6/10

Axelite Confidential Materials, do not copy or distribute without written consent.

Rev.1.4 Oct.17, 2019

AX3484



FUNCTION DESCRIPTIONS

The AX3484 is a synchronous rectified, current-mode, step-down regulator. It regulates

input voltages from 4.75V to 23V down to an output voltage as low as 0.925V, and supplies

up to 3A of load current.

The AX3484 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 Tran conductance error amplifier. The voltage at the COMP pin is compared to the

switch current measured internally to control the output voltage.

The converter uses internal N-Channel MOSFET switches 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 BS is needed to

drive the high side gate. The boost capacitor is charged from the internal 5V rail when SW is

low.



APPLICATION INFORMATION

COMPONENT SELECTION

Setting the Output Voltage

The output voltage is set using a resistive voltage divider from the output voltage to FB

pin. The voltage divider divides the output voltage down to the feedback voltage by the ratio:

VFB=VOUT ×

2

1

2

R

R

R



Where VFB is the feedback voltage and VOUT is the output voltage.

Thus the output voltage is:

VOUT=0.925 ×

2

2

1

R

R

R 

R2 can be as high as 100kΩ, but a typical value is 10kΩ. Using the typical value for R2, R1 is

determined by:

R1= 10.811 × (VOUT － 0.925) (kΩ)

For example, for a 3.3V output voltage, R2 is 10kΩ, and R1 is 25.7kΩ.