MIC5202 Datasheet, PDF (6/6 Pages) Micrel Semiconductor – Dual 100mA Low-Dropout Voltage Regulator Preliminary Information

MIC5202
Applications Information
External Capacitors
A 1µF capacitor is recommended between the MIC5202
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 adequate; film types will work, but are costly and
therefore not recommended. Many aluminum electrolytics
have electrolytes that freeze at about –30°C, so solid tantalums
are recommended for operation below –25°C. The important
parameters 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 MIC5202
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 supply.
ENABLE Input
The MIC5202 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 . The two
IN
portions of the MIC5202 may be enabled separately.
Thermal Considerations
Part I. Layout
Micrel
The MIC5202-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 MIC5202-xxBM at a 25°C ambient temperature will
operate 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 tempera-
ture of 125°C, the recommended maximum temperature for
non-military grade silicon integrated circuits.
General Notes
The MIC5202 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. Thermal shutdown is
independant on both halfs of the dual MIC5202, however an
over-temperature condition on one half might affect the other
because of proximity. 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.
Both MIC5202 GROUND pins must be tied to the same
ground potential. Isolation between the two halfs allows
connecting the two V_IN pins to different supplies.
245 mil
50 mil
150 mil
30 mil
50 mil
Minimum recommended board pad size, SO-8.
3-140
July 1998