LM39300/39301/39302
Minimum Load Current
The
LM39300/1/2
regulator is specified between finite loads.
If the output current is too small, leakage currents dominate
and the output voltage rises. A 10mA minimum load current
is necessary for proper regulation.
Error Flag
The
LM39301
version features an error flag circuit which
monitors the output voltage and signals an error condition
when the voltage drops 5% below the nominal output voltage.
The error flag is an open-collector output that can sink 10mA
during a fault condition.
Low output voltage can be caused by a number of problems,
including an overcurrent fault (device in current limit) or low
input voltage. The flag is inoperative during overtemperature
shutdown.
When the error flag is not used, it is best to leave it open. The
flag pin can be tied directly to pin 4, the output pin.
Enable Input
The
LM39301/2
version features an enable input for on/off
control of the device. Its shutdown state draws “zero” current
(only microamperes of leakage). The enable input is TTL/
CMOS compatible for simple logic interface, but can be
connected to up to 20V. When enabled, it draws approxi-
mately 15μA.
LM39302 Adjustable Regulator Design
The
LM39302 allows programming output any voltage,but
between 1.25V and 16V maximum operating rating voltage
of the family. Two resistors are used. Resistors can be
quite large, up to 1M ohms, because of the very high
input impedance and low bias current of the sense com-
parator: the resistor values are calculated by:
R1=R2(Vout/1.250-1)
Where Vout is the desired output voltage. Page 1 typical
application shows component definition. Application with
widely varying load currents may scale the resistors to
draw the minimum load current required for proper
operation.
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