Tag Archives: USB-C

What is USB Type-C Interface?

All new electronic devices are now coming with the USB-C interface, and this is revolutionizing the way people charge the devices. So far, most electronic devices had the micro-USB type-B connectors. With the USB Type-C connector, it is immaterial what orientation you use for the charging cable—the non-polarized connector goes in either the right side up or upside down. The connecting system is smart enough to figure out the polarity as a part of the negotiation process, and supports bidirectional power flow at a much higher level.

Earlier, the USB connectors handled only the 5 VDC fed into them. The USB-C port can take in the default 5 V, and depending on the plugged in device, raise the port voltage up to 20 V, or any mutually agreed on voltage, and a preconfigured current level. The maximum power delivery you can expect from a USB-C port is 20 V at 5 A or 100 W. This is more than adequate for charging a laptop. No wonder, electronic device manufacturers are opting for incorporating the USB-C into their next-generation products.

With the increasing power delivery through the USB Type-C ports, the computer industry has had to raise the performance requirement of the voltage regulator. Unlike the USB Type-B and the USB Type-A fixed voltage ports, the USB Type-C is a bidirectional port with a variable input, and an output range of 5-20 VDC. This adjustable output voltage feature allows manufacturers of notebooks and other mobile devices to use USB Type-C ports to replace the conventional AC/DC power adapters and USB Type-B and A terminals. Manufacturers are taking advantage of these features and incorporating dual or multiple USB Type-C ports into their devices.

However, using the current system architecture for implementing dual or multiple USB Type-C ports, leads to a complicated situation. It is unable to meet many requirements of the customers. As a solution, Intersil has proposed a new system architecture using the ISL95338 buck-boost type of regulator, and the ISL95521A, which is a combo battery charger. Use of these devices simplifies the design of the USB-C functions and fully supports all features. Applied on the adapter side, manufacturers can implement a programmable power supply, and it offers an adjustable output voltage that matches the USB-C variable input voltage.

In the proposed design, Intersil offers an architecture with two or more ISL95338 devices in parallel. Each of them interfaces a USB Type-C port to the ISL95521A battery charger. As this architecture eliminates several components from the conventional charging circuit, including individual PD controllers, ASGATE and OTG GATEs, it saves manufacturers significant costs. For charging a battery, power is drawn directly from the USB-C input to the ISL95521A, and the multiple ISL95338s offer additional options.

For instance, the user can apply two or more USB-C inputs with different power ratings for charging the battery fast. Therefore, the battery charge power is now higher than that supplied by a single USB-C input power. It also means there is no need for adding external circuitry to determine the different power rating operations of the paralleled ISL95338 voltage regulators.

What is the MHL Specification?

A present, we are inundated with a plethora of digital devices. For example, we have set-top boxes or STBs, Blu-ray players, AVRs, automobile information systems, monitors, TVs, tablets, smartphones and others making up this large and diverse ecosystem. For getting all these to plug-and-play together is no mean feat and the latest standard connector that manufacturers are adopting for compatibility is the USB Type-C.

The protocol that the USB Type-C will be using for the delivery of audio, video, data and power is the MHL Alt Mode for the superMHL and MHL 1, 2 and 3 specifications. MHL Alt Mode over USB Type-C will allow interconnections of more than 750 million MHL devices. With USB Type-C, you can never plug-in a device in the wrong way – this is a reversible connector.

Backward compatible with USB 2.0 and USB 3.1, both Gen 1 and Gen 2, MHL Alt Mode for USB Type-C features power charging and Immersive audio such as DTS:X, Dolby Digital, Dolby Atmos and more. It allows transmission of 4K data at 60fps over a single lane or 8K data at 60fps over 4 lanes. You can use your existing remote to control existing MHL phones, as there is backward compatibility with existing MHL specifications.

The MHL Consortium has developed and published the MHL Alternate Mode for the superMHL and MHL 1, 2 and 3 specifications. They have established a liaison with the USB-IF and USB 3.0 Promotion Group for obtaining the official SVID and for ensuring the development of the specification confirms to USB Type-C, USB Billboard and USB Power Delivery specifications.

MHL Alt Mode over USB Type-C presents a single, small form factor connector, an ideal for many devices for delivering audio, video, data and power. You can simultaneously charge your smartphone, tablet or notebook when you connect them with larger displays such as car information systems, projectors, monitors and TVs
You will know your USB Type-C port on your host and device supports MHL if you see the USB-IF logo near the port. Smartphones and tablets with the MHL Alt Mode can easily connect to existing car infotainment systems, projectors, monitors and TVs. With MHL cables and MHL-to-HDMI adapters supporting USB Type-C, you can connect to HDMI Type A devices as well. For this, you will need a simple, thin MHL cable that has an HDMI Type A connector on one end and a USB Type-C connector on the other.

A user can use his existing TV remote to control the device as the MHL Alt Mode supports Remote Control Protocol as well. In contrast, an alternative technology DisplayPort from MPEG-LA does not offer the same compatibility. With the DisplayPort Alt Mode, the user would have to actually go to the connected device and manually control it.

Protocol adapters for the DisplayPort Alt Mode will not work for the MHL Alt Mode and vice-versa. Manufacturers will have to use proper labeling to identify DP Alt Mode or MHL Alt Mode on adapters to avoid consumers from being confused. Proper protocol adapters are necessary for the MHL Alt Mode to support VGA, DVI and HDMI displays.

What is Buck-Boost Charging?

With Apple unveiling their new MacBook on April 10, 2015, they also opened up a new era in power management for computing devices. The USB-C port in the new MacBook features a true all-in-one port. It is capable of delivering power and bi-directional data at the same time. The technology eliminates a separate charging port, as it integrates the charging functions into the USB-C port.

Intel has released their 6th generation processors, and very soon, a new generation of ultrabook computers, 2-in-1s, tablets, and external devices are expected in the market, ready with the USB-C port. However, with USB-C, fundamental changes are necessary in the existing power delivery architecture. This presents a new challenge to the system designers.

Power Delivery at Present

At present, almost all electronic devices charge through USB-A/B in low power applications. The traditional USB-A/B port offers 5 V DC at up to 2 A current capabilities, but this is insufficient when charging high-power devices. At present, such high-power devices require a separate AC adapter with tens of watts power rating for charging.

For instance, ultrabook computers use different battery stacks ranging from a single-cell battery to 4-cell batteries. Since each Li-ion battery has a typical operating voltage of 2.5 to 4.3 V, from discharge to fully charged status, the ultrabook may have a battery voltage ranging from 2.5 to 17.2 V. Ultrabook computers generally come with a hefty AC adapter with a 20V output.

Therefore, the charger within the ultrabook battery stack has to step down the 20 V DC to make it suitable to charge the battery. This is done through a buck topology. Again, the ultrabook has to provide 5 V on its USB-A/B port for charging an external USB device. To generate this 5 V USB power rail, the ultrabook may have to apply a boost topology if it is using a single-cell battery pack. If it has battery stack of more than one cell, the ultrabook may use a similar buck topology as it does for charging.

Moving to USB-C

USB-C is a standard interface to connect anything to anything. Even though the default is 5 V, the USB-C port is capable of negotiating with a plugged-in device to raise the port voltage to 12 V, 20 V, or any other mutually agreed voltage and mutually agreed current level. Therefore, the maximum power a USB-C port can deliver is 20 V at 5 A, or 100 W. This is more than what most ultrabooks require – about 60 W.

The main consideration involving the use of USB-C technology lies in the absence of input-to-output relationship, which would warrant the use of buck technology when using a 5-20 V adapter voltage to charge a 2.5-17.2 V battery. Likewise, there is no definite output-to-input relationship either, for which a boost topology would be suitable.

This is where the buck-boost approach finds its merit. This operates in buck mode when there is an input-to-output connection and in boost mode when there is an output-to-input connection – the USB-C port being bi-directional. This flexibility allows for a more efficient design using the smallest solution size. It offers the best design solution, achieving all the requirements of a system designer.