Want to see what's inside a portable Wi-Fi router?
The HooToo TripMate. Image courtesy of Amazon.
The Tripmate is a 3-in-1 gadget that can act as a portable charger, a personal hotspot, or a file-sharing hub. This is a compact device that is only 96mm long, 44mm wide, and 29mm thick.
Opening It Up
There were no screws on this outside of this enclosure. The plastic shell was tightly clipped together. To open it, a small flathead screwdriver was used to separate the halves.
The two pieces of plastic shell open
Once the shell was separated, the battery, which was held in place with foam tape, could then be removed. The five-position connector on the battery was then unplugged from the circuit board. The circuit board was held in place with more plastic clips.
Plastic clips hold the PCB into place
Circuit Board
The top of the PCB
There is a single circuit board inside of this travel router, measuring 94mm by 32mm. This small PCB contains surface mount components on both sides. This a pretty typical looking circuit board with green solder mask and white silkscreen on both sides.
The bottom of the PCB
Battery Pack
The two-cell 18650 battery pack
As I mentioned, this device is not only a travel router but also a USB battery pack. The product description lists the capacity of the battery as 6000mAh. In this battery pack are two 18650-sized lithium ion cells in parallel with supporting circuitry for safety.
The cells in this battery are Samsung ICR-18650-30B cells with a nominal capacity of 2950mAh, close to the advertised capacity. The battery originally had a plastic wrapping on it that was removed for the images.
System on a Chip
The Ralink SOC
At the heart of this router is a Ralink RT5350F system on a chip. This SOC offers a 360MHz CPU core, a 5-port ethernet switch, USB host capability, and a Wi-Fi radio in a single package. Below is the block diagram for this SOC.
The block diagram for the SOC
As you can see from the diagram, this SOC has plenty of peripherals to work as a router. Paired to this SOC is a RAM. The 256Kbit RAM is ESMT’s part number M12L2561616A.
The ESMT RAM
Microcontroller
The Holtek microcontroller
In addition to having the SOC on board, there is a microcontroller. This is a Holtek HT66F30 microcontroller with an RISC-based core. This microcontroller is in a 20-pin package, but its footprint can also support a 24-pin package. It's difficult to tell exactly what the ancillary microcontroller does but it most likely controls the status LEDs and controls what mode the devices is in.
Ethernet
The TNK isolation transformer
In order to provide isolation between the SOC and the ethernet jack, an isolation transformer is used. The transformer is a TNK BT16A07. It features a 1:1 turns ratio transformer for used on both the RX and TX lines. This transformer is in a 16-pin package. Below is the schematic of the transformer from TNK’s datasheet.
The schematic of the transformer
Wrapping It Up
Several years ago routers were a lot larger and more expensive. This travel router was purchased for around $30 and there is quite a lot going on inside of this device. Thanks for taking a look at this teardown. Stop by next week for another teardown!
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