nt } \D, LTZIO00/LTZIOOOA TECHNOLOGY Ultra Precision Reference FEATURES DESCRIPTION The LTZ1000 and LTZ1000A are ultra stable temperature controllable references. They are designed to provide 7V outputs with temperature drifts of 0.05ppm/C, about 1.2uVp-p of noise and long term stabilities of 2nV per month. @ 1.2.Vp-p Noise 2uV Long Term Stability = Very Low Hysteresis 0.05ppm/C Drift = Temperature Stabilized Included on the chip is a subsurface zener reference, heater resistor for temperature stabilization, and a tem- APPLICATIONS perature 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. = Voltmeters = Calibrators m Standard Cells m Scales The LTZ1000 and LTZ1000A references can provide supe- = Low Noise RF Oscillators rior performance to older references such as the LM199 at the expense of increased circuit complexity and thermal layout considerations. The LTZ1000 is packaged in a standard TO-99 package while the LTZ1000A utilizes a proprietary high thermal resistance die attach which eases thermally insulating the reference. TYPICAL APPLICATION Low Noise Reference Long Term Stability LTZ1000 Vin2 10V 1-2. @ OUTPUT 1N4148 WY 0 10 20 30 DAYS LONG TERM STABILITY OF A TYPICAL DEVICE FROM TIME =0 WITH NO PRECONDITIONING OR AGING wee 3.9LTZ1000/LTZIOOOA ABSOLUTE MAXIMUM RATINGS PACKAGE/ORDER INFORMATION a ae Heater to Substrate .............cccee cece eee ea eee ees 35V Collector Emitter Breakdown Q1.........sssssseeeees 15V - BOTTOM VIEW ORDER Collector Emitter Breakdown Q2..............200008: 35V PART NUMBER Emitter Base Reverse Bias......... eee eens nena eens 2v Operating Temperature Range ....... - 55C <Tas125C Storage Temperature Range ......... ~ 65C <Tas 150C LTZ1000 Substrate Forward BiaS..................ceeeeeea ees 0.1V: LTZ1000A H8 PACKAGE PRECONDITIONING METAL CAN 150C Burn-in ELECTRICAL CHARACTERISTICS (ote 1) PARAMETER CONDITIONS MIN TYP MAX UNITS Zener Voltage I7=5mA, (Vz+ VBEg}) Igy = 100xA 7.0 7.2 75 V I7=1 MA, (Vz-+ VBEgy) lay = 100uA 6.9 7.15 7.45 Vv Zener Change with Current 1ImAslz<5mA 80 240 mV Zener Leakage Current V2=5V 20 200 pA Zener Noise I7=5mA, 0.1Hz<f<10Hz 1.2 2 pVp-p It = 100uA Heater Resistance 1, < 100pA 200 300 420 Hy Heater Breakdown Voltage 35 V Transistor Q1 Breakdown lo = 10xA, LVCEO 15 20 V Transistor Q2 Breakdown lp = 10nA, LVCEO 35 50 V Q1, Q2 Current Gain Io = 100nA 80 200 450 Thermal Resistance LTZ1000 Time=5 Minutes 80 Cw LTZ1000A Time=5 Minutes 400 CM Long Term Stability T=65C 2 uVWkhr Note 1: All testing is done at 25C. Pulse testing is used for LTZ1000A to minimize temperature rise during testing. LTZ1000 and LTZ1000A devices are QA tested at - 55C and 125C. 3-10 LWALTZIOQO/LTZIOOOA PIN FUNCTIONS Pin 1: Heater positive. Must be more positive than Pin 4 Pin 5: Temperature compensating transistor collector. and fess than 40V. Pin 6: Temperature sensing transistor base. If the base Pin 2: Heater negative. Must be more positive than Pin 4 emitter junction is Zenered (about 7V) the transistor will and less than 40V. suffer permanent beta degradation. Pin 3: Zener positive. Must be more positive than Pin 4. Pin 7: Emitter of sensing and compensating transistors. Pin 4: Substrate and Zener negative. Must be more posi- Pin 8: Collector of sensing transistor. tive than pin 7. If Q1 is Zenered (about 7V) a permanent degradation in beta will result. TYPICAL PERFORMANCE CHARACTERISTICS Zener Voltage vs Current Zener Voltage Noise Spectrum Zener Noise 500 T lz=4mA 450 = = 400 Ss ZENER ALONE s S & S 360 a oO = = #3 300 a 3 2 50 2 lz=0.5mA Q 3 z { = = 200 a mT S ZENER WITH KELVIN a CURRENT =0.5mA S we ai = 150 = uw va a i z B z i { HH fay! | Ni wy 100 N i ! ZENER CURRENT =4mA 50 0 0 05 1015 2025303540 45 50 0.1 1 10 100 0 10 20 30.40 50 60 ZENER CURRENT (mA} FREQUENCY (Hz) TIME (SECONDS) Die Temperature Rise vs Heater Power Die Temperature Rise vs Time Die Temperature Rise vs Time 0.8 125 125 L1Z1000A i LUA HEATER POWER =0 0.7 1721000 8 0.6 0.5 ~ wn ~ on HEATER POWER =0. 0.4 HEATER POWER =0.5W POWER =0.2W S sg 03 HEATER POWER (W) DIE TEMPERATURE RISE (C) DIE TEMPERATURE RISE (C) 0.2 MN on Nm an EATER POWER =0.1W 0.1 POWER =0.3W 0 25 35 45 55 65 75 85 95 105 115 125 0.1 1 10 100 1000 0.1 1 10 100 1000 DIE TEMPERATURE ABOVE AMBIENT (C) TIME (SECONDS) TIME (SECONDS) LY White 3-11LTZIO00/LTZIOOOA APPLICATION HINTS LTZ1000 and LTZ1000A are capable of providing ultimate voltage reference performance. Temperature drifts of bet- ter than 0.03ppm/C and long term stability on the order of 1nV 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 35xV/C. It is mandatory to keep the zener and transistor leads at the same temperature, otherwise 1 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 pack- age is heated. This will look like 1 to 5ppm of low fre- quency 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 coeffi- cients, can generate thermocouple effects. Some types of resistors can generate hundreds of microvolts of thermo- couple voltage. These thermocouple effects in the resistor can also interfere with the output voltage. Wire wound re- sistors usually have the lowest thermocouple voltage, while tin oxide type resistors have very high thermocouple voltage. Film resistors, especially Vishay precision film re- sistors, can have low thermocouple voltage. Ordinary breadboarding techniques are not good enough to give stable output voltage with the LTZ1000 family de- vices. 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 sub- tract from the reference voltage causing errors with tem- perature. 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 60C. Production variations in emitter-base voltage will typically cause about + 10C variation. Since the emitter-base volt- age changes about 2mV/C and is very predictable, other temperatures are easily set. The lowest temperature consistent with the operating environment should be used. Higher temperatures ac- celerate aging and decrease long term stability. The LTZ1000A should be set about 10C higher than the LTZ1000. This is because normal operating power dissipa- tion in the LTZ1000A causes a temperature rise of about 10C. 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 applica- tions requiring the very low noise or low drift with time of the LTZ1000 should use this device. Application help is available from Linear Technology. 3-12 WeeTYPICAL APPLICATIONS Negative Voltage Reference LTZIOOO/LTZIOOOA ZENER + SENSE V+15V GND = 2N3904 Re > 70k AAA $5 $A > > > 1k > 120 1N4148 ZENER FORCE PROVIDE TEMPERATURE COMPENSATION, DELETE FOR LTZ1000A. APPROXIMATE CHANGE IN REFERENCE VOLTAGE FOR A 100ppm CHANGE IN RESISTOR VALUES: 100ppm = AR(Q) AVz Ri 0.0120 Ippm R2 7a 0.3ppm R3 7a 0.2ppm R4/R5 RATIO AR=0.01% 1ppm BOTH A1 AND A2 CONTRIBUTE LESS THAN 2yV OF OUTPUT ORIFT OVER A 50C RANGE. Averaging Reference Voltages for Lower Noise and Better Stability Vin 18V 0.01% { s$ < 1.6k > 1.6k > S$ $ 300 2300" > > A+ aly. mA OUTPUT 150 2150 = RAT int wee Vin 15V V-210V ZENER SENSE Improving Supply Rejection 1.5k > 150 AAA cote. SUPPLY REJECTION AT Vouts =20mv/V < Voura SUPPLY REJECTION AT Vout2=3mv/VLTZIO00/LTZIOOOA TYPICAL APPLICATIONS Adjusting Temperature Coefficient in Unstabilized Applications 15V 1MIN Vour+ * x | 2002 1N4148 1 MIN HEATER 1N4148 *PULSE HEATER ON AND OFF TO HEAT AND COOL THE REFERENCE. ADJUST R1 FOR MINIMUM VOLTAGE CHANGE THROUGH A TEMPERATURE CYCLE. 7V Positive Reference Circuit ZENER + SENSE yr a 15V Mg $R3 3 $2 13k $70k > 70k - 5 4 aI 8 1N4148 tk 7 Al 8 AQ 1 2N3904 5 LT1013 10k LT1013 -o wrt , 4. Ot * 1M 4 ~ 0.1nF . ZENER ~ TL AMA SENSE O.tyF = 3 RIS == 0.022uF , ] Fik = 1209 GROUND + ZENER - FORCE 9 1N4148 aaah P+ (TIED TO GROUND) *PROVIDES TC COMPENSATION, DELETE FOR LTZ1000A. APPROXIMATE CHANGE IN REFERENCE VOLTAGE FOR A 100ppm (0.01%) CHANGE IN RESISTOR VALUES: AR(Q) AVz Rt 0.0122 1ppm R2 7a 0.3ppm R3 72 0.2ppm R4/R5 RATIO AR=0.01% 1ppm BOTH A1 AND A2 CONTRIBUTE LESS THAN 2uV OF OUTPUT DRIFT OVER A 50C RANGE. 3-14 LIT WeLTZ1000/LTZIO00A BLOCK DIAGRAM SUBSTRATE DIODES-DO NOT FORWARD BIAS PACKAGE DESCRIPTION Dimensions in inches (millimeters) unless otherwise noted. H8 Package Metal Can 0.335 0.370 (8.509 9.398) DIA 0.305 ~ 0.335 (7.747 8.509) 0.040 (1.016) 0050 I MAX (1270) 0.165 -0.185 MAX (4.191 4.699) Y Y REFERENCE SEATING bo i Tr }| GAUGE PLANE PLANE A t == | i PLANE 0.500-0.750 0.010 0.045 itl | ll (12:70, 19.06) (0.254 1.143) D01e-00M (0.406 0.533) / TYP 0.027 0.045 45 TY Wa ann bor -0.038 AN (0.686 1.143) | (0.686 0.864) 0.110 0.160 (2.794 4.064) INSULATING STANDOFF 0.200 0.230 (5.080 5.842) BSC Y NOTE: LEAD DIAMETER 1S UNCONTROLLED BETWEEN THE REFERENCE PLANE AND SEATING PLANE. 8188 Baa LTZ1000 80C LTZ1000A 400CW wee 3-15