Datasheet

LM5119/LM5119Q

www.ti.com

SNVS676F –AUGUST 2010–REVISED FEBRUARY 2013

INTERLEAVED OPERATION

Interleaved operation can offer many advantages in single output, high current applications. The output power

path is split between two identical channels reducing the current in each channel by one-half. Ripple current

reduction in the output capacitors is reduced significantly since each channel operates 180 degrees out of phase

from the other. Ripple reduction is greatest at 50% duty cycle and decreases as the duty cycle varies away from

50%.

Refer to Figure 13 to estimate the ripple current reduction. Also, the effective ripple in the input and output

capacitors occurs at twice the frequency of a single channel design due to the combining of the two channels. All

of these factors are advantageous in managing the higher currents and their effects in a high power design.

Figure 13. Cancellation Factor vs. Duty Cycle for Output Capacitor

To begin an interleaved design, use the previous equations in this datasheet to first calculate the required value

of components using one-half the current in the output power path. The Attenuation Factor in Figure 13 is the

ratio of the output capacitor ripple to the inductor ripple vs. duty cycle. The inductor ripple used in this calculation

is the ripple in either inductor in a two phase design, not the ripple calculated for a single phase design of the

same output power. It can be observed that operation around 50% duty cycle results in almost complete ripple

attenuation in the output capacitor. Figure 13 can be used to calculate the amount of ripple attenuation in the

output capacitors.

Figure 14. Normalized Input Capacitor RMS Ripple Current vs. Duty Cycle

Figure 14 illustrates the ripple current reduction in the input capacitors due to interleaving. As with the output

capacitors, there is near perfect ripple reduction near 50% duty cycle. This plot can be used to calculate the

ripple in the input capacitors at any duty cycle. In designs with large duty cycle swings, use the worst case ripple

reduction for the design.

Product Folder Links: LM5119/LM5119Q