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| Regulator ICs Reference voltage power supply BA3935 The BA3935 is a monolithic reference voltage power supply IC for use in CD radio cassette players. FApplications CD radio cassette players, mini-component stereo audio systems FFeatures 1) With 9V output for audio power supply, 5V output for microcontrollers, 5V output for radio, 5 and 7.5V outputs for CD players, 9.5V output for motor drivers, the IC is best suited for CD radio cassette players. 2) Precise power supply (5V 0.1V) can be obtained by using external reference voltage input (only AUDIO output has an internal reference voltage system). FBlock diagram 3) Zero standby current. (Type.) 4) Output current limit circuit protects the IC against short-circuiting damage. 5) Compact SIP-M12 package allows a large power dissipation (3W : no heat sink). 6) Thermal protection circuit prevents heat damage to the IC. 167 Regulator ICs FPin descriptions BA3935 FAbsolute maximum ratings (Ta = 25_C) FRecommended operating conditions 168 Regulator ICs FInput / output circuits BA3935 169 Regulator ICs FElectrical characteristics (unless otherwise noted, Ta = 25_C and VCC = 16.0V) BA3935 170 Regulator ICs BA3935 FCircuit operation (1) Timing chart (2) Estimate of allowable power dissipation Except under transitional conditions, the power dissipation of this IC is 3W per unit at 25_C. See Fig. 1 for thermal derating characteristics, including some cases where heat sinks are used. FThermal derating curve AUDIO 9V, MOTOR 9.5V, and COM 5V are output regardless of MODE SW. RADIO 5V rises when MODE SW is 1.4V (typical), and CD 5V and CD 7.5V rise when MODE SW is 3.2V (typical). 171 Regulator ICs FCircuit operation BA3935 Calculation of PMAX. S Power consumed by AUDIO 9V P1 = (VCC * 9.0V) I1 S Power consumed by MOTOR 9.5V I2 P2 = (VCC * 9.5V) S Power consumed by CD 7.5V I3 P3 = (VCC * 7.5V) S Power consumed by CD 5.0V I4 P4 = (VCC * 5.0V) S Power consumed by RADIO 5.0V I5 P5 = (VCC * 5.0V) S Power consumed by COM 5.0V I6 P6 = (VCC * 5.0V) S Power consumed internally by each circuit circuit current P7 = VCC I1 = maximum output for AUDIO 9.0V I2 = maximum output for MOTOR 9.5V I3 = maximum output for CD 7.5V I4 = maximum output for CD 5.0V I5 = maximum output for RADIO 5.0V I6 = maximum output for COM 5.0V 172 Regulator ICs FOperation notes (1) 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. (2) Power dissipation (Pd) Refer to the heat reduction characteristics (Fig. 1) and the rough estimation of IC power dissipation given on a separate page. Make sure to use the IC within the allowable power dissipation with a sufficient margin. (3) Preventing oscillation at each output and installing a ripple filter capacitor To stop oscillation of output, make sure to connect a capacitor between GND and each of the AUDIO 9V (pin 1), RADIO (pin 4), COM (pin 5), CD 5V (pin 6), CD 7.5V (pin 7), and MOTOR 9.5V (pin 11) output pins. We recommend using a tantalum electrolytic capacitor having a capacitance of 10F or greater (100F or greater for AUDIO 9V) with minimal temperature susceptibility. Also, sudden deterioration of the AUDIO 9V ripple rejection during a power drop can be prevented by connecting a capacitor (220F or greater recommended) to the C pin (pin 2). (4) Overcurrent protection circuit An overcurrent protection circuit is installed on the AUDIO 9V (pin 1), RADIO (pin 4), COM (pin 5), CD 5V (pin 6), CD 7.5V (pin 7), and MOTOR 9.5V (pin 11) 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. Note that these protection circuits are only good for preventing damage from sudden accidents. Make sure your design does not cause the protection circuit to operate continuously under transitional conditions (for instance, if output is clamped at 1VF or higher, short mode circuit operates at 1VF or lower). BA3935 (5) Reference voltage Because output voltage is dependent on the input reference voltage, unstable input results in output wavering and degradation of ripple rejection. Take care when setting the reference voltage power supply. Note that the AUDIO output, which has a built-in reference voltage system, is not affected by the external reference voltage. (6) 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. (7) Grounding Each ground line in the application circuit must be adequately short regarding the PREGND (pin 3) and GND (pin 12) pins. Make sure to arrange the ground lines, the AUDIO system, and other outputs in a pattern that prevents electric interference. 173 Regulator ICs FElectrical characteristic curve BA3935 FExternal dimensions (Units: mm) 174 |
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