ST VL53L8CX Ranging Sensor Module User Manual
- June 9, 2024
- ST
Table of Contents
ST VL53L8CX Ranging Sensor Module
Introduction
When used in continuous mode, the VL53L8CX module typically consumes 215 mW of power. Consequently, it requires careful thermal management to ensure optimum device performance and to avoid overheating.
Table 1. Main thermal parameters
| Parameter | Symbol | Min. | Typ. | Max. | Unit |
|---|---|---|---|---|---|
| Power consumption | P | — | 215 (1) | 320 | mW |
| Junction temperature (2) | TJ | — | — | 110 | °C |
| Die thermal resistance | θdie | — | — | 43 | °C/W |
| Operating temperature range | T | -30 | 25 | 85 | °C |
- AVDD = 2.8 V and IOVDD = 1.8 V of typical current consumption.
- To prevent thermal shutdown, the junction temperature must be kept below 110 °C.
Thermal design basics
The symbol θ is generally used to denote thermal resistance which is a measure
of a temperature difference by which an object or material resists a heat
flow. For example, when transferring from a hot object (such as silicon
junction) to a cool one (such as module backside temperature or ambient air).
The formula for thermal resistance is shown below and is measured in °C/W:
θ = ΔT/P
Where ΔT is the rise in junction temperature and P is the power dissipation. So, for example, a device with a thermal resistance of 100 °C/W exhibits a temperature differential of 100°C for a power dissipation of 1 W as measured between two reference points. The formula is as follows:
- θpcb = TJ − TA ÷ P − θdie
- θpcb = 110 − TA ÷ P − 43
Where:
- TJ is the junction temperature
- TA is the ambient temperature
- θdie is the die thermal resistance
- θpcb is the thermal resistance of the PCB or flex
Thermal resistance of PCB or flex
The maximum permitted junction temperature of the VL53L8CX is 110°C. The maximum permitted PCB or flex thermal resistance is calculated as shown below. This calculation is for a power dissipation of 0.320 W, and device operation at 85°C (worst case scenario of the maximum specified ambient temperature).
- θpcb = TJ − TA ÷ P − θdie
- θpcb = 110 − 85 ÷ 0.320 − 43
- θpcb = 35°C/W
Note: To ensure that the maximum junction temperature is not exceeded, and to ensure optimum module performance, do not exceed the above target thermal resistance. For a typical system dissipating 320 mW, the maximum temperature rise is < 11°C. This is recommended for optimum performance of the VL53L8CX
Layout and thermal guidelines
Use the following guidelines when designing the module PCB or flex:
- Maximize the copper cover on the PCB to increase the thermal conductivity of the board.
- Use the module, thermal pad B4 shown in Figure 2. VL53L8CX pinout and thermal pad. Add a single large rectangle of solder paste. It should be the same size as the thermal pad (eight rectangles) as per Figure 3. Recommendation for the thermal pad and via on the PCB. STMicroelectronics recommends to stitch the eight vias from top to bottom, so the bottom mask is open and the pad is exposed.
- Use wide tracking for all signals particularly power and ground signals. Track and connect them into adjacent power planes where possible.
- Add heat sinking to the chassis or frames to distribute heat away from the device.
- Do not place next to other hot components.
- Place the device in a low power state when not in use.
Revision history
| Date | Version | Changes |
|---|---|---|
| 30-Jan-2023 | 1 | Initial release |
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AN5897 – Rev 1 – January 2023
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