ACT88321 datasheet(39/55 Pages) QORVO

39 / 55 page

ACT88321

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

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

39 of 55

www.qorvo.com

LDO CONVERTERS

General Description

The ACT88321 contains two fully integrated low dropout

linear regulators (LDO). LDO1 and LDO2 are 390mA

outputs. The LDOs require only two small external com-

ponents (Cin, Cout) for operation. They ship with default

output voltages that can be modified via the I2C inter-

face for systems that require advanced power manage-

ment functions. LDO1 can also be configured for load

switch mode.

LDO1 has a dedicated input pin, VIN_LDO, so it can

operate from different input voltage than the Buck con-

verters and from LDO2. LDO2 input voltage comes from

the AVIN pin.

Enable / Disable Control

When power is applied to the IC, all LDOs automatically

turn on according to a pre-programmed sequence.

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

verter can be independently disabled via I2C or GPIO.

Each CMI version requires a different set of commands

to disable a converter, so contact the factory for specific

instructions if needed. Each converter contains an op-

tional integrated discharge resistor that actively dis-

charges the output capacitor when the regulator is dis-

abled. Each LDO’s discharge function is enabled via its

I2C bit DIS_PULLDOWN_Lx.

Soft-Start

Each LDO contains a softstart circuit that limits the rate

of change of the output voltage, minimizing input inrush

current and ensuring that the outputs power up in a

monotonically. This circuitry is effective any time the

LDO is enabled, as well as after responding to a short

circuit or other fault condition. Each LDO’s softstart time

is adjustable to either 200µs or 360µs via its I2C bits

SST_LDOx.

Output Voltage Setting

LDO1/2 regulate to the voltage defined by I2C registers

LDOx_VSET. Unlike the buck converters, the LDOs

only have one VSET register.

The LDO output voltage programming range is 0.6V to

3.75V in 50mV steps.

VLDOx = 0.6V + LDOx_VSET * 0.05V

Where LDOx_VSET is the decimal equivalent of the

value in the register. LDOx_VSET contains an unsigned

6-bit

binary

value.

example,

LDO1’s

LDO1_VSET register contains 011000b (24 decimal),

the output voltage is 1.8V.

Qorvo recommends that an LDO’s output voltage be

kept within +/- 25% of the default output voltage to main-

tain accuracy. Voltage changes larger than +/- 25% may

require different factory trim settings (new CMI) to main-

tain accuracy.

Overcurrent and Short Circuit Protection

Each LDO provides overcurrent and short circuit pro-

tection. The overcurrent threshold is set by their I2C

bits. The LDO1 current limit is set to 0.4A or 0.5A by

the ILIM_SCL_LDO1 I2C bit. The LDO2 current limit is

set to 0.4A or 0.5A by the ILIM_SCL_LDO2 I2C bit.

Note that the LDO2 bits are only configurable by the

factory.

In both an overload and a short circuit condition, the

LDO limits the output current which causes the output

voltage to drop. This can result in an undervoltage fault

in addition to the current limit fault. When the current

limiting results in a drop-in output voltage that triggers

an undervoltage condition, the IC shuts down all power

supplies, asserts nIRQ low, and enters the UVLOFLT

state. The IC restarts in 100ms and starts up with de-

fault sequencing. Overcurrent and short circuit condi-

tions can be masked via the I2C bit LDOx_ILIM_FLT-

MSK. Note that ILIM_FLTMSK, ILIM_WARN_FLT-

MSK, OV_FLTMSK and UV_FLTMSK default to 1

(masked) at power up. The user can un-mask faults by

setting these bits to 0 via I2C.

Input Capacitor Selection

Each LDO requires a high quality, low-ESR, ceramic

input capacitor. A 1uF is typically suitable, but this value

can be increased without limit. The input capacitor

should be a X5R, X7R, or similar dielectric.

Output Capacitor Selection

Each LDO requires a high quality, low-ESR, ceramic

output capacitor. When LDOx_ILIM is set to 0.4A, a 1µF

capacitor is typically suitable. The minimum allowable

capacitance value is 0.7µF. When LDOx_ILIM is set to

0.5A, 2.2µF capacitor is typically suitable, with a mini-

mum allowable capacitance value of 1.5µF. In both

cases, the maximum allowable output capacitance is

100µF. The output capacitor should be a X5R, X7R, or

similar dielectric.

LDO1 Load Switch Mode

LDO1 has the option to be used as a load switch. This

option is only accessible via factory I2C bits and requires

a custom CMI. When in load switch mode, LDO1 still

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