Regulator ICs System power supply for car stereos BA4900 The BA4900 is a single-chip power supply IC for use in car stereo audio systems. The IC contains one 5.8V output for a microcontroller, three 8V outputs, one 10V output, and two outputs interlocked with BACKUP and ACC systems. Applications Car stereo audio systems Features 1) All output circuits, except AMP and ANT circuits, use a PNP transistor with a low saturation voltage. 2) Output current limit circuit prevents damage to the IC in the event output is short-circuited. 3) Overvoltage protection circuit provides protection against surges from the ACC or BACKUP inputs. 4) Compact 12-pin POWER package allows a large power dissipation. 5) Thermal protection circuit prevents heat damage to the IC. Absolute maximum ratings (Ta = 25C) Recommended operating conditions (Ta = 25C) 251 Regulator ICs Block diagram Pin descriptions 252 BA4900 Regulator ICs BA4900 Input / output circuits 253 Regulator ICs Electrical characteristics (unless otherwise noted, Ta = 25C and VCC = 13.2V) 254 BA4900 Regulator ICs BA4900 255 Regulator ICs Input / output timing chart 256 BA4900 Regulator ICs BA4900 FEstimate of allowable power dissipation. Except under transitional conditions, the power dissipation of this IC is 3W per unit at 25_C. See Fig.3 for thermal derating characteristics, including some cases where heat sinks are used. Fig.1 A = maximum output voltage for VCC I1 = maximum output current for VDD I2 = maximum output current for COM I3 = maximum output current for AMP I4 = maximum output current for ANT I5 = maximum output current for RADIO I6 = maximum output current for FM I7 = maximum output current for VAR S Power consumed by VDD 5.8V S Power consumed by COM 8.0V S Power consumed by AMP S Power consumed by ANT S Power consumed by RADIO 8.0V S Power consumed by FM 8.0V S Power consumed by VAR 10.0V S Power consumed internally by each circuit P1 = (A 5.8V) I1 (I1 / 20 I1 / 10) A P2 = (A 8.0V) I2 (I2 / 30 I2 / 10) A P3 = 1V I3 (22mA) A P4 = 1V I4 (22mA) A P5 = (A 8.0V) I5 (I5 / 60 I5 / 10) A P6 = (A 8.0V) I6 (I6 / 60 I6 / 10) A P8 = (A 10.0V) I7 (I7 / 10 I7 / 10) A P7 = VCC supply current (about 13mA) PMax. = P1 P2 P3 P4 P5 P6 P7 P8 257 Regulator ICs Application example 258 BA4900 Regulator ICs Operation notes (1) Although the quality of this IC is rigorously controlled, the IC may be destroyed when supply voltage or operating temperature exceeds its absolute maximum rating. 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 special mode is expected. (2) Example of application The application circuit of Fig. 2 is recommended for use. Make sure to confirm the adequacy of parts characteristics. When using the circuit with changes to external circuit constants, make sure to leave sufficient margins in consideration of fluctuations in the IC and external components including static and transitional characteristics. Note that ROHM has not carried out extensive survey regarding the patent right of this application. (3) Operating power supply voltage When operating within 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. (4) Power dissipation (Pd) Refer to the heat reduction characteristics and the rough estimation of IC power dissipation given on separate pages. Make sure your design allows the maximum required power within the operating temperature range. (5) Overvoltage protection circuit The overvoltage protection circuit turns OFF each output when the potential difference between VCC (pin 7) and GND (pin 12) is more than about 26V at normal temperature. Make sure to use the IC within this voltage limit. (6) Preventing oscillation at each output To stop oscillation of output, make sure to connect a capacitor having a capacitance of 10µF or greater between GND and each of the VDD (pin 5), COM (pin 9), RADIO (pin 10), FM (pin 11), and VAR (pin 1) output pins. We recommend using a tantalum electrolytic capacitor whose capacitance is unsusceptible to temperature. BA4900 (7) Overcurrent protection circuit An overcurrent protection circuit is installed on the VDD (pin 5), AMP (pin 6), ANT (pin 8), COM (pin 9), RADIO (pin 10), FM (pin 11), and VAR (pin 1) outputs, based on the respective output current. This prevents IC destruction by 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 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). (8) Thermal shutdown circuit The thermal shutdown 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 chip temperature drops to a certain level. (9) Output circuit configurations Each of the VDD (pin 5), COM (pin 9), RADIO (pin 10), FM (pin 11), and VAR (pin 1) output circuits has a PNP power transistor. A measure is taken to protect the IC in case the voltage of VCC (pin 7) drops and the output-side voltage becomes greater than the VCC-side voltage due to the output-side external transistor. (10) Grounding Each ground line in the application circuit of Fig. 2 must be adequately short from GND (pin 12). Make sure to arrange the ground traces in a pattern that prevents mutual interference. 259 Regulator ICs Electrical characteristic curves External dimensions (Units: mm) 260 BA4900