R34DS0034EU0101 Rev.1.01

Page 24

Mar 13, 2024

ISL73006SLH Datasheet

Use Equation 12 to approximate the amplitudes of the voltage spikes caused by capacitor ESR and ESL, where

ITRAN = Output load current transient.:

In a typical converter design, the ESR of the output capacitor bank impacts the transient response. The ESR and

the ESL determine the number and types of output capacitors required to minimize the initial voltage spike at the

output transient response. It may be necessary to place multiple output capacitors of both ceramic (to provide low

ESR, ESL) and Tantalum (to provide the bulk capacitance in a small footprint) types in parallel to reduce the

parasitic ESR and ESL to achieve minimize the magnitude of the output voltage spike during a load transient

response.

The ESL of the capacitor is an important parameter and not usually listed in datasheets. You can use Equation 13

to approximate ESL if an Impedance vs Frequency curve is available, where fres is the frequency where the lowest

impedance is achieved (resonant frequency). The ESL of the capacitor becomes a concern when designing

circuits that supply power to loads with high rates of change in the current.

If ΔVDIP and/or ΔVPEAK is too large for the output voltage limits, you may need to increase the capacitance. A

trade-off between output inductance and output capacitance may be necessary in this situation.

5.16

Output Inductor Selection

The inductor value determines the ripple current of the converter. Choosing an inductor current requires a

somewhat arbitrary choice of ripple current, ∆I. A reasonable starting point is ~33% of the total load current. The

output inductor influences the response time of the regulator to a load transient. A smaller inductance value

improves transient response but increases output voltage ripple. The inductor value determines the inductor ripple

current, with the output voltage ripple being a function of the ripple current. Use Equation 14 to approximate the

Figure 41. Typical Transient Response

(EQ. 12)

(EQ. 13)

VOUT

IOUT

ΔVESL

ΔVESR

ΔVDIP

ΔVPEAK

ITRAN

V

ESR

ESR ITRAN



=

VESL ESL

dITRAN

dt

---------------------



=

ESL

1

C2

 f

res







2

------------------------------------------

=