MIC5319 Просмотр технического описания (PDF) - Micrel

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MIC5319

500mA µCap Ultra-Low Dropout High PSRR LDO Regulator

Micrel 

Micrel, Inc.

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

To 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 ⎟⎞

⎝

θJA

⎠

MIC5319

Substituting 0.25W for PD(max) and solving for the

ambient operating temperature will give the maximum

operating conditions for the regulator circuit. The

maximum power dissipation must not be exceeded for

proper operation.

0.25W = 125°C − TA

93°C/W

TA = 101.75°C

Therefore, a 2.8V application at 500mA of output current

can accept an ambient operating temperature of

101.75°C in a 2mm x 2mm 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: www.micrel.com/_PDF/other/LDOBk_ds.pdf

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

the die. θJA thermal resistance = 93°C/W.

Table 1 shows junction-to-ambient thermal resistance for

the MIC5319 in the 2mm x 2mm MLF® package.

Package

2mm × 2mm MLF®

SOT-23-5

θJA Recommended

Minimum Footprint

93°C/W

235°C/W

Table 1. Thermal Resistance

θJC

45°C/W

May 2010

10

M9999-052510

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