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Regulator ICs
Dual circuit, variable output voltage regulator
BA3960
The BA3960 is a dual circuit, variable output, series regulator. PNP output transistors allow minimum voltage differential between input and output. Each of the two circuits can be turned on or off independently by using the system logic control. When both circuits are off, the IC keeps a standby state with no supply current. FApplications Audio and video systems, CD and CD-ROM systems, computer peripheral devices, industrial equipment FFeatures 1) Containing two circuits of variable-output series regulator. 2) PNP output transistor characterized by low saturation voltage. 3) Logic control allowing ON / OFF switching of output. 4) No supply current when both circuits are off. FBlock diagram
5) Output current limit circuit protects the IC against short-circuiting damage. 6) Compact HSIP-B12 package allows a large power dissipation. 7) Thermal protection circuit prevents heat damage to the IC.
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Regulator ICs
FAbsolute maximum ratings (Ta = 25_C) FRecommended operating conditions
BA3960
FElectrical characteristics (unless otherwise noted, Ta = 25_C, VCC = 12.0V, ACTIVE 1 : IO = 640mA, ACTIVE 2 : IO = 400mA and R12, R22=3.9k)
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Regulator ICs
FInput pin descriptions and equivalent circuits
BA3960
FOutput voltage setting
Output voltage setting R11 (21) ) R12 (22) Vref S R12 (22) (1.26V) Example of output voltage setting resistance (VO1 = 6V, VO2 = 8V) R11 = 15k R12 = 3.9k R21 = 22k R22 = 3.9k
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Regulator ICs
FOutput voltage setting FApplication example
BA3960
FEstimate of allowable power dissipation
Except under transitional conditions, the power dissipation of this IC is 2.2W per unit at 25_C. See Fig. 5 for thermal derating characteristics, including some cases where heat sinks are used.
PMAX. calculation S Power consumed by ACTIVE 1 P1 = (VCC * set output voltage) maximum output voltage S Power consumed by ACTIVE 2 P2 = (VCC * set output voltage) maximum output voltage S Power consumed internally by each circuit P3 = VCC circuit current PMAX. = P1 ) P2 ) P3
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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. 5) and the rough estimation of IC power dissipation presented on a separate page. If power dissipation exceeds the allowable limit, the functionality of IC will be degraded (such as reduction of current capacity by increased chip temperature). Make sure to use the IC within the allowable range of power dissipation with a sufficient margin. (3) Preventing oscillation at each output To stop oscillation of output, make sure to connect a capacitor having a capacitance of 10 F or greater between GND and each of the Active 1 and 2 output pins. Oscillation can occur if capacitance is susceptible to temperature. We recommend using a tantalum electrolytic capacitor with minimal changes in capacitance. Also, output can be further stabilized by connecting a bypass capacitor between VCC and GND. (4) Overcurrent protection circuit An overcurrent protection circuit is installed on the Active 1 and 2 outputs, based on the respective current capacity. This prevents IC destruction when the load is shortcircuited, 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). Note that the circuit ability is negatively correlated with temperature.
BA3960
(5) Thermal protection circuit A built-in thermal protection circuit prevents thermal damage to the IC. All outputs are switched OFF when the circuit operates, and revert to the original state when temperature drops to a certain level. (6) Grounding To minimize the variation of output voltage due to variations in load current, the GND (pin 1, for large current) and the PRE GND (pin 3, for small current) pins are separately provided. Make sure to connect circuits to correct pins. (7) Output voltage setting ROHM recommends using a 3.9k resistor for R12 and R22. Refer to a separate page for the output voltage setting. Note that making a large change to the R12 and R22 values will affect the current capacity. (8) MODE voltage Due to the IC's internal structure, a reverse current flow will occur if the MODE voltage exceeds the VCC voltage. Make sure to avoid this. FExternal dimensions (Units: mm)
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