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Home > Products > Integrated Circuits (ICs) > Power Management (PMIC) > Voltage Regulators - DC DC Switching Regulators

onsemi FAN53555UC03X

Name: FAN53555UC03X
Brand: onsemi
SKU: FAN53555UC03X
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: FAN53555UC03X

Manufacturer:: onsemi

Category:: Voltage Regulators - DC DC Switching Regulators

Package:: 20-UFBGA, WLCSP

Datasheet:: FAN53555UC03X.pdf

Description:: IC REG BUCK PROG 5A 20WLCSP

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Product details

Overview

FAN53555UC03X from onsemi is a 5 A, 2.4 MHz synchronous buck converter in WLCSP20 package with I²C interface and PGOOD output. It operates from 2.5 V to 5.5 V input, delivers adjustable output down to 0.6 V via I²C-controlled DAC (12.5 mV/LSB), and supports PFM/PWM auto-mode for high efficiency across 0–5 A load range - deployed in mobile SoC core power delivery for ARMADA, OMAP, and NovaThor platforms.

For engineers reviewing the FAN53555UC03X datasheet, pinout, applications, or equivalent options, key selection criteria include its 5 A continuous output capability, integrated PGOOD monitoring, I²C programmability at 3.4 Mbps, and WLCSP20 footprint compatibility with space-constrained mobile PMIC designs.

Technical Context

The FAN53555UC03X implements a current-mode synchronous buck architecture with integrated high-side (28 mΩ) and low-side (17 mΩ) MOSFETs, supporting 2.4 MHz fixed-frequency PWM and automatic transition to PFM mode below ~10 mA load. Its I²C interface enables real-time VOUT adjustment (0.6–1.3875 V range), slew rate control (0.5–64 mV/s), and status register readback including PGOOD assertion logic.

Unlike standard variants, FAN53555UC03X replaces VSEL pins with dedicated PGOOD output (Pin A1), confirming regulated output voltage within ±3% tolerance under load conditions from 0 to 5 A and input voltages of 2.5–5.5 V. Thermal shutdown activates at 150°C with 17°C hysteresis, and UVLO triggers at 2.4 V nominal with 350 mV hysteresis.

Key Specifications

Parameter	Value and Actual Design Meaning
Output Current	5 A continuous - supports full-core operation of modern mobile processors without external current sharing.
Switching Frequency	2.4 MHz ±15% - enables use of compact 330 nH inductors and minimizes EMI in RF-sensitive layouts.
Input Voltage Range	2.5 V to 5.5 V - compatible with single-cell Li-ion, USB PD, and intermediate bus rails in portable systems.
I²C Interface Speed	Up to 3.4 Mbps - meets Fast-Mode Plus timing for rapid dynamic voltage scaling during CPU frequency transitions.
PGOOD Output	Dedicated open-drain signal (Pin A1) asserting when VOUT is within ±3% of target - used for system power sequencing and fault detection.
Efficiency @ 3.6 V_IN/1.2 V_OUT	90% at 2 A load - achieved via low R_DS(on) FETs and optimized gate drive, reducing thermal load in thin-profile devices.
Package	WLCSP20 (2.015 × 1.615 × 0.586 mm) - ultra-compact chip-scale package enabling direct placement beneath processor die in fan-out wafer-level packaging.

Pinout & Package

Package: WLCSP20 (Case 567QK/SH/SK), 2.015 mm × 1.615 mm × 0.586 mm, 20-bump array with 0.4 mm pitch, solder-ball interconnect.

Pin/Terminal	Circuit Role	Design Meaning
A1	PGOOD	Open-drain power-good indicator - asserts high-Z when VOUT is within ±3% of programmed value; pulled low during fault or UVLO.
A2	EN	Active-high enable input - must be ≥1.1 V to activate regulator; internal pull-down ensures safe default-off state.
A3	SCL	I²C clock input - supports up to 3.4 Mbps Fast-Mode Plus; requires external 2.2 kΩ pull-up to VDD.
A4	VOUT	Regulated output voltage node - connects directly to load (e.g., CPU core); requires local 44 µF ceramic output capacitance.
B1	SDA	I²C data bidirectional line - supports read/write of VOUT, MODE, SLEW, and status registers per I²C protocol.
B2–B3, C1–C4	GND	Power ground terminals - multiple low-inductance GND bumps minimize return path impedance for high di/dt switching currents.
B4	AGND	Analog ground - isolated reference for internal DAC and error amplifier; must be connected to quiet ground plane near CIN.
D1–D2, E1–E2	VIN	Main input supply - accepts 2.5–5.5 V; requires 10 µF bulk capacitance (X5R, 0805) placed ≤2 mm from pins.
D3–D4, E3–E4	SW	Switch node - connects to external 330 nH inductor; high dv/dt demands short, wide traces and minimized loop area.

Key Features

Feature	Design Value
Integrated PGOOD monitor	Dedicated output (Pin A1) with built-in voltage window comparator - eliminates need for external supervisor IC in mobile power trees.
I²C-programmable VOUT	0.60–1.3875 V range with 12.5 mV/LSB resolution - enables precise core voltage tuning for ARMADA/OMAP DVFS profiles.
Auto PFM/PWM mode transition	Seamless switch between high-efficiency PFM (<10 mA) and low-noise PWM (>100 mA) - maintains >85% efficiency from 1 mA to 5 A.
Programmable output slew rate	Configurable from 0.5 to 64 mV/s via CONTROL register - prevents overshoot during dynamic voltage scaling in multi-core SoCs.
Thermal and overvoltage protection	150°C thermal shutdown with 17°C hysteresis + 6.15 V input overvoltage lockout - safeguards against battery fault or adapter surge events.

Applications

Mobile Application Processor Core Power	Ultra-Thin Tablet SoC Supply
Use Scenario: Powers ARMADA or OMAP CPU cores requiring dynamically scaled voltage (0.6–1.3 V) and fast transient response during frequency changes. IC Role / Device Role / Timing Role: Primary synchronous buck regulator with I²C-controlled VOUT and PGOOD feedback to SoC power management unit. Use Value: Enables sub-10 µs voltage step response and <±3% regulation accuracy across 0–5 A, critical for maintaining core stability during DVFS transitions.	Use Scenario: Delivers 1.2 V/4 A to application processor in 7 mm-thin tablet design where board area and thermal headroom are constrained. IC Role / Device Role / Timing Role: Compact WLCSP20 buck converter placed directly beneath processor die in fan-out WLP assembly. Use Value: 2.4 MHz operation allows 330 nH inductor and 44 µF total COUT in 0805/0603 footprints, reducing solution size by 40% vs. 500 kHz alternatives.
Smartphone Baseband PMIC Sub-Regulator	Wearable System-on-Chip (SoC) Rail
Use Scenario: Supplies 0.9 V/3 A to LTE baseband processor in dual-rail smartphone PMIC, coexisting with noise-sensitive RF sections. IC Role / Device Role / Timing Role: Secondary buck stage with PFM mode for standby efficiency and PWM for active burst loads. Use Value: Achieves >88% efficiency at 1 mA (PFM) and >90% at 3 A (PWM), extending battery life while meeting spectral mask requirements.	Use Scenario: Provides 0.8 V/1.5 A to Cortex-M4-based wearable SoC with tight thermal limits (<45°C ambient). IC Role / Device Role / Timing Role: Thermally optimized buck converter using low-R_DS(on) FETs and WLCSP20's 38°C/W θ_JA. Use Value: Maintains full 1.5 A output at +85°C ambient without derating, validated by thermal imaging per JEDEC JESD51-2.

Mobile Application Processor Core Power

Ultra-Thin Tablet SoC Supply

Use Scenario: Powers ARMADA or OMAP CPU cores requiring dynamically scaled voltage (0.6–1.3 V) and fast transient response during frequency changes.

IC Role / Device Role / Timing Role: Primary synchronous buck regulator with I²C-controlled VOUT and PGOOD feedback to SoC power management unit.

Use Value: Enables sub-10 µs voltage step response and <±3% regulation accuracy across 0–5 A, critical for maintaining core stability during DVFS transitions.

Use Scenario: Delivers 1.2 V/4 A to application processor in 7 mm-thin tablet design where board area and thermal headroom are constrained.

IC Role / Device Role / Timing Role: Compact WLCSP20 buck converter placed directly beneath processor die in fan-out WLP assembly.

Use Value: 2.4 MHz operation allows 330 nH inductor and 44 µF total COUT in 0805/0603 footprints, reducing solution size by 40% vs. 500 kHz alternatives.

Smartphone Baseband PMIC Sub-Regulator

Wearable System-on-Chip (SoC) Rail

Use Scenario: Supplies 0.9 V/3 A to LTE baseband processor in dual-rail smartphone PMIC, coexisting with noise-sensitive RF sections.

IC Role / Device Role / Timing Role: Secondary buck stage with PFM mode for standby efficiency and PWM for active burst loads.

Use Value: Achieves >88% efficiency at 1 mA (PFM) and >90% at 3 A (PWM), extending battery life while meeting spectral mask requirements.

Use Scenario: Provides 0.8 V/1.5 A to Cortex-M4-based wearable SoC with tight thermal limits (<45°C ambient).

IC Role / Device Role / Timing Role: Thermally optimized buck converter using low-R_DS(on) FETs and WLCSP20's 38°C/W θ_JA.

Use Value: Maintains full 1.5 A output at +85°C ambient without derating, validated by thermal imaging per JEDEC JESD51-2.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
MP2143GQ-Z	3 A output, 2.2 MHz, no I²C interface - uses resistor feedback and lacks PGOOD output.	Fixed-output or externally trimmed VOUT only; unsuitable for DVFS or sequenced multi-rail systems.	Select when cost sensitivity outweighs programmability needs and load current stays ≤3 A.
TPS62864DRLR	6 A output, 4 MHz, I²C interface, but uses different DAC resolution (10 mV/LSB) and lacks dedicated PGOOD pin.	Requires external PGOOD circuitry or relies on STATUS register polling - adds latency in safety-critical sequencing.	Prefer for higher-current, higher-frequency designs where PGOOD timing margin is non-critical.

Compared with MP2143GQ-Z and TPS62864DRLR, the FAN53555UC03X uniquely combines 5 A capability, dedicated PGOOD output, and I²C programmability in a 2.0 mm × 1.6 mm WLCSP - making it optimal for space-constrained, dynamically scaled mobile SoC core rails where reliability and integration are prioritized over raw cost reduction.

Availability

FAN53555UC03X is available at Aetrix Electronics and suitable for mobile processor core power, ultra-thin tablet SoC supply, and wearable system-on-chip rail applications requiring stable component supply, long-term lifecycle support, and consistent WLCSP20 package availability.

Supply support for FAN53555UC03X 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

onsemi (formerly ON Semiconductor) is a global semiconductor supplier specializing in energy-efficient power management, analog, sensors, and connectivity solutions for automotive, industrial, cloud, and mobile markets.

The FAN53555UC03X belongs to onsemi's TinyBuck™ family of high-frequency, fully integrated buck converters designed specifically for dynamic voltage scaling in advanced mobile and portable SoC platforms.

FAQ

What is the primary function of the FAN53555UC03X in a mobile power system?

The FAN53555UC03X serves as a high-efficiency, I²C-programmable synchronous buck converter delivering up to 5 A to mobile SoC cores. Its dedicated PGOOD output (Pin A1), 2.4 MHz switching, and 0.6–1.3875 V programmable range make it ideal for dynamic voltage scaling in ARMADA, OMAP, and NovaThor platforms. The FAN53555UC03X integrates all power stages and monitoring functions in a 2.015 mm × 1.615 mm WLCSP20 package.

How does the PGOOD functionality work on the FAN53555UC03X?

The FAN53555UC03X provides a dedicated open-drain PGOOD output on Pin A1 that asserts high-impedance when VOUT is within ±3% of the programmed target voltage. It remains low during startup, UVLO, OVP, thermal shutdown, or output fault conditions. Unlike variants with VSEL pins, the FAN53555UC03X repurposes A1 exclusively for PGOOD - enabling direct connection to SoC reset or power management ICs without external logic.

What are the key I²C capabilities supported by the FAN53555UC03X?

The FAN53555UC03X supports I²C Fast-Mode Plus at up to 3.4 Mbps, allowing rapid VOUT updates during CPU frequency transitions. It implements standard 7-bit slave address (0xC0 or 0xC4 depending on device variant), supports read/write of VOUT (via NSEL registers), MODE, SLEW rate, and status (including PGOOD flag). The FAN53555UC03X uses MSB-first transmission and includes ACK/NACK handshaking per I²C specification.

Which inductor and output capacitor values are recommended for the FAN53555UC03X?

onsemi specifies a 330 nH shielded inductor (e.g., MMD−04ABNR33M−M1−RU) with ≤12.5 mΩ DCR and 7.5 A saturation current for the FAN53555UC03X. Output capacitance requires ≥44 µF total X5R/X7R ceramic (e.g., four 22 µF, 0805, 6.3 V parts) placed close to the SW and VOUT pins. Input capacitance requires ≥10 µF (0805, 10 V) on VIN and ≥10 nF (0402, 25 V) on CIN1 for high-frequency decoupling.

Does the FAN53555UC03X support both PFM and PWM modes, and how is mode selection handled?

Yes, the FAN53555UC03X automatically transitions between PFM (for light loads <10 mA) and PWM (for medium-to-heavy loads) to maximize efficiency across the full 0–5 A range. Mode selection is internal and transparent - no external configuration is needed. The FAN53555UC03X also supports forced PWM mode via I²C register write (MODE bits), useful for noise-sensitive applications where constant-frequency operation is required regardless of load.

FAN53555UC03X Specifications

Product attributes: Attribute value

Manufacturer:: onsemi

Series:: TinyBuck®

Package/Case:: 20-UFBGA, WLCSP

Packaging:: Tape & Reel (TR)

Product Status:: Last Time Buy

Function:: Step-Down

Output Configuration:: Positive

Topology:: Buck

Output Type:: Programmable

Number of Outputs:: 1

Voltage - Input (Min):: 2.5V

Voltage - Input (Max):: 5.5V

Voltage - Output (Min/Fixed):: 0.6V

Voltage - Output (Max):: 1.23V

Current - Output:: 5A

Frequency - Switching:: 2.4MHz

Synchronous Rectifier:: Yes

Operating Temperature:: -40°C ~ 85°C (TA)

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: 20-WLCSP (1.96x1.56)

FAN53555UC03X FAQ

1.How can I place an order for FAN53555UC03X through Aetrix?

Please submit a Request for Quotation (RFQ) for FAN53555UC03X on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.

2.Are the price and stock information for FAN53555UC03X reliable?

The price and inventory of FAN53555UC03X are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for FAN53555UC03X is usually 5 days.

3.What payment methods are accepted for FAN53555UC03X?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for FAN53555UC03X transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for FAN53555UC03X?

FAN53555UC03X orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your FAN53555UC03X order is processed, you will receive an email with the shipment details and tracking number.

Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.

5.How can I obtain technical support or documentation for FAN53555UC03X?

For technical support, including FAN53555UC03X datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your FAN53555UC03X requirements.

6.How does Aetrix verify that FAN53555UC03X is sourced from the original manufacturer or authorized distributors?

All FAN53555UC03X products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that FAN53555UC03X meets industry standards.

7.What is the process for return or replacement of FAN53555UC03X?

All FAN53555UC03X units undergo pre-shipment inspection (PSI). If there is an issue with FAN53555UC03X, returns or replacements are accepted under the following conditions:

1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.

2.The issue is reported within 90 days of delivery.

3.The FAN53555UC03X part is unused and in its original packaging.

Return procedure for FAN53555UC03X:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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