MIC37300/37301/37302
Minimum Load Current
The MIC37300/01/02 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 operation.
Error Flag
The MIC37301 features an error flag circuit that monitors the
output voltage and signals an error condition when the
voltage is 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.
Enable Input
The MIC37301/37302 also 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 up to V
IN
. When enabled, it draws approximately
15µA.
ENABLE
SHUTDOWN
Micrel
Adjustable Regulator Design
MIC37302
V
IN
IN
EN
OUT
R1
ADJ
GND
R2
C
OUT
V
OUT
R1
V
OUT
=
1.240V
1
+
R2
Figure 2. Adjustable Regulator with Resistors
The MIC37302 allows programming the output voltage any-
where between 1.24V and the 5.5V maximum operating
rating of the family. Two resistors are used. Resistors can be
quite large, up to 1MΩ, because of the very high input
impedance and low bias current of the sense comparator.
The resistor values are calculated by:
V
R1
=
R2
OUT
−
1
1.240
Where V
OUT
is the desired output voltage. Figure 2 shows
component definition. Applications with widely varying load
currents may scale the resistors to draw the minimum load
current required for proper operation (see above).
November 2003
9
M0307-112003
MICREL [ MICREL SEMICONDUCTOR ]
