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BA3918 데이터시트(PDF) 8 Page - Rohm |
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BA3918 데이터시트(HTML) 8 Page - Rohm |
8 / 9 page 249 Regulator ICs BA3918 FOperation notes (1) Example of application The application circuit of Fig. 3 is recommended for use. Make sure to confirm the adequacy of parts characteris- tics. When using the circuit with changes to external cir- cuit constants, make sure to leave sufficient margins in consideration of fluctuations in the IC and external com- ponents including static and transitional characteristics. Note that ROHM has not carried out extensive survey re- garding the patent right of this application. (2) Operating power supply voltage When operating within the proper ranges of power supply voltage and ambient temperature, most circuit functions are guaranteed. Although the rated values of electrical characteristics cannot be absolutely guaranteed, char- acteristic values do not change drastically within the proper ranges. (3) Power dissipation (Pd) Refer to the power dissipation curves (Fig. 4) and the rough estimation of IC power dissipation given on a sepa- rate page. Make sure your design allows a maximum power within the operating temperature range. (4) Overvoltage protection circuit The overvoltage protection circuit turns OFF all outputs when the potential difference between VCC (pin 7) and GND (pin 12) is more than about 26V at normal tempera- ture. Make sure to use the IC within this voltage limit. (5) Preventing oscillation at each output To stop output oscillation, make sure to connect a capaci- tor having a capacitance of 10 µF or greater between GND and each of the VDD (pin 5), COM (pin 9), AM (pin 10), and FM (pin 11) output pins. We recommend using a tantalum electrolytic capacitor whose capacitance is unsusceptible to temperature. (6) Overcurrent protection circuit An overcurrent protection circuit is installed on the VDD (pin 5), AMP (pin 6), ANT (pin 8), COM (pin 9), AM (pin 10), and FM (pin 11) outputs, based on the respective output current. This prevents IC destruction due to over- current, by limiting the current with a curve shape of “7” in the voltage-current graph. The IC is designed with margins so that current flow will be restricted and latching will be prevented even if a large current suddenly flows through a large capacitor. The circuit should be carefully set because output current is further restricted when out- put voltage is less than 1VF (considered as short mode). (7) Thermal protection circuit A built-in thermal protection circuit prevents thermal damage to the IC. All outputs except VDD are switched OFF when the circuit operates, and revert to the original state when temperature drops to a certain level. (8) Grounding Each ground trace in the application circuit of Fig. 3 must be adequately short from GND (pin 12). Make sure to ar- range the ground traces in a pattern that prevents mutual interference. (9) Although the quality of this IC is rigorously con- trolled, the IC may be destroyed when the supply voltage or the operating temperature exceeds their absolute maximum ratings. Because short mode or open mode cannot be specified when the IC is destroyed, be sure to take physical safety measures, such as fusing, if any of the absolute maximum ratings might be exceeded. (10) We recommend installing a bypass line in your ap- plication if there is a mode where potential difference be- tween each output and input (VCC) or GND is reversed from the normal state. FThermal derating characteristic curve |
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