Rainbow Electronics BA3938 - Manual (Page 7)

190
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 varia-
tions in load current, the GND (pin 12, for large current)
and the PRE GND (pin 11, for small current) pins are sep-
arately provided. Make sure to connect circuits to correct
pins.
(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
F
Thermal derating cueve
Estimate of allowable power dissipation (P
MAX.
)
S Power consumed by V
CC
+ B P
1
= (V
CC
* V
CC
+ B) maximum output current of V
CC
+ B
S
Power consumed by OUT 5V P
2
= (V
CC
*
5V) maximum output current of OUT 5V
S
Power consumed by CD 8.5V P
3
= (V
CC
*
8.5V) maximum output current of OUT 8.5V
S
Power consumed by OUT 9V P
4
= (V
CC
*
9V) maximum output current of OUT 9V
S Power consumed internally by each circuit P
5
= V
CC
supply current
P
MAX.
= P
1
) P
2
) P
3
) P
4
) P
5