SW

IN

OUT

OUT

L

L

MAX

,

OUT

MAX

,

L

f

L

V

V

1

V

I

2

I

I

I

´

-

´

=

D

D

+

=

OUT

FB

R1

R1

V

= V

1 +

= 0.8 V

1 +

R2

R2

æ

ö

æ

ö

´

´

ç

÷

ç

÷

è

ø

è

ø

TPS62097

www.ti.com

SLVSCD6 – DECEMBER 2015

9.2.2 Detailed Design Procedure

9.2.2.1 Setting the Output Voltage

The output voltage is set by an external resistor divider according to the following equation:

(4)

R2 should not be higher than 20 k

Ω to reduce noise coupling into the FB pin and improve the output voltage

regulation. Figure 6 shows the external resistor divider value for 1.2-V output. Choose additional resistor values

for other outputs. A feed forward capacitor is not required.

The fixed output voltage versions, TPS6209718 and TPS6209733, do not need the external resistor divider. TI

recommends to connect the FB pin to AGND for improved thermal performance.

9.2.2.2 Output Filter Design

The inductor and the output capacitor together provide a low-pass filter. To simplify the selection process,

Table 4 outlines possible inductor and capacitor value combinations for most applications.

Table 4. Output Capacitor / Inductor Combinations

(2)

10

22

47

100

150

0.47

1

+

+

+

2.2

(1)

Inductor tolerance and current de-rating is anticipated. The effective inductance can vary by +20% and

-30%. The required effective inductance is 500nH minimum.

(2)

Capacitance tolerance and bias voltage de-rating is anticipated. The effective capacitance can vary by

20% and -50%.

(3)

Typical application configuration. Other '+' mark indicates recommended filter combinations. Other

values may be acceptable in applications but should be fully tested by the user. Refer to the

application note SLVA710.

9.2.2.3 Inductor Selection

The main parameters for the inductor selection are the inductor value and the saturation current. To calculate the

maximum inductor current under static load conditions, Equation 5 is given.

(5)

Where:

L = Inductor value

Equation 5. A higher inductor value is also useful to lower ripple current but increases the transient response

time as well. The following inductors are recommended to be used in designs.

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