Renesas ISL6251AHAZ

Overview

ISL6251AHAZ from Renesas Electronics (formerly Intersil) is a multi-chemistry battery charger controller IC for Li-Ion/Li-Polymer and NiMH battery packs in portable computing systems. It implements a fixed-frequency 300kHz synchronous buck topology with diode emulation, ±0.5% charge voltage accuracy over –10°C to +100°C, programmable 2–4 cell selection via CELLS pin, and ±3% input current limit accuracy. It is used in notebook computers to manage simultaneous system load and battery charging from AC adapters.

For engineers reviewing the ISL6251AHAZ datasheet, ISL6251AHAZ pinout, ISL6251AHAZ application, or ISL6251AHAZ equivalent, this page delivers verified technical context, real-world design meaning of specifications, validated QSOP-24 pin functions, confirmed alternative parts with documented functional differences, and supply-chain support details specific to ISL6251AHAZ.

Technical Context

The ISL6251AHAZ integrates dual error amplifiers - one for voltage regulation (VCOMP) monitoring CSON, and two for current regulation (ICOMP) controlling both battery charge current (via CSOP/CSON) and adapter input current (via CSIP/CSIN). Its fixed 300kHz PWM current-mode control includes feed-forward line regulation and adaptive dead-time gate drive to prevent shoot-through between UGATE and LGATE outputs.

It supports three battery configurations: CELLS = VDD for 4S (up to 17.64V), CELLS = GND for 3S (12.6V), and CELLS = floating for 2S (8.4V); VADJ adjusts per-cell termination voltage by ±5% around 4.2V using VREF (2.39V). The ISL6251A variant adds ±25% accurate trickle charge current limit capability not present in ISL6251.

Key Specifications

Pinout & Package

ISL6251AHAZ is housed in a 24-lead QSOP package (M24.15), RoHS-compliant, with operating temperature range –10°C to +100°C. Thermal resistance θ_JA = 88°C/W.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar battery charger controller applications.

Compared with ISL6251HAZ, ISL6251AHAZ adds verified trickle charge accuracy for battery recovery, while RT9466E trades external MOSFET flexibility and adapter current visibility for integration - making ISL6251AHAZ the only choice for high-fidelity, adapter-coordinated multi-chemistry charging in portable computing.

Availability

ISL6251AHAZ is available at Aetrix Electronics and suitable for notebook computers, sub-notebooks, and desknotes requiring stable component supply with guaranteed long-term lifecycle support and RoHS-compliant sourcing.

Supply support for ISL6251AHAZ 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

Renesas Electronics acquired Intersil in 2017 and maintains full product support, documentation, and manufacturing continuity for the ISL6251A family.

The ISL6251A series was designed specifically for cost-sensitive, high-efficiency battery charging in portable computing - integrating adapter current limiting, multi-cell Li-ion regulation, and thermal-safe shutdown in a single QSOP package.

FAQ

What battery chemistries does the ISL6251AHAZ support?

The ISL6251AHAZ supports Li-Ion, Li-Polymer, NiMH, and NiCd batteries. Its programmable VADJ pin allows adjustment of per-cell termination voltage from 3.99V to 4.41V, and the CELLS pin configures 2-, 3-, or 4-cell topologies. The ISL6251AHAZ datasheet explicitly confirms compatibility with all these chemistries, and its ±25% trickle charge current limit (unique to the 'A' variant) enhances safe recovery of deeply discharged NiMH cells.

How does the ISL6251AHAZ prevent AC adapter overload?

The ISL6251AHAZ prevents AC adapter overload using its dedicated adapter current sensing path (CSIP/CSIN) and ACLIM pin. When the differential voltage across CSIP–CSIN exceeds the threshold set by ACLIM (e.g., 75mV when ACLIM is floating), the IC dynamically reduces battery charge current while maintaining system load - ensuring total input current stays within limit. This real-time regulation is confirmed in the ISL6251AHAZ datasheet's "Input Current Limit Threshold" table and functional block diagram.

What is the purpose of the VADJ pin on the ISL6251AHAZ?

The VADJ pin on the ISL6251AHAZ adjusts the per-cell battery charge termination voltage between 4.2V ±5% (3.99V to 4.41V). Connecting VADJ to VREF sets +5%, floating sets nominal 4.2V/cell, and grounding sets –5%. This enables chemistry-specific optimization - for example, lowering VADJ to extend Li-ion cycle life or raising it for higher capacity NiMH packs. The ISL6251AHAZ datasheet specifies ±0.5% overall voltage accuracy across this range.

Does the ISL6251AHAZ require external MOSFETs?

Yes, the ISL6251AHAZ requires external N-channel MOSFETs driven by its UGATE and LGATE pins. It is a controller IC - not a monolithic charger - and relies on external high-side and low-side switches, an inductor, and input/output capacitors. This architecture allows scalable current handling (up to 10A+ with appropriate FET selection) and thermal partitioning, as confirmed in the ISL6251AHAZ typical application circuits (Figures 12 and 13) and "Theory of Operation" section.

What is the difference between ISL6251AHAZ and ISL6251HAZ?

The ISL6251AHAZ includes ±25% accurate trickle charge current limiting, while the ISL6251HAZ does not. Both share identical pinout, package (QSOP-24), core charging specs (±0.5% voltage accuracy, ±3% current limits), and operating range. The 'A' suffix denotes the enhanced trickle charge capability - critical for safe pre-charging of deeply discharged batteries. This distinction is explicitly stated in the ISL6251AHAZ datasheet's "Features" list and electrical specifications table.