MCP1726 datasheet(18/30 Pages) MICROCHIP

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MCP1726

DS21936B-page 18

5.0

APPLICATION

CIRCUITS/ISSUES

5.1

Typical Application

The MCP1726 is used for applications that require high

LDO output current and a power good output.

FIGURE 5-1:

Typical Application Circuit.

5.1.1

APPLICATION CONDITIONS

5.2

Power Calculations

5.2.1

POWER DISSIPATION

The internal power dissipation within the MCP1726 is a

function of input voltage, output voltage, output current

and quiescent current. The following equation can be

used to calculate the internal power dissipation for the

LDO.

EQUATION 5-1:

In addition to the LDO pass element power dissipation,

there is power dissipation within the MCP1726 as a

result of quiescent or ground current. The power dissi-

pation as a result of the ground current can be

calculated using the following equation:

EQUATION 5-2:

The total power dissipated within the MCP1726 is the

sum of the power dissipated in the LDO pass device

and the P(IGND) term. Because of the CMOS construc-

tion, the typical IGND for the MCP1726 is 140 µA.

Operating at a maximum of 3.63V results in a power

dissipation of 0.51 milli-Watts. For most applications,

this is small compared to the LDO pass device power

dissipation and can be neglected.

The maximum continuous operating junction tempera-

ture specified for the MCP1726 is +125°C. To estimate

the internal junction temperature of the MCP1726, the

total internal power dissipation is multiplied by the ther-

mal resistance from junction to ambient (R

θJA) of the

device. The thermal resistance from junction to ambi-

ent for the 3X3DFN package is estimated at 41° C/W.

EQUATION 5-3:

Package Type = 3X3DFN8

Input Voltage Range = 3.3V ± 10%

VIN maximum = 3.63V

VIN minimum = 2.97V

VOUT typical = 2.5V

IOUT = 1.0A maximum

VIN

SHDN

GND PWRGD

CDELAY

VOUT

10 µF

VOUT = 2.5V @ 1A

10 µF

VIN = 3.3V

Off

VIN

1000 pF

MCP1726-2.5

10k

PWRGD

LDO

IN MAX

)

() VOUT MIN

()

–

() I

OUT MAX

)

()

PLDO = LDO Pass device internal power

dissipation

VIN(MAX)= Maximum input voltage

VOUT(MIN) = LDO minimum output voltage

IGND

()

IN MAX

()

VIN

PI(GND) = Power dissipation due to the

quiescent current of the LDO

VIN(MAX) = Maximum input voltage

IVIN = Current flowing in the VIN pin with

no LDO output current (LDO

quiescent current)

JMAX

()

TOTAL

AMAX

TJ(MAX) = Maximum continuous junction

temperature

PTOTAL = Total device power dissipation

θJA = Thermal resistance from junction

to ambient

TAMAX = Maximum ambient temperature

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