MIC5212 datasheet(9/18 Pages) MICROCHIP

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DS20005774B-page 9

MIC5212

4.0

DEVICE OVERVIEW

4.1

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.

4.2

Output Capacitor

An output capacitor is required between OUT and GND

prevent

oscillation.

1.0 μF

minimum

recommended. Larger values improve the regulator’s

transient response. The output capacitor value may be

increased without limit.

The output capacitor should have an ESR (Effective

Series Resistance) of about 5Ω or less and a resonant

frequency above 1 MHz. Ultra-low-ESR capacitors

may cause a low-amplitude oscillation and/or

underdamped transient response. Most tantalum or

aluminum electrolytic capacitors are adequate; film

types will work, but are more expensive. Since many

aluminum electrolytic capacitors have electrolytes that

freeze at about –30°C, solid tantalum capacitors are

recommended 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 0.47 μF for current below

10 mA or 0.33 μF for currents below 1 mA.

4.3

No-Load Stability

The MIC5212 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.

4.4

Dual-Supply Operation

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.

4.4.1

POWER SO-8 THERMAL

CHARACTERISTICS

One of the secrets of the MIC5212’s performance is its

power SO-8 package featuring half the thermal

resistance of a standard SO-8 package. Lower thermal

resistance means more output current or higher input

voltage for a given package size.

Lower thermal resistance is achieved by joining the

four ground leads with the die attach paddle to create a

single-unit electrical and thermal conductor. This

concept has been used by MOSFET manufacturers for

years, proving very reliable and cost effective for the

user.

Thermal resistance consists of two main elements, θJC

(junction-to-case thermal resistance) and θCA

(case-to-ambient thermal resistance). See Figure 4-1.

θJC is the resistance from the die to the leads of the

package. θCA is the resistance from the leads to the

ambient air and it includes θCS (case-to-sink thermal

resistance) and θSA (sink-to-ambient thermal

resistance).

FIGURE 4-1:

Thermal Resistance.

Using the power SO-8 reduces the θJC dramatically

and allows the user to reduce θCA. The total thermal

resistance,

θJA

(junction-to-ambient

thermal

resistance) is the limiting factor in calculating the

maximum power dissipation capability of the device.

Typically, the power SO-8 has a θJC of 20°C/W, this is

significantly lower than the standard SO-8 which is

typically 75°C/W. θCA is reduced because pins 5

through 8 can now be soldered directly to a ground

plane which significantly reduces the case-to-sink

thermal resistance and sink to ambient thermal

resistance.

These low dropout linear regulators are rated to a

maximum junction temperature of 125°C. It is important

not to exceed this maximum junction temperature

printed circuit board

ground plane

heat sink area

SO-8

AMBIENT

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