AOZ2264VQI

Rev. 3.0 July 2021

www.aosmd.com

Page 10 of 19

Detailed Description

The AOZ2264VQI is a high-efficiency, easy-to-use DC/

DC synchronous buck regulators capable of operation

from a 4V to 28V input bus. The device is capable of

supplying 16A of continuous output current with an

output voltage adjustment from 0V to 1.8V by controlling

VID0 and VID1 signals.

Constant on-time PWM with input feed-forward control

scheme results in ultra-fast transient response while

maintaining relatively constant switching frequency over

the entire input range. True AC current mode control

scheme guarantees the regulators can be stable with

ceramics output capacitor. Protection features include

VCC under-voltage lockout, cycle-by-cycle current limit,

output over voltage and under voltage protection, short-

circuit protection, and thermal shutdown.

The AOZ2264VQI is available in 23-pin 4mm×4mm QFN

package.

Enable and Soft Start

The AOZ2264VQI has internal soft start feature to limit

in-rush current and ensure the output voltage ramps up

smoothly to regulation voltage. A soft start process

begins when VCC rises to 4.5V and voltage on EN pin is

HIGH. The output voltage follows the internal voltage of

soft-start (VSS) when it is lower than initial output voltage.

When VSS is higher than initial output voltage, the

voltage of VOUT pin is regulated by internal precise

band-gap voltage. Moreover, the soft start period

between EN and PGOOD is 1.5ms. The soft start

sequence of AOZ2264VQI is shown in Figure 3.

Figure 3. Soft Start Sequence

Constant-On-Time PWM Control with Input Feed-

Forward

The control algorithm of AOZ2264VQI is constant-on-

time PWM Control with input feed-forward.

The simplified control schematic is shown in Figure 4.

The high-side switch on-time is determined solely by a

one-shot whose pulse width is inversely proportional to

input voltage (IN). The one-shot is triggered when the

internal setting output voltage is higher than the

combined information of output voltage and the AC

current information of inductor and load line signal, which

is processed and obtained through the sensed low-side

MOSFET current once it turns-on. The added AC current

information can help the stability of constant-on time

control even with pure ceramic output capacitors, which

have very low ESR. The AC current information has no

DC offset, which does not cause offset with output load

change, which is fundamentally different from other V2

constant-on time control schemes.

Figure 4. Simplified Control Schematic

True Current Mode Control

The constant-on-time control scheme is intrinsically

unstable if output capacitor’s ESR is not large enough as

an effective current-sense resistor. Ceramic capacitors

usually cannot be used as output capacitor.

The AOZ2264VQI senses the low-side MOSFET current

and processes it into DC current and AC current

information using AOS proprietary technique. The AC

current information is decoded and added on the VOUT

pin on phase. With AC current information, the stability of

constant-on-time control is significantly improved even

without the help of output capacitor’s ESR; and thus the

pure ceramic capacitor solution can be applicant. The

pure ceramic capacitor solution can significantly reduce

the output ripple (no ESR caused overshoot and

undershoot) and less board area design.

VOUT

VSS

VEN

PGOOD

TSS=1.5ms

(Internal)

VOUT Setting

VCC Level

Setting Output Voltage

Output Voltage /AC

Current Information

Comp

Programmable

One-Shot

IN

PWM

+

-

RGND Signal

VOUT

-