167
Regulator ICs
Reference voltage power supply
BA3935
The BA3935 is a monolithic reference voltage power supply IC for use in CD radio cassette players.
Applications
CD radio cassette players, mini-component stereo audio systems
Features
1) With 9V output for audio power supply , 5V output for
microcontrollers, 5V output for radio, 5 and 7.5V out-
puts 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).
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 dis-
sipation (3W : no heat sink).
6) Thermal protection circuit prevents heat damage to
the IC.
Block diagram
168
Regulator ICs BA3935
FPin descriptions
FAbsolute maximum ratings (Ta = 25_C)
FRecommended operating conditions
169
Regulator ICs BA3935
Input / output circuits
170
Regulator ICs BA3935
FElectrical characteristics (unless otherwise noted, Ta = 25_C and VCC = 16.0V)
171
Regulator ICs BA3935
FCircuit operation
(1) T iming chart
AUDIO 9V, MOTOR 9.5V, and COM 5V are output re-
gardless 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 (typi-
cal).
(2) Estimate of allowable power dissipation
Except under transitional conditions, the power dissipa-
tion of this IC is 3W per unit at 25_C. See Fig. 1 for ther-
mal derating characteristics, including some cases
where heat sinks are used.
FThermal derating curve
172
Regulator ICs BA3935
FCircuit operation Calculation of PMAX.
SPower consumed by AUDIO 9V
P1 = (VCC 9.0V) I1
SPower consumed by MOTOR 9.5V
P2 = (VCC 9.5V) I2
SPower consumed by CD 7.5V
P3 = (VCC 7.5V) I3
SPower consumed by CD 5.0V
P4 = (VCC 5.0V) I4
SPower consumed by RADIO 5.0V
P5 = (VCC 5.0V) I5
SPower consumed by COM 5.0V
P6 = (VCC 5.0V) I6
SPower consumed internally by each circuit
P7 = VCC circuit current
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
173
Regulator ICs BA3935
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, char-
acteristic 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 allow-
able 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 ca-
pacitor 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 recom-
mend using a tantalum electrolytic capacitor having a ca-
pacitance of 10µF or greater (100µF or greater for AU-
DIO 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 (220µF or greater recommended) to the C pin
(pin 2).
(4) Overcurrent protection circuit
An overcurrent protection circuit is installed on the AU-
DIO 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 re-
stricted and latching will be prevented even if a large cur-
rent 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 continu-
ously under transitional conditions (for instance, if output
is clamped at 1VF or higher, short mode circuit operates
at 1VF or lower).
(5) Reference voltage
Because output voltage is dependent on the input refer-
ence voltage, unstable input results in output wavering
and degradation of ripple rejection. Take care when set-
ting 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 ade-
quately 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 pre-
vents electric interference.
External dimensions (Units: mm)
174
Regulator ICs BA3935
Electrical characteristic curve
