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LM169H Datenblatt(PDF) 5 Page - National Semiconductor (TI) |
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LM169H Datenblatt(HTML) 5 Page - National Semiconductor (TI) |
5 / 14 page Application Hints The LM169LM369 can be applied in the same way as any other voltage reference The adjacent Typical Applications Circuits suggest various uses for the LM169LM369 The LM169 is recommended for applications where the highest stability and lowest noise is required over the full military temperature range The LM369 is suitable for limited-tem- perature operation The curves showing the Noise vs Ca- pacitance in the Typical Performance Characteristics sec- tion show graphically that a modest capacitance of 01 to 03 microfarads can cut the broadband noise down to a lev- el of only a few microvolts less than 1 ppm of the output voltage The capacitor used should be a low-leakage type For the temperature range 0 to 50 C polyester or Mylar will be suitable but at higher temperatures a premium film capacitor such as polypropylene is recommended For oper- ation at a125 C a Teflon capacitor would be required to ensure sufficiently low leakage Ceramic capacitors may seem to do the job but are not recommended for produc- tion use as the high-K ceramics cannot be guaranteed for low leakage and may exhibit piezo-electric effects convert- ing vibration or mechanical stress into excessive electrical noise Additionally the inherent superiority of the LM169369’s buried Zener diode provides freedom from low-frequency noise wobble and jitter in the frequency range 001 to 10 Hertz where capacitive filtering is not feasible Pins 1 3 7 and 8 of the LM169369 are connected to internal trim circuits which are used to trim the device’s out- put voltage and Tempco during final testing at the factory Do not connect anything to these pins or improper opera- tion may result These pins would not be damaged by a short to ground or by Electrostatic Discharges however keep them away from large transients or AC signals as stray capacitance could couple noises into the output These pins may be cut off if desired Alternatively a shield foil can be laid out on the printed circuit board surrounding these pins and pin 5 and this guard foil can be connected to ground or to Vout effectively acting as a guard against AC coupling and DC leakages The trim pin (pin 5) should also be guarded away from noise signals and leakages as it has a sensitivity of 15 millivolts of D Vout per microampere The trim pin can also be used in the circuits shown to provide an output trim range of g10 millivolts Trimming to a wider range is possible but is not recommended as it may degrade the Tempco and the Tempco linearity at temperature extremes For example if the output were trimmed up to 10240V the Tempco would be degraded by 8 ppm C As a general rule Tempco will be degraded by 1 ppm C per 30 mV of output adjustment The output can sink current as well as source it but the output impedance is much better for sourcing current Also the LM169369 requires a 01 mF tantalum capacitor (or 01 mF in series with 10X) bypass from the output to ground for stable operation in shunt mode (output sinking current) The output has a class-B stage so if the load current chang- es from sourcing to sinking an output transient will occur To avoid this transient it may be advisable to preload the output with a few milliamperes of load to ground The LM169369 does have an excellent tolerance of load ca- pacitance and in cases of load transients electrolytic or tantalum capacitors in the range 1 to 500 microfarads have been shown to improve the output impedance without de- grading the dynamic stability of the device The LM169369 are rated to drive an output of g10 mA but for best accura- cy any load current larger than 1 mA can cause thermal errors (such as 1 mA c 5V c 4 ppm100 mW e 02 ppm or 2 microvolts) and degrade the ultimate precision of the output voltage The output is short-circuit-proof to ground However avoid overloads at high ambient temperatures as a prolonged short-circuit may cause the junction temperature to exceed the Absolute Maximum Temperature The device does not include a thermal shut-down circuit If the output is pulled to a positive voltage such as a15 or a20V the output current will be limited but overheating may occur Avoid such over- loads for voltages higher than a20 V for more than 5 sec- onds or at high ambient temperatures The LM169369 has an excellent long-term stability and is suitable for use in high-resolution Digital Voltmeters or Data Acquisition systems Its long-term stability is typically 3 to 10 ppm per 1000 hours when held near Tmax and slightly bet- ter when operated at room temperature Contact the factory for availability of devices with proven long-term stability Typical Applications Series Reference TLH9110 – 2 Shunt Reference with Optional Trim TLH9110 – 3 Series Reference with Optional Filter for Reduced Noise TLH9110 – 4 NOTE Pin numbers for H M or N packages 5 |
Ähnliche Teilenummer - LM169H |
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Ähnliche Beschreibung - LM169H |
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