PCA9420BS datasheet(17/85 Pages) NXP

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NXP Semiconductors

PCA9420

Power management IC for low-power microcontroller applications

On-the-fly output voltage change is defined as the following: for any output rail, its output voltage changes from

one level (initial level) to another level (target level). Note this assumes the output rail is always enabled before

and after the on-the-fly change transition. It does not include the case when any output rail is changed from

disabled state to enabled state, or vice versa.

If a user prefers to change any rail voltage on-the-fly, depending on the scenarios listed below, the chip behavior

is described as follows:

1. While the chip remains in its current operation mode, and the user programs the output voltage setting I2C

command

2. While the user chooses to switch modes, i.e. change mode between any of the two mode settings among

Mode 0/1/2/3, and if this involves on-the-fly voltage change for one or some output rails, such change

should occur simultaneously when the chip switches from initial mode to the target mode.

CAUTION: The user should not send an I2C command related to changing the setting of the output rails during

the power up/down or mode setting change process.

8.12.4 BUCK1 (SW1, core buck regulator)

The SW1 supplies the core power.

Its output voltage can be programmed via I2C from 0.5 V to 1.5 V at 25 mV step and a fixed 1.8 V, which is

capable of providing up to 250 mA loading. The application circuit uses typical 2.2 µH inductor and 10 µF/6.3 V

output capacitor.

8.12.5 BUCK2 (SW2, system buck regulator)

The SW2 output voltage can be programmed via I2C register from 1.5 V to 2.1 V, or from 2.7 V to 3.3 V in both

at 25 mV/step and is capable of providing up to 500 mA loading. The application circuit uses a 2.2 µH inductor

and 10 µF output capacitor.

In SW2, a pass-through mode is implemented. When its input (ASYS) is close to the output voltage (within

typical 200 mV), the SW2 enters the pass-through mode operation; the high-side switch is fully turned on and

the low-side switch is turned off, and the output voltage can be calculated as input voltage – (RDSON*ILOAD),

where RDSON is the on-resistance of the high-side switch, and the ILOAD refers to the load current. When the

input voltage rises again, so that the voltage different between input and output crosses the typical 250 mV

threshold, the SW2 exits the pass-through mode and re- enters the normal switching mode operation.

While SW2 operates in pass-through mode, protection features such as over-current protection are also

implemented as well.

aaa-033081

VSW2_Regulation

VPSYS2

(VPSYS2 - VSW2_Regulation)=200mV

50mV

SW2 in regulation mode

SW2 in pass-through mode

SW2 in regulation mode

Delta V=RRDS_ON_High_side x ILOAD

Delta V

Figure 8. Pass-Through mode of BUCK2 (SW2)

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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