www.ti.com

Designing for Load Transients

PTH08000W

SLTS248B – JUNE 2005 – REVISED FEBRUARY 2008

CAPACITOR CHARACTERISTICS

QUANTITY

85

°C

CAPACITOR VENDOR/

EQUIVALENT

VENDOR

WORKING

MAXIMUM

PHYSICAL

COMPONENT

VALUE

SERIES

INPUT

OUTPUT

NUMBER

VOLTAGE

RIPPLE

SIZE

SERIES

(µF)

RESISTANCE

BUS

(V)

CURRENT

(mm)

(ESR) (

Ω)

Panasonic WA (SMT)

20

150

0.026

3700

10

× 10,2

1

≤ 2

EEFWA1D151P

FC (SMT)

25

220

0.150

670

10

× 10,2

1

1

EEVFC1E221P

Panasonic SL

6.3

47

0.018

2500

7,3

× 4,3

≤ 3

EEFCD0J470R

SP-cap(SMT)

6.3

120

0.007

3500

7,3

× 4,3

≤ 1

EEFSD0J121R

United Chemi-con

PXA (SMT)

16

150

0.026

3400

10

× 7,7

1

≤ 2

PXA16VC151MJ80TP

PS

25

100

0.020

4300

10

× 12,5

1

≤ 2

25PS100MJ12

LXZ

35

220

0.180

760

10

× 12,5

1

1

LXZ35VB221M10X12LL

MVY (SMT)

35

333

0.150

670

10

× 10

1

1

MVY35VC331MJ10TP

Nichicon UWG (SMT)

35

100

0.150

670

10

× 10

1

1

UWG1V101MNR1GS

F559(Tantalum)

10

100

0.055

2000

7,7

× 4,3

≤ 3

F551A107MN

HD

25

220

0.072

760

8

× 11,5

1

1

UHD1E221MPR

Sanyo Os-con\ POS-Cap

10

68

0.025

2400

7,3

× 4,3

≤ 2

10TPE68M

SVP (SMT)

20

150

0.020

4320

10

× 12,7

1

≤ 1

20SVP150M

SP

20

120

0.024

3110

8

× 10,5

1

≤ 2

20SP120M

AVX Tantalum TPS (SMD)

35

47

0.100

1430

7,3

× 4,3 × 4,1

2

≤ 4

TPSV476M035R0100

25

47

0.100

1150

7,3

× 4,3 × 4,1

2

≤ 4

Kemet T520 (SMD)

10

100

0.025

> 2000

7,3

× 5,7 × 4

≤ 1

T520V107M010ASE025

AO-CAP

6.3

100

0.018

> 2900

7,3

× 5,7 × 4

≤ 1

A700V107M006AT

Vishay/Sprague

35

47

0.280

> 1000

7,3

× 6 × 4,1

2

≤ 5

595D476X0035R2T

594D/SVP(SMD)

20

100

0.025

3200

8

× 12

1

≤ 2

94SVP107X0020E12

94SS

20

150

0.030

3200

10

× 10,5

1

≤ 2

94SS157X0020FBP

Murata Ceramic X5R

16

47

0.002

> 1400

3225

≤ 3

GRM32ER61C476M

TDK ceramic X5R

6.3

47

0.002

> 1400

3225

≤ 3

Kemet Ceramic X5R

6.3

47

0.002

> 1400

3225

≤ 3

TDK Ceramic X7R

25

10

0.002

> 1400

3225

≤ 4

C3225X7R1E106K

Murata Ceramic X5R

25

10

0.002

> 1400

≤ 4

GRM32DR61E106KA12

Kemet

16

10

0.002

> 1400

≤ 4

C1210C106M4PAC

TDK Ceramic X7R

25

2.2

0.002

> 1400

3225

1

1

C3225X7R1E225KT/MT

Murata Ceramic X7R

25

2.2

0.002

> 1400

1

1

GRM32RR71J225KC01L

Kemet

25

2.2

0.002

> 1400

1

1

C1210C225K3RAC

(1)

Check with capacitor manufacturers for availability and lead-free status.

(2)

The voltage rating of the input capacitor must be selected for the desired operating input voltage range of the regulator. To operate the

regulator at a higher input voltage, select a capacitor with a higher voltage rating.

(3)

Not Recommended (N/R). The voltage rating of this capacitor does not meet the minimum operating limit in most applications.

(4)

Not Recommended (N/R). The voltage rating of this capacitor does not meet the minimum operating limit in most applications.

(5)

Ceramic capacitors can be used to complement electrolytic types at the input bus by reducing high-frequency ripple current.

The transient response of the dc/dc converter has been characterized using a load transient with a di/dt of 1A/µs.

The typical voltage deviation for this load transient is given in the data-sheet specification table using the optional

value of output capacitance. As the di/dt of a transient is increased, the response of a converter's regulation

circuit ultimately depends on its output capacitor decoupling network. This is an inherent limitation with any dc/dc

converter once the speed of the transient exceeds its bandwidth capability. If the target application specifies a

higher di/dt or lower voltage deviation, the requirement can only be met with additional output capacitor

decoupling. In these cases, special attention must be paid to the type, value, and ESR of the capacitors selected.

If the transient performance requirements exceed those specified in the data sheet, the selection of output

capacitors becomes more important. Review the minimum ESR in the characteristic data sheet for details on the

capacitance maximum.

10

Submit Documentation Feedback

Copyright © 2005–2008, Texas Instruments Incorporated

Product Folder Link(s) :PTH08000W