STMicroelectronics recently announced their new laser-ranging time-of-flight sensor with a range of up to 4 meters.

The VL53L1X, which was recently announced by STMicroelectronics, is a Time-of-Flight (ToF), long-distance laser-ranging sensor. With a maximum range of 400 cm (or ~157 inches), I suppose the descriptor "long-distance" is a relative term depending on your project; after all, this "fully-integrated miniature module" (see the following figure) lives in a rather tiny package of only 4.9 × 2.5 × 1.5 mm, according to its datasheet (PDF).

 
The fully-integrated VL53L1X resides in a small module measuring only 4.9 × 2.5 × 1.5 mm
The fully-integrated VL53L1X resides in a small module measuring only 4.9 × 2.5 × 1.5 mm. Image taken from the datasheet (PDF).

 

A Fully-Integrated Miniature Module

This ranging sensor is referred to as being "fully integrated," and I'd say that description is correct given all that it offers:

  • a low-powered microcontroller running advanced firmware;
  • contains physical infrared filters and optics;
  • combines a 16×16 SPAD's (single-photon avalanche diode) receiving array with an integrated lens;
  • housed in a miniature reflowable package;
  • features a programmable region-of-interest (ROI), which allows for the sensor's field-of-view (FOV) to be reduced, or for providing multizone operation control;
  • uses the I2C interface bus for communications.

 

The VL53L1X block diagram

The VL53L1X block diagram. Taken from the datasheet (PDF).

 

Speaking of the I2C bus, while the Features section (on page 1) makes reference to a maximum I2C bus speed of 1 MHz, it looks like this specification is incorrect since Table 10 (see the following figure) states a maximum I2C bus speed of 400 kHz. Perhaps this minor oversight will be corrected in the datasheet's next revision.

 

The maximum speed of the I2C bus is 400 kHz and not 1 MHz, as called out on page 1 of the datasheet...a minor goof.
The maximum speed of the I2C bus is 400 kHz and not 1 MHz, as called out on page 1 of the datasheet...a minor goof.

 

A Maximum Range of 4 Meters (Under Specific Conditions)

Although this sensor is capable of ranging distances of up to 4 meters (400 cm), apparently this maximum-distance parameter can only be achieved under specific conditions, such as when "ambient light = dark," according to Section 3.4 (entitled Performances in Dark Conditions)—see the following figure. Also, take note of the target reflectance specs.

 

The sensor can range up to 400 cm, but only under specific conditions.
The sensor can range up to 400 cm, but only under specific conditions.

 

Section 3.1 of the datasheet (page 15) calls out some additional test conditions, including:

  • nominal voltage = 2.8 V
  • nominal temperature = 23°C
  • an absence of cover glass
  • timing budget is 100ms

Just to be clear, I don't mean to belittle or otherwise put down this sensor. However, I am suggesting that if your design requires a sensing range at or near the maximum range offered from this sensor (400 cm), just be sure to review the testing conditions section of this datasheet to ensure that you're not overlooking something. It would also behoove you to check out Section 2.5 (entitled Key Parameters) on page 10, which discusses the various distance modes and the sensor's timing budget (TB).

 

Requires an API

According to the System Functional Description section, on page 7, the host controls this sensor using an API (application programming interface) that is delivered as a driver. And while this section also makes reference to the API's user manual (UM2356)—of which contains a detailed description of the driver—a hyperlink to said document is not included. So, for your convenience, I've included a link here (PDF).


An API, which is delivered as a driver, is required for operating this ranging sensor.

An API, which is delivered as a driver, is required for operating this ranging sensor.

 

Yes, it's a laser. So be careful.

As is called out—multiple times—throughout the datasheet, this long-distance laser-ranging device does indeed contain a laser emitter; a Class 1 940 nm invisible laser, to be exact. And although, according to this article, "A Class 1 laser is safe under all conditions of normal use," proper laser safety considerations should still be exercised when using this sensor. For more information on this topic, see Section 7 (entitled Laser safety considerations) on page 28 of the datasheet.


Just in case you forgot, the datasheet reminds us that this sensor contains a laser. So, exercise caution when using this device.

Just in case you forgot, the datasheet reminds us that this sensor contains a laser. So, exercise caution when using this device.

 

Have you had a chance to use STMicroelectronics' new long-distance ranging Time-of-Flight sensor, the VL53L1X? If so, leave a comment and tell us about your experiences.

 

Comments

4 Comments


  • kenif 2018-04-27

    Sounds great apart from the API. I would expect to drive this from an 8-bit microcontroller, not a PC.

  • Hemi 2018-04-29

    The VL53L0X was a disappointment for me too because ST didn’t publish anything but a driver/API for it either.  Feels kinda like a middle finger to makers and hobbyists.  I’d rather have a datasheet available to make it work with my microcontroller than try to reverse engineer their API… :(

  • pyroartist 2018-05-09

    Nothing was stated about a high voltage supply, either internal or external. Avalanche Photo Diodes require voltages typically above 150 VDC. How is this acheived?

    • RK37 2018-05-19

      That’s a good question. I looked briefly at the datasheet, and I don’t think that it gives any information on how they generate the SPAD bias voltage. I assume that it’s something along these lines:

      “On-chip high-voltage SPAD bias generation using a dual-mode, closed-loop charge pump”
      https://ieeexplore.ieee.org/document/8050855/

      Note, however, that the output voltage of this circuit is 15 V. You might be mistaken about how high the voltage needs to be.