Rainbow Electronics BA3940A - Manual (Page 6)

197
Regulator ICs BA3940A
F
Operation notes
(1) Operating power supply
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 thermal derating curve (Fig. 4) 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 ca-
pacitor having a capacitance of 1
µ
F or greater between
GND and each output pin. (To avoid the noise effect, lay
out the grounding close to the IC) Oscillation can occur
if capacitance is susceptible to temperature. We recom-
mend using a tantalum electrolytic capacitor with minimal
changes in capacitance.
(4)
Overcurrent protection circuit
An overcurrent protection circuit is installed in each out-
put 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. 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 capaci-
tor. 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 oper-
ate continuously under transitional conditions (for
instance, when output is clamped at 1V
F
or higher). Note
that the circuit ability is negatively correlated with temper-
ature.
(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)
Improving ripple rejection by capacitors
Ripple rejection of the 9V and 7V (current capacity = 1A)
outputs can be improved by installing a capacitor that re-
duces the AC gain.
(7)
Malfunction in intense electric fields
Note that bringing the IC into an intense electric field
(such as a radio relay station) may result in malfunction.