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Regulator ICs
System power supply for CD radio
cassette players
BA3938
The BA3938 is a system power supply IC for use in CD radio cassette players. With one 11V output and interlocked
outputs of 8.5V, 5V, 9V, and V
Applications
CD radio cassette players
Features
1) One 11V output (external transistor required) and interlocked outputs of 8.5V , 5V , 9V , and V
2) Output current limit circuit protects the IC against
short-circuiting damage.
CC, the IC is best suited for CD radio cassette players.
3) Compact HSIP-B12 package allows a large power
CC are built in.
dissipation.
Absolute maximum ratings (Ta = 25C)
Recommended operating conditions (Ta = 25C)
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Regulator ICs BA3938
Block diagram
Pin descriptions
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Regulator ICs BA3938
Input / output circuits
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Regulator ICs BA3938
Electrical characteristics (unless otherwise noted, Ta = 25C and VCC = 15.0V)
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Regulator ICs BA3938
Circuit operation
All outputs rise when voltage is applied on the STANDBY pin.
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Regulator ICs BA3938
Application example
Operation 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 given 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 10µF or greater between
GND and each output pin. 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 sta-
bilized by connecting a bypass capacitor between V
and GND.
(4) Overcurrent protection circuit
An overcurrent protection circuit is installed in each output system, 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 (a curve shape of “inverted -L” for V
CC B). 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 1V
F or lower). Note that the circuit ability is negatively
at 1V
F or higher, short mode circuit operates
correlated with temperature.
CC
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Regulator ICs BA3938
(5) Thermal protection circuit
A built-in thermal protection circuit prevents thermal
damage to the IC. All outputs except V
CC + B 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 12, for large current)
and the PRE GND (pin 1 1, for small current) pins are separately provided. Make sure to connect circuits to correct
pins.
FThermal derating cueve
(7) STANDBY voltage
Note that ON-state voltage and HIGH-state input current
of each output change when the external resistors of the
STANDBY pin are changed. These values are roughly
estimated as :
STB voltage when ON = 0.7 (R1 ) R2) / R2
STB current when HIGH = (5*0.7) / R1
Estimate of allowable power dissipation (P
S Power consumed by V
CC + B P1 = (VCC * VCC + B) maximum output current of VCC + B
MAX.)
S Power consumed by OUT 5V P
S Power consumed by CD 8.5V P
S Power consumed by OUT 9V P
S Power consumed internally by each circuit P
MAX. = P1 ) P2 ) P3 ) P4 ) P5
P
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2 = (VCC * 5V) maximum output current of OUT 5V
3 = (VCC * 8.5V) maximum output current of OUT 8.5V
4 = (VCC * 9V) maximum output current of OUT 9V
5 = VCC supply current
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Regulator ICs BA3938
External dimensions (Units: mm)
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