Understanding OTG

LAVA SimulCharge adapters provide simultaneous charging and data access to select smartphones and tablets. It’s a technology that’s unique to LAVA and ensures the mobile device remains a USB Host when it’s plugged into power. This is what allows the mobile device to communicate with USB peripherals while it is receiving a charge.

LAVA’s Home Series adapters also feature a more common mobile adapter technology: OTG. This article will look at what OTG is and how it can be used.

Simply put, OTG stands for “On-the-Go.” It’s a mode available on many mobile devices that allows them to power and communicate with USB accessories. OTG adapters can connect to these mobile devices (usually via USB-C or Micro USB) and often provide additional ports, such as USB-A for peripherals or Ethernet for a wired network connection.

The Charge-Plus LAN HUB, for example, is a USB-C adapter that provides both a reliable 10/100 Fast Ethernet connection and two USB-A ports for peripherals. If the adapter is for personal use, you might add a USB keyboard and mouse to get PC-like functionality out of your tablet. If the mobile device is being used in a kiosk setup or as a POS terminal, you might connect a barcode scanner and receipt printer.

OTG adapters do not require external power as the OTG-capable mobile device can actually power the adapter and the peripherals connected to it. However, it’s the data connection that’s a necessity for OTG, not power. In fact, the amount of power a mobile device can deliver in OTG mode is limited.

If the peripherals require more power than the mobile device is capable of delivering in OTG mode, it may be advantageous to purchase a third-party powered USB hub. Powered USB hubs come with their own power supplies and so don’t need to be powered by the mobile device’s battery. The hub would connect to the OTG adapter through USB. The adapter, in turn, would be connected to the mobile device through its USB-C or Micro USB power port. Any additional peripherals would then be connected to the powered hub instead of the adapter. The mobile device still remains in OTG mode (it is still USB Host and can still communicate with the peripherals through the adapter) but the powered USB hub is what is actually powering them, not the mobile device.

Using a Home Series SimulCharge adapter, such as the Charge-Plus or LAN HUB, you can also do similar setup with the tablet or smartphone powering from an AC power source through the adapter. The key commonality of OTG and SimulCharge is that in both modes of operation, the mobile device remains USB Host. This is required for the mobile device to be able to interact with peripherals over USB.  A mobile device running on battery power is in USB Host mode by default. However, when it is charging, it loses its data access. This setup makes sense, considering most mobile devices only have the one USB port (USB-C or Micro USB). If the device is charging, there are not any free USB ports to plug anything else in.

However, a LAVA SimulCharge adapter allows the tablet or smartphone to both charge and communicate with peripherals. So you can power the mobile device through a Home Series SimulCharge adapter using its USB power supply. Like with the battery power setup, you can connect the powered USB hub to one of the Charge-Plus’ USB-A ports and additional peripherals to the powered hub’s ports.

For this implementation to work, you need to be able to keep the power domains of the mobile device’s power supply and powered USB hub separate. This means you need to purchase a powered USB hub that has an isolating diode, which is needed to prevent power feeding through from the power domain of the powered USB hub to the power domain of the mobile device’s power supply. Many cheaper powered USB hubs lack this functionality. If the powered USB hub attempts to deliver power to the adapter while it is also receiving power from the mobile device or power, it will not work properly.

While LAVA’s Charge-Plus SimulCharge adapters are capable of OTG, which most people use to both power peripherals from the mobile device’s battery, OTG has other uses. If the peripherals require more power than the mobile device can provide in OTG mode, you can hook up a third-party powered USB hub to the adapter. You can then add additional USB peripherals to the powered hub. OTG mode allows the mobile device to communicate with the peripherals but because the hub has its own power supply, it only draws data over the USB cable not power.

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