PCA9421 - PMIC 2 Buck + 2 LDO I2C, Li-ion | NXP
MPN: PCA9421 β Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $1.95 | $1.95 |
| 10 | $1.76 | $17.60 |
| 100 | $1.46 | $146.00 |
| 500 | $1.25 | $625.00 |
| 1,000 | $1.05 | $1,050.00 |
PCA9421 Overview
A PMIC (Power Management IC) is a specialized voltage regulator and power management device that integrates multiple power conversion stages - typically buck converters, LDOs, load switches, and supervision functions - into a single semiconductor. In the power management hierarchy, a PMIC sits above individual DC-DC converters and linear regulators, replacing several discrete power management ICs with one programmable solution, reducing board area, bill-of-materials count, and overall system cost.
Key features of the PCA9421 include its dual buck converter architecture with I2C-programmable output voltages, two integrated LDO regulators for low-noise analog or digital rails, and operation from a 5V adapter or regulated supply as indicated by distributor listings. This level of integration makes the part a full power management solution rather than a single-rail regulator, which is its principal differentiator against discrete buck-plus-LDO combinations.
Technically, the PCA9421 belongs to the NXP PCA9420/PCA9421 PMIC family, which NXP targets specifically at low-power microcontroller applications and similar systems powered by Li-ion battery and/or a 5V adapter in non-portable applications. The I2C interface allows a host microcontroller to adjust buck output voltages dynamically, supporting dynamic voltage scaling and power-mode sequencing in embedded designs. The two package options - HVQFN24 (BS suffix) and WLCSP25 (UK suffix) - give designers a choice between a hand-inspectable QFN footprint and an ultra-compact wafer-level chip-scale package for space-constrained boards.
Typical applications include low-power microcontroller power supplies, battery-powered IoT sensor nodes, portable and non-portable devices powered by Li-ion cells or 5V adapters, and general embedded systems requiring multiple sequenced voltage rails from a single input.
When designing with the PCA9421, consult the NXP datasheet for the exact buck and LDO current limits, programmable output voltage ranges, and I2C register map, and verify thermal performance for the chosen package option before finalizing the PCB layout.
This page synthesizes distributor pricing context, same-family drop-in alternatives, application guidance, and design notes that go beyond the information available on the manufacturer datasheet alone, providing engineers with a consolidated selection resource.
Drop-in alternatives for PCA9421 β same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Quick Comparison Tool β Select alternative parts for side-by-side comparison:
PCA9421BS
β Drop-Inπ Reference alternative (not in catalog)
PCA9421BSZ
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View Datasheet βPCA9420BS
β Drop-Inπ Reference alternative (not in catalog)
PCA9420BSZ
β Drop-Inπ Reference alternative (not in catalog)
PCA9421 Maximum Ratings & Electrical Characteristics
| Function | Power Management IC (PMIC) |
| Buck Converters | 2 (I2C-programmable output voltage) |
| LDO Regulators | 2 |
| Control Interface | I2C |
| Applications | Low-power microcontroller power management, Li-ion battery and/or 5V adapter powered applications |
| Package (BS suffix) | HVQFN-24 |
| Package (UK suffix) | WLCSP-25 |
| Mounting Type | Surface Mount |
| Family | PCA9420/PCA9421 |
PCA9421 wlcsp-25 Pin Configuration Guide
Pin configuration for PCA9421 (wlcsp-25 package). This power device features gate, drain, and source terminals. For non-polarized packages, refer to the manufacturer datasheet for exact pin 1 orientation and footprint details. Common applications include power supply design, motor driving, and load switching.
No detailed pinout data available for PCA9421.
Refer to the datasheet for full pin configuration.
Typical Applications
PCA9421 is suitable for 6 applications: Low-Power Microcontroller Power Supply, Li-ion Battery Powered Portable Devices, 5V Adapter Powered Non-Portable Systems, IoT Sensor Nodes and Smart Home Devices, Wearables and Space-Constrained Designs, Industrial Embedded Control Boards.
Low-Power Microcontroller Power Supply
The PCA9421's core target application, per NXP's product description, is a full power management solution for low-power microcontroller systems. Its two buck converters with I2C-programmable output voltages let the MCU's host firmware set core and I/O rail voltages precisely, while the two integrated LDOs supply low-noise analog functions such as ADC references or RF modules. Placing the PCA9421 between a 5V adapter input and the MCU rails replaces multiple discrete converters with one IC, shrinking solution size and BOM count. The dynamic programmability also enables power-mode sequencing and voltage scaling during sleep/active transitions, directly reducing system energy consumption in always-on embedded designs.
Recommended
Li-ion Battery Powered Portable Devices
NXP explicitly targets the PCA9420/PCA9421 family at applications powered by a Li-ion battery and/or a 5V adapter. In battery-powered portable products, the two I2C-programmable bucks convert the Li-ion cell's varying voltage into stable, firmware-adjustable digital rails, while the LDOs provide clean power for sensors and wireless modules whose performance degrades with switching ripple. Because rail voltages are register-programmable, the host MCU can lower core voltage in low-power states to extend battery runtime. Designers should verify in the NXP datasheet the accepted input range against the Li-ion discharge window and budget LDO headroom so the linear regulators stay in dropout-free operation across the full battery curve.
Recommended
5V Adapter Powered Non-Portable Systems
For non-portable equipment running from a regulated 5V adapter, the PCA9421 acts as a compact multi-rail power tree in a single package. Distributor listings (DigiKey: 'Power Management IC 5V 2 Buck + 2 LDO') confirm the 5V input operating point. The two bucks step the 5V input down to core and peripheral voltages with I2C adjustability for margining during production test, and the two LDOs generate low-noise rails for analog front ends. Compared with building the same tree from discrete converters, the integrated PMIC reduces component count, PCB area, and assembly cost, while the I2C interface supports in-system voltage trimming without hardware changes.
Recommended
IoT Sensor Nodes and Smart Home Devices
Battery- or adapter-powered IoT nodes benefit from the PCA9421's combination of high-efficiency bucks for the MCU radio chain and LDOs for noise-sensitive sensors. Typical loads include microcontrollers, wireless modules, and MEMS sensors; the I2C-programmable rails allow the node firmware to sequence power-up (radio after logic) and to cut analog rails in deep-sleep states, cutting quiescent draw. The HVQFN24 package fits compact sensor-node PCBs, while the WLCSP25 (UK) option serves wearable-scale designs. Engineers should size the buck inductors and output capacitors per the NXP datasheet recommendations to keep switching ripple below sensor accuracy thresholds, and verify register default output voltages against the sensor supply limits.
Recommended
Wearables and Space-Constrained Designs
The PCA9421UKZ option in a 25-ball WLCSP package targets wearable and ultra-compact products where board area is the binding constraint. In such designs the PMIC's integration advantage is maximized: two bucks and two LDOs occupy a chip-scale footprint instead of several scattered converters, freeing area for the battery cell. The I2C interface connects directly to the wearable's MCU for runtime rail adjustment, supporting aggressive duty-cycling that extends battery life. Layout discipline is critical at WLCSP geometry - follow the datasheet PCB layout guidelines for via-in-pad or fanout patterns, keep buck switching loops minimal, and verify assembly capability for 0.4 mm-pitch-class chip-scale packages before committing.
Recommended
Industrial Embedded Control Boards
In industrial controllers powered from a 24V bus rectified to a 5V rail or from a 5V auxiliary supply, the PCA9421 provides the low-voltage digital power tree: MCU core, I/O, and analog sensor rails from one HVQFN24 device. The I2C-programmable outputs support production margining and in-field firmware-controlled power modes, useful for functional-safety or low-standby-power requirements. The two LDOs isolate sensitive analog inputs (e.g., 4-20 mA sense front ends) from buck switching noise. Designers must confirm ambient temperature against the datasheet operating range for cabinet environments and provide adequate thermal copper area under the QFN exposed pad to keep junction temperature within limits at full load.
Recommended
Recommended Products Summary
Engineering reference data for PCA9421 β comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PCA9421BS | PCA9421BSZ | PCA9420BS | PCA9420BSZ |
|---|---|---|---|---|---|
| Package | HVQFN-24 (BS) | HVQFN-24 - same | HVQFN-24 - same | HVQFN-24 - same | HVQFN-24 - same |
| Brand | NXP Semiconductors | NXP Semiconductors | NXP Semiconductors | NXP Semiconductors | NXP Semiconductors |
| I2C-Programmable Buck Outputs | Yes, 2 bucks | Yes, 2 bucks | Yes, 2 bucks | Yes (family feature) | Yes (family feature) |
| Target Application | Low-power MCU, Li-ion / 5V adapter | Low-power MCU, Li-ion / 5V adapter | Low-power MCU, Li-ion / 5V adapter | Low-power MCU, Li-ion / 5V adapter | Low-power MCU, Li-ion / 5V adapter |
| Drop-in Compatible with PCA9421 | - | Yes (identical die) | Yes (identical die) | Same footprint, functional review required | Same footprint, functional review required |
Key Differentiators
- Full multi-rail integration in one IC (vs PCA9420BS)
- Two package options for the same silicon (vs PCA9421BSZ)
- Distributor-stocked availability (vs PCA9420BSZ)
Design Notes
For the HVQFN24 (BS) package, create the land pattern exactly per the NXP datasheet recommended footprint and connect the exposed thermal pad to a grounded copper pour with an array of thermal vias. The buck converters switch at high frequency, so keep the input capacitor, buck inductor, and output capacitor loops as small as possible to minimize EMI. For the WLCSP25 (UK) variant, follow the datasheet fanout guidance and confirm your assembly house supports chip-scale pitch before layout release.
Because the buck output voltages on the PCA9421 are I2C-programmable, do not assume hardware-default register values meet your rail requirements - verify the power-up defaults in the datasheet register map, and ensure your MCU's I2C initialization runs before or safely during rail bring-up. Also remember that the BS (HVQFN24) and UK (WLCSP25) pinouts differ, per NXP pinning documentation; a schematic symbol drawn from one package must never be reused for the other.
Budget LDO headroom carefully: the two linear regulators should operate with enough input-to-output differential to stay in regulation, but not so much that dissipation overheats the QFN at load. Estimated: for a 100 mA LDO dropping 1.5 V, dissipation is about 0.15 W - acceptable on a HVQFN24 with solid exposed-pad copper, but re-check at higher loads. Consult the NXP datasheet for exact per-rail current limits and thermal resistance before finalizing the power budget.
Compliance Information
Compliance data was not present in the provided verified web data; consult the NXP product page (nxp.com/part/PCA9421BS) for official RoHS/REACH declarations.
