LTZ1000/LTZ1000A Ultra Precision Reference FEATURES ■ ■ ■ ■ ■ ■ ■ ■ DESCRIPTION 1.2µVP-P Noise 2µV/√kHr Long Term Stability Very Low Hysteresis 0.05ppm/°C Drift Temperature Stabilized 400°C/W Thermal Resistance for LTZ1000A reduces insulation requirements Specified for –55°C to 125°C Temperature Range Offered in TO-99 package APPLICATIONS ■ ■ ■ ■ ■ The LTZ®1000 and LTZ1000A are ultra stable temperature controllable references. They are designed to provide 7V outputs with temperature drifts of 0.05ppm/°C, about 1.2µVP-P of noise and long term stability of 2µV/√kHr. Included on the chip is a subsurface Zener reference, a heater resistor for temperature stabilization, and a temperature sensing transistor. External circuitry is used to set operating currents and to temperature stabilize the reference. This allows maximum flexibility and best long term stability and noise. The LTZ1000 and LTZ1000A references can provide superior performance to older devices such as the LM199, provided that the user implements the heater control and properly manages the thermal layout. To simplify thermal insulation, the LTZ1000A uses a proprietary die attach method to provide significantly higher thermal resistance than the LTZ1000. Voltmeters Calibrators Standard Cells Scales Low Noise RF Oscillators , LTC and LT are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. TYPICAL APPLICATION Low Noise Reference Long Term Stability 2 VIN ≥ 10V LTZ1000 OUTPUT 30k + LT®1006 2 120Ω – 1N4148 7 (ppm) 3 6 0 4 0.02µF –2 1000 TA01 0 20 10 30 DAYS LONG TERM STABILITY OF A TYPICAL DEVICE FROM TIME = 0 WITH NO PRECONDITIONING OR AGING 1000 TA01b 1000afb 1 LTZ1000/LTZ1000A ABSOLUTE MAXIMUM RATINGS INFORMATION (Note 1) BOTTOM VIEW Heater to Substrate ...................................................35V Collector Emitter Breakdown Q1 ...............................15V Collector Emitter Breakdown Q2 ...............................35V Emitter Base Reverse Bias ..........................................2V Operating Temperature Range .........–55°C ≤ TA ≤ 125°C Storage Temperature Range.............–65°C ≤ TA ≤ 150°C Substrate Forward Bias ............................................0.1V 8 7 1 Q2 6 2 Q1 7V 3 5 4 H8 PACKAGE TO-5 METAL CAN θJA = 80°C/W, θJA = 400°C/W ORDER PART NUMBER PART MARKING LTZ1000ACH LTZ1000CH Order Options Lead Free: Add #PBF Lead Free Part Marking: http://www.linear.com/leadfree/ Consult LTC Marketing for parts specified with wider operating temperature ranges. ELECTRICAL CHARACTERISTICS (Note 2) PARAMETER CONDITIONS MIN TYP MAX UNITS Zener Voltage lZ = 5mA, (VZ + VBEQ1) IQ1 = l00µA lZ = 1mA, (VZ + VBEQ1) IQ1 = l00A 7.0 6.9 7.2 7.15 7.5 7.45 V V Zener Change with Current 1mA ≤ IZ < 5mA 80 240 mV Zener Leakage Current VZ = 5V 20 200 Zener Noise lZ = 5mA, 0.1Hz < f < 10Hz 1Q1 = 100µA 1.2 2 Heater Resistance IL ≤ 100µA 300 420 200 Heater Breakdown Voltage 35 µA µVP-P V Transistor Q1 Breakdown IC = 10µA, LVCEO 15 20 V Transistor Q2 Breakdown IC = 10µA, LVCEO 35 50 V Q1, Q2 Current Gain IC = 100µA 80 200 Thermal Resistance LTZ1000 LTZ1000A Long Term Stability T = 65°C Time = 5 Minutes Time = 5 Minutes Note 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and lifetime. 80 400 2 450 °C/W °C/W µV√kHr Note 2: All testing is done at 25°C. Pulse testing is used for LTZ1000A to minimize temperature rise during testing. LTZ1000 and LTZ1000A devices are QA tested at –55°C and 125°C. 1000afb 2 LTZ1000/LTZ1000A PIN FUNCTIONS Pin 1: Heater positive. Must have a higher positive value than Pin 2 and Pin 4. Pin 2: Heater negative. Must have a higher positive value than Pin 4. Must have equal or lower potential than Pin 1. Pin 3: Zener positive. Must have a higher positive value than Pin 4. Pin 5: Temperature compensating transistor collector. Pin 6: Temperature sensing transistor base. If the base emitter junction is Zenered (about 7V) the transistor will suffer permanent beta degradation. Pin 7: Emitter of sensing and compensating transistors. Pin 8: Collector of sensing transistor. Pin 4: Substrate and Zener negative. Must have a higher positive value than Pin 7. If Q1 is Zenered (about 7V) a permanent degradation in beta will result. TYPICAL PERFORMANCE CHARACTERISTICS Zener Voltage Noise Spectrum 90 450 80 ZENER ALONE 70 60 50 40 30 20 ZENER WITH KELVIN SENSED Q1 10 0 0 IZ = 4mA 400 350 300 250 ZENER CURRENT = 0.5mA 200 150 100 ZENER CURRENT = 4mA 50 0 0.1 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 ZENER CURRENT (mA) Zener Noise 1 10 FREQUENCY (Hz) 1000 G01 ZENER VOLTAGE NOISE (2µV/D) 500 ZENER VOLTAGE NOISE (nV/√Hz) ZENER VOLTAGE CHANGE (mV) Zener Voltage vs Current 100 IZ = 0.5mA 100 0 20 30 40 TIME (SECONDS) 10 1000 G02 Die Temperature Rise vs Heater Power 125 60 1000 G03 Die Temperature vs Time 0.8 50 Die Temperature Rise vs Time 125 LTZ1000A LTZ1000 0.6 0.5 LTZ1000 0.4 0.3 0.2 LTZ1000A 100 HEATER POWER = 0.3W DIE TEMPERATURE RISE (°C) DIE TEMPERATURE RISE (°C) HEATER POWER (W) 0.7 75 HEATER POWER = 0.2W 50 25 HEATER POWER = 0.1W 0.1 100 75 50 HEATER POWER = 0.7W HEATER POWER = 0.5W 25 HEATER POWER = 0.3W 0 25 35 45 55 65 75 85 95 105 115 125 DIE TEMPERATURE ABOVE AMBIENT (°C) 0 0.1 1 10 100 TIME (SECONDS) 1000 0 0.1 1 10 100 TIME (SECONDS) 1000 1000 G06 1000 G04 1000 G05 1000afb 3 LTZ1000/LTZ1000A APPLICATIONS INFORMATION LTZ1000 and LTZ1000A are capable of providing ultimate voltage reference performance. Temperature drifts of better than 0.03ppm/°C and long term stability on the order of 1µV per month can be achieved. Noise of about 0.15ppm can also be obtained. This performance is at the expense of circuit complexity, since external influences can easily cause output voltage shifts of more than 1ppm. Thermocouple effects are one of the worst problems and can give apparent drifts of many ppm/°C as well as cause low frequency noise. The kovar input leads of the TO-5 package form thermocouples when connected to copper PC boards. These thermocouples generate outputs of 35µV/°C. It is mandatory to keep the zener and transistor leads at the same temperature, otherwise 1ppm to 5ppm shifts in the output voltage can easily be expected from these thermocouples. Air currents blowing across the leads can also cause small temperature variations, especially since the package is heated. This will look like 1ppm to 5ppm of low frequency noise occurring over a several minute period. For best results, the device should be located in an enclosed area and well shielded from air currents. Certainly, any temperature gradient externally generated, say from a power supply, should not appear across the critical circuitry. The leads to the transistor and zener should be connected to equal size PC traces to equalize the heat loss and maintain them at similar temperatures. The bottom portion of the PC board should be shielded against air currents as well. Resistors, as well as having resistance temperature coefficients, can generate thermocouple effects. Some types of resistors can generate hundreds of microvolts of thermocouple voltage. These thermocouple effects in the resistor can also interfere with the output voltage. Wire wound resistors usually have the lowest thermocouple voltage, while tin oxide type resistors have very high thermocouple voltage. Film resistors, especially Vishay precision film resistors, can have low thermocouple voltage. Ordinary breadboarding techniques are not good enough to give stable output voltage with the LTZ1000 family devices. For breadboarding, it is suggested that a small printed circuit board be made up using the reference, the amplifier and wire wound resistors. Care must be taken to ensure that heater current does not flow through the same ground lead as the negative side of the reference (emitter of Q1). Current changes in the heater could add to, or subtract from, the reference voltage causing errors with temperature. Single point grounding using low resistance wiring is suggested. Setting Control Temperature The emitter-base voltage of the control transistor sets the stabilization temperature for the LTZ1000. With the values given in the applications, temperature is normally 60°C. This provides 15°C of margin above a maximum ambient of 45°C, for example. Production variations in emitter-base voltage will typically cause about ±10°C variation. Since the emitter-base voltage changes about 2mV/°C and is very predictable, other temperatures are easily set. Because higher temperatures accelerate aging and decrease long term stability, the lowest temperature consistent with the operating environment should be used. The LTZ1000A should be set about 10°C higher than the LTZ1000. This is because normal operating power dissipation in the LTZ1000A causes a temperature rise of about 10°C. Of course both types of devices should be insulated from ambient. Several minutes of warm-up is usual. For applications not requiring the extreme precision or the low noise of the LTZ1000, Linear Technology makes a broad line of voltage references. Devices like the LT1021 can provide drifts as low as 2ppm/°C and devices such as the LM399A can provide drifts of 1ppm/°C. Only applications requiring the very low noise or low drift with time of the LTZ1000 should use this device. See Application Notes AN-82 and AN-86 for further information. Consult the Linear Technology Applications department for additional help. 1000afb 4 LTZ1000/LTZ1000A TYPICAL APPLICATIONS Negative Voltage Reference ZENER + SENSE V+ 15V GND 0.1µF 1 1k 2N3904 7 + 5 – 6 R4 13k R2 70k R3 70k 8 5 3 LT1013 10k 4 1M 7 2 2 8 – 1 LT1013 0.1µF 3 400k* R5 1k + 4 1N4148 R1 120 0.022µF ZENER – FORCE ZENER – SENSE *PROVIDE TEMPERATURE COMPENSATION, DELETE FOR LTZ1000A APPROXIMATE CHANGE IN REFERENCE VOLTAGE FOR A 100ppm CHANGE IN RESISTOR VALUES: R1 R2 R3 R4/R5 RATIO 100ppm = ∆R(Ω) 0.012Ω 7Ω 7Ω ∆R = 0.01% V – ≥ 10V ∆VZ 1ppm 0.3ppm 0.2ppm 1ppm BOTH A1 AND A2 CONTRIBUTE LESS THAN 2µV OF OUTPUT DRIFT OVER A 50°C RANGE 1000 TA02 Averaging Reference Voltage for Lower Noise and Better Stability Improving Supply Rejection VIN 15V VIN 15V 0.01% 1.6k 1.6k 30Ω* 30Ω* 1.5k VOUT1 SUPPLY REJECTION AT VOUT1 = 20mV/V VOUT2 SUPPLY REJECTION AT VOUT2 = 3mV/V 50Ω 150Ω OUTPUT 150Ω IC 1000 TA04 150Ω 1000 TA03 *R = kT q IC 1000afb 5 LTZ1000/LTZ1000A TYPICAL APPLICATIONS Adjusting Temperature Coefficient in Unstabilized Applications 15V 1 MIN VOUT + * ON R1 200Ω* 70k 3 3 5 1N4148 4 1 + LT1006 2 – OFF 1 MIN 6 HEATER 4 7 2 120Ω 0.022µF 1N4148 * PULSE HEATER ON AND OFF TO HEAT AND COOL THE REFERENCE. ADJUST R1 FOR MINIMUM VOLTAGE CHANGE THROUGH A TEMPERATURE CYCLE. THE –2mV/°C TEMPCO OF THE VBE CANCELS THE +2mV/°C TEMPCO OF THE ZENER. 1000 TA05 7V Positive Reference Circuit ZENER + SENSE V+ 15V 1k 2N3904 + 7 A1 LT1013 – R4 13k 5 R3 3 70k R2 70k 8 5 10k 6 3 2 + A2 LT1013 – 1N4148 8 1 4 7 4 1M 0.1µF ZENER – SENSE 400k* 1 0.1µF R5 1k R1 120 1N4148 2 0.002µF GROUND ZENER – FORCE HEATER RETURN (TIED TO GROUND) *PROVIDES TC COMPENSATION, DELETE FOR LTZ1000A APPROXIMATE CHANGE IN REFERENCE VOLTAGE FOR A 100ppm (0.01%) CHANGE IN RESISTOR VALUES: R1 R2 R3 R4/R5 RATIO ∆R(Ω) 0.012Ω 7Ω 7Ω ∆R = 0.01% ∆VZ 1ppm 0.3ppm 0.2ppm 1ppm BOTH A1 AND A2 CONTRIBUTE LESS THAN 2µV OF OUTPUT DRIFT OVER A 50°C RANGE 1000 TA06 1000afb 6 LTZ1000/LTZ1000A BLOCK DIAGRAM 1 8 3 5 * * 2 Q2 6 *SUBSTRATE DEVICES–DO NOT FORWARD BIAS Q1 4 7 1000 TA07 1000afb 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. 7 LTZ1000/LTZ1000A PACKAGE DESCRIPTION H Package 8-Lead TO-5 Metal Can (.200 Inch PCD) (Reference LTC DWG # 05-08-1320) .335 – .370 (8.509 – 9.398) DIA .305 – .335 (7.747 – 8.509) .040 (1.016) MAX .050 (1.270) MAX SEATING PLANE .165 – .185 (4.191 – 4.699) GAUGE PLANE .010 – .045* (0.254 – 1.143) REFERENCE PLANE .500 – .750 (12.700 – 19.050) .016 – .021** (0.406 – 0.533) .027 – .045 (0.686 – 1.143) 45° .028 – .034 (0.711 – 0.864) PIN 1 .200 (5.080) TYP .110 – .160 (2.794 – 4.064) INSULATING STANDOFF *LEAD DIAMETER IS UNCONTROLLED BETWEEN THE REFERENCE PLANE AND THE SEATING PLANE .016 – .024 **FOR SOLDER DIP LEAD FINISH, LEAD DIAMETER IS (0.406 – 0.610) H8(TO-5) 0.200 PCD 0204 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LM399 7V Precision Shunt Reference 0.2% Accuracy, 0.5ppm/°C Drift, 20µVRMS Noise LT1021 5V, 7V and 10V Precision Reference Available in T0-5, –55°C to 125°C, Series or Shunt Operation LT1236 5V and 10V Low Drift Precision Reference 0.05% Accuracy, 5ppm/°C Drift, Series or Shunt Operation LT1389 1.25V, 2.5V, 4V and 5V Nanopower Shunt Reference 800nA, 0.05% Accuracy, 10ppm/°C Drift LT1634 1.25V and 2.5V Micropower Shunt Reference 0.05%, 10ppm/°C, 10µA Current 1000afb 8 Linear Technology Corporation LT 0206 REV B • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com © LINEAR TECHNOLOGY CORPORATION 1987