onsemi FAN53526UC00X

Overview

FAN53526UC00X from onsemi is a digitally programmable 3.0 A synchronous step-down DC-DC regulator with I²C interface, operating from 2.5 V to 5.5 V input and delivering 0.600 V output by default. It uses a proprietary fixed-frequency PWM architecture at 2.4 MHz, achieves >80% efficiency across 10 mA–3.0 A load range, and supports programmable slew rate for voltage transitions - deployed in mobile SoC core power delivery.

For engineers reviewing the FAN53526UC00X datasheet, pinout, applications, or equivalent options, key selection criteria include its 0.600 V factory-default output, 6.25 mV I²C-programmable steps, 2.4 MHz switching frequency enabling compact 330 nH inductors, PFM/PWM auto-mode operation, and WLCSP-15 package compatibility with high-density portable PCB layouts.

Technical Context

The FAN53526UC00X implements a non-linear, fixed-frequency PWM modulator with synchronous rectification, maintaining constant 2.4 MHz switching across input voltages (2.5–5.5 V) and loads (10 mA–3.0 A) via an internal frequency loop. Its architecture eliminates ESR dependency, enabling stable regulation with low-ESR ceramic capacitors.

It integrates dual enable control (hardware EN pin + software BUCK_EN bits), programmable output discharge (via OUTPUT_DISCHARGE bit), and real-time status monitoring (PGOOD, UVLO, OVP flags in Monitor register). Voltage transitions are slew-rate limited using three-bit SLEW field (0.5–64 mV/s), while light-load efficiency is sustained via single-pulse PFM mode with 50 µA typical quiescent current.

Key Specifications

Pinout & Package

Package: 15-bump Wafer-Level Chip Scale Package (WLCSP), 1.310 mm × 2.015 mm, 0.4 mm ball pitch, RoHS-compliant.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar step-down regulator applications.

Compared with TPS62864B18ARQYR and RTQ2132BGQW, the FAN53526UC00X uniquely combines factory-default 0.600 V, 6.25 mV resolution, VSEL-pin-selectable dual register banks, and 2.4 MHz operation in a 1.31 × 2.02 mm WLCSP - optimizing for space-constrained, dynamically scaled mobile SoC core rails.

Availability

FAN53526UC00X is available at Aetrix Electronics and suitable for smartphone SoC core power, LPDDR4 termination, and ultra-mobile PC I/O rail applications requiring stable component supply, long-term lifecycle support, and verified production-grade WLCSP handling.

Supply support for FAN53526UC00X 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 is a global semiconductor leader delivering energy-efficient, intelligent power and sensing solutions for automotive, industrial, cloud, medical, and IoT applications.

The FAN53526UC00X belongs to onsemi's TinyBuck family of ultra-compact, high-efficiency DC-DC regulators designed specifically for dynamic voltage scaling in mobile and portable SoC platforms.

FAQ

What is the default output voltage of the FAN53526UC00X at power-up?

The FAN53526UC00X powers up with a default output voltage of 0.600 V, corresponding to the VSEL0 register value per Table 1. This is set by the GA slave address configuration and remains active until reprogrammed via I²C or changed by asserting the VSEL pin high to select VSEL1. The FAN53526UC00X maintains this setting across enable cycles unless modified through its CONTROL register or external programming.

Does the FAN53526UC00X support forced PWM mode, and how is it enabled?

Yes, the FAN53526UC00X supports forced PWM mode to eliminate PFM frequency variation. It is enabled by setting the MODE bits (bits 1:0) in the CONTROL register (address 02h) to '10' and driving the VSEL pin high. When VSEL is high and MODE = 10, the device operates exclusively in fixed-frequency 2.4 MHz PWM regardless of load current. The FAN53526UC00X retains this configuration until changed, and the setting persists across soft resets but not full power-on resets.

What is the maximum recommended output capacitance for reliable startup of the FAN53526UC00X?

The FAN53526UC00X has a maximum recommended output capacitance of approximately COUTMAX = 320 × VOUT / ILOAD (in µF), where ILOAD is the constant-current load during soft-start in amperes. For example, with VOUT = 0.600 V and ILOAD = 0.5 A, COUTMAX ≈ 384 µF. Exceeding this limit may cause startup failure due to insufficient charge current during the internal soft-start ramp. The FAN53526UC00X datasheet specifies two 47 µF X5R 0603 capacitors as the reference design, well within safe limits for typical mobile loads.

How does the FAN53526UC00X handle output voltage transitions from high to low?

During high-to-low output voltage transitions, the FAN53526UC00X stops switching and relies on the output load to discharge VOUT to the new setpoint. The IC monitors the transition via the NEG flag in the MONITOR register (address 05h). Once VOUT reaches the target, regulation resumes. No active sinking is performed unless OUTPUT_DISCHARGE is enabled - in which case an internal 11 Ω pull-down engages only after EN is deasserted or BUCK_ENx is cleared. This behavior is intrinsic to the FAN53526UC00X architecture and applies uniformly across all output voltage steps.

What I²C slave address does the FAN53526UC00X use, and is it configurable?

The FAN53526UC00X uses I²C slave address 0xC0 (7-bit address 0x60), as indicated by the GA marking in Table 1. This address is hardwired and not user-configurable via pins or registers. While the datasheet notes that "other slave addresses can be assigned" upon contacting onsemi, no mechanism (e.g., ADDR pin, OTP programming, or register write) is documented in the FAN53526UC00X datasheet to modify the slave address. Therefore, the FAN53526UC00X operates exclusively at 0xC0 in standard deployments.