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Regulator ICs System power supply for car stereos BA3915B The BA3915B is an one-chip power supply IC for use in car audio systems. The IC has seven output systems : one 5V output (VDD), four 8.5V outputs (COM, FM, AM, AR), and two high-side switch outputs (ANT, AMP). The 5V outputs operate all the time if only the BCAD input is provided. The other outputs operate with BACKUP and ACC inputs, and their ON / OFF is controlled by the STANDBY and MODE inputs. FApplications Car audio systems FFeatures 1) ACC and BACKUP voltages are monitored, compared with the internally set values; one-shot pulses are output to MUTE, which synchronizes with the rising and falling of the STANDBY input. 2) ACC voltage is monitored, compared with the internally set value, and the result is output to ACCB. 3) All outputs use a PNP transistor with low saturation voltage. FAbsolute maximum ratings (Ta = 25_C) 4) Output current limit circuit prevents damage to the IC due to short-circuiting. 5) Overvoltage protection circuit provides protection against surges from the ACC or BACKUP input. 6) Compact 16-pin POWER package allows large power dissipation. FRecommended operating conditions (Ta = 25_C) 226 Regulator ICs FBlock diagram BA3915B 227 Regulator ICs FPin descriptions (Ta = 25_C, BACKUP / ACC = 13.2V) BA3915B 228 Regulator ICs FInput / output circuits BA3915B 229 Regulator ICs BA3915B 230 Regulator ICs FElectrical characteristics (unless otherwise noted, Ta = 25_C, BACKUP / ACC = 13.2V) BA3915B 231 Regulator ICs BA3915B 232 Regulator ICs FMeasurement circuits BA3915B 233 Regulator ICs BA3915B 234 Regulator ICs BA3915B 235 Regulator ICs FInput / output timing chart BA3915B 236 Regulator ICs FMUTE timing chart BA3915B 237 Regulator ICs FAM / FM output timing chart BA3915B 238 Regulator ICs BA3915B FEstimate of allowable power dissipation Except under transitional conditions, the power dissipation of this IC is 3.4W per unit at 25_C. See Fig. 4 for heat reduction characteristics, including some cases where heat sinks are used. A = maximum BACKUP voltage B = maximum BCAP voltage I1 = maximum output current for VDD (80mA) I2 = maximum output current for COM (300mA) I3 = maximum output current for FM (300mA) I4 = maximum output current for AM (200mA) I5 = maximum output current for AR (200mA) I6 = maximum output current for ANT (250mA) I7 = maximum output current for AMP (100mA) S Power consumed by VDD 5.0V S Power consumed by COM 8.5V S Power consumed by FM 8.5V S Power consumed by AM 8.5V S Power consumed by AR 8.5V S Power consumed by ANT S Power consumed by AMP S Power consumed internally by each circuit P1 = (B * 5.0V) I1 ) (I1 / 16 ) I1 / 10) I2 ) (I2 / 60 ) I2 / 10) P2 = (A * 8.5V) I3 ) (I3 / 60 ) I3 / 10) P3 = (A * 8.5V) I4 ) (I4 / 40 ) I4 / 10) P4 = (A * 8.5V) I5 ) (I5 / 40 ) I5 / 10) P5 = (A * 8.5V) I6 ) (I6 / 50 ) I6 / 10) A P6 = (0.6V) P7 = (0.6V) I7 ) (I7 / 50 ) I7 / 10) A circuit current (about 10mA) P8 = A B A A A A PMAX = P1 ) P2 ) (P3 or P4, whichever is larger) ) P5 ) P6 ) P7 ) P8 239 Regulator ICs FOperation notes (1) Although the quality of this IC is rigorously controlled, 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. (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, characteristic values do not change drastically within the proper ranges. (3) Power dissipation (Pd) Refer to the power dissipation characteristics (Fig. 4) and the rough estimation of IC power dissipation given on a separate page. Make sure your design allows the maximum required power within the operating temperature range. (4) Overvoltage protection circuit The overvoltage protection circuit turns OFF all outputs when the potential difference between BACKUP (pin 14), BCAP (pin 13), or ACC (pin 12) and GND (pin 16) is more than about 26V at normal temperature. 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 capacitor having a capacitance of 10F or greater between GND and each of the ANT (pin 1), AMP (pin 2), VDD (pin 3), AM (pin 10), FM (pin 11), and COM (pin 15) 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 ANT (pin 1), AMP (pin 2), VDD (pin 3), AM (pin 10), FM (pin 11), and COM (pin 15) outputs, based on the respective output current. This prevents IC destruction due to overcurrent, 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 BA3915B a large capacitor. The circuit should be carefully set because output current is further restricted when output 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 the temperature drops to a certain level. (8) BACKUP-ACC potential difference If the BACKUP voltage exceeds the ACC voltage, a current flows through a protection diode connected internally between BACKUP and ACC. If the potential difference is more than 1VF, this diode is fully turned on. (9) BCAP pin external diode Voltage is supplied to BCAP from BACKUP through an external diode. The maximum current consumption is about 100mA. A reverse bias will be applied to the diode if the BACKUP pin becomes 0V. Select a diode that has sufficient electrical characteristics to cope with the above conditions. (10) Grounding Each ground trace must be adequately short from GND (pin 16). Make sure to arrange the ground traces in a pattern that prevents mutual interference. (11) We recommend installing a bypass line in your application if there is a mode where potential difference between each output and input (VCC) or GND is reversed from the normal state. 240 Regulator ICs FElectrical characteristic curves BA3915B FExternal dimensions (Units: mm) 241 |
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