Renesas ISL85033-12VEVAL3Z

Overview

ISL85033-12VEVAL3Z from Renesas Electronics is an evaluation board for the ISL85033 wide-input negative-output buck-boost regulator, configured to deliver a fixed -12V output at up to 5A continuous current, with input voltage range from 4.5V to 16V (28V − |−12V|), current-mode control, and 500kHz default switching frequency. It supports adjustable negative VOUT from −3.3V to −15V and is used to validate power delivery in industrial and test equipment requiring stable negative rail generation.

For engineers reviewing the ISL85033-12VEVAL3Z datasheet, ISL85033-12VEVAL3Z pinout, ISL85033-12VEVAL3Z application, or ISL85033-12VEVAL3Z equivalent, this board enables rapid validation of negative-output DC/DC conversion, phase configuration, soft-start tuning, and power-good signaling referenced to VOUT - critical for embedded systems with split-rail or isolated analog front-ends.

Technical Context

The ISL85033-12VEVAL3Z implements a dual-channel synchronous buck topology reconfigured for negative output, where both channels operate out-of-phase by default to reduce input/output voltage ripple and minimize required bulk capacitance. The board uses the ISL85033IRTZ QFN28 IC with internal current-mode loop compensation and external feedback resistors (R3 = 112kΩ, R5 = 120kΩ) to set −12V output.

It features VOUT-referenced logic signaling: EN, FS, PGOOD, and SYNCIN are all referenced to VNEG (−12V), not GND, requiring level-shifting for host control. Protection includes hiccup-mode overcurrent, thermal shutdown, UVLO, and boot undervoltage detection - all validated per the ISL85033 datasheet under negative-rail operating conditions.

Key Specifications

Availability

ISL85033-12VEVAL3Z is available at Aetrix Electronics and suitable for industrial test equipment, analog signal conditioning modules, and embedded instrumentation requiring stable negative rail generation with fast design validation and layout verification.

Supply support for ISL85033-12VEVAL3Z 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 is a global semiconductor manufacturer specializing in microcontrollers, analog power devices, and timing solutions, with leadership in high-efficiency DC/DC regulation and automotive-grade power management.

The ISL85033-12VEVAL3Z belongs to Renesas' wide-VIN buck-boost evaluation platform family, designed specifically to accelerate development of negative-output power supplies in space-constrained industrial and test applications where GND-referenced controllers cannot be used.

FAQ

What is the primary function of the ISL85033-12VEVAL3Z evaluation board?

The ISL85033-12VEVAL3Z evaluation board demonstrates the negative-output configuration of the ISL85033 dual buck regulator, delivering a fixed −12V output at up to 5A. It provides a fully assembled, tested reference design with validated component selection, layout, and thermal performance - enabling immediate bench testing without custom PCB development. The board is not a standalone product but a tool to verify system-level behavior of the ISL85033IRTZ IC in negative-rail applications.

Can the ISL85033-12VEVAL3Z generate output voltages other than −12V?

Yes - the ISL85033-12VEVAL3Z can be reconfigured for −3.3V to −15V outputs by changing the feedback resistor R3 (and optionally R5 and C4 per Table 1). For example, −5V requires R3 = 43.2kΩ and −15V requires R3 = 142kΩ. The board includes solder pads and documentation (AN1636) for these modifications, preserving all protection and control functionality across the supported range.

Why are the EN and FS pins referenced to VNEG instead of GND on the ISL85033-12VEVAL3Z?

Because the ISL85033 operates with its ground reference at VNEG (−12V), all logic inputs - including EN and FS - must be referenced to that node to maintain correct voltage thresholds relative to the IC's internal circuitry. Driving EN from a GND-referenced source without level shifting risks invalid logic states or latch-up. The ISL85033-12VEVAL3Z schematic and AN1636 explicitly require level-shifting circuitry for host interface compatibility.

What is the default switching frequency of the ISL85033-12VEVAL3Z, and how is it changed?

The ISL85033-12VEVAL3Z defaults to 500kHz switching frequency when FS is tied to VCC via R9 (0Ω). To adjust frequency between 300kHz and 2MHz, remove R9 and connect R10 between FS and VNEG; values range from 383kΩ (300kHz) to 40.2kΩ (2MHz). This allows trade-offs between efficiency (lower fSW) and component size (higher fSW), as confirmed in Figures 2–4 of AN1636.

Does the ISL85033-12VEVAL3Z support phase interleaving, and what benefit does it provide?

Yes - the ISL85033-12VEVAL3Z supports user-selectable phase operation, with default out-of-phase (180°) channel timing. This reduces input and output voltage ripple amplitude and lowers RMS current stress on input capacitors and inductors, enabling smaller passive components and improved EMI performance. Phase control is implemented via internal register settings or external pin configuration per the ISL85033IRTZ datasheet.