MIC5363 Datasheet, PDF (8/12 Pages) Micrel Semiconductor – High-PSRR, 300mA, μCap LDO in 1.2mm × 1.2mm Thin MLF®

Micrel, Inc.
Application Information
The MIC5363/4 is a 300mA LDO, packaged in a 1.2mm
x 1.2mm Thin MLF^® package. The MIC5364 includes an
auto-discharge feature which automatically discharges
the output capacitor when the output is disabled. The
MIC5363/4 consists of an internal reference, error
amplifier, P-channel pass transistor, and internal
feedback resistors. The error amplifier compares the
feedback voltage with that of the reference. Depending
upon whether the feedback is lower or higher than the
reference determines whether the gate of the pass
transistor is pulled low to allow more current and
increase output voltage or pulled high to reduce current.
The MIC5363/4 regulator is fully protected from damage
due to fault conditions through linear current limiting and
thermal shutdown.
Input Capacitor
The MIC5363/4 is a high-performance, high-bandwidth
device. An input capacitor of 1µF from the input pin to
ground is required to provide stability. Low-ESR ceramic
capacitors provide optimal performance in small board
area. Additional high-frequency capacitors, such as
small valued NPO dielectric type capacitors, help filter
out high-frequency noise and are good practice in any
RF-based circuit. X5R or X7R dielectrics are
recommended for the input capacitor. Y5V dielectrics
lose most of their capacitance over temperature and are
therefore not recommended.
Output Capacitor
The MIC5363/4 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 and X5R dielectric ceramic capacitors are
recommended for their temperature performance. X7R
capacitors change capacitance by 15% over their
operating temperature range and are the most stable
type of ceramic capacitors. 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.
MIC5363/4
No Load Stability
The MIC5363/4 will remain stable and in regulation
without the need of a minimum load. This reduces the
amount and therefore cost of external components.
Enable/Shutdown
The MIC5363/4 comes with an active-high enable pin
that allows the regulator to be disabled. Forcing the
enable pin low disables the regulator and sends it into an
off-mode current state drawing virtually zero current.
When disabled, the MIC5364 switches an internal 30Ω
load on the regulator output to discharge the external
capacitor.
Forcing the enable pin high enables the output voltage.
The active-high enable pin uses CMOS technology and
cannot be left floating. A floating enable pin may cause
an indeterminate state on the output.
Thermal Considerations
The MIC5363/4 is designed to provide a 300mA
continuous current output in a very-small package.
Maximum operating temperature can be calculated
based on the output currents and the voltage drop
across the part. For example, if the input voltage is 3.6V,
V_OUT = 2.8V and the output current = 300mA. The actual
power dissipation of the regulator circuit can be
determined using the equation:
P_D = (V_IN − V_OUT) I_OUT + V_IN I_GND
Because this is a CMOS device and the ground current
is typically <60µA over the load range, the power
dissipation contributed by the ground current is < 1%
which can be ignored for this calculation:
P_D = (3.6V − 2.8V) × 300mA
P_D = 0.24W
To determine the maximum ambient operating
temperature of the package, use the junction to ambient
thermal resistance of the device and the following basic
equation:
P_D(MAX)
=
⎜⎛
⎜⎝
T_J(MAX)
θ _JA
-
T_A
⎟⎞
⎟⎠
T_J(MAX) = 125°C
θ_JA = 173°C/W
April 2012
8
M9999-043012-A