Renesas ISL85403EVAL1Z

Overview

ISL85403EVAL1Z from Renesas Electronics is an evaluation board designed to rapidly assess the ISL85403 synchronous switching regulator in 2-stage boost-buck and synchronous buck configurations. It supports 4V–40V input, delivers 5.0V/2.5A output, operates at 500kHz, and targets low-power point-of-load applications requiring both step-up and step-down voltage conversion.

For engineers reviewing the ISL85403EVAL1Z datasheet, ISL85403EVAL1Z pinout, ISL85403EVAL1Z application, or ISL85403EVAL1Z equivalent, this board enables fast functional validation, switching frequency programming via R8, external clock synchronization via J13, and hardware reconfiguration between boost-buck and buck topologies using documented jumper and component changes.

Technical Context

The ISL85403EVAL1Z implements the ISL85403 IC - a flexible DC/DC controller with integrated 127mΩ high-side MOSFET - in a fully assembled, tested PCB layout optimized for performance and thermal management. It demonstrates dual-mode operation: default 2-stage boost-buck (VIN 4–40V → VOUT 5V) and field-modifiable synchronous buck (VIN 8–40V → VOUT 5V).

Key design features include programmable switching frequency (500kHz default, adjustable via R8), SYNC input (J13) for external clock synchronization, soft-start control, and configurable feedback network (R3/R4) for output voltage adjustment. The board includes discrete power components - DR125-100-R and DR125-6R8-R inductors, SS6P3LHM3/86A Schottky diodes, and BSZ100N06LS3G MOSFET - selected to match ISL85403's drive and current-handling capabilities.

Key Specifications

Availability

ISL85403EVAL1Z is available at Aetrix Electronics and suitable for power supply validation, embedded system prototyping, and industrial point-of-load design requiring stable component supply, rapid topology verification, and hardware reconfigurability.

Supply support for ISL85403EVAL1Z 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 and power management ICs, and SoC solutions for automotive, industrial, and enterprise applications.

The ISL85403EVAL1Z belongs to Renesas' evaluation platform portfolio for its ISL85403 flexible switching regulators - engineered to simplify development of compact, efficient, multi-topology DC/DC converters for wide-input industrial and embedded systems.

FAQ

What is the primary function of the ISL85403EVAL1Z?

The ISL85403EVAL1Z is a dedicated evaluation board for the ISL85403 synchronous switching regulator IC. It provides a ready-to-use hardware platform to validate the device's performance in two key configurations: 2-stage boost-buck (4V–40V input to 5V output) and synchronous buck (8V–40V input to 5V output). The ISL85403EVAL1Z includes all necessary passive and active components, test points, and configuration options - enabling immediate bench testing without custom PCB design.

Can the ISL85403EVAL1Z be used to evaluate other topologies beyond boost-buck and buck?

No - the ISL85403EVAL1Z is specifically configured and validated for the 2-stage boost-buck and synchronous buck modes only. While the underlying ISL85403 IC supports noninverting buck-boost operation per its datasheet, the ISL85403EVAL1Z board layout, component selection (e.g., fixed inductor values L1/L2, diode D1 placement), and documented modification procedures do not support or validate that topology. Users requiring buck-boost evaluation must refer to alternate reference designs or custom implementation.

How is output voltage adjusted on the ISL85403EVAL1Z?

Output voltage on the ISL85403EVAL1Z is set by the feedback resistor divider formed by R3 (52.3kΩ) and R4 (10kΩ), yielding a default 5.0V output per Equation 1 in the user manual. To change VOUT, replace R3 and/or R4 with values calculated using VOUT = VREF × (1 + R3/R4), where VREF = 0.8V (ISL85403 internal reference). Note: increasing VOUT requires upgrading output capacitors (e.g., C57/C59) to higher voltage ratings as specified in the manual.

Does the ISL85403EVAL1Z support external clock synchronization?

Yes - the ISL85403EVAL1Z supports external clock synchronization via the SYNC terminal located at J13. When an external clock signal is applied to J13, the ISL85403 IC synchronizes its internal switching frequency to that signal, enabling noise reduction in systems with multiple switching regulators or compliance with EMI timing constraints. This functionality is confirmed in the "Quick Test Setup" and "Functional Description" sections of UG024 Rev 0.00.

What modifications are required to convert the ISL85403EVAL1Z from boost-buck to synchronous buck mode?

Converting the ISL85403EVAL1Z to synchronous buck mode requires seven documented hardware changes: (1) populate Q1 with a suitable MOSFET, (2) remove shunt from J16, (3) install 0Ω at R32 and 4.7kΩ at R5, (4) remove R22, (5) short EXT_BOOST to ground by replacing R30 with 0Ω and removing R31, (6) optionally remove D1, and (7) adjust VCC switch-over components (R28/R29/R6) if needed. All steps are detailed in the "Board Modification for the Synchronous Buck Configuration" section of UG024.