ACT88321 datasheet(35/55 Pages) QORVO

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ACT88321

Advanced PMIC with 3 Bucks, 2 LDOs, and Load Bypass Switches

Datasheet Rev. D , June 17, 2022 | Subject to change without notice

35 of 55

www.qorvo.com

Operating Mode – Buck2 and Buck3

By default, Buck2 and Buck3 operate in adaptive con-

stant on time (ACOT) mode at medium to heavy loads.

At light loads, the converters automatically transition to

DCM operation to save power. Buck2 and Buck3 can be

forced into continuous conduction mode, CCM, at light

loads by setting their FCCM bit to 1. When FCCM = 1,

it overrides all other low power settings and forces CCM

mode.

BUCK23 LPM

To further optimize efficiency and reduce power losses

at extremely light loads, an additional lower power mode,

LPM, is available. LPM minimizes quiescent current in

between switching cycles. This LPM mode reduces in-

put current to approximately 40µA at no load. LPM al-

lows the customer to test the IC in their use case and

optimize the balance between power consumption, volt-

age ripple, and transient response in their system.

Buck2 and Buck3’s LPM mode can be controlled inde-

pendently. Setting SAVE_IQQ = 1 enables LPM while

setting SAVE_IQQ = 0 disables LPM.

BUCK23 ULPM

Buck2 and Buck3 have factory level bit (EN_LPM) to al-

low operate in ultra-low power mode, ULPM, that pro-

vides significant efficiency improvements at very light

loads. ULPM mode reduces the buck converters quies-

cent current from 40µA to 12µA. ULPM mode helps sys-

tems like SSDs achieve very low power loss at ex-

tremely light loads, which is a requirement in their

standby modes. ULPM mode regulates the output volt-

age between 101.5% to 104% of the setpoint. When the

output voltage increases to 103%, the buck converter

shuts down to save quiescent current until the output

voltage drops to 101.5%. It then turns back on and in-

creases the output voltage to 104% again. ULPM mode

should only be used when the load current is less than

5mA. With higher load currents, the efficiency is lower

than LPM or normal mode operation.

Synchronous Rectification

Buck1/2/3 each feature integrated synchronous rectifi-

ers (or LS FETs) to maximize efficiency and minimize

the total solution size and cost by eliminating the need

for external rectifiers.

Enable / Disable Control

When power is applied to the IC, all converters automat-

ically turn on according to a pre-programmed sequence.

Once in normal operation (ACTIVE state), each con-

verter can be independently disabled via I2C. Each CMI

version requires a different set of command to disable a

converter, so contact the factory for specific instructions

if needed. Each converter contains an optional inte-

grated discharge resistor that actively discharges the

output capacitor when the regulator is disabled. The dis-

charge function is enabled via the I2C bit Dis_Pulldown.

Soft-Start

Each buck regulator contains a softstart circuit that lim-

its the rate of change of the output voltage, minimizing

input inrush current and ensuring that the outputs power

up monotonically. This circuitry is effective any time the

regulator is enabled, as well as after responding to a

short circuit or other fault condition. The Buck1 softstart

time is adjustable to either 250µs or 500µs via its I2C

SST register. The Buck2/3 softstart time is adjustable to

50µs, 100µs, 250µs, or 500µs via its I2C SST bits.

Output Voltage Setting

Buck1/2/3 regulate to the voltage defined by I2C register

VSET0 in normal operation and by VSET1 in DVS mode.

For Buck1, the output voltage programming range is

0.6V to 3.775V in 25mV steps.

VBUCK1 = 0.6V + VSETx * 0.025V

Where VSETx is the decimal equivalent of the value in

I2C VSETx register. The VSETx registers contain an un-

signed 7-bit binary value.

For Buck2, the output voltage programming range is

0.5V to 1.77V in 10mV steps.

VBUCK2 = 0.5V + VSETx * 0.01V

For Buck3, the output voltage programming range is

0.5V to 3.6V in 100mV steps.

VBUCK3 = 0.5V + VSETx * 0.1V

Qorvo recommends that a buck converter’s output volt-

age be kept within +/- 25% of the default output voltage

to maintain accuracy. Voltage changes larger than +/-

25% may require different factory trim settings (new

CMI) to maintain accuracy.

100% Duty Cycle Operation

Buck1 supports 100% duty cycle operation. This allows

operating conditions where the output voltage is very

close to the input voltage. During 100% duty cycle op-

eration, the P-ch high-side power MOSFET is turned on

continuously, providing a direct connection from the in-

put to the output (through the inductor), ensuring the

lowest possible dropout voltage in battery powered ap-

plications.

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