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TPS72115

1.8 V

1.5 V

Boost Converter

3.3 V

1.8 V – 3 V

VIO

VCORE

DSP or

Controller

Two AAA

Batteries

EXTERNAL CAPACITOR REQUIREMENTS

POWER DISSIPATION AND JUNCTION TEMPERATURE

P

D(max) +

T

J

max * TA

R

q

JA

(1)

P

D +

V

I *

V

O

I

O

(2)

PROGRAMMING THE TPS72101 ADJUSTABLE LDO REGULATOR

V

O +

V

ref

1 )

R1

R2

(3)

TPS72101

,, TPS72115

TPS72116, TPS72118

SLVS352C – DECEMBER 2001 – REVISED MARCH 2006

APPLICATION INFORMATION (continued)

Figure 19. Dual Supply Application Circuit

A 0.1-µF ceramic bypass capacitor is required on both the input and output for stability. Larger capacitors

improve transient response, noise rejection, and ripple rejection. A higher value electrolytic input capacitor may

be necessary if large, fast rise time load transient are anticipated, and/or there is significant input resistance from

the device to the input power supply.

Specified regulator operation is assured to a junction temperature of 125°C; the maximum junction temperature

allowable without damaging the device is 150°C. This restriction limits the power dissipation the regulator can

handle in any given application. To ensure the junction temperature is within acceptable limits, calculate the

maximum allowable dissipation, PD(max), and the actual dissipation, PD, which must be less than or equal to

PD(max).

The maximum-power-dissipation limit is determined using Equation 1 :

Where:

• T

Jmax is the maximum allowable junction temperature.

• Rθ

JA is the thermal resistance junction-to-ambient for the package; see the package dissipation rating table.

• T

A is the ambient temperature.

The regulator dissipation is calculated using Equation 2:

Power dissipation resulting from quiescent current is negligible.

The output voltage of the TPS72101 adjustable regulator is programmed using an external resistor divider as

shown in Figure 20. The output voltage is calculated using Equation 3:

Where:

• V

ref = 1.225 V typ (the internal reference voltage)

8

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