Maxim\'s USB Emulator Consolidates In-Car Device Charging

Madison, Wisc. -- Carmakers are scrambling to keep up with the growing demand by drivers and passengers with portable devices who expect every car to accommodate their communication and entertainment needs. Against that backdrop, Maxim Integrated, an analog integration company, has found a new market opportunity.

For example, Maxim has developed an automotive-quality USB solution that can recognize and charge directly from the vehicle's battery any portable device people bring into a car. Maxim recently rolled out MAX 16984, an automotive-grade DC-DC converter with USB emulator.

Previously, many consumers were frustrated when they tried to charge their portable devices in cars. Typically, they found the process not so reliable, as witnessed by their iPhones not getting charged fast enough in a car.

Cars need to be prepared for a variety of scenarios to accommodate disparate devices. Carmakers also need a scalable solution because vehicles are now expected to accommodate, not just a single mobile device, but also a growing number of USB modules.

As Maxim explained, cars need to support the constantly evolving specifications of consumer devices, and they must offer charging and data transfer capabilities for those USB-equipped portable devices. Further, these mobile devices will require added protection so that they can reliably interface with the often harsh automotive environment, the company added.

More specifically, vehicles need a solution with an automotive-quality DC-DC converter that can drive up to 2.5 A with dynamic voltage adjustment, Maxim said. They require a USB charge emulator that can establish a handshake between a mobile device and upstream host instructing the mobile device to increase its charge current. The vehicles also need integrated electrostatic discharge (ESD) diodes and USB protection switches for automotive USB host applications.

Functions that used to be carried out by three separate ICs -- a separate power supply chip, a USB protection device and a device handing external functions -- are now integrated into one chip in MAX 16984, said Kent Robinett, Maxim’s Global Automotive Segment Leader.

It’s also important to note that passengers in a car aren’t always charging their devices or getting entertained by their mobile devices in the front seat. USB ports in the back seat mean that a passenger’s mobile device is placed at the end of three-meter embedded USB cables. The longer the distance, the likelier a drop in voltage and a reduction in charging current to happen. “That’s when adaptive voltage capability becomes important,” said Robinett.

He noted, by showing the chart below, that portable devices "will not charge properly, unless voltage drop across long captive cables is accounted for.