PCA9421BSZ - PMIC, 2 Buck + 2 LDO, I2C | NXP
MPN: PCA9421BSZ ✓ Active| Qty | Unit Price | Extended |
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| 1 | $0 | $0.00 |
| 10 | $0 | $0.00 |
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| 500 | $0 | $0.00 |
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PCA9421BSZ Overview
A PMIC (Power Management IC) is an integrated circuit that consolidates multiple voltage regulators, power sequencing, and control functions into a single device. Within the power-management hierarchy, a PMIC sits above discrete DC-DC converters and LDOs, replacing several components with one programmable, space-saving part. This reduces board area, bill-of-materials count, and design risk in battery-powered embedded systems.
Key features of the PCA9421 include two buck converters with I2C-programmable output voltage, allowing the firmware to scale MCU core rails dynamically for power optimization, plus two LDOs for low-noise analog or always-on domains. The device integrates power path management for Li-ion battery and 5 V adapter inputs, supporting seamless transitions between power sources. High integration makes it a natural companion for NXP i.MX RT crossover MCUs and other low-power microcontroller systems.
Architecturally, the PCA9420/PCA9421 family shares a common platform: the bucks provide the main processor core and I/O rails, while the LDOs supply analog, PLL, or real-time-clock domains. I2C control enables runtime configuration of rail voltages, enable states, and sequencing, which is essential for multi-rail processors that require specific power-up and power-down order.
Typical applications include battery-powered IoT sensor nodes, wearable devices, portable medical accessories, and industrial wireless endpoints built around i.MX RT or similar low-power MCUs. The dual-input (battery/5 V adapter) topology also suits smart-home devices and USB-adapter-powered accessories.
When designing with the PCA9421, verify buck inductor selection and LDO headroom against the actual load currents in the manufacturer datasheet, and implement the recommended I2C configuration early in firmware bring-up since rail voltages default to programmable states rather than hard-wired dividers.
This page synthesizes verified distributor listings, the official NXP datasheet, drop-in family alternatives, and practical design guidance not found together on any single manufacturer or distributor page.
Drop-in alternatives for PCA9421BSZ — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Variants in this series
Same-series models that are drop-in compatible with PCA9421BSZ (same form factor and footprint) — differing in Buck Converters.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PCA9420BS
✅ Drop-In ⚠️ 参数待验证📋 Reference alternative (not in catalog)
PCA9421BSZ Maximum Ratings & Electrical Characteristics
| Function | Power Management IC (PMIC) |
| Buck Converters | 2 (step-down, I2C-programmable output voltage) |
| LDO Regulators | 2 |
| Input Source | Li-ion battery and/or 5 V adapter |
| Control Interface | I2C |
| Target Application | Low-power microcontroller applications (e.g., i.MX RT) |
| Package | HVQFN24 |
| Mounting Type | Surface Mount |
PCA9421BSZ hvqfn24 Pin Configuration Guide
Pin configuration for PCA9421BSZ (hvqfn24 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 PCA9421BSZ.
Refer to the datasheet for full pin configuration.
Typical Applications
PCA9421BSZ is suitable for 6 applications: i.MX RT Crossover MCU Systems, Li-ion Battery-Powered IoT Sensor Nodes, 5 V Adapter-Powered Smart Home Devices, Wearable and Portable Devices, Portable Medical and Health Monitoring Accessories, Industrial Wireless Endpoints and Battery Sensors.
i.MX RT Crossover MCU Systems
The PCA9421 is explicitly positioned by NXP as the power management IC for i.MX RT low-power microcontroller applications. Its two I2C-programmable buck converters supply the MCU core and I/O rails, enabling dynamic voltage scaling during runtime so the processor can trade clock frequency against power consumption. The two integrated LDOs power noise-sensitive analog domains such as PLLs, ADC references, and RTC circuitry. Because the entire multi-rail solution, power path, and I2C control live in one HVQFN24 device, board area and BOM count shrink substantially compared to a discrete buck-plus-LDO design. Place the PMIC close to the MCU with short, wide buck power loops and follow the NXP reference layout for the i.MX RT power tree to preserve load-transient response and minimize rail ripple at the core supply.
Recommended
Li-ion Battery-Powered IoT Sensor Nodes
For battery-operated IoT endpoints, the PCA9421 accepts a Li-ion cell directly and manages the discharge curve through its regulated buck and LDO outputs, maintaining stable rails as the cell voltage falls from full charge toward cutoff. The I2C interface lets the host MCU disable individual rails during sleep periods, cutting system standby power - a decisive parameter for multi-year battery life targets. The integration of two bucks and two LDOs in one package suits compact sensor nodes combining a wireless MCU, a low-power radio, and analog sensors. Engineers should budget buck inductor size and quiescent current against the node's sleep-duty cycle, and verify per-rail current limits from the NXP datasheet against the radio's transmit burst current to avoid core-rail droop during RF events.
Recommended
5 V Adapter-Powered Smart Home Devices
The PCA9421 supports non-portable applications powered by a 5 V adapter, making it suitable for smart-home devices such as connected sensors, doorbell accessories, and plug-in controllers. In this configuration the 5 V adapter input feeds the buck converters, which step down to the processor core and I/O rails, while the LDOs supply clean analog rails for audio, sensing, or RF front ends. The dual-source design also enables battery-backup schemes where the system runs from the adapter when present and falls back to Li-ion seamlessly - valuable for security and monitoring products that must never lose state. Designers should confirm input voltage tolerance for adapter sag and surge conditions and add input bulk capacitance per the NXP datasheet recommendations to ride through adapter transients.
Recommended
Wearable and Portable Devices
Wearables demand extreme miniaturization and low standby power, both core strengths of the PCA9421 platform. The WLCSP25 (UK) package option provides the smallest footprint for space-constrained wearable PCBs, while the HVQFN24 (BS) variant simplifies assembly and inspection for mid-volume builds. The I2C-programmable rails let wearable firmware aggressively scale the MCU core voltage during sleep and burst-activity profiles, directly extending battery life from a small Li-ion cell. The two LDOs handle low-noise domains such as heart-rate sensor analog front ends or display bias. Because thermal dissipation is limited in body-worn enclosures, engineers should estimate total converter losses at worst-case load and validate junction temperature against the package thermal resistance given in the NXP datasheet before freezing the mechanical design.
Recommended
Portable Medical and Health Monitoring Accessories
Battery-powered medical accessories - pulse oximeters, glucose monitors, portable diagnostic pods - benefit from the PCA9421's combination of programmable rails and integrated LDOs. Analog measurement front ends are highly sensitive to supply ripple; routing them from the dedicated LDO outputs rather than a buck rail reduces noise coupling into the biosignal chain, improving measurement resolution at low signal amplitudes. The Li-ion input path with power management supports rechargeable Designs meeting portability requirements, while I2C control enables measured, orderly power sequencing for precision analog and digital sections. Designers working on medical devices should additionally verify the component's qualification documentation and compliance declarations directly with NXP, and derate rail loads conservatively to guarantee stable operation across the full battery discharge range.
Recommended
Industrial Wireless Endpoints and Battery Sensors
Industrial environments impose wide temperature ranges, noisy electrical conditions, and strict uptime requirements on wireless sensor endpoints. The PCA9421's integrated power path tolerates both battery and 5 V auxiliary supply operation, allowing installations that switch between a local Li-ion cell and externally supplied power. Its I2C rail control supports scheduled sleep/wake cycles typical of duty-cycled industrial monitoring, and the dual-buck architecture separates the radio supply domain from the MCU core domain, improving transmit burst immunity. Protection components on the input, layout discipline for the buck loops, and confirmation of operating-temperature ratings against the datasheet are the key engineering steps; the single-package integration also simplifies conformal-coated, sealed-enclosure builds common in factory and agriculture sensing.
Recommended
Recommended Products Summary
Engineering reference data for PCA9421BSZ — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PCA9420BS | PCA9420UK |
|---|---|---|---|
| Package | HVQFN24 (BS) | HVQFN24 - same footprint | WLCSP25 (UK footprint variant) |
| Brand | NXP Semiconductors | NXP Semiconductors | NXP Semiconductors |
| Buck Converters | 2 (I2C-programmable) | 2 (I2C-programmable) | 2 (I2C-programmable) |
| LDO Regulators | 2 | 2 | 2 |
| Input Source | Li-ion battery and/or 5 V adapter | Li-ion battery and/or 5 V adapter | Li-ion battery and/or 5 V adapter |
| Control Interface | I2C | I2C | I2C |
| Target Application | Low-power MCU (i.MX RT) | Low-power MCU (i.MX RT) | Low-power MCU (i.MX RT) |
Key Differentiators
- Newest family addition with I2C-programmable bucks (vs PCA9420BS)
- Dual power source (Li-ion battery AND 5 V adapter) (vs PCA9420UK)
- Two package footprints on one silicon (vs PCA9420BS)
Design Notes
For the HVQFN24 (BS) package, place the buck input capacitors within 2-3 mm of the VIN pins and minimize the high-side switch loop area to contain EMI. Use the exposed die-attach pad as the primary ground return, soldered to a via-stitched ground plane - thermal and switching performance both depend on this connection. Keep the buck inductors' SW nodes short and away from the I2C lines and LDO feedback traces. Follow the NXP PCA9421 datasheet layout recommendation section, which is tuned for i.MX RT reference designs.
Because both buck outputs are I2C-programmable, default power-up rail voltages come from register configuration rather than hardware dividers. Establish a deterministic boot sequence: the PMIC default rails must be safe for the MCU at reset, and firmware must reconfigure rails before any rail is pushed out of processor tolerance. Verify with an oscilloscope during power-up that core-rail overshoot and sequencing meet the MCU requirements, and check per-rail current limits against worst-case loads (especially radio transmit bursts) in the NXP datasheet electrical characteristics.
A frequent mistake is treating the PCA9421 as a hard-wired regulator set: changing output voltage with resistors does not work here, so prototype firmware must implement the I2C init sequence from day one. Also, the family offers two footprints (HVQFN24 BS and WLCSP25 UK) that are not interchangeable - order the exact suffix your PCB uses. Finally, when evaluating the sibling PCA9420, do not assume identical default register values; confirm them in the shared PCA9420/PCA9421 datasheet before substituting in production.
Compliance Information
Compliance status was not stated in the verified web data. Confirm RoHS/REACH/lead-free status via the official NXP product page (nxp.com/part/PCA9421BS) and NXP material declarations.
