MIC5337 Datasheet, PDF (7/11 Pages) Micrel Semiconductor – 1.2mm x 1.6mm 300mA Low IQ LDO Ultra Low Dropout with Auto Discharge

Micrel, Inc.
Functional Diagram
VIN
LDO
EN
REFERENCE
Auto-
Discharge
GND
MIC5337
VOUT
Applications Information
The MIC5337 is a low quiescent current, low dropout
regulator designed for optimal performance in a small
space. The MIC5337 regulator is fully protected from
damage due to fault conditions, offering linear current
limiting and thermal shutdown.
Input Supply Voltage
V_IN provides the supply to power the LDO. The minimum
input voltage is 2.3V allowing conversion from typical
lithium ion batteries and low voltage supplies.
Input Capacitor
The MIC5337 is a high performance, high bandwidth
device; therefore it requires a well-bypassed input supply
for optimal performance. A 1µF capacitor is required
from the input to ground to provide stability. Low ESR
ceramic capacitors provide optimal performance with
minimum space required. Additional high frequency
capacitors, such as small value NPO dielectric type
capacitors, help filter out high frequency noise and are
good practice in any RF circuit.
Output Capacitor
The MIC5337 requires an output capacitor of 1µF or
greater to maintain stability. The design is optimized for
use with low ESR ceramic chip capacitors. High ESR
capacitors may cause high frequency oscillation. The
output capacitor can be increased, but performance has
been optimized for a 1µF ceramic output capacitor.
X7R/X5R dielectric type ceramic capacitors are
recommended because of their temperature
performance. X7R type capacitors change capacitance
by 15% over their operating temperature range. Z5U and
Y5V dielectric capacitors change value by as much as
50% and 60% respectively over their operating
temperature ranges. To use a ceramic chip capacitor
with Y5V dielectric the value must be much higher than
an X7R ceramic capacitor to ensure the same minimum
capacitance over the equivalent operating temperature
range.
Minimum Load Current
The MIC5337 does not require a minimum load to
maintain output voltage regulation.
Enable/Shutdown
The MIC5337 comes with an active high enable pin that
enables the regulator. Forcing the enable pin low
disables the regulator and sends it into a “zero” off mode
current state. In this state, current consumed by the
regulator goes nearly to zero. When disabled, the
MIC5337 switches a 280Ω load on the regulator output
to discharge the external capacitor. The active high
enable pin uses CMOS technology and cannot be left
floating; a floating enable pin may cause an unknown
output state.
Thermal Considerations
The MIC5337 is designed to provide 300mA continuous
output current from a very small footprint package.
Maximum ambient operating temperature can be
calculated based on the output current and the voltage
September 2008
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M9999-090908-A