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AMS2931M-X Datasheet(PDF) 7 Page - Advanced Monolithic Systems |
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AMS2931M-X Datasheet(HTML) 7 Page - Advanced Monolithic Systems |
7 / 9 page Advanced Monolithic Systems, Inc. www.advanced-monolithic.com Phone (925) 443-0722 Fax (925) 443-0723 AMS2931 TYPICAL PERFORMANCE CHARACTERISTICS (Continued) Maximum Power Dissipation (TO-263) 1 2 3 4 AMBIENT TEMPERATURE (° C) 10 20 30 40 50 60 70 80 90 100 0 0 θ JA = 32° C/W 0.01 0.1 100 0 20 40 60 100 OUTPUT CURRENT (mA) Output Capacitor ESR 1 10 V O = 5V C OUT= 100µF 80 3.0 4.0 On/Off Treshold 2.2 2.4 2.6 2.8 3.2 3.4 3.6 3.8 3 6 9 121518 2124 0 2.0 ON OFF OUTPUT VOLTAGE (V) STABLE REGION θ JA = 37° C/W θ JA = 50° C/W θ JA = 73° C/W AMS2931C ADJUSTABLE APPLICATION HINTS The AMS2931 series require an output capacitor for device stability. The value required depends on the application circuit and other factors. Because high frequency characteristics of electrolytic capacitors depend greatly on the type and even the manufacturer, the value of capacitance that works well with AMS2931 for one brand or type may not necessary be sufficient with an electrolytic of different origin. Sometimes actual bench testing will be the only means to determine the proper capacitor type and value. To obtain stability in all general applications a high quality 100 µF aluminum electrolytic or a 47 µF tantalum electrolytic can be used. A critical characteristic of the electrolytic capacitors is their performance over temperature. The AMS2931 is designed to operate to -40 °C, but some electrolytics will freeze around -30°C therefore becoming ineffective. In such case the result is oscillation at the regulator output. For all application circuits where cold operation is necessary, the output capacitor must be rated to operate at the minimum temperature. In applications where the regulator junction temperature will never be lower than 25 °C the output capacitor value can be reduced by a factor of two over the value required for the entire temperature range (47 µF for a high quality aluminum or 22 µF for a tantalum electrolytic capacitor). With higher output currents, the stability of AMS2931 decreases. Considering the fact that in many applications the AMS2931 is operated at only a few milliamps (or less) of output current, the output capacitor value can be reduced even further. For example, a circuit that is required to deliver a maximum of 10mA of output current from the regulator output will need an output capacitor of only half the value compared to the same regulator required to deliver the full output current of 100mA. In the case of AMS2931C (adjustable), the minimum value of output capacitance is a function of the output voltage. As a general rule, with higher output voltages the value of the output capacitance decreases, since the internal loop gain is reduced. In order to determine the minimum value of the output capacitor, for an application circuit, the entire circuit including the capacitor should be bench tested at minimum operating temperatures and maximum operating currents. To maintain internal power dissipation and die heating to a minimum, the input voltage should be maintain at 0.6V above the output. Worst-case occurs just after input power is applied and before the die had the chance to heat up. After the minimum capacitance value has been found for the specific brand and type of electrolytic capacitor, the value should be doubled for actual use to cover for production variations both in the regulator and the capacitor. |
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Similar Description - AMS2931M-X |
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