Renesas ISL6446IAZ

Overview

ISL6446IAZ from Renesas (formerly Intersil) is a triple-output power controller integrating two 180° out-of-phase voltage-mode PWM buck controllers and one linear regulator controller, designed for broadband, DSL, and networking point-of-load regulation. It delivers precise 0.6V reference-based output regulation (±1.5% tolerance), programmable 100kHz–2.5MHz switching frequency, and lossless r_DS(ON)-based overcurrent protection - enabling compact, high-efficiency ATX and FPGA/ASIC power supplies.

For engineers reviewing the ISL6446IAZ datasheet, ISL6446IAZ pinout, ISL6446IAZ application, or ISL6446IAZ equivalent, this page provides verified technical context, validated pin functions, confirmed dual-PWM interleaving behavior, exact soft-start timing derivation, and real-world PGOOD delay dependency on f_SW.

Technical Context

The ISL6446IAZ implements independent voltage-mode PWM control per channel with dedicated error amplifiers (88dB DC gain, 15MHz GBWP), synchronized 180° phase-shifted operation to reduce input ripple, and a transconductance-based linear controller (2A/V gain) driving external PNP or PMOS pass devices. Each PWM uses lossless current sensing via upper MOSFET r_DS(ON) and a 110µA OCSET current source.

It features dual independent SS/EN pins (30µA pull-up, 0.85–1.05V enable threshold), programmable oscillator via RT-to-SGND resistor, and a PGOOD open-drain output that asserts only after both PWM outputs settle within ±10% and the linear output exceeds 75% of nominal - with delay inversely proportional to f_SW (e.g., 46ms at 1.4MHz).

Key Specifications

Pinout & Package

ISL6446IAZ is housed in a 24-lead QSOP package (M24.15), RoHS-compliant, with exposed pad not electrically connected. Pin layout optimized for dual-buck layout separation and thermal management: PGND (Pin 18) serves as common power ground for both lower gate drivers; SGND (Pin 6) is isolated signal ground referenced for all analog circuitry.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar triple-output power controller applications.

Compared with ISL6446IAZ, ISL65414IRZ offers higher phase count but omits the linear controller and independent enable logic, while TPS51220ARGER provides tighter integration for mobile but lacks lossless sensing and linear regulation - making ISL6446IAZ uniquely suited for fixed-logic broadband and industrial systems needing three coordinated, low-noise rails.

Availability

ISL6446IAZ is available at Aetrix Electronics and suitable for ATX power supplies, DSP/ASIC point-of-load regulation, and industrial networking applications requiring stable component supply, long-term lifecycle assurance, and RoHS-compliant packaging.

Supply support for ISL6446IAZ 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 technical and supply chain support for legacy Intersil power management ICs including the ISL6446 family.

The ISL6446 product line was engineered for high-density, multi-rail DC/DC conversion in broadband infrastructure - emphasizing interleaved efficiency, robust fault coverage, and flexible sequencing for DSL, cable modem, and enterprise switch applications.

FAQ

What is the minimum output voltage supported by the ISL6446IAZ PWM controllers?

The ISL6446IAZ PWM controllers support output voltages as low as 0.6V, set by the internal precision reference (0.600V ±0.0085V over –40°C to +85°C). This allows direct generation of core voltages for modern DSPs and FPGAs without external reference scaling. The ISL6446IAZ achieves ±1.5% total regulation tolerance across line, load, and temperature when using matched feedback resistors.

How does the ISL6446IAZ implement lossless overcurrent protection?

The ISL6446IAZ implements lossless overcurrent protection by using the upper MOSFET's r_DS(ON) as the current-sense element. A 110µA current source pulls down the OCSET pin, establishing a voltage threshold. When the PHASE node voltage falls below OCSET during the high-side FET on-time, an overcurrent condition is detected. This eliminates the need for a discrete sense resistor, reducing power loss and board area - a key feature confirmed in the ISL6446IAZ datasheet Section 3.10.

Can the ISL6446IAZ soft-start into a prebiased output voltage?

Yes, the ISL6446IAZ supports soft-start into prebiased outputs on both PWM channels. When the SS/EN pin voltage ramp crosses the prebiased output voltage, the high-side FET begins switching and the output ramps smoothly upward. If the output is prebiased above the target (but below OVP threshold), the ISL6446IAZ holds off switching until soft-start completes, then pulls the output down. This behavior is explicitly verified in Figures 14 and 20 of the ISL6446IAZ datasheet.

What determines the PGOOD assertion delay for the ISL6446IAZ?

The PGOOD assertion delay for the ISL6446IAZ is determined solely by the switching frequency: t_PGOOD = 0.065 / f_SW. At 1.4MHz, the delay is 46ms; at 300kHz, it extends to 217ms. There is no independent delay adjustment - the timer starts only after both PWM outputs reach regulation and the linear output exceeds 75% of nominal. This fixed relationship is documented in Equation 3 on page 12 of the ISL6446IAZ datasheet.

Is the linear controller in the ISL6446IAZ capable of supplying significant current?

No, the ISL6446IAZ linear controller is a transconductance amplifier (2A/V gain) driving an external PNP transistor or PMOS pass device - it does not supply current directly. Its LCDR output sinks ≥50mA to control the pass element base/gate. Output current capability depends entirely on the external pass device and heatsinking; typical implementations deliver up to 1A with proper thermal design. The ISL6446IAZ datasheet specifies LCDR sink current, not linear output current.