STMicroelectronics PM6680A

Overview

PM6680A from STMicroelectronics is a dual synchronous step-down controller with integrated 5 V/100 mA LDO, designed for industrial and FPGA power systems requiring two independently adjustable DC/DC outputs (0.9–5 V and 0.9–3.3 V), valley current sensing via R_DS(on), and constant-on-time architecture enabling fast transient response. It operates from 6–36 V input and delivers independent PGOOD signals, soft-start (2 ms fixed), and thermal shutdown.

For engineers reviewing the PM6680A datasheet, PM6680A pinout, PM6680A application, or PM6680A equivalent, key selection considerations include its VFQFPN-32 (5×5 mm) package, selectable switching frequencies (200/300 kHz to 400/500 kHz), pulse-skip vs. ultrasonic skip mode control, and use of external 1.237 V ±1% reference for precision feedback.

Technical Context

The PM6680A implements a constant-on-time (COT) PWM control architecture with voltage feed-forward, delivering near-constant switching frequency across input (6–36 V) and output (0.9–5 V / 0.9–3.3 V) ranges. Each channel features independent ENx, FBx, COMPx, and PGOODx pins, enabling asynchronous sequencing and loop compensation.

Valley current sensing uses low-side MOSFET R_DS(on) with dedicated CSENSE1/CSENSE2 inputs and zero-crossing comparators (±6 mV offset). The embedded integrator compensates DC error from output ripple, while SKIP pin selection enables PWM, pulse-skip, or no-audible-skip (≥33 kHz) modes - critical for noise-sensitive industrial environments.

Key Specifications

Pinout & Package

PM6680A is housed in a VFQFPN-32 (5 mm × 5 mm, 0.5 mm pitch) package with exposed thermal pad for enhanced power dissipation (R_thJA = 35 °C/W). Pin functions are validated per STMicroelectronics datasheet Rev 2 (Dec 2007), Table 2.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual synchronous step-down controller applications.

Compared with TPS54620RGYR and ISL6269CRZ, the PM6680A uniquely combines dual independent controllers, 6–36 V operation, integrated 5 V/100 mA LDO, and R_DS(on) current sensing - making it the only option for compact, high-VIN, self-contained dual-rail industrial power supplies.

Availability

PM6680A is available at Aetrix Electronics and suitable for industrial PLCs, FPGA power systems, high-density DC/DC modules, and embedded computer systems requiring stable component supply across extended temperature (-40 to +125 °C) and long-lifecycle production.

Supply support for PM6680A 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 specializing in power management, microcontrollers, and analog ICs for industrial, automotive, and embedded markets.

The PM6680A belongs to ST's high-efficiency DC/DC controller product line, engineered specifically for industrial automation and FPGA power delivery where wide-input-voltage operation, dual-rail flexibility, and robust protection are mandatory.

FAQ

What is the purpose of the V5SW pin?

V5SW controls the internal 5 V LDO (LDO5) bypass function. When V5SW > 4.9 V, the LDO shuts down and LDO5 connects directly to the external 5 V source via a 3 Ω max switch - improving efficiency under high load. When tied to GND, the LDO remains active. This pin enables dynamic efficiency optimization based on system power state.

How does the SKIP pin affect light-load efficiency?

The SKIP pin selects among three operating modes: tied to LDO5 enables continuous PWM; tied to GND enables standard pulse-skipping; tied to VREF enables ultrasonic pulse-skip (≥33 kHz). The latter avoids audible noise in sensitive environments while maintaining >85% efficiency at 10 mA load - confirmed in Figure 7 of the datasheet.

Can PM6680A drive high-side N-channel MOSFETs without external bootstrap diodes?

Yes. The HGATE1/HGATE2 outputs are fully integrated high-side drivers with internal charge pumps. BOOT1/BOOT2 pins connect to external 0.1 µF ceramic capacitors (not diodes) to sustain gate voltage during high-side conduction - per Figure 27 application schematic and Section 7.8 of the datasheet.

What is the minimum off-time (T_OFFMIN) and why does it matter?

T_OFFMIN is 350–500 ns at VIN = 24 V. This parameter limits the maximum achievable switching frequency and defines the lowest duty cycle possible - critical for regulating very low output voltages (e.g., 0.9 V from 24 V requires ~3.75% duty cycle). Exceeding T_OFFMIN causes pulse skipping or regulation loss.