USB Power Delivery & PMIC Integration on Embedded Systems Development

USB Power Fundamentals

Mon, 01 Jan 0001 00:00:00 +0000

USB Power Fundamentals#

USB power delivery has evolved through several specification revisions, each increasing the available current and introducing new detection mechanisms. What started as a simple 5V bus with a 100mA default has grown into a system that can advertise up to 3A at 5V through passive resistor configuration alone — before any digital negotiation takes place. Understanding each layer of this evolution is essential for embedded power design, because a device that fails to detect its source type correctly may draw too little current (leaving charging performance on the table) or attempt to draw too much (causing the source to shut down or the cable to overheat).

USB PD Negotiation

Mon, 01 Jan 0001 00:00:00 +0000

USB PD Negotiation#

USB Power Delivery (PD) is a digital protocol that runs over the CC pin of a USB Type-C connection, enabling source and sink to negotiate voltage and current levels far beyond the 5V default. PD uses Biphase Mark Coding (BMC) at 300 kbaud to exchange structured messages that describe what the source can provide and what the sink wants to consume. The protocol is layered — a physical layer handles encoding and signaling, a protocol layer manages message framing and CRC, and a policy layer implements the negotiation state machine.

PMIC Selection & Integration

Mon, 01 Jan 0001 00:00:00 +0000

PMIC Selection & Integration#

A Power Management IC (PMIC) integrates multiple power functions — battery charger, DC-DC converters, LDOs, power path management, and supervisory logic — into a single package. For battery-powered embedded systems that charge via USB, a PMIC replaces what would otherwise be three to six discrete ICs: a charger controller, a boost converter, one or two buck regulators, an LDO, and a fuel gauge. The integration reduces BOM count, PCB area, and design risk, since the PMIC vendor has already verified the interactions between the charger, power path, and voltage regulators in a tested reference design.

USB OTG & Source Mode

Mon, 01 Jan 0001 00:00:00 +0000

USB OTG & Source Mode#

USB On-The-Go (OTG) allows a battery-powered device to switch from its normal role as a USB peripheral (sink) to acting as a USB host (source), providing 5V power and data connectivity to downstream devices. In the legacy Micro-B connector world, OTG detection used the ID pin — grounding the ID pin through a special OTG cable signaled the device to assume the host role. With USB Type-C, OTG is subsumed into the broader concept of Dual Role Port (DRP), where the CC pin resistor configuration determines whether a port acts as source or sink, and roles can be swapped dynamically through USB PD role-swap messages.