MP9472–0.45A, 18V, NON-SYNCHRONOUS, RECTIFIED, STEP-DOWN CONVERTER

MP9472 Rev. 1.0

www.MonolithicPower.com

10

12/9/2015

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OPERATION

The MP9472 is a non-synchronous, current-

mode, step-down regulator. It regulates input

voltages from 4.75V to 18V down to output

voltages as low as 0.923V and supplies up to

0.45A of load current.

The MP9472 uses current-mode control to

regulate the output voltage. The output voltage

is measured at FB through a resistive voltage

divider and amplified through the internal trans-

conductance error amplifier.

The voltage at COMP is compared to the switch

current and is measured internally to control the

output voltage. The MP9472 stops switching

once the COMP voltage drops to about 920mV

in light-load condition.

The converter uses an internal N-channel

MOSFET switch to step down the input voltage

to the regulated output voltage. Since the high-

side MOSFET requires a gate voltage greater

than the input voltage, a boost capacitor

connected between SW and BST is needed to

drive the high-side gate. The boost capacitor is

charged from the internal 5V rail when SW is low.

To maintain normal regulation, a certain amount

of loading current is always required to pull SW

to 0V at every cycle so the boost capacitor can

be charged by an internal 5V rail.

When FB exceeds 20% of the nominal

regulation voltage (0.923V), the over-voltage

comparator is tripped, and COMP and SS are

discharged to GND, forcing the high-side switch

off.

Figure 1: Functional Block Diagram