Renesas ISL91108IINR-EVZ

Overview

ISL91108IINR-EVZ from Intersil is a dedicated evaluation board for the ISL91108IINZ fixed-output (3.3V) buck-boost regulator IC, supporting input voltages from 1.8V to 5.5V and delivering up to 1.6A DC output current with 2.6MHz switching frequency and 27.5µA quiescent current. It enables rapid validation of power delivery in space-constrained mobile applications using a single 1µH inductor and minimal external components.

For engineers reviewing the ISL91108IINR-EVZ datasheet, ISL91108IINR-EVZ pinout, ISL91108IINR-EVZ application, or ISL91108IINR-EVZ equivalent, this page provides verified board-level specifications, supported test conditions, layout guidance, and integration notes for smartphone, tablet, and wireless PA power supply design.

Technical Context

The ISL91108IINR-EVZ implements a complete reference design for the ISL91108IINZ IC, featuring a 20-bump WLCSP package (2.34mm × 1.72mm), synchronous 4-switch buck-boost topology, and automatic seamless mode transition between buck and boost operation. It supports both PFM and forced PWM modes via the MODE/SYNC pin and includes full protection against short-circuit, over-temperature (150°C shutdown), and undervoltage lockout (1.775V rising threshold).

This evaluation board validates key performance metrics including up to 95% peak efficiency at 3.3V output, soft-start ramp times of 2ms (buck) and 3ms (boost), and VOUT soft-discharge via a 110Ω internal resistor when EN is low. It uses two 10µF X5R input capacitors and two 22µF X5R output capacitors, aligned with recommended PCB layout practices for high-frequency switching stability.

Key Specifications

Availability

ISL91108IINR-EVZ is available at Aetrix Electronics and suitable for smartphone power management, tablet system-on-chip (SoC) rail generation, and 4G/LTE power amplifier biasing requiring stable component supply and fast prototyping support.

Supply support for ISL91108IINR-EVZ 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 solutions, now part of Renesas Electronics, with deep expertise in high-efficiency DC/DC conversion for portable and wireless systems.

The ISL91108 product line was designed specifically for ultra-compact, high-efficiency buck-boost regulation in battery-powered mobile devices where input voltage may fall below or rise above the required output rail.

FAQ

What is the primary purpose of the ISL91108IINR-EVZ evaluation board?

The ISL91108IINR-EVZ evaluation board is a fully assembled and tested platform for validating the ISL91108IINZ fixed 3.3V buck-boost regulator IC under real-world conditions. It demonstrates proper implementation of the IC's 2.6MHz switching, automatic buck-boost mode transition, and light-load PFM efficiency - all using the recommended 1µH inductor and dual 10µF/22µF ceramic capacitor layout. Engineers use ISL91108IINR-EVZ to verify performance before integrating the ISL91108IINZ into final designs.

Does the ISL91108IINR-EVZ support adjustable output voltages?

No - the ISL91108IINR-EVZ is configured exclusively for the ISL91108IINZ variant, which delivers a fixed 3.3V output. It connects the VOUT pin directly to FB per the datasheet Figure 5 schematic. For adjustable output testing (1.0V–5.2V), the ISL91108IIA-EVZ board must be used with the ISL91108IIAZ IC and external resistor divider network. The ISL91108IINR-EVZ does not include R1/R2 or feed-forward capacitor provisions.

What are the critical layout requirements confirmed by the ISL91108IINR-EVZ board?

The ISL91108IINR-EVZ validates three critical layout practices: (1) placement of input (2×10µF) and output (2×22µF) X5R ceramic capacitors as close as possible to the ISL91108IINZ IC pins, (2) direct connection of PGND and GND planes with minimal vias to avoid ground bounce from high di/dt switching currents, and (3) routing LX1 and LX2 traces with short, wide copper paths to reduce EMI and conduction losses. These practices are documented in the AN1903 User Guide referenced in the ISL91108IINR-EVZ datasheet.

Can the ISL91108IINR-EVZ be synchronized to an external clock?

Yes - the ISL91108IINR-EVZ exposes the MODE/SYNC pin (D3) of the ISL91108IINZ IC, enabling external synchronization to a 2.75MHz–3.25MHz clock signal. When driven with a clean square wave within this range, the ISL91108IINZ switches at the external frequency instead of its internal 2.6MHz oscillator, reducing beat frequencies and improving EMI control in noise-sensitive RF sections. This capability is fully functional on the ISL91108IINR-EVZ board.

How does the ISL91108IINR-EVZ demonstrate soft-start and soft-discharge behavior?

The ISL91108IINR-EVZ implements the ISL91108IINZ's built-in soft-start (2ms buck / 3ms boost ramp) and soft-discharge (110Ω internal pull-down) functions. When EN is asserted, VOUT ramps smoothly to 3.3V without overshoot; when EN is pulled low, VOUT discharges through the internal resistor at a controlled rate - both behaviors measurable at test points on the ISL91108IINR-EVZ board. These features prevent inrush current and system reset glitches during power sequencing.