MIC5353 datasheet(8/12 Pages) MICREL

8 / 12 page

Micrel, Inc.

MIC5353

May 2010

M9999-052510

Because this device is CMOS and the ground current is

typically <100µA over the load range, the power

dissipation contributed by the ground current is < 1%

and can be ignored for this calculation:

PD = (3.3V – 2.8V) × 500mA

PD = 0.25W

determine

the

maximum

ambient

operating

temperature of the package, use the junction-to-ambient

thermal resistance of the device and the following basic

equation:

PD(MAX) =

TJ(MAX) - TA

⎝

⎛

TJ(max) = 125°C, the maximum junction temperature of

the die θJA thermal resistance = 92.4°C/W.

Thermal Resistance

Substituting PD for PD(max) and solving for the ambient

operating temperature will give the maximum operating

conditions for the regulator circuit. The junction-to-

ambient thermal resistance for the minimum footprint is

92.4°C/W.

The maximum power dissipation must not be exceeded

for proper operation.

For example, when operating the MIC5353-2.8YMT at

an input voltage of 3.3V and 500mA load with a

minimum footprint layout, the maximum ambient

operating temperature TA can be determined as follows:

0.25W = (125°C – TA)/(92.4°C/W)

TA=101°C

Therefore, a 2.8V application with 500mA of output

current can accept an ambient operating temperature of

101°C in a 1.6mm x 1.6mm Thin MLF

® 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. This information can be found on

Micrel's website at:

http://www.micrel.com/_PDF/other/LDOBk_ds.pdf

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