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Designing for Very Fast Load Transients

PTH03050Y

PTH05050Y

PTH12050Y

SLTS221A–MARCH 2004–REVISED OCTOBER 2005

APPLICATION INFORMATION (continued)

Table 1. Input/Output Capacitors (continued)

Capacitor Characteristics

Quantity

Capacitor Vendor,

Vendor

Working

Max ESR

Max Ripple

Physical

Value

Input

Output

Type/Series (Style)

Part Number

Voltage

at 100 kHz

Current at 85°CSize

(µF)

Bus

Bus

(V)

(Ω)

(Irms) (mA)

(mm)

Nichicon Aluminum

WG (SMD)

10

470

0.150

670

10×10

1

1

UWG1A471MNR1GS

HD (Radial)

10

470

0.072

760

8×11.5

1

1

UHD1A471MPR

PM (Radial)

10

470

0.120

600

10×12.5

1

1

UPM1A471MPH6

Sanyo

SP, Os-con (Radial)

10

470

0.015

4500

10×10.5

1

≤2

10SP470M

SVPA (SMD)

6.3

470

0.020

>4100

7,9×10

1

≤2

6SVPA470M

TPE, Poscap (SMD)

6.3

220

0.025

2400

7.3×4.3

1

≤3

6TPE220ML

AVX, Tantalum

10

330

0.045

1723

1

≤5

TPSE337M010R0045

7.3L ×5.7W

×4.1H

TPS (SMD)

10

330

0.060

1826

1

≤5

TPSV337M010R0060

Kemet, Poly-Tantalum

4.3W ×7.3L

T520 (SMD)

10

330

0.040

1800

1

≤5

T520X337M010ASE045

×4.0H

T530 (SMD)

10

330

0.010

>5000

1

≤1

T530X337M010ASE010

Vishay-Sprague

7.2L×6W

595D, Tantalum (SMD)

10

330

0.100

1040

1

≤5

595D377x0010D2T

×4.1H

594D, Tantalum (SMD)

10

330

0.045

2360

1

≤5

594D337X0016R2T

10x10.5

94SVP, Poly-Aluminum (Radial)

6.3

330

0.025

3500

1

≤3

94SA337X06R3FBP

Kemet, Ceramic X5R (SMD)

16

10

0.002

–

1210 /3225

1

≤5

C1210C106M4PAC

6.3

47

0.002

3225 mm

1

≤5

C1210C476K9PAC

Murata, Ceramic X5R (SMD)

6.3

100

0.002

–

3225 mm

1(4)

≤3

GRM32ER60J107M

6.3

47

0.002

3225 mm

1(4)

≤5

GRM32ER60J476M

16

22

0.002

1(4)

≤5

GRM32ER61C226K

16

10

0.002

1(4)

≤5

GRM32DR61C106K

TDK, Ceramic X5R (SMD)

6.3

100

0.002

–

3225 mm

1(4)

≤3

C3225X5R0J107MT

6.3

47

0.002

3225 mm

1(4)

≤5

C3225X5R0J476MT

16

22

0.002

1(4)

≤5

C3225X5R1C226MT

16

10

0.002

1(4)

≤5

C3225X5R1C106MT

(4) A ceramic capacitor can be used to compliment electrolytic types at the input to further reduce 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 that specified in the data sheet, or the total amount of load

capacitance is above 3300 µF, the selection of output capacitors becomes more important.

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