NXP Semiconductors PCA9421BSZ

Overview

PCA9421BSZ from NXP Semiconductors is a highly integrated Power Management IC (PMIC) designed for low-power microcontroller systems, featuring two I²C-programmable buck converters (SW1: 0.5–1.5 V/1.8 V fixed, 250 mA; SW2: 1.5–2.1 V or 2.7–3.3 V, 500 mA), two programmable LDOs (LDO1: always-on 1.7–1.9 V, 1 mA; LDO2: 1.5–2.1 V or 2.7–3.3 V, 250 mA), and an Fm+ I²C interface up to 1 MHz - deployed in battery-powered IoT edge nodes and i.MXRT-based embedded controllers.

For engineers reviewing the PCA9421BSZ datasheet, PCA9421BSZ pinout, PCA9421BSZ application, or PCA9421BSZ equivalent, this page delivers verified regulator output ranges, validated HVQFN24 pin functions, confirmed thermal warning thresholds (75–90 °C), exact mode-selection logic (MODESEL0/MODESEL1), and real-world power-up sequencing behavior per NXP Rev. 1.0 (16 Oct 2023).

Technical Context

The PCA9421BSZ implements dual independent buck regulators with integrated high-side/low-side MOSFETs and PFM control for light-load efficiency, plus two LDOs with separate input domains: LDO1 powered by the higher of ASYS or VBAT_BKUP (enabling always-on RTC backup), and LDO2 sourced solely from ASYS. All four rails support on-the-fly voltage reconfiguration across four I²C-configurable mode settings.

Its power control architecture includes VIN_UVLO, VIN_OVP (5.5 V or 6 V), ASYS pre-warning interrupt, thermal regulation (95–125 °C, 5 °C steps), watchdog timer (16/32/64 s), and active discharge control per rail - coordinated via a state machine that enforces strict power-up priority (enable-before-disable) and supports long-press ON-pin reset (4/8/12/16 s).

Key Specifications

Pinout & Package

HVQFN24 package: 3 mm × 3 mm, 24-terminal thermally enhanced quad flat no-lead package with exposed thermal pad connected to system ground. Pin numbering follows JEDEC standard top-view orientation with index area at pin A1.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar PMIC applications.

Compared with TPS650361RGER and MAX20029ATPA/VY+, the PCA9421BSZ uniquely integrates four independently programmable rails, four-mode I²C-controlled power states, VBAT_BKUP-aware LDO1, and thermal/interrupt reporting - making it optimal for adaptive, battery-constrained microcontroller platforms requiring runtime power agility.

Availability

PCA9421BSZ is available at Aetrix Electronics and suitable for wearable health monitors, smart sensor nodes, i.MXRT-based edge gateways, and low-power industrial controllers requiring stable component supply across extended production lifecycles.

Supply support for PCA9421BSZ includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

NXP Semiconductors is a global semiconductor leader focused on secure connectivity solutions for automotive, industrial, and IoT markets, with deep expertise in power management and microcontroller ecosystems.

The PCA9421BSZ belongs to NXP's dedicated low-power PMIC product line, engineered specifically to simplify power architecture design for energy-constrained microcontroller applications including i.MXRT, RT5xx, and RT6xx families.

FAQ

What is the maximum input voltage rating for the VIN pin on the PCA9421BSZ?

The VIN pin of the PCA9421BSZ is rated for up to 20 V, with built-in overvoltage protection (OVP) configurable via I²C to either 5.5 V or 6 V. This tolerance allows direct connection to unregulated 12 V or 19 V adapter inputs while maintaining safe operation under transient conditions - critical for robust industrial and automotive accessory designs using the PCA9421BSZ.

Does the PCA9421BSZ support backup battery operation for real-time clock (RTC) functionality?

Yes, the PCA9421BSZ supports RTC backup via its VBAT_BKUP pin, which powers the always-on LDO1 (1.7–1.9 V). When main supply ASYS drops, LDO1 automatically switches to the higher of ASYS or VBAT_BKUP - enabling continuous RTC operation from a coin cell. This behavior is intrinsic to the PCA9421BSZ's power architecture and requires no external circuitry beyond connecting the battery to VBAT_BKUP.

How does the PCA9421BSZ handle power-up sequencing across its four voltage rails?

The PCA9421BSZ enforces strict power-up priority: rails transitioning from disabled to enabled must reach 90 % of target voltage before any rail transitions from enabled to disabled. This sequencing is hardwired into the PCA9421BSZ's state machine and applies during initial boot, mode switching, and on-the-fly voltage changes - ensuring reliable initialization of complex microcontrollers like the i.MXRT series without external supervision.

Can the PCA9421BSZ's output voltages be changed dynamically during system operation?

Yes, the PCA9421BSZ supports on-the-fly voltage reconfiguration for all four rails via its I²C interface - including SW1, SW2, LDO1, and LDO2 - without interrupting system operation. Voltage transitions occur smoothly with active discharge control, and SYSRSTn remains deasserted during the change, as confirmed in Section 8.9 of the PCA9421BSZ datasheet Rev. 1.0.

What thermal protection features are implemented in the PCA9421BSZ?

The PCA9421BSZ includes two independent thermal features: a programmable thermal warning (75–90 °C, 2-bit) that asserts INTB, and a programmable thermal shutdown (95–125 °C, 3-bit) that forces regulator shutdown. Both thresholds are set via I²C registers and operate independently of ambient temperature - providing precise, field-configurable thermal management for the PCA9421BSZ in enclosed or high-density PCB layouts.