MIC5252 datasheet(11/22 Pages) MICROCHIP

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

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DS20006579B-page 11

MIC5252

EQUATION 4-2:

Substituting PD(MAX) for PD and solving for the

operating conditions that are critical to the application

will give the maximum operating conditions for the

regulator circuit. For example, when operating the

MIC5252-2.8YM5 at 50°C with a minimum footprint

layout, the maximum input voltage for a set output

current can be determined as follows:

EQUATION 4-3:

The junction-to-ambient thermal resistance for the

minimum footprint is 235°C/W, from Table 4-1. The

maximum power dissipation must not be exceeded for

proper operation. Using the output voltage of 2.8V and

an output current of 150 mA, the maximum input

voltage can be determined. Because this device is

CMOS and the ground current is typically 100 μA over

the load range, the power dissipation contributed by the

ground current is <1% and can be ignored for this

calculation.

EQUATION 4-4:

Therefore, a 2.8V application at 150 mA of output

current can accept a maximum input voltage of 4.9V in

a SOT-23-5 package. For a full discussion of heat

sinking and thermal effects on voltage regulators, refer

to the “Regulator Thermals” section of Micrel’s

Designing with Low-Dropout Voltage Regulators

handbook.

VIN VOUT

–





IOUT







VINIGND

PD MAX





125C 50C

–

235C/W

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









Where:

PD(MAX) = 315 mW

315mW

VIN 2.8V

–





150 mA



315mW

VIN 150 mA 420 mW

–



735 mW

VIN 150 mA



VIN MAX





4.9V

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