MIC37150 Datasheet, PDF (9/10 Pages) Micrel Semiconductor – 1.5 A LOW VOLTAGE UCAP LDO REGULATOR

MIC37150/37151/37152
2.25V, respectively. This gives the PNP-based regulators a
distinct advantage over older, NPN-based linear regulators.
Minimum Load Current
The MIC37150/51/52 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 MIC37151 features an error flag circuit that monitors the
output voltage and signals an error condition when the
voltage 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 MIC37151/37152 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 to up to V_IN. When enabled, it draws approxi-
mately 15µA.
Adjustable Regulator Design
Micrel
V_IN
ENABLE
SHUTDOWN
MIC37152
IN OUT
R1
EN ADJ
GND
R2
V_OUT
C_OUT
V_OUT = 1.240V ^{}1+ _RR21^{}
Figure 1. Adjustable Regulator with Resistors
The MIC37152 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:
R1 =
R2


V_OUT
1.240
−
1^{}
Where V_OUT is the desired output voltage. Figure 1 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).
August 2003
9
MIC37150/37151/37152