TC1302A datasheet(14/26 Pages) MICROCHIP

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TC1302A/B

DS21333B-page 14

6.0

APPLICATION CIRCUITS/

ISSUES

6.1

Typical Application

The TC1302A/B is used for applications that require

the integration of two LDOs.

FIGURE 6-1:

Typical Application Circuit

TC1302A/B.

6.1.1

APPLICATION INPUT CONDITIONS

6.2

Power Calculations

6.2.1

POWER DISSIPATION

The internal power dissipation within the TC1302A/B 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 each LDO.

EQUATION 6-1:

In addition to the LDO pass element power dissipation,

there is power dissipation within the TC1302A/B as a

result of quiescent or ground current. The power

dissipation, as a result of the ground current, can be

calculated using the following equation.

EQUATION 6-2:

The total power dissipated within the TC1302A/B is the

sum of the power dissipated in both of the LDOs and

the P(IGND) term. Because of the CMOS construction,

the typical IGND for the TC1302A/B is 116 µA.

Operating at a maximum of 4.2V results in a power

dissipation of 0.5 milliWatts. For most applications, this

is small compared to the LDO pass device power dissi-

pation and can be neglected.

The

maximum

continuous

operating

junction

temperature specified for the TC1302A/B is +125°C. To

estimate the internal junction temperature of the

TC1302A/B, the total internal power dissipation is

multiplied by the thermal resistance from junction to

ambient (R

θJA) of the device. The thermal resistance

from junction-to-ambient for the 3x3DFN8 pin package

is estimated at 41° C/W.

EQUATION 6-3:

Package Type = 3x3DFN8

Input Voltage Range = 2.7V to 4.2V

VIN maximum = 4.2V

VIN typical = 3.6V

VOUT1 = 300 mA maximum

VOUT2 = 150 mA maximum

GND

BATTERY

COUT1

1µF Ceramic

X5R

CIN

1µF

TC1302A

COUT2

1 µF Ceramic

X5R

Cbypass

10 nF Ceramic

Bypass

VIN

2.7V

4.2V

VOUT2

SHDN2

ON/OFF Control VOUT2

2.8V @ 300 mA

1.8V

VOUT1

BATTERY

COUT1

1µF Ceramic

X5R

CIN

1µF

TC1302B

COUT2

1µF Ceramic

X5R

Bypass

VIN

2.7V

4.2V

VOUT2

SHDN2

ON/OFF Control VOUT2

2.8V @ 300 mA

1.8V

ON/OFF Control VOUT1

VOUT1

@ 150 mA

GND

@ 150 mA

SHDN1

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) = Total current in ground pin.

VIN(MAX)= Maximum input voltage.

IVIN

= Current flowing in the VIN pin with

no output current on either LDO output.

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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