LT1021 Precision Reference U DESCRIPTIO FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ 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: <1ppm P-P (0.1Hz to 10Hz) >100dB Ripple Rejection Minimum Input/Output Differential of 1V 100% Noise Tested UO APPLICATI ■ ■ ■ ■ ■ ■ S A/D and D/A Converters Precision Regulators Digital Voltmeters Inertial Navigation Systems Precision Scales Portable Reference Standard 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. UO TYPICAL APPLICATI Typical Distribution of Temperature Drift 24 Basic Positive and Negative Connections 21 LT1021 (7 AND 10 ONLY) VIN IN OUT VOUT NC IN GND 18 OUT GND –VOUT V – (V – ) R1 = OUT ILOAD + 1.5mA 15 12 9 6 R1 –15V (V – ) UNITS (%) LT1021 DISTRIBUTION OF THREE RUNS 3 1021 TA01 –0 – 5 – 4 – 3 – 2 –1 0 1 2 3 OUTPUT DRIFT (ppm/°C) 4 5 1021 TA01 1 LT1021 W W W AXI U U ABSOLUTE RATI GS (Note 1) 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 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 U W U PACKAGE/ORDER I FOR ATIO TOP VIEW NC* 8 NC* 1 7 NC* 6 VIN 2 NC* 3 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 ORDER PART NUMBER 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 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 8 DNC* VIN 2 7 DNC* DNC* 3 6 V0UT GND 4 5 TRIM** N8 PACKAGE 8-LEAD PDIP 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 2 LT1021 ELECTRICAL CHARACTERISTICS The ● denotes specifications that apply over the full operating temperature range, otherwise specifications are TA = 25°C. VIN = 10V, IOUT = 0, unless otherwise noted. PARAMETER CONDITIONS Output Voltage (Note 2) LT1021C-5 LT1021B-5/LT1021D-5 Output Voltage Temperature Coefficient (Note 3) TMIN ≤ TJ ≤ TMAX LT1021B-5 LT1021C-5/LT1021D-5 Line Regulation (Note 4) MIN LT1021-5 TYP MAX 4.9975 4.9500 5.000 5.000 5.0025 5.0500 2 3 5 20 ppm/°C ppm/°C 4 12 20 6 10 ppm/V ppm/V ppm/V ppm/V 10 20 35 ppm/mA ppm/mA 60 100 150 ppm/mA ppm/mA 0.8 1.2 1.5 mA mA 3.5 µVP-P µVRMS ● ● 7.2V ≤ VIN ≤ 10V ● 10V ≤ VIN ≤ 40V 2 ● Load Regulation (Sourcing Current) Load Regulation (Sinking Current) 0 ≤ IOUT ≤ 10mA (Note 4) ● 0 ≤ IOUT ≤ 10mA (Note 4) ● Supply Current ● UNITS V V 0.1Hz ≤ f ≤ 10Hz 10Hz ≤ f ≤ 1kHz 3.0 2.2 Long Term Stability of Output Voltage (Note 7) ∆t = 1000Hrs Noncumulative 15 ppm Temperature Hysteresis of Output ∆T = ±25°C 10 ppm Output Voltage Noise (Note 6) The ● denotes specifications that apply over the full operating temperature range, otherwise specifications are TA = 25°C. VIN = 12V, IOUT = 0, unless otherwise noted. PARAMETER CONDITIONS Output Voltage (Note 2) Output Voltage Temperature Coefficient (Note 3) Line Regulation (Note 4) TMIN ≤ TJ ≤ TMAX LT1021B-7 LT1021D-7 ● ● 8.5V ≤ VIN ≤ 12V ● 12V ≤ VIN ≤ 40V ● Load Regulation (Sourcing Current) Load Regulation (Shunt Mode) 0 ≤ IOUT ≤ 10mA (Note 4) ● 1.2mA ≤ ISHUNT ≤ 10mA (Notes 4, 5) ● Supply Current (Series Mode) MIN LT1021-7 TYP MAX UNITS 6.95 7.00 7.05 V 2 3 5 20 ppm/°C ppm/°C 1.0 2.0 0.5 1.0 4 8 2 4 ppm/V ppm/V ppm/V ppm/V 12 25 40 ppm/mA ppm/mA 50 100 150 ppm/mA ppm/mA 0.75 1.2 1.5 mA mA 0.7 1.0 1.2 mA mA 4.0 µVP-P µVRMS ● Minimum Current (Shunt Mode) VIN is Open ● Output Voltage Noise (Note 6) 0.1Hz ≤ f ≤ 10Hz 10Hz ≤ f ≤ 1kHz 4.0 2.5 Long Term Stability of Output Voltage (Note 7) ∆t = 1000Hrs Noncumulative 7 ppm Temperature Hysteresis of Output ∆T = ±25°C 3 ppm 3 LT1021 ELECTRICAL CHARACTERISTICS The ● denotes specifications that apply over the full operating temperature range, otherwise specifications are TA = 25°C. VIN = 15V, IOUT = 0, unless otherwise noted. PARAMETER CONDITIONS MIN LT1021-10 TYP MAX Output Voltage (Note 2) LT1021C-10 LT1021B-10/LT1021D-10 9.995 9.950 10.00 10.00 10.005 10.050 Output Voltage Temperature Coefficient (Note 3) TMIN ≤ TJ ≤ TMAX LT1021B-10 LT1021C-10/LT1021D-10 2 5 5 20 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 4) ● ● 11.5V ≤ VIN ≤ 14.5V ● 14.5V ≤ VIN ≤ 40V 0.5 ● Load Regulation (Sourcing Current) Load Regulation (Shunt Mode) 0 ≤ IOUT ≤ 10mA (Note 4) ● 1.7mA ≤ ISHUNT ≤ 10mA (Notes 4, 5) ● Supply Current (Series Mode) ● Minimum Current (Shunt Mode) VIN is Open ● UNITS V V 0.1Hz ≤ f ≤ 10Hz 10Hz ≤ f ≤ 1kHz 6.0 3.5 Long Term Stability of Output Voltage (Note 7) ∆t = 1000Hrs Noncumulative 15 ppm Temperature Hysteresis of Output ∆T = ±25°C 5 ppm Output Voltage Noise (Note 6) 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. 4 6 µVP-P µVRMS 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. LT1021 U W TYPICAL PERFOR A CE CHARACTERISTICS VIN = 15V COUT = 0 LT1021-7 120 REJECTION (dB) 105 LT1021-7 110 LT1021-10 100 LT1021-5 95 100 LT1021-10 90 LT1021-5 80 70 90 60 0 5 10 15 20 25 30 INPUT VOLTAGE (V) 35 VIN = 0V TO 12V 6 LT1021-5 VOUT + 2V 0V 9 NC 8 7 1k VOUT OUT IN GND LT1021-7 6 4 2 4 6 8 TIME (µs) 10 12 0 14 2 6 4 TIME (µs) 8 150 LT1021-10 100 LT1021-7 50 LT1021-5 12 Load Regulation LT1021-5 5 LT1021-7 LT1021-10 4 LT1021-5 5.002 5.000 4.998 2 1 0 –1 –2 –3 4.996 2 VIN = 8V 3 OUTPUT CHANGE (mV) OUTPUT VOLTAGE (V) 8 10k LT1021 G06 5.004 10 100 1k FREQUENCY (Hz) 10 4 12 RMS NOISE (µV) 10 5.006 COUT = 0 FILTER = 1 POLE fLOW = 0.1Hz 6 200 Output Voltage Temperature Drift LT1021-5 Output Voltage Noise 14 250 LT1021 G05 LT1021 G04 16 300 0 5 3 0 6 8 10 12 14 16 18 20 OUTPUT CURRENT (mA) 350 NOISE VOLTAGE (nV/√Hz) OUTPUT VOLTAGE (V) OUTPUT VOLTAGE (V) LT1021-7 7 4 Output Voltage Noise Spectrum LT1021-10 9 2 400 10 11 LT1021-10 0 1021 G03 11 5 0.4 Start-Up (Shunt Mode) LT1021-7, LT1021-10 13 8 0.6 LT1021 G02 Start-Up (Series Mode) 10 0.8 10k LT1021 G01 12 TJ = 25 °C 1.0 0 100 1k FREQUENCY (Hz) 10 40 TJ = –55 °C 1.2 0.2 50 85 TJ = 125 °C 1.4 INPUT/OUTPUT VOLTAGE (V) f = 150Hz 110 REJECTION (dB) 1.6 130 115 Minimum Input/Output Differential LT1021-7, LT1021-10 Ripple Rejection Ripple Rejection –4 0 10 100 1k BANDWIDTH (Hz) 10k LT1021 G07 4.994 – 50 –25 50 0 75 25 TEMPERATURE (°C) 100 125 LT1021 G08 –5 –10 – 8 – 6 – 4 – 2 SOURCING 0 2 4 6 8 SINKING OUTPUT CURRENT (mA) 10 LT1021 G09 5 LT1021 U W TYPICAL PERFOR A CE CHARACTERISTICS Sink Mode* Current Limit LT1021-5 Quiescent Current LT1021-5 60 IOUT = 0 CURRENT INTO OUTPUT (mA) 1.6 INPUT CURRENT (mA) 1.4 1.2 TJ = – 55°C 1.0 TJ = 25°C 0.8 TJ = 125°C 0.6 0.4 Thermal Regulation LT1021-5 VIN = 8V VIN = 25V ∆POWER = 200mW 50 OUTPUT CHANGE (mV) 1.8 40 30 20 LOAD REGULATION 0 – 0.5 THERMAL REGULATION – 1.0 ILOAD = 10mA 10 0.2 0 0 5 10 15 20 25 30 INPUT VOLTAGE (V) 35 40 0 2 4 6 8 10 12 14 OUTPUT VOLTAGE (V) ∆ISOURCE = 100µAP-P 0 1 2 OUTPUT CHANGE (20mV/DIV) OUTPUT CHANGE (50mV/DIV) 50mV ISINK = 0.2mA ISINK = 2-10mA ISOURCE = 2-10mA 1 3 2 20mV 20mV ISOURCE = 2-10mA 0 4 ISINK = 0.2mA ISOURCE = 0.2mA ISINK = 2-10mA ∆ISOURCE = 100µAP-P ∆ISINK = 100µAP-P 3 4 0 TIME (µs) 5 10 15 20 0 TIME (µs) 5 7.003 5 4 6.999 6.998 100 125 LT1021 G16 4 3 2 TIME (MINUTES) 1 6 5 LT1021 G15 Quiescent Current LT1021-7 1.8 VIN = 12V IOUT = 0 1.6 1.4 INPUT CURRENT (mA) 7.000 5µV (1ppm) 0 3 OUTPUT CHANGE (mV) OUTPUT VOLTAGE (V) 7.002 6 10 15 20 Load Regulation LT1021-7, LT1021-10 7.001 FILTERING = 1 ZERO AT 0.1Hz 2 POLES AT 10Hz LT1021 G14 Output Voltage Temperature Drift LT1021-7 50 0 75 25 TEMPERATURE (°C) 100 120 140 ∆ISINK = 100µAP-P LT1021 G13 6.997 – 50 –25 40 60 80 TIME (ms) Output Noise 0.1Hz to 10Hz LT1021-5 ISINK = 0 ISOURCE = 0 ISINK = 0 ISOURCE = 0.5mA 20 LT1021 G12 Load Transient Response LT1021-5, CLOAD = 1000pF Load Transient Response LT1021-5, CLOAD = 0 50mV 0 18 *NOTE THAT AN INPUT VOLTAGE IS REQUIRED FOR 5V UNITS. LT1021 G11 LT1021 G10 ISOURCE = 0 16 OUTPUT VOLTAGE NOISE (5µV/DIV) 0 2 1 0 –1 –2 1.2 1.0 TJ = – 55°C 0.8 TJ = 25°C –3 0.4 –4 0.2 –5 –10 – 8 – 6 – 4 – 2 SOURCING 0 2 4 6 8 SINKING OUTPUT CURRENT (mA) 10 LT1021 G17 TJ = 125°C 0.6 0 0 5 10 15 20 25 30 INPUT VOLTAGE (V) 35 40 LT1021 G18 LT1021 U W TYPICAL PERFOR A CE CHARACTERISTICS Shunt Mode Current Limit LT1021-7 Shunt Characteristics LT1021-7 60 0.8 TJ = – 55°C TJ = 25°C 0.6 0.4 TJ = 125°C 0.2 Thermal Regulation LT1021-7 INPUT PIN OPEN VIN = 27V ∆POWER = 200mW 50 OUTPUT CHANGE (mV) INPUT PIN OPEN 1.0 CURRENT INTO OUTPUT (mA) CURRENT INTO OUTPUT (mA) 1.2 40 30 20 LOAD REGULATION 0 – 0.5 THERMAL REGULATION* –1.0 –1.5 ILOAD = 10mA 10 0 0 0 7 1 3 8 2 5 6 4 OUTPUT TO GROUND VOLTAGE (V) 0 9 2 4 6 8 10 12 14 OUTPUT VOLTAGE (V) 16 0 18 40 60 80 TIME (ms) 100 120 140 *INDEPENDENT OF TEMPERATURE COEFFICIENT LT1021 G20 1021 G19 20 LT1021 G21 Load Transient Response LT1021-7, CLOAD = 0 Load Transient Response LT1021-7, CLOAD = 1000pF ISOURCE = 0 ISINK = 0.6mA OUTPUT VOLTAGE CHANGE OUTPUT VOLTAGE CHANGE ISOURCE = 0 ISINK = 1.2mA 5mV 50mV ISOURCE = 0.5mA ISINK = 1.4mA 0 1 2 ISINK = 0.8mA ISINK = 1mA 1 3 2 ISINK = 2-10mA ISOURCE = 2-10mA ∆ISOURCE = 100µAP-P ∆ISINK = 100µAP-P 3 4 0 TIME (µs) 20mV ISOURCE = 0.5mA ISINK = 2-10mA ISOURCE = 2-10mA ∆ISOURCE = 100µAP-P 5mV 0 4 NOTE VERTICAL SCALE CHANGE BETWEEN SOURCING AND SINKING 5 10 15 20 0 5µs/DIV 5 4 3 2 TIME (MINUTES) 1 LT1021 G24 Load Regulation LT1021-7, LT1021-10 5 4 10.004 Input Supply Current LT1021-10 1.8 VIN = 12V 10.000 9.998 9.996 100 125 LT1021 G25 INPUT CURRENT (mA) OUTPUT CHANGE (mV) 3 10.002 6 5 LT1021 G23 10.006 OUTPUT VOLTAGE (V) 0 10 15 20 NOTE VERTICAL SCALE CHANGE BETWEEN SOURCING AND SINKING Output Voltage Temperature Drift LT1021-10 50 0 75 25 TEMPERATURE (°C) 5µV (0.7ppm) ∆ISINK = 100µAP-P LT1021 G22 9.994 – 50 –25 FILTERING = 1 ZERO AT 0.1Hz 2 POLES AT 10Hz OUTPUT VOLTAGE NOISE (5µV/DIV) ISINK = 0.8mA Output Noise 0.1Hz to 10Hz LT1021-7 2 1 0 –1 –2 TJ = – 55°C 1.4 TJ = 25°C 1.2 0.8 0.6 –3 –4 0.2 0 2 4 6 8 SINKING OUTPUT CURRENT (mA) 10 1021 G26 TJ = 125°C 1.0 0.4 –5 –10 – 8 – 6 – 4 – 2 SOURCING IOUT = 0 1.6 0 0 5 10 15 20 25 30 INPUT VOLTAGE (V) 35 40 1021 G27 7 LT1021 U W TYPICAL PERFOR A CE CHARACTERISTICS Shunt Mode Current Limit LT1021-10 Shunt Characteristics LT1021-10 60 INPUT PIN OPEN CURRENT INTO OUTPUT (mA) CURRENT INTO OUTPUT (mA) 1.6 1.4 1.2 TJ = – 55°C 1.0 0.8 TJ = 25°C 0.6 0.4 TJ = 125°C Thermal Regulation LT1021-10 INPUT PIN OPEN VIN = 30V ∆POWER = 200mW 50 OUTPUT CHANGE (mV) 1.8 40 30 20 LOAD REGULATION 0 – 0.5 –1.0 THERMAL REGULATION* –1.5 ILOAD = 10mA 10 0.2 0 0 0 2 4 6 10 8 OUTPUT TO GROUND VOLTAGE (V) 12 0 2 4 6 8 10 12 14 OUTPUT VOLTAGE (V) 16 1021 G29 1021 G28 0 18 20 40 60 80 TIME (ms) 100 120 140 *INDEPENDENT OF TEMPERATURE COEFFICIENT 1021 G30 Load Transient Response LT1021-10, CLOAD = 0 Load Transient Response LT1021-10, CLOAD = 1000pF ISINK = 0.8mA ISOURCE = 0 OUTPUT VOLTAGE CHANGE OUTPUT VOLTAGE CHANGE ISOURCE = 0 50mV 10mV ISINK = 0.8mA ISOURCE = 0.2mA ISINK = 1mA 0 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 1021 G31 8 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 1021 G32 FILTERING = 1 ZERO AT 0.1Hz 2 POLES AT 10Hz OUTPUT VOLTAGE NOISE (10µV/DIV) ISINK = 0.6mA Output Noise 0.1Hz to 10Hz LT1021-10 10µV (1ppm) 0 1 4 3 2 TIME (MINUTES) 5 6 1021 G33 LT1021 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 0.5LSB error. For this reason, the LT1021 family has been optimized for low drift. MAXIMUM TEMPERATURE COEFFICIENT FOR 0.5LSB ERROR (ppm/°C) Maximum Allowable Reference Drift 100 8-BIT 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. 10-BIT LT1021-5 10 IN 12-BIT GND VOUT OUT TRIM R1 27k R2 50k 14-BIT 1N4148 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. 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 U U W U 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 OUT R2* 14k 1% GND R3 10k R1* 200Ω 1% VOUT 6.950V TC TRACKING TO 50ppm/°C 1021 AI03 OUT GND R3 50k R2** 182k 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. LT1021-7 IN Kelvin Connections R1* 7.15k 1.000mA Standard Series Mode – OP AMP + LT1021 INPUT 1021 AI04 *RESISTOR TC DETERMINES IOUT TC **TC ≤ (10 • R1) TC. R2 AND R3 SCALE WITH R1 FOR DIFFERENT OUTPUT CURRENTS IN KEEP THIS LINE RESISTANCE LOW OUT + GND LOAD GROUND RETURN 1021 AI05 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 on 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. 10 Series Mode with Boost Transistor INPUT R1 220Ω 2N3906 IN LT1021 OUT GND GROUND RETURN R2* LOAD 1021 AI06 *OPTIONAL—REDUCES CURRENT IN OUTPUT SENSE LEAD R2 = 2.4k (LT1021-5), 3k (LT1021-7), 5.6k (LT1021-10) LT1021 U W U U APPLICATIONS INFORMATION 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 OUTPUT VOLTAGE NOISE (20µV/DIV) Effects of Air Movement on Low Frequency Noise 20µV 0 FOAM CUP REMOVED 8 6 4 TIME (MINUTES) 2 12 10 1021 AI07 U TYPICAL APPLICATIONS Restricted Trim Range for Improved Resolution, 10V, “C” Version Only LT1021-10 Full Trim Range (±0.7%) Negative Series Reference 15V LT1021-10 LT1021C-10 VIN IN 10.000V OUT GND VIN IN GND TRIM R1 75k R2 50k 1021 TA11 TRIM RANGE ≈ ±10mV OUT R1 4.7k VOUT LT1021-10 IN TRIM R1* 10k 1021 TA03 *CAN BE RAISED TO 20k FOR LESS CRITICAL APPLICATIONS R2 4.7k –15V D1 15V Q1 2N2905 OUT GND –10V AT 50mA LT1021 TA04 11 LT1021 U TYPICAL APPLICATIONS Boosted Output Current with No Current Limit Boosted Output Current with Current Limit V + ≥ (VOUT + 1.8V) Ultraprecise Current Source V + ≥ VOUT + 2.8V D1* LED R1 220Ω R1 220Ω LT1021-7 8.2Ω 15V 2N2905 IN 2N2905 IN OUT 17.4k 1% GND TRIM 100Ω IN LT1021 10V AT 100mA + 10V AT 100mA OUT 2µF SOLID TANT GND + 6.98k* 0.1% 15V 7 2µF SOLID TANT 2 – OUT GND LT1021 6 *LOW TC LT1001 1021 TA05 3 + 1021 TA06 4 *GLOWS IN CURRENT LIMIT, DO NOT OMIT –15V IOUT = 1mA REGULATION < 1ppm/V COMPLIANCE = –13V TO 7V 1021 TA07 Operating 5V Reference from 5V Supply 2-Pole Lowpass Filtered Reference 5V LOGIC SUPPLY 1N914 VIN CMOS LOGIC GATE** – IN R1 36k R2 36k f = 10Hz TOTAL NOISE ≤2µVRMS 1Hz ≤ f ≤ 10kHz 0.5µF MYLAR + C1* 5µF + OUT GND VREF LT1001 LT1021 VIN fIN ≥ 2kHz* 1N914 + 1µF MYLAR ≈ 8.5V C2* 5µF LT1021-5 IN OUT 5V REFERENCE GND *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 R3 4.02K 1% OUT LT1021-10 TRIM GND FB R1 4.99k 1% REF CMOS DAC 7520, ETC 30pF IOUT R2 40.2Ω 1% 1.2k –15V 12 *TC LESS THAN 200ppm/°C **NO ZERO ADJUST REQUIRED WITH LT1007 (V0S ≤ 60µV) VIN R4* 100Ω FULL-SCALE ADJUST – LT1007C + 10V F.S. IN TRIM OUT VOUT = 10.24V GND 4.32k 5k V – = –15V* LT1236 TA15 *MUST BE WELL REGULATED dVOUT 15mV = V dV – 1021 TA12 1021 TA16 LT1021 U TYPICAL APPLICATIONS Negative Shunt Reference Driven by Current Source Strain Gauge Conditioner for 350Ω Bridge R1 357Ω 1/2W LT1021-10 15V IN OUT 28mA LT1021-10 GND 28.5mA OUT 5V 350Ω STRAIN GAUGE BRIDGE** GND + 6 LM301A 100pF 2 R4 20k † – 1 3 R2 20k –10V (ILOAD ≤ 1mA) R3 2M 2 2.5mA – LM334 6 LT1012C 3 + VOUT × 100 27Ω R5 2M 8 R6* 2M –11V TO – 40V –5V 1021 TA14 1021 TA09 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 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 Precision DAC Reference with System TC Trim Handling Higher Load Currents 15V 30mA LT1021-10 15V IN OUT GND IN 8.87k 1% LT1021-10 D1 1N457 1.24k 1% 50k TC TRIM* 10k 1% 10k 1% D2 1N457 50k *TRIMS 1mA REFERENCE CURRENT TC BY ± 40ppm/°C. THIS TRIM SCHEME HAS VERY LITTLE EFFECT ON ROOM TEMPERATURE CURRENT TO MINIMIZE ITERATIVE TRIMMING 50k ROOM TEMP TRIM R1* 169Ω VOUT 10V OUT GND 10.36k 1% RL TYPICAL LOAD CURRENT = 30mA 1021 TA08 200k 1% 8.45k 1mA *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 U TYPICAL APPLICATIONS Ultralinear Platinum Temperature Sensor* LT1021-10 IN OUT R2* 5k 20V GND 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 **WIREWOUND RESISTORS WITH LOW TC 1021 TA10 U W EQUIVALE T SCHE ATIC INPUT Q3 D1 D2 OUTPUT D3 R1 Q1 + – A1 R2 D4 6.3V Q2 GND LT1021 ES 14 LT1021 U 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 SEATING PLANE 0.165 – 0.185 (4.191 – 4.699) GAUGE PLANE 0.010 – 0.045* (0.254 – 1.143) REFERENCE PLANE 0.500 – 0.750 (12.700 – 19.050) 0.016 – 0.021** (0.406 – 0.533) 0.027 – 0.045 (0.686 – 1.143) 45°TYP PIN 1 0.028 – 0.034 (0.711 – 0.864) 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 1 2 3 4 0.255 ± 0.015* (6.477 ± 0.381) 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 ) 0.045 – 0.065 (1.143 – 1.651) 0.130 ± 0.005 (3.302 ± 0.127) 0.065 (1.651) TYP 0.100 (2.54) BSC 0.125 (3.175) 0.020 MIN (0.508) MIN 0.018 ± 0.003 (0.457 ± 0.076) N8 1098 *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. 15 LT1021 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) 2 3 4 0.053 – 0.069 (1.346 – 1.752) 0.004 – 0.010 (0.101 – 0.254) 0°– 8° TYP 0.016 – 0.050 0.406 – 1.270 0.014 – 0.019 (0.355 – 0.483) 0.050 (1.270) 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 SO8 0996 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LT1019 Precision Bandgap Reference 0.05%, 5ppm/°C LT1027 Precision 5V Reference 0.02%, 2ppm/°C LT1236 Precision Reference SO-8, 5V and 10V, 0.05%, 5ppm/°C ® LTC 1258 Micropower Reference 200mV Dropout, MSOP LT1389 Nanopower Shunt Reference 800nA Operating Current LT1460 Micropower Reference SOT-23, 2.5V, 5V, 10V LT1634 Micropower Shunt Reference 0.05%, 10ppm/°C, MSOP 16 Linear Technology Corporation 1021fa LT/GP 0399 2K REV A • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408)432-1900 ● FAX: (408) 434-0507 ● www.linear-tech.com LINEAR TECHNOLOGY CORPORATION 1995