LMZ22010

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SNVS687H – MARCH 2011 – REVISED AUGUST 2015

Feature Description (continued)

Figure 48. Prebiased Start-Up

7.4 Device Functional Modes

7.4.1 Discontinuous Conduction and Continuous Conduction Modes

At light load the regulator will operate in discontinuous conduction mode (DCM). With load currents above the

critical conduction point, it will operate in continuous conduction mode (CCM). When operating in DCM, inductor

current is maintained to an average value equaling IOUT. In DCM the low-side switch will turn off when the

inductor current falls to zero, this causes the inductor current to resonate. Although it is in DCM, the current is

allowed to go slightly negative to charge the bootstrap capacitor.

In CCM, current flows through the inductor through the entire switching cycle and never falls to zero during the

off-time.

Figure 49 is a comparison pair of waveforms showing both the CCM (upper) and DCM operating modes.

VIN = 12 V, VO = 3.3 V, IO = 3 A / 0.3 A

Figure 49. CCM and DCM Operating Modes

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