Brian Dorey provides a teardown of the Amazon Alexa Echo Dot 3rd generation with a clock.
Most of this Echo Dot is the same as the normal 3rd gen model with the main differences on the processor board and the clock board.
This version of the Echo Dot uses the same MediaTek MT8516BAAA processor but the combined DDR ram and NAND memory chip on the original Echo has been replaced with two chips. A MT41K128M16JT-107 DDR3 2Gb RAM chip provides the memory while a MT29F4G08ABAFAH4-IT 4Gb Serial NAND Flash chip provides the storage.
The underside of the top PCB contains most of the components found inside the Echo Dot. An array of 12 RGB LEDs is located around the edge of the board. The LEDs are driven using an ISSI IS31FL3236 36 channel LED driver.
Four microphones are placed next to the buttons and these feed into two TLV320ADC3101 chips from Texas Instruments. The TLV320ADC3101 is a Stereo ADC with an embedded mini digital signal processor. The Echo dot uses the four microphones to locate the direction the voice is coming from and filter out background noise.
In the centre of the PCB is a metal shield. Under the shield you will find a MediaTek MT7658CSN dual-band Wi-Fi and Bluetooth controller with an ARM Cortex-R4 CPU. The MT7658CSN manages communication to WiFi and Bluetooth devices and connects to two PCB antennas located on the outer edges of the board.
There is also a Fairchild 74LCX74 dual D-Type flip-flop which appears to switch the microphones on and off.
See the video below and more on the blog post here.