0

0.5

1

1.5

2

2.5

3

3.5

0

0.5

1

1.5

2

2.5

3

3.5

Curr ent from BUCK2 [A] @ 1.2V or less

S afe Operating Area

0

0.5

1

1.5

2

2.5

3

3.5

0

0.5

1

1.5

2

2.5

3

3.5

Curr ent from BUCK2 [A] @ 1.8V

Safe Operat ing Area

0

0.5

1

1.5

2

2.5

3

3.5

0

0.5

1

1.5

2

2.5

3

3.5

Curre nt from BUCK2 [A] @ 2.5V

Sa fe Operating Area

For any voltage / current comination inside the shaded area, the dissipated power inside the chip is below the allowable

maximum. The examples assume T

< 60°C,

= 90% and

< 44°C/W.

ambient

JA

h

q

COMPONENT SELECTION PROCEDURE

TPS65230, TPS65231

A minimum of two layers of 1-oz Cu with 20% Cu coverage on the top and 90% coverage on the bottom and the

use of thermal vias to connect the thermal pad to the bottom layer is recommended. Note that the maximum

allowable power inside the device will depend on the board layout. For recommendations on board layout for

thermal management using TPS6523x consult your TI field application engineer.

In the example shown above the maximum allowable power dissipation for the IC has been calculated. This

figure includes all heat sources inside the device including the power dissipated in BUCK1, BUCK2, BUCK3,

USB switches, and all supporting circuitry. Power dissipated in BUCK1, USB switches (500 mA full load) , and all

supporting circuitry is approximately 0.4 W and almost independent of the application. Power dissipated in

BUCK2 and BUCK3 depends on the output voltage, output current, and efficiency of the switching converters.

The following examples of safe operating area assume 90% efficiency for BUCK2 and BUCK3, 3.3-V output from

BUCK3 and 1.2-V, 1.8-V, and 2.5-V output from BUCK2, respectively.

Figure 9. Examples of Thermal Safe Operating Area for V(BUCK3) = 3.3 V and V(BUCK1) = 1.2 V, 1.8 V

and 2.5 V, Respectively

The following example illustrates the design procedure for selecting external components for the three buck

converters. The example focuses on BUCK1 but the procedure can be directly applied to BUCK2 and 3 as well.

The design goal parameters are given in the table below. A list of symbol definitions is found at the end of this

section. For this example the schematic in Figure 10 will be used.

16

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Product Folder Link(s): TPS65230 TPS65231

Not Recommended for New Designs