MIC23153 datasheet(17/26 Pages) MICROCHIP

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2021-2022 Microchip Technology Inc. and its subsidiaries

DS20006489B-page 17

MIC23153

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.

5.7

HyperLight Load® Mode

The MIC23153 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, MIC23153 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

MIC23153 during light load currents. As the load

current increases, the MIC23153 goes into continuous

conduction mode (CCM) at a constant frequency of

4 MHz. The equation to calculate the load when the

MIC23153 goes into continuous conduction mode may

be approximated by the following Equation 5-6:

EQUATION 5-6:

As shown in the above equation, the load at which

MIC23153 transitions from HyperLight Load® mode to

PWM mode is a function of the input voltage (VIN),

output voltage (VOUT), duty cycle (D), inductance (L)

and frequency (f). As shown in Figure 5-3, as the

output current increases, the switching frequency also

increases until the MIC23153 goes from HyperLight

Load® mode to PWM mode at approximately 120 mA.

The MIC23153 will switch at a relatively constant

frequency around 4 MHz once the output current is

over 120 mA.

FIGURE 5-3:

Switching Frequency vs.

Output Current.

ILOAD

VIN VOUT

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2 L

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