gps-details

Apple Watch Series 4

Overview

The Apple Watch Series 4 supports GPS, GLONASS, Galileo, and QZSS. It cannot be using the same GNSS receiver as the Series 2, because the BCM47734 does not support Galileo.

There are two different versions of the S4 SiP for the Apple Watch Series 4, corresponding to the cellular and non-cellular models. The Apple Watch Series 4 was released in Sep 2018, so it could have used one of the following Broadcom chips:

Whatever the chipset, it is almost certain the GNSS receiver will have been produced by Broadcom.

Teardown

Apple Watch Series 4 (non-cellular)

Without a teardown of the non-cellular SiP the components inside the resin cannot be confirmed. There is very little on the outside of the SiP, but in addition to the connectors and the Bosch accelerometer / gyroscope there is a silver module which appears to be a GNSS module.

An executive summary from SystemPlus Consulting says an IMU and GPS module are soldered beneath the SiP. The GPS module looks to be the same size as the BCM47754 found inside the Apple Watch Series 5 and Apple Watch SE.

series-4-gps-front

Apple Watch Series 4 (cellular)

The teardown by Mobile China Alliance clearly shows the addition of some cellular components.

The other components will be largely the same as the non-cellular SiP, but the circuit board design will be different. The main cellular components (Intel, Skyworks and Qorvo) are quite large and do not leave sufficient room for a Broadcom GNSS receiver.

Note: This teardown has incorrectly labelled the Intel Baseband Chip (cyan) as Toshiba Flash Memory, so the labels need to be taken with a pinch of salt.

series-4-cellular-back

A teardown by Electronics 360 also shows the inside of the cellular SiP, which correctly identifies the Intel baseband processor.

series-4-cellular-back-alt

The teardown by Mobile China Alliance also labels some of the components on the outside of the SiP.

Note: This teardown has also mis-labelled the GPS module (green), referring to it as a Skyworks RF power amplifier.

series-4-cellular-front

SystemPlus Consulting (now Yole Group) have provided an image clearly identifying the GPS module.

series-4-cellular-front-alt

Another image also shows the part numbers very clearly. The use of 4 alphanumeric characters on the GPS module is consistent with other products such as the Apple Watch Series 5 and Series 6. It is interesting how the code differs for SystemPlus Consulting (OV 5B), iFixit (OU JQ) and YouTube (11 OE). Perhaps the code is a serial number or batch number?

series-4-cellular-gnss

Summary

The teardown by Mobile China Alliance describes the Apple W3 as Wireless, Bluetooth, and GPS. It seems somewhat unlikely that the W3 is used for GPS because the Apple Watch Series 4 to Series 7 also have the Apple W3, but also have a dedicated Broadcom GNSS receiver.

The SystemPlus Consulting executive summary says the following about the Apple Watch Series 4:

The smartwatch came with two version of the SiP. The first is a non-cellular version with a single side molding and soldered beneath the package, an IMU and a GPS Front-End-Module (FEM). The second, analyzed by this report, is the cellular version with addition RF FEM, inside and outside the SiP, and a baseband processor included in the packaging, all in a single package smaller than 700 mm2, representing 40% of the watch form factor.

The executive summary is consistent with all of the images on this page, and the GPS module being located on the outside of the SiP.

The Apple Watch Series 6 evolution by Reverse Costing (Yole Group) also hinted at Broadcom GPS chip:

The similarities between the series are much more numerous…

Broadcom wireless charging, custom sensing, and GPS chips

The Apple Watch Series 4 almost certainly uses a Broadcom GNSS receiver, perhaps identical to the Series 5 and Series 6.

Which one is not clear at this time… perhaps it is the BCM47754?