151

Regulator ICs

BA3924

(3)

Preventing oscillation at each output

To stop output oscillation, make sure to connect a capaci-

tor between GND and each of the MOTOR (pin 3), AU-

DIO (pin 5), COMMON (pin 6), and CD (pin 8) output

pins. Use capacitors whose valve are not below the val-

ues denoted in the application circuit (Fig. 4) and not sus-

ceptible to temperature.

(4)

Ground pins

Pre GND (pin 10) and Pow GND (pin 12) are the ground

pins of the IC. Pin 10 is the reference ground pin for pow-

er supplies, including the built-in reference power supply,

and the comparators. Voltage and threshold values may

shift if the potential of pin 10 is unstable. Take sufficient

care when designing the conductor pattern near this pin.

The source current from this pin is in the level of a few mil-

liamperes. Pin 12, which is connected to the ground

traces other than those connected to pin 10, is connected

with the IC substrate and the back metal.

(5)

External PNP transistors

ROHM’s 2SB1370 (E- or F-rank) is recommended. This

is a TO-220FP type transistor.

(6)

Overvoltage protection circuit

Although the absolute maximum voltage is 22V, a peak

voltage of 30V for 200ms is assured only during the

standby state (pin 11 is LOW). The overvoltage circuit is

circuit is activated, a standby circuit current (IST) of a few

milliamperes flows in the IC.

The overvoltage protection circuit is also activated if a

voltage exceeding the absolute maximum rating is ap-

plied while the STANDBY pin is HIGH. As a result all the

output voltage is turned off.

(7)

Overcurrent protection circuit

If the output current of any of the MOTOR (pin 3), AUDIO

(pin 5), COMMON (pin 6), and CD (pin 8) exceeds the

current capacity, the built-in current limit circuit limits the

current to a set level. If the potential of each pin is about

the same as that of Pow GND (pin 12), the output current

is reduced to the level of the ground short-circuit current

given in the “Electrical Characteristics.”

(8)

Thermal protection

The circuit current, the limit current of each power supply

output, and the ground short-circuit current decrease

gradually with increasing temperature. For further

protection, the thermal shutdown circuit turns off all out-

puts when the IC is overheated, and brings back to nor-

mal operation when the temperature is decreased to a

certain level.