PM6685TR

Overview

The PM6685TR is a dual step-down switching controller from STMicroelectronics, designed for notebook system power applications. It features a constant on-time architecture with lossless current sensing using low-side MOSFET RDS(on). The device provides fixed 5 V and 3.3 V outputs capable of delivering 100 mA peak current each. Input voltage ranges from 6 V to 28 V. Selectable switching frequencies include 200 kHz/300 kHz, 300 kHz/400 kHz, or 400 kHz/500 kHz, with a minimum selectable frequency of 33 kHz in pulse skip mode to avoid audio noise. Quiescent power is maximized at 4 mW.

Feature Summary

• Dual step-down topology with lossless current sensing via low-side MOSFETs
• Fixed 5 V and 3.3 V outputs with independent power good signals
• Selectable switching frequencies and pulse skipping for light load efficiency
• Embedded voltage feed-forward and output ripple compensation

Applications

• Notebook system power management
• Dual rail DC-DC conversion for portable electronics
• Battery-powered devices requiring high efficiency

Procurement Notes

Verify component status as the PM6685 series is listed as obsolete in official documentation. Confirm availability through authorized distributors or secondary market channels. Ensure compatibility with existing design specifications before procurement. Check for moisture sensitivity level (MSL) requirements during storage and handling. Validate that replacement components meet original electrical and thermal performance criteria.

Selection Notes

Select this controller for applications requiring dual independent buck converters with fixed output voltages. Consider its constant on-time architecture for fast transient response needs. Evaluate the selectable frequency options against EMI constraints and acoustic noise requirements. Assess the 6 V to 28 V input range suitability for specific battery or bus configurations. Review the 100 mA peak current capability per channel against load demands.

Part Context

The PM6685TR belongs to the PM6685 family of dual step-down controllers by STMicroelectronics. It is part of the PMIC - Power Management ICs subcategory. The device is specifically engineered for notebook power systems, offering integrated features like soft-start, under-voltage lockout, and over-voltage protection within a compact surface-mount package.

Replacement Considerations

Public confirmed substitute part numbers are not available in the provided source material. Due to the obsolete status of the PM6685 series, engineers should consult STMicroelectronics technical support or authorized distributors for potential last-time buys or equivalent alternatives.