PCA9421 datasheet(10/66 Pages) NXP

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NXP Semiconductors

PCA9421

Power management IC for low-power microcontroller applications

8.2 VIN

The VIN pin serves as the input power for ASYS and has the following functions implemented:

• An I2C undervoltage lockout protection threshold (VIN_UVLO_SEL)

• An I2C programmable input current limiting threshold (falling, VIN_ILIM_SEL [2:0] ) which can be disabled.

When the VIN_ILIM threshold is reached, the VIN current clamps at that VIN_ILIM_SEL level. This current

limiting only applies to VIN

• 20 V tolerance on VIN pin

• An I2C programmable overvoltage protection threshold (rising, VIN_OVP_SEL)

8.3 VIN_AUX

VIN_AUX is an auxiliary input power which, depending on ASYS_INPUT_SEL [1:0] register configuration, could

be the power source for VSYS. By default VSYS is powered from VIN or VIN_AUX (whichever is greater). In

the case of a current limit from VIN as the main power source, when VSYS < VIN_AUX, a current path from

VIN_AUX to VSYS is enabled (supplemental mode feature) to provide the needed current as VIN current is

limited. There is no internal current limit from VIN_AUX to VSYS.

8.4 ASYS

The ASYS pin serves as the input power pin for PSYS1, PSYS2 and LDO2. Internally by default it’s powered

by either VIN or VIN_AUX, whichever is greater. The internal ASYS input selection circuit ensures a seamless

transition when its input source changes from VIN to VIN_AUX, or vice versa.

Through I2C register setting selection (ASYS_INPUT_SEL [1:0]), the user also has the option to choose the

ASYS input source. However, upon power cycling and/or chip reset, the ASYS input source goes back to the

default setting (option 1 below).

SYS_INPUT_SEL [1:0]

1. 2b’00: From either VIN_AUX or VIN, whichever is greater (default setting);

2. 2b’01: From VIN_AUX only;

3. 2b’10: From VIN only;

4. 2b’11: Disconnect from VIN_AUX or VIN (not a normal operation condition, for INTERNAL test purposes

only).

An I2C programmable pre-warning ASYS voltage threshold (ASYS_PRE_WARNING [1:0]) can also be used to

indicate when ASYS voltage drops below the ASYS pre-warning threshold voltage, which triggers an interrupt

event.

If any peripheral regulators are connected to ASYS node, the ASYS node follows a VIN voltage up to a

programmed OVP threshold (either 5.5 V or 6 V) with a various voltage difference depending on a load current.

8.5 VBAT_BKUP (back-up battery input)

Internally, the input power source for LDO1 is provided by either VBAT_BKUP or ASYS, whichever is greater.

When a coin cell battery (or similar battery) is used in the system as a backup battery, it can be connected to

VBAT_BKUP; thus the LDO1 is powered by either ASYS or the backup battery. When no such backup battery is

used, the VBAT_BKUP pin should always be connected to VIN_AUX.

8.6 ON

The ON pin has the following functions implemented:

PCA9421

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

Product data sheet

Rev. 1.0 — 16 October 2023

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