIV 0 1 4 3 2 TIME (MINUTES) 5 6 NOTE VERTICAL SCALE CHANGE BETWEEN SOURCING AND SINKING LT1021 G23 LT1021 G24 Load Regulation LT1021-7, LT1021-10 5 4 3 VIN = 12V 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 Input Supply Current LT1021-10 IOUT = 0 TJ = – 55°C TJ = 25°C TJ = 125°C 100 125 –5 –10 – 8 – 6 – 4 – 2 SOURCING 0 2 468 SINKING 10 0 0 5 10 15 20 25 30 INPUT VOLTAGE (V) 35 40 LT1021 G25 OUTPUT CURRENT (mA) 1021 G26 1021 G27 7 LT1021 TYPICAL PERFOR A CE CHARACTERISTICS Shunt Characteristics LT1021-10 1.8 1.6 CURRENT INTO OUTPUT (mA) CURRENT INTO OUTPUT (mA) INPUT PIN OPEN 1.2 1.0 0.8 0.6 0.4 0.2 0 0 2 4 6 10 8 OUTPUT TO GROUND VOLTAGE (V) 12 TJ = 125°C TJ = 25°C TJ = – 55°C 40 30 20 10 0 0 2 4 6 8 10 12 14 OUTPUT VOLTAGE (V) 16 18 OUTPUT CHANGE (mV) 1.4 Load Transient Response LT1021-10, CLOAD = 0 ISINK = 0.6mA ISOURCE = 0 ISOURCE = 0 OUTPUT VOLTAGE CHANGE 50mV 10mV ISINK = 0.8mA ISOURCE = 0.2mA 20mV 5mV ISINK = 1.2mA OUTPUT VOLTAGE NOISE (10µV/DIV) OUTPUT VOLTAGE CHANGE ISINK = 1mA ISINK = 2-10mA ∆ISINK = 100µAP-P 1 2 3 4 ISOURCE = 2-10mA ∆ISOURCE = 100µAP-P 0 1 2 340 TIME (µs) NOTE VERTICAL SCALE CHANGE BETWEEN SOURCING AND SINKING 1021 G31 8 UW 1021 G28 Shunt Mode Current Limit LT1021-10 60 50 0 – 0.5 –1.0 –1.5 Thermal Regulation LT1021-10 VIN = 30V ∆POWER = 200mW LOAD REGULATION INPUT PIN OPEN THERMAL REGULATION* ILOAD = 10mA 0 20 40 60 80 TIME (ms) 100 120 140 1021 G29 *INDEPENDENT OF TEMPERATURE COEFFICIENT 1021 G30 Load Transient Response LT1021-10, CLOAD = 1000pF ISINK = 0.8mA Output Noise 0.1Hz to 10Hz LT1021-10 FILTERING = 1 ZERO AT 0.1Hz 2 POLES AT 10Hz 10µV (1ppm) ISOURCE = 0.5mA ISINK = 1.4mA ISOURCE = 2-10mA ∆ISOURCE = 100µAP-P 0 1 2 ISINK = 2-10mA ∆ISINK = 100µAP-P 1 2 3 4 340 TIME (µs) 0 1 4 3 2 TIME (MINUTES) 5 6 1021 G33 NOTE VERTICAL SCALE CHANGE BETWEEN SOURCING AND SINKING 1021 G32 LT1021 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 0.5LSB error. For this reason, the LT1021 family has been optimized for low drift. Maximum Allowable Reference Drift MAXIMUM TEMPERATURE COEFFICIENT FOR 0.5LSB ERROR (ppm/°C) 100 8-BIT 10-BIT 10 IN LT1021-5 OUT TRIM R1 27k R2 50k 1N4148 VOUT 12-BIT 14-BIT 1.0 0 10 20 30 40 50 60 70 80 90 100 TEMPERATURE SPAN (°C) LT1021 AI01 Trimming Output Voltage LT1021-10 The LT1021-10 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 LT1021 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. U W U U The LT1021-10 “C” version is pre-trimmed to ± 5mV and therefore can utilize a restricted trim range. A 75k resistor 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 “C” device to 10.000V. LT1021-5 The LT1021-5 does have an output voltage trim pin, but the TC of the nominal 4V open-circuit voltage at this pin 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 LT1021-5 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. GND 1021 AI02 LT1021-7 The 7V version of the LT1021 has no trim pin because the internal architecture does not have a point which could be driven conveniently from the output. Trimming must therefore be done externally, as is the case with ordinary reference diodes. Unlike these diodes, however, the output of the LT1021 can be loaded with a trim potentiometer. The following trim techniques are suggested; one for voltage output and one for current output. The voltage output is trimmed for 6.95V. Current output is 1mA, as shown, into a summing junction, but all resistors may be scaled for currents up to 10mA. Both of these circuits use the trimmers in a true potentiometric mode to reduce the effects of trimmer TC. The voltage output has a 200Ω impedance, so loading must be 9 LT1021 APPLICATIONS INFORMATION minimized. In the current output circuit, R1 determines output current. It should have a TC commensurate with the LT1021 or track closely with the feedback resistor around the op amp. LT1021-7 IN GND R3 10k OUT R2* 14k 1% R1* 200Ω 1% VOUT 6.950V TC TRACKING TO 50ppm/°C 1021 AI03 LT1021-7 IN GND R3 50k R2** 182k OUT R1* 7.15k 1.000mA – OP AMP + 1021 AI04 *RESISTOR TC DETERMINES IOUT TC **TC ≤ (10 • R1) TC. R2 AND R3 SCALE WITH R1 FOR DIFFERENT OUTPUT CURRENTS Capacitive Loading and Transient Response The LT1021 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 worst-case at light load currents. Because of internal current drain on the output, actual worstcase occurs at I LOAD = 0 o n LT1021-5, I LOAD = – 0.8mA (sinking) on LT1021-7 and ILOAD = 1.4mA (sinking) on LT1021-10. 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. Series Mode with Boost Transistor INPUT R1 220Ω 2N3906 10 U W U U Kelvin Connections Although the LT1021 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 LT1021 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. Standard Series Mode LT1021 INPUT IN GND OUT KEEP THIS LINE RESISTANCE LOW + LOAD GROUND RETURN 1021 AI05 IN LT1021 OUT GND R2* LOAD GROUND RETURN 1021 AI06 *OPTIONAL—REDUCES CURRENT IN OUTPUT SENSE LEAD R2 = 2.4k (LT1021-5), 3k (LT1021-7), 5.6k (LT1021-10) LT1021 APPLICATIONS INFORMATION Effects of Air Movement on Low Frequency Noise The LT1021 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 (especially kovar lead TO-5) and printed circuit board materials and/or sockets. Power dissipation in the reference, even though it rarely exceeds 20mW, is enough to cause small 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. The following XY plotter trace dramatically illustrates this effect. The first half of the plot was done with the LT1021 shielded from ambient air with a small foam cup. The cup was then removed for the second half of the trace. Ambient in both cases was a lab environment with no excessive air turbulence from air conditioners, opening/closing doors, etc. Removing the foam cup increases the output noise by almost an order of magnitude in the 0.01Hz to 1Hz band! The kovar leads of the TO-5 (H) package are the primary culprit. Alloy 42 and copper lead frames used on dual-in-line packages are not nearly as sensitive to thermally generated noise because they are intrinsically matched. There is nothing magical about foam cups—any enclosure which blocks air flow from the reference will do. Smaller enclosures are better since they do not allow the build-up of internally generated air movement. Naturally, heat generating components external to the reference itself should not be included inside the enclosure. Noise Induced By Air Turbulence (TO-5 Package) LT1021-7 (TO-5 PACKAGE) f = 0.01Hz TO 10Hz 20µV OUTPUT VOLTAGE NOISE (20µV/DIV) TYPICAL APPLICATIONS Restricted Trim Range for Improved Resolution, 10V, “C” Version Only LT1021-10 Full Trim Range (± 0.7%) Negative Series Reference 15V LT1021C-10 VIN IN GND OUT TRIM R1 75k R2 50k 10.000V VIN LT1021-10 IN GND OUT TRIM R1* 10k VOUT 1021 TA11 TRIM RANGE ≈ ± 10mV U W U U U FOAM CUP REMOVED 0 2 8 6 4 TIME (MINUTES) 10 12 1021 AI07 R1 4.7k D1 15V LT1021-10 IN OUT GND R2 4.7k 1021 TA03 –15V *CAN BE RAISED TO 20k FOR LESS CRITICAL APPLICATIONS Q1 2N2905 –10V AT 50mA LT1021 TA04 11 LT1021 TYPICAL APPLICATIONS Boosted Output Current with No Current Limit V + ≥ (VOUT + 1.8V) R1 220Ω 2N2905 IN LT1021 OUT GND 10V AT 100mA + 6 LT1001 3 1021 TA06 4 –15V IOUT = 1mA REGULATION < 1ppm/V COMPLIANCE = –13V TO 7V 1021 TA07 *GLOWS IN CURRENT LIMIT, DO NOT OMIT 2-Pole Lowpass Filtered Reference Operating 5V Reference from 5V Supply 5V LOGIC SUPPLY 1µF MYLAR VIN 1N914 CMOS LOGIC GATE** fIN ≥ 2kHz* 1N914 ≈ 8.5V C2* 5µF LT1021-5 IN GND OUT 5V REFERENCE – LT1021 VIN IN GND OUT R1 36k f = 10Hz R2 36k LT1001 VREF + 0.5µF MYLAR TOTAL NOISE ≤ 2µVRMS 1Hz ≤ f ≤ 10kHz C1* 5µF + *FOR HIGHER FREQUENCIES C1 AND C2 MAY BE DECREASED **PARALLEL GATES FOR HIGHER REFERENCE CURRENT LOADING –VREF 1021 TA13 Trimming 10V Units to 10.24V CMOS DAC with Low Drift Full-Scale Trimming** LT1021-10 OUT LT1021-10 TRIM GND R1 4.99k 1% REF R2 40.2Ω 1% 1.2k –15V *TC LESS THAN 200ppm/°C **NO ZERO ADJUST REQUIRED WITH LT1007 (V0S ≤ 60µV) CMOS DAC 7520, ETC FB 30pF IOUT R3 4.02K 1% VIN R4* 100Ω FULL-SCALE ADJUST 10V F.S. IN TRIM OUT GND – LT1007C + V – = –15V* *MUST BE WELL REGULATED dVOUT 15mV = V dV – 1021 TA12 LT1236 TA15 12 + 1021 TA05 – 2µF SOLID TANT + U Boosted Output Current with Current Limit V + ≥ VOUT + 2.8V D1* LED R1 220Ω 8.2Ω 15V IN Ultraprecise Current Source LT1021-7 OUT GND TRIM 100Ω 17.4k 1% 2N2905 IN LT1021 OUT GND 10V AT 100mA 15V 7 2 6.98k* 0.1% *LOW TC + 2µF SOLID TANT 1021 TA16 VOUT = 10.24V 4.32k 5k LT1021 TYPICAL APPLICATIONS Strain Gauge Conditioner for 350Ω Bridge R1 357Ω 1/2W LT1021-10 15V IN GND OUT 28mA 28.5mA 5V 350Ω STRAIN GAUGE BRIDGE** R2 20k R4 20k 3 6 1 LM301A † 2 100pF 8 *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 Precision DAC Reference with System TC Trim LT1021-10 15V IN GND OUT 8.87k 1% D1 1N457 1.24k 1% 50k TC TRIM* 10k 1% 50k ROOM TEMP TRIM *TRIMS 1mA REFERENCE CURRENT TC BY ± 40ppm/°C. THIS TRIM SCHEME HAS VERY LITTLE EFFECT ON ROOM TEMPERATURE CURRENT TO MINIMIZE ITERATIVE TRIMMING U Negative Shunt Reference Driven by Current Source LT1021-10 OUT GND –10V (ILOAD ≤ 1mA) 2.5mA R3 2M 2 – + – LT1012C 6 LM334 VOUT × 100 27Ω 3 R5 2M + R6* 2M –5V 357Ω 1/2W –15V **BRIDGE IS ULTRALINEAR 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 1021 TA09 –11V TO – 40V 1021 TA14 Handling Higher Load Currents 15V 30mA IN LT1021-10 OUT GND 10.36k 1% R1* 169Ω VOUT 10V RL TYPICAL LOAD CURRENT = 30mA 10k 1% D2 1N457 50k 200k 1% 1mA 8.45k 1021 TA08 *SELECT R1 TO DELIVER TYPICAL LOAD CURRENT. LT1021 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 DAC 1021 TA17 13 LT1021 TYPICAL APPLICATIONS Ultralinear Platinum Temperature Sensor* LT1021-10 OUT R2* 5k R1** 253k R11 6.65M 1% R15 10k R12 1k R13 24.3k 6 VOUT =100mV/°C – 50°C ≤ T ≤ 150°C R10 182k 1% GND IN 20V R9 100k R8 10M R3** 5k RS† 100Ω AT 0°C R7 392k 1% –15V EQUIVALE T SCHE ATIC INPUT Q3 D1 D2 OUTPUT D3 Q1 R1 14 U R14 5k RF** 654k 20V R4 4.75k 1% R5 200k 1% 2 – + 7 LT1001 3 4 –15V R6 619k 1% 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 **WIREWOUND RESISTORS WITH LOW TC 1021 TA10 † W U – A1 D4 6.3V + R2 Q2 GND LT1021 ES LT1021 PACKAGE DESCRIPTION Dimensions in inches (millimeters) unless otherwise noted. H Package 8-Lead TO-5 Metal Can (0.200 PCD) (LTC DWG # 05-08-1320) 0.335 – 0.370 (8.509 – 9.398) DIA 0.305 – 0.335 (7.747 – 8.509) 0.040 (1.016) MAX 0.050 (1.270) MAX GAUGE PLANE 0.010 – 0.045* (0.254 – 1.143) 0.016 – 0.021** (0.406 – 0.533) 0.165 – 0.185 (4.191 – 4.699) REFERENCE PLANE 0.500 – 0.750 (12.700 – 19.050) SEATING PLANE 45°TYP 0.028 – 0.034 (0.711 – 0.864) 0.300 – 0.325 (7.620 – 8.255) 0.009 – 0.015 (0.229 – 0.381) ( +0.035 0.325 –0.015 8.255 +0.889 –0.381 ) *THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.010 INCH (0.254mm) 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. U 0.027 – 0.045 (0.686 – 1.143) PIN 1 0.200 (5.080) TYP 0.110 – 0.160 (2.794 – 4.064) INSULATING STANDOFF *LEAD DIAMETER IS UNCONTROLLED BETWEEN THE REFERENCE PLANE AND 0.045" BELOW THE REFERENCE PLANE 0.016 – 0.024 **FOR SOLDER DIP LEAD FINISH, LEAD DIAMETER IS (0.406 – 0.610) H8(TO-5) 0.200 PCD 1197 N8 Package 8-Lead PDIP (Narrow 0.300) (LTC DWG # 05-08-1510) 0.400* (10.160) MAX 8 7 6 5 0.255 ± 0.015* (6.477 ± 0.381) 1 2 3 4 0.130 ± 0.005 (3.302 ± 0.127) 0.045 – 0.065 (1.143 – 1.651) 0.065 (1.651) TYP 0.125 (3.175) 0.020 MIN (0.508) MIN 0.018 ± 0.003 (0.457 ± 0.076) N8 1098 0.100 (2.54) BSC 15 LT1021 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 0.010 – 0.020 × 45° (0.254 – 0.508) 0.008 – 0.010 (0.203 – 0.254) 0°– 8° TYP 0.016 – 0.050 0.406 – 1.270 *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 RELATED PARTS PART NUMBER LT1019 LT1027 LT1236 LTC 1258 LT1389 LT1460 LT1634 ® DESCRIPTION Precision Bandgap Reference Precision 5V Reference Precision Reference Micropower Reference Nanopower Shunt Reference Micropower Reference Micropower Shunt Reference 16 Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408)432-1900 q FAX: (408) 434-0507 q www.linear-tech.com U 0.228 – 0.244 (5.791 – 6.197) 0.150 – 0.157** (3.810 – 3.988) 1 2 3 4 0.053 – 0.069 (1.346 – 1.752) 0.004 – 0.010 (0.101 – 0.254) 0.014 – 0.019 (0.355 – 0.483) 0.050 (1.270) TYP SO8 0996 COMMENTS 0.05%, 5ppm/°C 0.02%, 2ppm/°C SO-8, 5V and 10V, 0.05%, 5ppm/°C 200mV Dropout, MSOP 800nA Operating Current SOT-23, 2.5V, 5V, 10V 0.05%, 10ppm/°C, MSOP 1021fa LT/GP 0399 2K REV A • PRINTED IN USA © LINEAR TECHNOLOGY CORPORATION 1995