STMicroelectronics EVAL5985

Overview

EVAL5985 from STMicroelectronics is an evaluation board for the L5985 2 A step-down switching regulator IC, designed to demonstrate and validate its operation in buck converter applications. It supports input voltages from 2.9 V to 18 V, delivers up to 2 A DC output current, features adjustable output voltage starting at 0.6 V, and operates at a programmable switching frequency from 250 kHz up to 1 MHz. The board implements the VFQFPN8 (3 mm × 3 mm) packaged L5985 with internal P-channel MOSFET, soft-start, inhibit control, and thermal/overcurrent protection - validated for use in LCD TV power supplies and FPGA core voltage regulation.

For engineers reviewing the EVAL5985 datasheet, EVAL5985 pinout, EVAL5985 application, or EVAL5985 equivalent, this board enables rapid functional validation of the L5985's voltage-mode PWM control, synchronization capability, zero-load operation, and feedforward-enhanced transient response - critical for industrial DC-DC module design and consumer audio power staging.

Technical Context

The EVAL5985 board hosts the L5985 IC in VFQFPN8 package and implements a complete non-isolated synchronous-buck reference design with external diode, input/output capacitors, compensation network, and test points. It exposes all key control pins - INH for enable/disable, SYNCH for master/slave synchronization, COMP for loop compensation, and FB for feedback - enabling full characterization of soft-start timing (7.4–9.1 ms), UVLO behavior (2.9 V turn-on, 0.175 V hysteresis), and hiccup-mode overcurrent recovery.

Thermal performance is optimized via the exposed pad of the VFQFPN8 package (R_thJA ≈ 60 °C/W on demo board) and layout-optimized copper pour. The board supports both fixed-frequency operation (250 kHz default) and resistor-programmed frequencies up to 1 MHz using the FSW pin, while preserving voltage and frequency feedforward functionality to maintain stable PWM gain across input and frequency variations.

Key Specifications

Availability

EVAL5985 is available at Aetrix Electronics and suitable for LCD TV power supplies, FPGA/PLD core voltage regulation, and XDSL modem DC-DC modules requiring stable component supply, fast prototyping turnaround, and production-ready reference design validation.

Supply support for EVAL5985 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

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, specializing in power management, microcontrollers, and analog/mixed-signal ICs for automotive, industrial, and consumer markets.

The EVAL5985 belongs to ST's dedicated evaluation platform series for DC-DC regulators, engineered to accelerate design-in of high-efficiency, thermally robust buck converters targeting space-constrained and thermally demanding applications such as set-top boxes and optical storage drives.

FAQ

What input and output capacitors are populated on the EVAL5985 board?

The EVAL5985 board uses a 10 µF/25 V multilayer ceramic capacitor (MLCC) at the input (Murata GRM31 or equivalent) and a 47 µF/6.3 V low-ESR tantalum or polymer capacitor at the output. These values are selected per ST's application guidelines to ensure RMS current handling, stability with the L5985's Type II/III compensation, and minimal voltage ripple under 2 A load steps.

Can the EVAL5985 be used to evaluate synchronization between multiple L5985 devices?

Yes - the board exposes the SYNCH pin with appropriate routing and test points, enabling direct connection to a second EVAL5985 or another L5985-based board. When synchronized, one device acts as master (higher frequency) and the other as slave, achieving 180° phase shift to reduce input capacitor RMS current - verified per Figure 4 and Section 4.1 of the L5985 datasheet.

Does the EVAL5985 support adjustable output voltage, and how is it configured?

Yes - output voltage is adjusted via an external resistor divider from V_OUT to the FB pin. The L5985 regulates to 0.6 V at FB; thus, V_OUT = 0.6 V × (1 + R1/R2). The board includes footprint options for R1/R2 and pre-populates a standard divider for 3.3 V output, but users can replace resistors to target 1.2 V, 1.8 V, or other values within the 0.6–V_IN range.

Is thermal performance characterized on the EVAL5985, and what is the maximum ambient temperature for 2 A operation?

Yes - ST characterizes thermal performance on the EVAL5985 with R_thJA ≈ 60 °C/W (mounted on demo board). At 2 A, 12 V_IN, 3.3 V_OUT, and 250 kHz, junction temperature rise is ~60 °C above ambient. Therefore, continuous 2 A operation is validated up to +70 °C ambient while staying below the 150 °C thermal shutdown threshold - confirmed in Section 5.5 and Table 3 of the datasheet.