STMicroelectronics PM6681ATR

Overview

PM6681ATR from STMicroelectronics is a dual synchronous step-down controller with integrated 5 V and adjustable (0.9–3.3 V) LDOs, designed for high-efficiency power conversion in FPGA and embedded computer systems. It supports 6–36 V input, delivers two independently adjustable outputs (OUT1: 0.9–5 V; OUT2: 0.9–3.3 V), employs lossless R_DS(on) current sensing, and features constant-on-time architecture for fast transient response.

For engineers reviewing the PM6681ATR datasheet, PM6681ATR pinout, PM6681ATR application, or PM6681ATR equivalent, key selection criteria include its dual-channel COT control, selectable pulse-skip/no-audible-skip modes, independent Power Good signals, 1.237 V ±1% reference, and VFQFPN-32 package with exposed thermal pad.

Technical Context

The PM6681ATR implements a constant-on-time (COT) PWM control architecture per channel, using output ripple voltage for timing-enabling near-fixed frequency operation without external compensation. Each section integrates independent gate drivers, soft-start (2 ms fixed), soft-discharge, and negative current limit detection via PHASE-to-PGND sensing.

It embeds two LDOs: a fixed 5 V regulator (100 mA peak, shutdown-capable when V5SW > 4.9 V) and an adjustable 0.9–3.3 V LDO (100 mA peak, feedback via LDO FB). The 1.237 V reference (±1%, 50 µA drive) feeds both FB inputs and supports external divider-based output programming.

Key Specifications

Pinout & Package

VFQFPN-32 (5 mm × 5 mm) with exposed thermal pad - optimized for high-power density and thermal performance in space-constrained DC-DC modules.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual-buck controller applications.

Compared with TPS54620RTQR and ISL6269CRZ, the PM6681ATR uniquely integrates dual wide-VIN buck control, two LDOs, and a precision reference in VFQFPN-32-reducing total solution size and simplifying design for industrial and FPGA applications where flexibility and integration outweigh protocol-specific features.

Availability

PM6681ATR is available at Aetrix Electronics and suitable for FPGA system power, industrial 24 V embedded systems, and high-density DC-DC modules requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for PM6681ATR 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, specializing in power management, microcontrollers, and analog ICs for industrial, automotive, and consumer markets.

The PM6681ATR belongs to ST's high-efficiency DC-DC controller product line, engineered for space-constrained, high-reliability applications demanding wide input range, integrated bias supplies, and robust protection features.

FAQ

What is the purpose of the V5SW pin on the PM6681ATR?

The V5SW pin controls the operational mode of the internal 5 V LDO (LDO5). When V5SW is connected to an external 5 V supply and exceeds 4.9 V, the LDO5 shuts down and the LDO5 pin connects directly to that supply via an internal 3 Ω switch. When tied to GND, LDO5 remains active to power gate drivers and external loads. This enables flexible power architecture choices.

How does the PM6681ATR achieve lossless current sensing?

The PM6681ATR uses the R_DS(on) of the low-side MOSFET as the current sense element. The CSENSE1 and CSENSE2 pins monitor the voltage drop across the MOSFET's channel during conduction, eliminating the need for discrete sense resistors. This reduces power loss, PCB area, and cost while maintaining accurate current limiting and negative current detection.

Can the two buck channels operate at different switching frequencies?

Yes. The FSEL pin accepts three logic levels (GND, VREF, or LDO5) to select one of three predefined frequency sets for both channels. While both channels share the same FSEL setting, their actual frequencies may differ slightly due to output voltage and input conditions - e.g., at VIN = 24 V, OUT1 = 3.3 V, and OUT2 = 1.8 V, typical frequencies are 200/300 kHz and 300/450 kHz respectively under FSEL = GND.

What protection features does the PM6681ATR provide?

The PM6681ATR includes latched undervoltage protection (UVP), non-latched overvoltage protection (OVP), thermal shutdown, and negative current limit detection. It also provides soft-start, soft-discharge, and independent open-drain Power Good signals for each output. These features ensure safe startup, fault containment, and system-level monitoring without external circuitry.