How iPhone X Face ID Works
related with Face ID circuit
The first one
U1000, CPU
It mainly performs as an over controller of the Face ID circuit
Also, it will process the Face ID data
U2700, PMU
It mainly used to provide power
to flood illuminator and infrared camera
U4400, Face ID power IC
It's mainly provides power for flood illuminator and dot projector
U2700, camera PMU
it mainly used to provide power to the infrared camera
Next
Let's have a look about the main connectors related with Face ID circuit
J4500, Dot projector connector
It makes possible the connection between the dot projector and the motherboard
J4600, the flood illuminator connected
This connector is not only control the flood illuminator
but also control like earpiece, ambient light sensor, proximity sensor, etc
So, in this circuit
it makes possible the connection between the flood illuminator and the motherboard
The last one
J4530, Infrared camera connector
it makes possible the connection between the infrared camera and the motherboard
Let's have an overview about related chips and connectors
CPU, like the brain for overall control and process the Face ID data
PMU
Face ID power IC
And the camera PMU
the three chips, they mainly responsible for providing powers to the Face ID circuit
And the three connectors
They make it possible the connection between the motherboard and the Face ID related parts
Flood illuminator
it will emit low power infrared light onto the surface of the object
So that to help the infrared camera to
detect and capture the image of the object
Infrared camera
It can detect the infrared energy and capture the infrared image of the object
After that
the captured image will be sent to CPU for further processing
Dot projector
the dot projector could project over 30,000 dots
onto users face to create a sequence of depth map
And this kind of map can be also captured by the infrared camera
then sent to the CPU for further processing
Like Face ID enrollment
or comparison within enrolled Face ID data to unlock the phone
We will focus on the Flood illuminator Circuit today
For a detailed explanation of the infrared camera circuit
and the dot Projector circuit, please visit REWA Academy
So let's move on to have a look about how each related part circuit works
Flood illuminator
You can also call it Rosaline
So in this block diagram
we can see the CPU for overall control
The connector
which makes possible the connection between the Rosaline and the motherboard
and the rest chips, they are mainly responsible for the power supplies
So let's have a look about how this circuit works
First step, is power
Power always comes to the first
And here, two powers are required
PP3V0_YOGI_PROX_ALS_CONN
it sent out from PMU to the Rosaline connector
Also, the PP_ROSALINE_ANODE
This power is sent out from Face ID power IC to the connector
when the power get fulfilled
a feedback status signal will be sent out
to both the Face ID power IC
and the camera PMU
this is to tell them the currently status
the power supply is get fulfilled
After that
The Rosaline should be also controlled by CPU via the I2C bus
So once the three conditions get fulfilled
the Rosaline will be standby to work
which could be able to emit the low-power infrared light
Also, we can see there're two rails
These two rails are related with proximity sensor and ambient light sensor
So when the two functions are required
an interrupt signal will be sent out from CPU to this connector
So that the proximity sensor or ambient light sensor function can be activated
So this whole process and here we also have a tip
The infrared light is applied to the face
so that the infrared camera can clearly recognize the face in any environment
So this is the process of how flood illuminator circuit works
So first part
is to find out if this Face ID issue can be fixed or not to evaluate the repair possibilities
Let's see the detail process
So when you receive the phone with Face ID issue
the first thing we do is to exclude the software issue first
After that, we should also check the cosmetic of Face ID related part
like the flood illuminator, infrared camera and dot projector to check the cosmetics
Also, we should check the related components on the motherboard to check if the cable is cracked or scratched
and to see the related components on the motherboard
to see if there are corrosion or damage or missing, something like that
If we find any abnormal
For example, if we find the flex cable damaged. We should fix the flex cable
You can choose to jump wire or swap the relative chip and this detail process you can refer to our blog
or check our YouTube channel to find the related videos
If its components missing or corrosive
you should change a new component (sorry, not cable)
If everything is normal
then we should continue to observe
the proximity sensor and flood illuminator works status under the infrared camera
This light is invisible for the human eyes
You can only observe under the special camera
like the digital camera or infrared camera
to see if this light can be emitted out or not
If we find any abnormal
then it means it should be the proximity and flood illuminator problem
So we should check the related circuit
or swap the flood illuminator chip to another cable
if it's normal, we can see the light emit out from the proximity sensor and flood the illuminator
Then it means they work fine, we're going to continue to check if the dot projector is okay or not
Because in the portrait mode
The dot projector can emit light, So we can check in the portrait mode
to see if there's any light outputted from dot projector
if yes, it means by now
the flood illuminator and dot projector they are OK
so the issue might be the infrared camera
We should check the infrared camera circuit
Let's go to Re fox Bitmap to have a look
So we should check the infrared camera connector first
to measure each pin diode values
Measure each pin one by one
to see if the measured value is OK or not
If we find any value abnormal
just track the pin related components
But if we measured all the pin diode values they are normal
then we should go to check the related power supply chip for the infrared camera
It's the camera PMU
so we should check the camera PMU power supplies
If the power supply also OK
then it might be the camera PMU problem
So let's come back to here
If we cannot find the light outputted from the dot projector then we should check the dot projector related circuit
Let's go to bitmap to have a look
dot projector connector is J4500
So it's the same
We should measure each pin diode value
to see if the diode value is OK or not
If we measured any abnormal, track the line
if they are ok
Then we should also go to the infrared camera circuit to find out the root cause
So this is the process
By observing the light is on or not
we can locate the range of the problem
Want to learn more about Face ID
Start your learning journey at REWA Academy now