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Modern electronic devices increasingly rely on intelligent sensing to improve user experience, power efficiency, and system automation. The VCNL4040 light sensor is designed to meet these needs by combining proximity detection and ambient light measurement in a single, compact solution. This article will discuss the VCNL4040’s basics, internal operation, specifications, features, pinout, alternatives, application circuit, and more.
The VCNL4040 Proximity and Ambient Light Sensor from Vishay is a compact, fully integrated sensor designed to detect nearby objects and measure surrounding light levels at the same time. It combines an infrared emitter, photodiodes, and signal processing in a single surface-mount package, making it ideal for space-constrained electronic designs.
For proximity sensing, the VCNL4040 emits infrared light and measures the reflected signal from nearby objects, enabling reliable presence or distance detection. Its ambient light sensing function accurately monitors environmental brightness, allowing systems to automatically adjust display backlighting or power settings. The sensor communicates through a standard I²C interface, supports high-resolution digital output, and operates at low voltage for energy-efficient designs.
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| Pin No. | Pin Name | Description |
| 1 | GND | Ground reference for the device |
| 2 | Cathode (Sensor) | Cathode connection for the internal proximity sensor photodiode |
| 3 | VDD | Power supply input (typically 2.5 V to 3.6 V) |
| 4 | Anode | Anode connection for the internal infrared LED emitter |
| 5 | Cathode (LED) | Cathode connection for the internal infrared LED |
| 6 | INT | Interrupt output pin for proximity or ambient light threshold events |
| 7 | SDAT | I²C serial data line (SDA) |
| 8 | SCLK | I²C serial clock line (SCL) |
• VCNL4030
• VCNL4200
• VCNL4010
• VCNL4020
• APDS-9960
• APDS-9930
• TMD2620
• TMD2725
• MAX44009
• ISL29125
• OPT3001
• VEML7700
The VCNL4040 functional block diagram illustrates how proximity and ambient light sensing are integrated into one compact device. The internal IR LED emits infrared light toward nearby objects, and the reflected light is detected by the proximity photodiode. This signal is conditioned by the photodiode buffer and processed by the internal DSP, which filters noise and improves measurement accuracy.
For ambient light sensing, the ALS photodiode detects surrounding light and passes the signal through a low-pass filter before storing it in a 16-bit data buffer. This enables accurate brightness measurement for automatic display and power control. Both sensing paths are controlled through the I²C interface, with an interrupt pin for event signaling and a built-in temperature sensor to maintain stable performance.
| Parameter | Specification |
| Manufacturer | Vishay |
| Sensor Type | Proximity Sensor (PS) + Ambient Light Sensor (ALS) |
| Package Type | Surface-mount |
| Dimensions (L × W × H) | 4.0 × 2.0 × 1.1 mm |
| Integrated Modules | IR emitter (IRED), ALS, PS, signal conditioning IC |
| Sensing Operation | ALS and PS operate in parallel |
| Interface | I²C (SMBus compatible) |
| Output Type | I²C bus (ALS / PS data) |
| Operating Voltage | 2.5 V to 3.6 V |
| Operating Temperature | −40 °C to +85 °C |
| Proximity Resolution | Selectable 12-bit / 16-bit |
| Ambient Light Accuracy | ±10 % |
| ALS Detection Range | 819 / 1638 / 3277 / 6553 lux |
| ALS Sensitivity | 0.0125 lux/step |
| IR Wavelength | 940 nm |
| IR LED Current | Programmable sink current |
| Light Immunity | Red glow and fluorescent flicker immunity |
| Optical Technology | Filtron™ background light cancellation |
| Crosstalk Reduction | Intelligent cancellation |
| Interrupt Function | Programmable upper and lower thresholds (ALS / PS) |
| Persistence Control | Adjustable to reduce false triggers |
| Moisture Sensitivity Level | MSL 3 |
| Floor Life | 168 hours (J-STD-020 compliant) |
| Compliance | RoHS, Halogen-free, Pb-free |
The VCNL4040 combines a proximity sensor and an ambient light sensor into a single device. This integration reduces component count, saves PCB space, and simplifies system design while allowing both distance detection and light measurement in one solution.
With its small 4.0 × 2.0 × 1.1 mm package, the VCNL4040 is well suited for compact electronics such as smartphones, wearables, and portable devices where board space is limited.
Ambient light sensing and proximity sensing can operate simultaneously. This allows real-time brightness adjustment and object detection without performance trade-offs.
Filtron™ technology minimizes the effect of unwanted ambient light, improving proximity accuracy even under strong or fluctuating lighting conditions.
The ambient light sensor offers ±10% accuracy and a spectrum response close to the human eye, enabling reliable automatic brightness control.
The IR LED drive current is adjustable, allowing designers to optimize sensing range, power consumption, and performance.
Built-in cancellation logic reduces false proximity readings caused by internal reflections or mechanical design limitations.
The sensor uses a standard I²C (SMBus-compatible) interface, enabling easy integration with microcontrollers while maintaining low power consumption.
Operating from 2.5 V to 3.6 V, the VCNL4040 supports common low-voltage systems and battery-powered applications.
Configurable interrupts and adjustable persistence help prevent false triggers, allowing the system to respond only to meaningful proximity or light changes.
Catalogue
FPGA / CPLD
Memory
MOS 
MCU 
DSP
OCEP
Secondary 
Other