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

Rev.2.1 Oct.04, 2019

AX3050/A



FUNCTION DESCRIPTIONS

CV/CC Loop Regulation

As seen in Functional Block Diagram, the AX3050/A is a peak current mode pulse

width modulation (PWM) converter with CC and CV control. The converter operates as

follows:

A switching cycle starts when the rising edge of the Oscillator clock output causes

the High-Side Power Switch to turn on. With the LX side of the inductor now connected to

Sense1, the inductor current ramps up to store energy in the magnetic field. The inductor

current level is measured by the Current Sense Amplifier and added to the Oscillator ramp

signal. If the resulting summation is higher than the COMP voltage, the output of the PWM

Comparator goes high. When this happens or when Oscillator clock output goes low, the

High-Side Power Switch turns off.

At this point, the LX side of the inductor swings to a diode voltage below ground,

causing the inductor current to decrease and magnetic energy to be transferred to output.

This state continues until the cycle starts again. The High-Side Power Switch is driven by

logic using BS as the positive rail. This pin is charged to VLX + 5V when the Low-Side

Power Switch turns on. The COMP voltage is the integration of the error between FB input

and the internal 1V reference. If FB is lower than the reference voltage, COMP tends to go

higher to increase current to the output. Output current will increase until it reaches the CC

limit set by the R1 resistor. At this point, the device will transition from regulating output

voltage to regulating output current, and the output voltage will drop with increasing load.

Current Limit Protection

The Current limit is set by outside resistance (RSENSE), When the SENSE1-SENSE2

voltage larger than 100mV, the current limit is happened that driver can be turned off. The

current limit set according to the following equation:

SENSE

R

mV

100

=

(A)

Limit

Current