Datasheet

 2018 Microchip Technology Inc. DS20006021A-page 13
MIC5219
4.0 APPLICATION INFORMATION
The MIC5219 is designed for 150 mA to 200 mA output
current applications where a high-current spike
(500 mA) is needed for short, start-up conditions. Basic
application of the device will be discussed initially
followed by a more detailed discussion of higher
current applications.
4.1 Enable/Shutdown
Forcing EN (enable/shutdown) high (>2V) enables the
regulator. EN is compatible with CMOS logic. If the
enable/shutdown feature is not required, connect EN to
IN (supply input). See Figure 4-5.
4.2 Input Capacitor
A 1 μF capacitor should be placed from IN to GND if
there is more than 10 inches of wire between the input
and the AC filter capacitor or if a battery is used as the
input.
4.3 Output Capacitor
An output capacitor is required between OUT and GND
to prevent oscillation. The minimum size of the output
capacitor is dependent upon whether a reference
bypass capacitor is used. 1 μF minimum is
recommended when C
BYP
is not used (see Figure 4-5).
2.2 μF minimum is recommended when C
BYP
is 470 pF
(see Figure 4-6). For applications <3V, the output
capacitor should be increased to 22 μF minimum to
reduce start-up overshoot. Larger values improve the
regulator’s transient response. The output capacitor
value may be increased without limit.
The output capacitor should have an ESR (equivalent
series resistance) of about 1Ω or less and a resonant
frequency above 1 MHz. Ultra-low ESR capacitors
could cause oscillation and/or under-damped transient
response. Most tantalum or aluminum electrolytic
capacitors are adequate; film types will work, but are
more expensive. Many aluminum electrolytics have
electrolytes that freeze at about –30°C, so solid
tantalums are recommended for operation below
–25°C.
At lower values of output current, less output
capacitance is needed for stability. The capacitor can
be reduced to 0.47 μF for current below 10 mA, or
0.33 μF for currents below 1 mA.
4.4 No-Load Stability
The MIC5219 will remain stable and in regulation with
no load (other than the internal voltage divider) unlike
many other voltage regulators. This is especially
important in CMOS RAM keep-alive applications.
4.5 Reference Bypass Capacitor
BYP is connected to the internal voltage reference. A
470 pF capacitor (C
BYP
) connected from BYP to GND
quiets this reference, providing a significant reduction
in output noise (ultra-low noise performance). C
BYP
reduces the regulator phase margin; when using C
BYP
,
output capacitors of 2.2 μF or greater are generally
required to maintain stability.
The start-up speed of the MIC5219 is inversely
proportional to the size of the reference bypass
capacitor. Applications requiring a slow ramp-up of
output voltage should consider larger values of C
BYP
.
Likewise, if rapid turn-on is necessary, consider
omitting C
BYP
.
4.6 Thermal Considerations
The MIC5219 is designed to provide 200 mA of
continuous current in two very small profile packages.
Maximum power dissipation can be calculated based
on the output current and the voltage drop across the
part. To determine the maximum power dissipation of
the package, use the thermal resistance,
junction-to-ambient, of the device and the following
basic equation.
EQUATION 4-1:
T
J(MAX)
is the maximum junction temperature of the
die, +125°C, and T
A
is the ambient operating
temperature. θ
JA
is layout-dependent; Ta b le 4 -1 shows
examples of thermal resistance, junction-to-ambient,
for the MIC5219.
TABLE 4-1: MIC5219 THERMAL
RESISTANCE
Package
θ
JA
Rec. Min.
Footprint
θ
JA
1” Square
2 oz.
Copper
θ
JC
MSOP-8 160°C/W 70°C/W 30°C/W
SOT23-5 220°C/W 170°C/W 130°C/W
2x2 VDFN 90°C/W — —
2x2TDFN 90°C/W — —
P
DMAX
T
JMAX
T
A
–

JA
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