Page 34 - EngineerIT April 2022

ELECTRONICS

Simplify a USB-C PD design using a

standalone PD controller

By Sagar Khare, Business Manager, Battery Power Solutions Business Unit at Maxim Integrated

he USB power delivery (PD) market continues to grow in portable, battery-operated,
electronic devices like cell phones, laptops, wireless speakers, power tools and much
Tmore. USB PD provides a great benefit to consumers because it can provide up to
240W (in the USB PD Revision 3.1 specification) from the same USB Type-C connector.
Figure 1 depicts a cell phone being charged by a USB Type-C connector.
USB PD poses new power requirement challenges because of the variety of voltage and
current combinations available – 5V, 9V, 15V, 20V, 28V, 36V, 48V and 1.5A, 3A, 5A, etc. – to
supply the wide range of power the USB PD standard can provide. The power source such
as a wall adapter and the in-line devices such as a cell phone, communicate their power
capabilities and power needs respectively, in proper voltage and current levels before the
source provides power over the USB cable.
Some solutions require multiple integrated circuits (ICs), including port detectors,
micro-controllers and chargers for power delivery. While these solutions work, they take
up space on a board, increase the solution cost and require custom firmware, which can be
time-consuming to create.
A standalone PD controller can help address these challenges by managing the power Sagar Khare
negotiations without firmware development.
This article will briefly show how the assimilation of 5V, 9V, 15V, 20V, 28V, 36V and 48V be a thing of the past.
voltage rails provides versatility in power delivery, requiring fewer cables around the house. Before we begin looking at USB PD,
It then introduces Analog Devices’ MAX77958 standalone PD controller that eliminates the it is essential to revisit previous USB
need for custom firmware by including port detection and non-volatile memory. standards to understand some of the
USB PD benefits and challenges. The first
USB-C PD power requirements USB standards — USB 1.1 and USB 2.0 —
One of USB PD’s significant benefits is allowing consumers to charge their 2.5W cell were for data delivery rather than power
phones and their 25W cordless power drills using the same cable and power adapter. The delivery. They only allow for maximum
days of having drawers filled with different cables or never finding the correct charger will delivery of 5V and 500mA across a USB
cable.
Over time, consumers began
demanding more from USB. They wanted
to quickly charge a battery over a USB
cable, where a 500mA maximum current
was no longer adequate. The BC1.2
standard answered these consumer
demands by allowing the transfer of up to
7.5W — 5V and 1.5A — over a USB cable.
The BC 1.2 standard expands the
ability to charge a battery over USB, and
each new USB standard after BC1.2 has
added to power capacity. Type-C 1.3
extends the power capability to 15W
(max) while USB PD 3.0 upgrades the
system wattage to 100W (max). The most
recent specification update, USB PD3.1,
extends the power capability even further
Figure 1. A Cell Phone with a USB Type-C connector for charging up to 240W (max).

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