onsemi FAN48630UC45X

Overview

FAN48630UC45X from onsemi is a synchronous boost regulator with forced bypass mode, designed for Li-ion battery-powered systems requiring stable 4.5 V output from inputs as low as 2.35 V. It delivers up to 1500 mA continuous load current at VIN = 2.6 V boosting to 3.5 V, operates at 2.5 MHz switching frequency, and features true bypass operation when VIN exceeds target VOUT - enabling brownout prevention in portable audio and USB OTG applications.

For engineers reviewing the FAN48630UC45X datasheet, pinout, applications, or equivalent options, key selection criteria include its 4.50–4.76 V fixed output range, SLOW soft-start (1300 µs), OCP-activated forced bypass mode, 16-bump WLCSP package (1.78 × 1.78 mm), and integrated synchronous rectifier with 65–85 mΩ RDS(ON)P.

Technical Context

The FAN48630UC45X implements valley-current-mode control with 2.5 MHz nominal switching frequency in CCM and automatic frequency reduction in DCM for high light-load efficiency. Its dual-stage linear startup (LIN1/LIN2) and stepped soft-start ensure controlled inrush current during power-up, while the VSEL pin enables dynamic output voltage adjustment to mitigate undershoot during line transients.

Bypass entry is triggered when VIN > VOUT_TARGET + 25 mV (with hysteresis), activating internal P-channel switches Q1 and Q3 to establish a low-impedance path; exit occurs when VOUT falls below target. Forced Bypass Mode (via BYP pin) disables most bias circuits except OCP and thermal protection, achieving ≤90 µA quiescent current at VIN = 3.5 V.

Key Specifications

Pinout & Package

Package: 16-bump Wafer-Level Chip-Scale Package (WLCSP), 0.4 mm pitch, 1.78 × 1.78 × 0.586 mm, case 567SY. Exposed die attach pad is not electrically connected.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar boost regulator applications.

Compared with TPS610995YFFR and MAX17222ETA+T, the FAN48630UC45X uniquely combines 1500 mA capability, OCP-protected forced bypass, VSEL-driven transient mitigation, and PG fault signaling in a 1.78 mm² WLCSP - making it optimal for space-constrained, high-reliability portable systems demanding robust brownout immunity.

Availability

FAN48630UC45X is available at Aetrix Electronics and suitable for portable audio, USB OTG host supply, LTE/3G RF power management, and low-power sensor node applications requiring stable component supply across production lifecycles.

Supply support for FAN48630UC45X 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, sensing, and connectivity solutions for automotive, industrial, cloud, and consumer markets.

The FAN48630UC45X belongs to the TINYBOOST® family of ultra-compact synchronous boost regulators, engineered specifically for Li-ion battery-powered portable electronics where minimal footprint, high efficiency at light loads, and seamless bypass transition are critical design requirements.

FAQ

What is the exact output voltage range of the FAN48630UC45X?

The FAN48630UC45X is factory-trimmed to deliver a fixed output voltage between 4.50 V and 4.76 V under all operating conditions - this range is specified in Table 1 of the datasheet and confirmed across −40°C to +85°C ambient temperature. The device does not support external feedback or adjustable output; the voltage is set internally and cannot be modified by external resistors or pins. This precise range ensures compatibility with 4.5 V USB OTG host specifications and 4.5 V logic rails in portable audio subsystems. The FAN48630UC45X achieves ±2% DC accuracy over load and temperature per Table 7's VREG parameter.

How does the Forced Bypass Mode function in the FAN48630UC45X?

In Forced Bypass Mode, the FAN48630UC45X asserts a LOW signal on the BYP pin to fully enhance internal P-channel switches Q1 and Q3, creating a low-resistance path from VIN to VOUT. Unlike Auto Bypass, this mode remains active regardless of VIN–VOUT relationship and disables most internal circuitry - reducing quiescent current to ≤90 µA at VIN = 3.5 V. Critically, OCP protection remains active: if the voltage drop across the bypass path exceeds 200 mV (indicating short-circuit), the FAULT state triggers and PG is pulled LOW. The FAN48630UC45X exits Forced Bypass only when BYP is released HIGH and EN remains asserted.

What inductor value is required for the FAN48630UC45X, and why is saturation current critical?

The FAN48630UC45X requires a 0.47 µH shielded inductor rated for ≥3.8 A saturation current - as specified in Table 2 and Figure 1's typical application. This high saturation rating is essential because the device employs valley-current limiting, allowing peak inductor current to reach 3.8 A briefly during overload or startup transients. Using an inductor with lower saturation current causes premature core saturation, increasing ripple, reducing efficiency, and potentially triggering overcurrent faults. The FAN48630UC45X's 2.5 MHz switching frequency enables physically small 0603-size inductors like Toko DFE201612C, but their DC resistance must remain ≤40 mΩ to maintain >94% efficiency at full load.

Can the FAN48630UC45X operate with input voltage below 2.35 V?

No - the FAN48630UC45X incorporates an under-voltage lockout (UVLO) circuit that disables regulation when VIN falls below 2.35 V (with 200 mV hysteresis), as defined in Table 7's VUVLO parameter. Below this threshold, the device enters shutdown mode with IQ ≤5 µA, and VOUT collapses. This behavior is intentional to prevent unstable operation and potential damage to downstream components. While some Li-ion cells may briefly dip below 2.35 V during heavy discharge, the FAN48630UC45X is not rated for such operation. For systems requiring deeper discharge support, a different regulator with lower UVLO (e.g., 2.0 V) must be selected. The FAN48630UC45X's minimum functional VIN is strictly 2.35 V.

What is the purpose of the VSEL pin on the FAN48630UC45X, and how is it used?

The VSEL pin on the FAN48630UC45X enables dynamic adjustment of the output voltage target (VOUT_TARGET) during active boost operation - not in bypass mode. When asserted HIGH, it increases VOUT_TARGET by a fixed amount (e.g., +100 mV or +200 mV depending on internal trimming) to pre-empt voltage droop during rapid load transients. This feature mitigates undershoot without requiring oversized output capacitance, as demonstrated in Figure 28 of the datasheet. VSEL must be driven by a clean logic signal (VIH ≥1.2 V, VIL ≤0.4 V); floating or AC-coupled connections will cause unpredictable behavior. The FAN48630UC45X uses VSEL exclusively for transient response enhancement - it does not provide programmable output voltage selection across multiple values.