MIC5209 datasheet(14/30 Pages) MICROCHIP

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MIC5209

DS20005720B-page 14



2017 - 2022 Microchip Technology Inc. and its subsidiaries

the number of clock outputs, and the type of level

shifter (from core logic levels to 2.5V levels). Intel

estimates a “worst-case” load of 320 mA.

The MIC5209 was designed to provide the 2.5V power

requirement for Slot-1 applications. Its guaranteed

performance of 2.5V ±3% at 500 mA allows adequate

margin for all systems, and the dropout voltage of

500 mV means that it operates from a “worst-case”

3.3V supply where the voltage can be as low as 3.0V.

FIGURE 4-5:

Slot-1 Power Supply.

A Slot-1 power supply (Figure 4-5) is easy to

implement. Only two capacitors are necessary, and

their values are not critical. CIN bypasses the internal

circuitry and should be at least 0.1 µF. COUT provides

output filtering, improves transient response, and

compensates the internal regulator control loop. Its

value should be at least 22 µF. CIN and COUT can be

increased as much as desired.

4.10.1

SLOT-1 POWER SUPPLY POWER

DISSIPATION

Powered from a 3.3V supply, the Slot-1 power supply

illustrated in Figure 4-5 has a nominal efficiency of

75%. At the maximum anticipated Slot-1 load

(320 mA), the nominal power dissipation is only

256 mW.

The SOT-223 package has sufﬁcient thermal

characteristics for wide design margins when mounted

on a single-layer copper-clad printed circuit board. The

power dissipation of the MIC5209 is calculated using

the voltage drop across the device output current plus

supply voltage ground current.

Considering “worst-case” tolerances, the power

dissipation could be as high as:

EQUATION 4-2:

So:

EQUATION 4-3:

Resulting in:

EQUATION 4-4:

Using the maximum junction temperature of +125°C

and a θJC of 15°C/W for the SOT-223, 25°C/W for the

SOIC-8, or 3°C/W for the DDPAK package, the

following worst-case heat-sink thermal resistance (θSA)

requirements are:

EQUATION 4-5:

Table 4-2 and Figure 4-6 show that the Slot-1 power

supply application can be implemented with a minimum

footprint layout.

Figure 4-6 shows the necessary copper pad area to

obtain specific heatsink thermal resistance (θSA)

values. The θSA values highlighted in Table 4-2 require

much less than 500 mm2 of copper and, per Figure 4-6,

can be easily accomplished with the minimum footprint.

MIC5209-x.xYS

2, TAB

OUT

GND

OUT

0.1μF

OUT

22μF

VIN MAX





VOUT MAX





–





IOUT



VIN MAX





IGND



TABLE 4-2:

MAXIMUM ALLOWABLE

THERMAL RESISTANCE

+40°C

+50°C

+60°C

+70°C

θJA Limit 209°C/W 184°C/W 160°C/W 135°C/W

θSA

SOT-223

194°C/W 169°C/W 145°C/W 120°C/W

θSA

SOIC-8

184°C/W 159°C/W 135°C/W 110°C/W

θSA

DDPAK

206°C/W 181°C/W 157°C/W 132°C/W

3.6V 2.375V

–





320mA







3.6V 4mA







PD 407mW

JA

TJ MAX





–

--------------------------------

Where: θSA = θJA - θJC

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