PCA9420BS datasheet(18/85 Pages) NXP

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NXP Semiconductors

PCA9420

Power management IC for low-power microcontroller applications

8.12.6 LDO1 (always-on LDO)

The LDO1 (Always-on LDO) output can be programmed from 1.7 V to 1.9 V at 25 mV step, depending on the

system requirements (selectable through I2C register). Typically, a 1 µF/6.3 V MLCC output capacitor providing

at least 1 mA loading capability is needed.

LDO1 operates based on the principle of hysteretic on/off regulation. The LDO1 output voltage is generated

from a frequent activation/deactivation of the output stage connecting VBAT to the LDO1 output depending

on the programmed output voltage for LDO1. The ripple frequency and amplitude are dependent on the load

current and external capacitance. The greater the load current, the higher the on/off activation of this output

stage to ensure LDO1 stays within the defined output voltage accuracy specified in the electrical specification

section. LDO1 is powered by the greater of ASYS or VBAT_BKUP.

SW_RST event does not shut down LDO1, but sets LDO1 to default value. Watchdog Reset does not shut

down LDO1, but changes LDO1 to Mode 0 setting. SHIP mode/ Hardware Reset (ON Long Press) shuts down

LDO1 and recycles power up to default output voltage.

8.12.7 LDO2 (system LDO)

The LDO2 (system LDO) output can be programmed via the I2C register from 1.5 V to 2.1 V, or 2.7 V to 3.3 V

at 25 mV/step. Typically, a 2.2 µF/6.3 V MLCC output capacitor providing at least 250 mA loading current is

needed.

8.13 Linear battery charger

The battery charger is a linear charger. Its charging is done through a linear switch with the following output

protections:

• If VIN is not present and ASYS is supplied by VBAT, there is no current limiting on that power path

• Reverse current protection

– (triggers when ASYS < VBAT+ VINBAT_HEADROOM*)

• JEITA compliant charging current limiting

– (a function of programmed threshold and battery temperature)

• VBAT short circuit protection

– Short circuit output voltage threshold: (typ 0.8 V with 80 mV hysteresis)

– Maximum output sourcing current during “short circuit” detection ~ 13 mA (VIN2BAT_HEADROOM =

100 mV, typical)

If the battery voltage is below the VBAT_LOW threshold, the battery is considered discharged and a

preconditioning cycle begins. The amount of pre-charge current (ICHG_LOW) can be programmed through

I2C register setting. This feature is useful when there is a load connected directly across the battery (at VBAT

pin) “stealing” the battery current. The pre-charge current can be set higher to account for the system loading

while allowing the battery to be properly conditioned. Once the battery voltage has charged to the VBAT_LOW

threshold, fast charge is initiated and a programmed fast charge current (ICHG_CC) is applied. The fast charge

constant current is programmed using I2C register. The constant current provides the bulk of the charge. Power

dissipation in the device is greatest in fast charge with a lower battery voltage.

If the device reaches a programmed thermal regulation threshold temperature (defined by the configuration on

the THM_REG bit fields on the CHG_CNTL7 register) from 85 °C to 115 °C in 5 °C steps, the device enters

thermal regulation. This is indicated by the TREG_STATUS bit field on the CHG_STATUS_1 register. Thermal

regulation increases the safe-charging-timer period by 2x and reduces the charge current in half (if the initial

current is 5 mA, it remains unchanged) to keep the temperature from rising any further when battery charger

works in constant current charging mode, or at a reduced regulated voltage when battery charger works in

constant voltage charging mode.

PCA9420

All information provided in this document is subject to legal disclaimers.

Product data sheet

Rev. 4.2 — 26 July 2023

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