Renesas ISL91108IIAZ-T

Overview

ISL91108IIAZ-T from Intersil is a highly-integrated synchronous buck-boost DC/DC regulator with 4.2A internal switches, supporting adjustable output voltages from 1.0V to 5.2V across 1.8V–5.5V input range. It delivers up to 1.6A DC output current (PVIN = 2.8V, VOUT = 3.3V), achieves up to 95% efficiency, and features seamless auto-transition between buck and boost modes-ideal for battery-powered mobile power rails where input voltage crosses the regulated output.

For engineers reviewing the ISL91108IIAZ-T datasheet, ISL91108IIAZ-T pinout, ISL91108IIAZ-T application, or ISL91108IIAZ-T equivalent, key selection criteria include its 2.6MHz switching frequency, 27.5µA no-load quiescent current, WLCSP-20 (2.34mm × 1.72mm) package, and support for external synchronization (2.75–3.25MHz) in noise-sensitive RF power amplifier supplies.

Technical Context

The ISL91108IIAZ-T implements a fully synchronous 4-switch buck-boost topology with automatic mode transition logic that avoids output disturbance during VIN-to-VOUT crossover. Its PWM controller dynamically selects buck, boost, or hybrid operation based on real-time input/output voltage and load conditions.

It integrates dual MOSFET gate drivers with anti-shoot-through protection, a precision 0.80V FB reference (±1.2% accuracy), thermal shutdown (150°C trip, 35°C hysteresis), and short-circuit protection via FB voltage monitoring. The device supports both PFM (light-load optimized) and forced PWM (low-noise) modes via the MODE/SYNC pin.

Key Specifications

Pinout & Package

ISL91108IIAZ-T uses a 20-bump Wafer-Level Chip-Scale Package (WLCSP) with 0.4mm pitch, measuring 2.34mm × 1.72mm. The package features separate PGND (power ground) and GND (analog ground) pins to isolate high di/dt switching currents from sensitive feedback circuitry.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TPS63020DSJR and MAX77827AEWE+T, the ISL91108IIAZ-T provides the highest DC current density in the smallest WLCSP footprint while maintaining standalone operation and seamless mode transition-critical for space- and performance-constrained mobile power rails.

Availability

ISL91108IIAZ-T is available at Aetrix Electronics and suitable for smartphone core power rails, 4G LTE power amplifier supplies, and wearable health sensor hubs requiring stable component supply, long-term lifecycle assurance, and RoHS-compliant packaging.

Supply support for ISL91108IIAZ-T 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

Intersil Corporation is a leading provider of precision analog and power management ICs, now part of Renesas Electronics, with deep expertise in high-efficiency DC/DC conversion for mobile and portable systems.

The ISL91108 product line was designed specifically for ultra-compact, high-efficiency buck-boost regulation in battery-powered consumer electronics where input voltage frequently crosses the output setpoint.

FAQ

What output voltage range does the ISL91108IIAZ-T support?

The ISL91108IIAZ-T supports an adjustable output voltage range from 1.0V to 5.2V, set via an external resistor divider connected to the FB pin. Its internal feedback reference is tightly regulated at 0.80V ±1.2%, enabling accurate programming-for example, 187kΩ and 60kΩ resistors yield 3.3V output. This flexibility makes ISL91108IIAZ-T ideal for multi-rail systems where a single regulator can serve various I/O or core voltage requirements without changing the BOM.

How does the ISL91108IIAZ-T handle input voltage crossing the output voltage?

The ISL91108IIAZ-T automatically and seamlessly transitions between buck and boost operating modes as the input voltage rises above or falls below the regulated output voltage-without output disturbance or control-loop interruption. This behavior is enabled by its proprietary 4-switch synchronous architecture and real-time mode arbitration logic. For instance, when powering a 3.3V rail from a discharging Li-ion battery (4.2V → 2.8V), ISL91108IIAZ-T begins in buck mode, smoothly shifts to hybrid operation near 3.3V, then enters boost mode below 3.3V-all while maintaining ±2% output regulation and <10mVpp ripple.

What is the maximum continuous output current capability of the ISL91108IIAZ-T?

The ISL91108IIAZ-T delivers up to 1.6A of continuous DC output current under specified conditions: PVIN = 2.8V, VOUT = 3.3V, TA = +25°C. This rating reflects thermal and electrical limits of its integrated 4.2A MOSFETs operating in steady-state. At higher ambient temperatures or lower input voltages, derating applies per the thermal resistance (θJA = 66°C/W) and efficiency curves in the datasheet. The ISL91108IIAZ-T also supports 2.7A burst current for short durations (<600µs on-time, 4.6ms period), making it suitable for pulsed loads like RF power amplifiers.

Can the ISL91108IIAZ-T be synchronized to an external clock?

Yes, the ISL91108IIAZ-T supports external clock synchronization via its MODE/SYNC pin. When driven with a clean square wave signal between 2.75MHz and 3.25MHz, the device locks its internal oscillator to the external frequency-enabling EMI reduction through frequency dithering or alignment with system clocks. This feature is especially valuable in noise-sensitive applications such as RF front-ends or audio subsystems. The MODE/SYNC pin retains dual functionality: pulled HIGH for auto PFM mode, LOW for forced PWM, and driven with AC signal for sync-requiring no additional configuration pins or registers.

What package type and dimensions does the ISL91108IIAZ-T use?

The ISL91108IIAZ-T uses a 20-bump Wafer-Level Chip-Scale Package (WLCSP) with 0.4mm pitch, measuring 2.34mm × 1.72mm and 0.5mm maximum height. Its footprint is defined in Package Outline Drawing W4x5.20F, featuring separate PGND and GND balls to isolate high-current switching paths from analog reference circuitry. This ultra-compact, low-profile package enables placement directly beneath thin displays or within narrow bezels-common in modern smartphones and wearables-while maintaining thermal performance via direct die-to-PCB conduction through the exposed metal pad.