MIC5200
Micrel, Inc.
Applications Information
External Capacitors
A 1µF capacitor is recommended between the MIC5200 output
and ground to prevent oscillations due to instability. Larger
values serve to improve the regulator’s transient response.
Most types of tantalum or aluminum electrolytics will be ad-
equate; film types will work, but are costly and therefore not
recommended. Many aluminum electrolytics have electrolytes
that freeze at about –30°C, so solid tantalum capacitors are
recommended for operation below –25°C. The important pa-
rameters of the capacitor are an effective series resistance
of about 5Ω or less and a resonant frequency above 500kHz.
The value of this capacitor may be increased without limit.
At lower values of output current, less output capacitance is
required for output stability. The capacitor can be reduced to
0.47µF for current below 10mA or 0.33µF for currents below
1 mA. A 1µF capacitor should be placed from the MIC5200
input to ground 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.
The MIC5200 will remain stable and in regulation with no load
in addition to the internal voltage divider, unlike many other
voltage regulators. This is especially important in CMOS RAM
keep-alive applications.
When used in dual supply systems where the regulator load
is returned to a negative supply, the output voltage must be
diode clamped to ground.
ENABLE Input
The MIC5200 features nearly zero OFF mode current. When
the ENABLE input is held below 0.7V, all internal circuitry is
powered off. Pulling this pin high (over 2.0V) re-enables the
device and allows operation. The ENABLE pin requires a small
amount of current, typically 15µA. While the logic threshold is
TTL/CMOS compatible, ENABLE may be pulled as high as
30V, independent of the voltage on V
IN
.
Thermal Considerations
Part I. Layout
The MIC5200-xxBM (8-pin surface mount package) has the
following thermal characteristics when mounted on a single
layer copper-clad printed circuit board.
PC Board
Dielectric
FR4
Ceramic
θ
JA
160°C/W
120°C/W
Multi-layer boards having a ground plane, wide traces near
the pads, and large supply bus lines provide better thermal
conductivity.
The “worst case” value of 160°C/W assumes no ground plane,
minimum trace widths, and a FR4 material board.
Part II. Nominal Power Dissipation and Die Temperature
The MIC5200-xxBM at a 25°C ambient temperature will oper-
ate reliably at up to 625mW power dissipation when mounted
in the “worst case” manner described above. At an ambient
temperature of 55°C, the device may safely dissipate 440mW.
These power levels are equivalent to a die temperature of
125°C, the recommended maximum temperature for non-
military grade silicon integrated circuits.
For MIC5200-xxBS (SOT-223 package) heat sink character-
istics, please refer to Micrel Application Hint 17, “Calculating
P.C. Board Heat Sink Area for Surface Mount Packages”.
50 mil
245 mil
150 mil
30 mil
50 mil
Minimum recommended board pad size, SO-8.
April 2005
8
M9999-040805
MICREL [ MICREL SEMICONDUCTOR ]
