onsemi FAN53526UC89X

Overview

FAN53526UC89X from onsemi is a digitally programmable 3.0 A synchronous step-down DC-DC regulator with I²C interface, operating at 2.4 MHz fixed frequency and delivering 1.15625 V output by default. It supports 2.5–5.5 V input, achieves >80% efficiency from 10 mA to 3.0 A load, and integrates PFM/PWM auto-mode switching for ultra-low quiescent current (50 µA typical) in light-load conditions - ideal for powering ARM/Tegra application processors and LPDDR memory rails.

For engineers reviewing the FAN53526UC89X datasheet, pinout, applications, or equivalent options, key selection criteria include its 6.25 mV programmable output resolution (0.600–1.39375 V), 2.4 MHz switching frequency enabling compact 330 nH inductors, I²C slave address C0h, and WLCSP-15 package with integrated thermal/overcurrent protection.

Technical Context

The FAN53526UC89X uses a proprietary non-linear fixed-frequency PWM modulator with synchronous rectification, maintaining constant 2.4 MHz operation across input voltages (2.5–5.5 V) and loads (0–3.0 A) via an internal frequency loop. Its architecture eliminates ESR dependency, enabling stable regulation with low-ESR ceramic capacitors.

It implements dual-mode control: automatic transition between PFM (for <10 mA loads, 50 µA IQ) and forced PWM (for noise-sensitive or high-transient applications), selectable via MODE bits and VSEL pin logic. Voltage transitions are slew-rate programmable (0.5–64 mV/s) through register 02h, while hardware enable (EN) and software buck control (BUCK_ENx) provide layered power sequencing flexibility.

Key Specifications

Pinout & Package

Package: 15-bump Wafer-Level Chip Scale Package (WLCSP), 1.310 mm × 2.015 mm, 0.4 mm ball pitch, case 567QS.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TPS6286418RTER and RTQ2132BWGEED, the FAN53526UC89X uniquely combines 2.4 MHz operation, 50 µA PFM quiescent current, and dedicated slew-rate control - making it optimal for mobile SoC core rails demanding both efficiency and precise transient behavior.

Availability

FAN53526UC89X is available at Aetrix Electronics and suitable for smartphone power management, LPDDR memory regulation, and ARM-based application processor core rails requiring stable component supply and long-term production continuity.

Supply support for FAN53526UC89X 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 supplier delivering energy-efficient silicon solutions for automotive, industrial, cloud, medical, and edge applications.

The FAN53526UC89X belongs to onsemi's TinyBuck family of ultra-compact, high-frequency DC-DC regulators designed specifically for mobile and portable electronics requiring high efficiency, small size, and digital programmability.

FAQ

What is the default output voltage of the FAN53526UC89X at power-up?

The FAN53526UC89X powers up with a default output voltage of 1.15625 V, corresponding to the VSEL0 register value programmed at factory. This setting is confirmed in Table 1 of the datasheet and remains active when the VSEL pin is held low. The FAN53526UC89X retains this default until modified via I²C write to register 00h or by toggling VSEL high to select VSEL1.

Does the FAN53526UC89X support true I²C High-Speed Mode (3.4 Mbps)?

Yes, the FAN53526UC89X fully supports I²C High-Speed Mode up to 3.4 Mbps, as specified in Table 9 and the Operating Description section. It complies with HS Mode timing requirements including tRCL/tFCL ≤ 80 ns (CB ≤ 100 pF) and requires the master to send the HS master code (00001XXX) after START. The FAN53526UC89X slave address is C0h in HS Mode, identical to Fast Mode.

How does the FAN53526UC89X handle output voltage transitions between different setpoints?

The FAN53526UC89X supports programmable positive-transition slew rates (0.5–64 mV/s) via bits 6:4 in CONTROL register (02h). Negative transitions rely on load discharge; the IC stops switching until VOUT reaches the new setpoint. During transitions, the MONITOR register (05h) flags POS/NEG bits to indicate progress. The FAN53526UC89X ensures monotonicity and avoids undershoot/overshoot through controlled ramping.

What thermal protection mechanisms are implemented in the FAN53526UC89X?

The FAN53526UC89X incorporates thermal shutdown at 150 °C (typical) with 17 °C hysteresis, as defined in Table 8. When junction temperature exceeds this threshold, switching halts until temperature falls below 133 °C. The MONITOR register (bit 6) reports UVLO status but does not directly indicate thermal state; designers must infer thermal events from load derating or external temperature monitoring. The FAN53526UC89X also features θJA = 42 °C/W (simulated), requiring proper PCB copper area for thermal dissipation.

Can the FAN53526UC89X operate with only hardware enable (EN pin), without using I²C communication?

Yes, the FAN53526UC89X can operate solely with hardware enable: asserting EN high activates regulation using the default VSEL0 voltage (1.15625 V for FAN53526UC89X). All registers retain their values during EN low, and the part draws <1 µA in shutdown. I²C is optional for dynamic reconfiguration; basic on/off and fixed-voltage operation require only EN, VIN, and proper passive components. The FAN53526UC89X functions as a standalone regulator without I²C firmware overhead.