SW

IN

OUT

OUT

L

L

MAX

,

OUT

MAX

,

L

f

L

V

V

1

V

I

2

I

I

I

´

-

´

=

D

D

+

=

÷

ø

ö

ç

è

æ

+

´

=

÷

ø

ö

ç

è

æ

+

´

=

2

R

1

R

1

V

45

.

0

2

R

1

R

1

V

V

FB

OUT

13

TPS62080, TPS62080A, TPS62081, TPS62082

www.ti.com

SLVSAE8F – SEPTEMBER 2011 – REVISED NOVEMBER 2016

Product Folder Links: TPS62080 TPS62080A TPS62081 TPS62082

Submit Documentation Feedback

Copyright © 2011–2016, Texas Instruments Incorporated

9.2.2.1 Setting the Output Voltage

The TPS608x devices are available as fixed and adjustable output voltage versions. The fixed voltage versions

are internally programmed to a fixed output voltage, whereas the adjustable output voltage version needs to be

programmed via an external voltage divider to set the desired output voltage.

9.2.2.1.1

Adjustable Output Voltage Version

For the adjustable output voltage version, an external resistor divider is used. By selecting R1 and R2, the output

voltage is programmed to the desired value.

When the output voltage is regulated, the typical voltage at the FB pin is VFB for the adjustable devices. The

following equation can be used to calculate R1 and R2.

(2)

For best accuracy, R2 should be kept smaller than 40kΩ to ensure that the current flowing through R2 is at least

100 times larger than IFB. Changing towards a lower value increases the robustness against noise injection.

Changing towards higher values reduces the input current. For lowest input current during Snooze Mode, it is

recommended to use a fixed output voltage version such as TPS62081 and TPS62082.

9.2.2.2 Output Filter Design

The inductor and the output capacitor together provide a low pass filter. To simplify this process, Table 4 outlines

possible inductor and capacitor value combinations for most applications. Checked cells represent combinations

that are proven for stability by simulation and lab test. Further combinations should be checked for each

individual application.

(1)

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

+20% and –50%. Inductor tolerance and current de-rating is anticipated. The effective inductance can

vary by +20% and –30%.

(2)

Plus mark indicates recommended filter combinations.

(3)

Filter combination in typical application.

Table 4. Matrix of Output Capacitor and Inductor Combinations

L [µH](1)

COUT [µF]

(1)

10

22

47

100

150

0.47

1

+

+(2)(3)

+

+

2.2

+

+

+

+

4.7

9.2.2.3 Inductor Selection

The main parameters for the inductor selection are the inductor value and then the saturation current of the

inductor. To calculate the maximum inductor current under static load conditions, Equation 3 is given.

where

•

IOUT,MAX = Maximum output current

•

ΔIL = Inductor current ripple

•

fSW = Switching frequency

•

L = Inductor value

(3)