MIC33050 datasheet(13/22 Pages) MICROCHIP

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DS20006120B-page 13

MIC33050

EQUATION 5-3:

Efficiency loss due to DCR is minimal at light loads and

gains significance as the load is increased. Inductor

selection becomes a trade-off between efficiency and

size in this case.

5.5

HyperLight Load® Mode

The MIC33050 uses a minimum on and off time

proprietary control loop. When the output voltage falls

below the regulation threshold, the error comparator

begins a switching cycle that turns the PMOS on and

keeps it on for the duration of the minimum on-time.

When the output voltage is over the regulation

threshold, the error comparator turns the PMOS off for

a minimum off-time. The NMOS acts as an ideal

rectifier that conducts when the PMOS is off. Using a

NMOS switch instead of a diode allows for lower

voltage drop across the switching device when it is on.

The asynchronous switching combination between the

PMOS and the NMOS allows the control loop to work

in discontinuous mode for light load operations. In

discontinuous mode, MIC33050 works in pulse

frequency modulation (PFM) to regulate the output. As

the output current increases, the switching frequency

increases. This improves the efficiency of the

MIC33050 during light load currents. As the load

current increases, the MIC33050 goes into continuous

conduction mode (CCM) at a constant frequency of

4 MHz. The equation to calculate the load when the

MIC33050 goes into continuous conduction mode may

be approximated by the following Equation 5-4:

EQUATION 5-4:

EfficiencyLoss

VOUT IOUT



VOUT IOUT PD L



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









–

100



ILOAD

VIN VOUT

–







2L f



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









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