MIC5208_02 Datasheet, PDF (6/8 Pages) Micrel Semiconductor – Dual 50mA LDO Regulator

MIC5208
Micrel
Applications Information
Supply/Ground
Both MIC5208 GND pins must be connected to the same
ground potential. INA and INB can each be connected to a
different supply.
Enable/Shutdown
ENA (enable/shutdown) and ENB may be enabled sepa-
rately. Forcing ENA/B high (> 2V) enables the associated
regulator. ENA/B requires a small amount of current, typically
15µA. While the logic threshold is TTL/CMOS compatible,
ENA/B may be forced as high as 20V, independent of V_IN.
Input Capacitor
A 0.1µF 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.
Output Capacitor
An output capacitor is required between OUT and GND to
prevent oscillation. Larger values improve the regulator’s
transient response. The output capacitor value may be in-
creased without limit.
The output capacitor should have an ESR (effective series
resistance) of about 5Ω or less and a resonant frequency
above 500kHz. Most tantalum or aluminum electrolytic ca-
pacitors are adequate; film types will work, but are more
expensive. Since many aluminum electrolytics have electro-
lytes that freeze at about –30°C, solid tantalums are recom-
mended for operation below –25°C.
At lower values of output current, less output capacitance is
required for output stability. The capacitor can be reduced to
0.22µF for current below 10mA or 0.1µF for currents below
1mA.
No-Load Stability
The MIC5208 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.
Thermal Shutdown
Thermal shutdown is independent on both halves of the dual
MIC5208, however, an overtemperature condition in one half
may affect the other half because of proximity.
Thermal Considerations
Multilayer boards having a ground plane, wide traces near the
pads, and large supply bus lines provide better thermal
conductivity.
The MIC5208-xxBMM (8-lead MSOP) has a thermal resis-
tance of 200°C/W when mounted on a FR4 board with
minimum trace widths and no ground plane.
PC Board
θ_JA
Dielectric
FR4
200°C
MSOP Thermal Characteristics
For additional heat sink characteristics, please refer to Micrel
Application Hint 17, “Calculating P.C. Board Heat Sink Area
For Surface Mount Packages”.
MIC5208
6
1997