Approximation sensor in Xiaomi smartphones: the official name, device and repair

Ever wondered why your Xiaomi screen goes out while you’re talking, as soon as you hold your phone to your ear? This “magic” is the tiny but critical component of the proximity sensor. Despite its tiny size (usually no more than 3-5 mm in diameter), this sensor performs several key functions at once, from saving battery power to protecting against accidental pressing.

Xiaomi smartphone owners (especially Redmi Note series models, POCO flagship Mi/Xiaomi 13/14) Often faced with questions: what exactly is the name of this sensor in the documentation, where it is located on the board, and why sometimes stops working? In this article, we will examine not only its official name (which differs from the household term), but also the principles of operation, typical malfunctions, as well as methods of checking without disassembling the phone. AMOLED-screens – where the proximity sensor is often integrated directly into the display!

The official name of the proximity sensor in Xiaomi

In everyday life, users simply refer to this component as the “approximation sensor,” but in Xiaomi’s service documentation, motherboard diagrams, and chipmaker specifications, it appears under different terms:

• 🔹 Proximity Sensor is the most common name in international firmware and dataset versions.
• 🔹 PS Sensor (short for Proximity Sensor) – used in board labeling and diagnostic menus (e.g. ##6484##).
• 🔹 Infrared proximity sensor - full name on the principle of operation (uses IR radiation).
• 🔹 STK3x1x or APDS-99xx — models of specific chips from manufacturers Sitronix and Broadcom, which Xiaomi installs in their devices.

It is important to understand that the proximity sensor and the ambient light sensor are two different components, although they are often combined in one module (for example, in the APDS-9960 chip). In Xiaomi smartphones, they can be located side by side, but they perform different functions: the first is responsible for approximation, the second is for automatic adjustment of the brightness of the screen.

If you disassemble the phone for repair, the proximity sensor on the board is usually marked as PS or PROX. In the models with AMOLED-displays (e.g. Xiaomi 13 Ultra or POCO F5 Pro) it can be embedded directly into the screen and visually inseparable from the matrix, which makes it difficult to replace it - if such a sensor is damaged, it is often necessary to change the entire display module.

Where is the proximity sensor in Xiaomi smartphones

The location of the sensor depends on the phone model and the type of screen, and in most cases, it can be found at the top of the front panel, next to the speaker or front camera.

In the models with AMOLED-In screens, the proximity sensor is often based on an optical sensor that analyzes the light reflected from an object (like your ear), which allows you to hide it under the screen, but makes it more sensitive to glass contamination. If you notice that the screen doesn’t go out during a call, try to wipe the top of the display – sometimes this solves the problem!

⚠️ Note: In smartphones Xiaomi with AMOLED-displays (e.g., Xiaomi) 12T or Redmi K60) The approximation sensor can be part of the Under-Display Camera module (UDC). When damaged, the camera often fails and the proximity sensor – they are changed together.

How the approximation sensor works: physics and algorithms

The sensor is based on infrared radiation, and there are two key elements inside it:

1. IR emitter sends a light signal invisible to a person.
2. IR receiver - captures the signal reflected from the object.

The algorithm of the work looks like this:

1. The sensor constantly emits IR rays with a frequency of ~100-200 Hz.
2. If an object appears near you (like your ear), the rays are reflected and returned to the receiver.
3. The microcontroller analyzes the strength of the reflected signal, and if it exceeds a threshold value (usually ~5-10 cm), the command to turn off the screen is triggered.
4. When the object is removed, the signal weakens and the screen is turned on again.

On Xiaomi smartphones, the trigger threshold can be set through an engineering menu (code ##6484## → Proximity Sensor). For example, the POCO X3 models have a default value of 5 cm, but it can be increased to 8 cm for reliability. However, too high a threshold can lead to false positives (for example, when you just hold the phone in your hand).

Interesting fact: some flagship models (for example, Xiaomi 13 Ultra) use a laser proximity sensor instead of the traditional IR. It is more accurate and less sensitive to external lighting, but it costs more. You can check the type of sensor in your phone through the AIDA64 app (Sensors section).

Typical malfunctions of the proximity sensor and their causes

If the proximity sensor in your Xiaomi has stopped working, it can manifest as follows:

• 📵 The screen does not go out during the call (remains active, leading to occasional taps).
• 🔦 The screen goes off arbitrarily, even when the phone is on the table.
• 🔄 The sensor is delayed (for example, the screen turns on 2-3 seconds after the phone is removed from the ear).
• 🚨 In the engineering menu (#6484##) the sensor shows 0 cm or a constant maximum value.

The causes of breakdowns can be divided into software and hardware:

⚠️ Note: Xiaomi smartphones with Always-On Display feature (AOD) (For example, Xiaomi 13 or Redmi. K60 Pro) the proximity sensor may conflict with the operation of the screen. AOD turns off when you bring your hand to the phone – this is normal: the sensor perceives the hand as an object of approach.

One of the most insidious defects is the false positives from the protective glass, so if you've recently put a new glass on, check if it's covering the sensor area. AMOLED-The problem with screens (where the sensor is hidden under the display) may be a poor-quality glass glue that refracts the IR rays. Solution: use glass with a cutout under the sensor or special models with optical transparency.

How to check the proximity sensor without disassembling the phone

You can diagnose the malfunction yourself before you bring the phone to the service. Here's a step-by-step instruction:

1. Launch the engineering menu with code ##6484##

2. select Proximity Sensor

3. Raise your hand to the top of the phone 5–10 cm

4. Check if the values change (should be 0→5 or 0→1)

5. Make sure that the sensor does not work at a distance of >15 cm

-->

If the engineering menu is not available (e.g. in some versions of MIUI for Europe), use alternative methods:

1. Phone Tester (Play Market) app: Open the Sensors tab. Find Proximity Sensor. Hold your hand, and it should change from 5.0 cm to 0.0 cm.

Calling another phone

• Testing through ADB (for advanced users): adb shell dumpsys sensorservice In the output, find the string with Proximity Sensor and check the current value.

If the sensor doesn't respond at all (it's always 0 or -1), the problem is more hardware. If it does, but with a delay or incorrectly, try resetting the sensors through the engineering menu (#6484## → Reset All Sensors).

💡

If the sensor is working too late, try increasing the sensitivity threshold in the engineering menu. To do this, type in the code ##36446337##, select Proximity Sensor Calibration and set the High value.

Repair and Replacement of the Approach Sensor: What You Need to Know

If the diagnosis shows that the sensor is faulty, you have several options:

• 📱 Software Repair: Flashing the phone through the Mi Flash Tool. reset to factory settings (sometimes helps with driver crashes).

To replace the sensor in Xiaomi models, the following parts are most often used:

⚠️ Note: In Xiaomi smartphones with Face Unlock (e.g. Xiaomi) 11T or Redmi K40) The proximity sensor may be coupled to the front camera, and it may require reconfiguration of facial recognition when it is replaced!

If you decide to replace the sensor yourself, follow the following rules:

1. Turn off the battery before disassembling (risk of short circuit!).
2. Use plastic mediators to avoid damaging the plumes.
3. When soldering, use a thermo-air station (temperature not higher than 350 ° C).
4. After replacement, check the sensor in the engineering menu before assembling the phone.

💡

In 90% of cases, Xiaomi's proximity sensor malfunction is not due to its failure, but to contamination or firmware failure. Start your diagnosis with cleaning and resetting!

Frequent questions about the proximity sensor in Xiaomi