Teardown Benton B15 Bluetooth Headphones

2017-04-07 | By All About Circuits

License: See Original Project Wireless

 Courtesy of All About Circuits

Without wires, electronics could have never existed. Yet, despite their importance we seem to be trying to get rid of them whenever we can! In this teardown, we will look at a Bluetooth headphone set (Benton B15’s) to see what goes inside a modern wireless device.

Well Built = Bad For Teardowns

When purchasing an electronics device (or any item for that matter), it is an added bonus if the unit is put together well with high quality materials. However, that is not the case with teardowns as it can be a real nightmare to get inside them!

The headphones in this teardown have an audio jack for wired use, a charging USB port, and several buttons for generic media player controls such as play, stop, increase volume, and decrease volume. The first screws were located by removing the padding material that sits on the strip which connects the left and right speakers.

Function buttons

Audio jack and USB charging port

Screws found on the strip

It was amazing to see how many screws keep these headphones together. Eventually, the individual left and right speakers were isolated, but getting inside them was challenging. There were no visible outside screws even after removing padding and surrounding parts. It turned out that a small flat head screwdriver is needed to pry the discs off the headphones which reveals more screws.

Headphone disc which sits on top

Disc removed

Just one more screw after this!

The final screw

The PCB

Getting to the PCB took its time but was worth it in the end. The PCB has a curved shape similar to a donut. It has four screws holding it down and very few components. From the top side, a few electrolytic capacitors can be seen, an IC, an audio jack, a microphone, and various other parts.

The PCB sitting in place

The PCB removed from the headphones

The main brain of the Bluetooth headphone set is the AIROHA AB1512 which is a Bluetooth SoC. With emphasis around audio transmission, the SoC is loaded with many features including a 48MIPS dual core DSP co-processor, built in noise reduction, EEPROM interface, built-in radio circuitry (with the exception of the antenna), speaker driver, voice prompt support, integrated switching regulator, and more. Some similar SoC’s are Qualcomm’s BlueCore CSR8645 series and ST Micro’s BlueNRG series.

The SoC AIROHA AB1512 IC

Block diagram for a AB1512 powered device

Also integrated on the top side of the PCB is an audio jack (for wired transmission of audio), a microphone, and various supporting components. The electrolytic capacitors located on the left side of the PCB are most likely for driving the speakers.

The audio jack and microphone

The “audio coupling capacitors”

The Battery

Battery in the headphone

The battery sits in the speaker opposite to the PCB (due to size and weight) and is housed in an identical manner to the PCB speaker. Judging by the indents printed onto the battery and some teardown experience, this battery is of the lithium-polymer variety. The battery has a 400mAh capacity and contains short circuit protection circuitry. Trying to measure the max current output results in an immediate shut off which is reassuring to know. The video shown below demonstrates the “pulse” of current that can be obtained from the battery before the auto shut off circuit kicks in.

Summary

To see how IC producers are constantly integrating as much as they can is truly amazing. Instead of needing a Bluetooth IC, a power IC, a main controller, and audio controllers, all of the circuitry is essentially in one package with just a few external support components. The use of lithium ion batteries shows that handheld devices are becoming more common with longer operation times and shorter charging times. Overall, this Bluetooth headphone set clearly demonstrates how much technology has improved a device that was invented a 100 years ago.

Circuit diagram made in Scheme-It

Mfr Part # CSR8645A04-IBBC-R

IC RF TXRX+MCU BLE 68VFBGA

Qualcomm

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