F

=

P

OUT

OUT

1

2

L

x C

p

OUT

R1 0.8 V

R2 =

V

-0.8V

´

10µF

C4

10µH

L1

10µF

C5

VIN 4.5-17V

VOUT 1.05V, 0.5 A

0.1µF

C2

C3

TPS560200

VIN

4

EN

1

VSENSE

5

GND

2

PH

3

U1

10µF

C1

6.19k

R1

20.0k

R2

open

TPS560200

SLVSC81 – SEPTEMBER 2013

www.ti.com

APPLICATION INFORMATION

Design Guide

To begin the design process, the user must know a few application parameters:

•

Input voltage range

•

Output voltage

•

Output current

•

Output voltage ripple

•

Input voltage ripple

Figure 7. Typical Application Schematic

Output Voltage Resistors Selection

The output voltage is set with a resistor divider from the output node to the VFB pin. It is recommended to use

To improve efficiency at light loads consider using larger value resistors, high resistance is more susceptible to

noise, and the voltage errors from the VSENSE input current are more noticeable.

(2)

Output Filter Selection

The output filter used with the TPS560200 is an LC circuit. This LC filter has double pole at:

(3)

At low frequencies, the overall loop gain is set by the output set-point resistor divider network and the internal

gain of the TPS560200. The low frequency phase is 180 degrees. At the output filter pole frequency, the gain

rolls off at a –40 dB per decade rate and the phase drops rapidly. D-CAP2™ introduces a high frequency zero

that reduces the gain roll off to –20 dB per decade and increases the phase to 90 degrees one decade above the

zero frequency. The inductor and capacitor selected for the output filter must be selected so that the double pole

of Equation 3 is located below the high frequency zero but close enough that the phase boost provided be the

high frequency zero provides adequate phase margin for a stable circuit. To meet this requirement use the

values recommended in Table 1

Table 1. Recommended Component Values

L1

Output Voltage

R1

R2

C5

C3 + C4

(µH)

(V)

(k

Ω)

(k

Ω)

(pF)

(µF)

Min

Typ

Max

1.0

4.99

20.0

10

10 + 10

1.05

6.19

20.0

10

10 + 10

1.2

10.0

20.0

10

10 + 10

1.5

17.4

20.0

10

10 + 10

1.8

24.9

20.0

optional

10

10 + 10

2.5

42.2

20.0

optional

10

10 + 10

8

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