AX3702



APPLICATION CIRCUIT

VIN

EN

GND

SW

FB

C1

4.7uF

R1

60kΩ

R2

30kΩ

C3

330pF

(Option)

C2

22uF

VOUT=1.8V

L1

2.2uH

VIN



FUNCTION DESCRIPTIONS

Theory of Operation

AX3702 is a constant on-time control synchronous step-down converter that offers

excellent transient response over a wide range of input voltage. It achieves superior light-load

efficiency with extremely low quiescent current.

Constant On-time Control

Constant on-time control step-down converters turn on HS immediately when FB

droops below reference. The HS is turned on for a pre-determined period (on-time) of time to

ramp up the inductor current, and then the LS will be turned on to ramp down the inductor

current. The cycle repeats itself if FB droops below reference again. AX3702 uses proprietary

technique to take into account the load current impact and adjusts the on-time accordingly to

achieve a constant switching frequency over entire load current range.

For AX3702, the on-time is approximately:

Due to its immediate response on FB voltage droop and simplified loop compensation, constant

on-time offers a superior transient response compare to traditional fixed frequency PWM

control step-down converters.

Light Load Operation

In light load condition where the converter operates in discontinuous mode, AX3702

cuts down its quiescent current to as low as 15uA and achieves excellent light load efficiency.

Enable

When input voltage is above the under voltage lock-out threshold, AX3702 can be

enabled by pulling the EN pin to above 1V. AX3702 is disabled if the EN pin is pulled below 0.4

V.

6/22

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

Rev1.4 Sep.30, 2021