VL6522 datasheet(28/35 Pages) STMICROELECTRONICS

28 / 35 page

Electrical characteristics

VL6522

28/35

6.4

AC electrical characteristics

6.4.1

USB2.0 interface

Conforms to the USB2.0 chapter 7.1.

6.4.2

External crystal

The primary reason for choosing the crystal frequency and tolerance is because of the USB

data rate. To comply with the USB2.0 specification, when in high speed mode (480 Mb/s),

the bit accuracy has to be +/- 500 ppm.

It is recommended to use a crystal with a frequency of 12 MHz and a frequency accuracy of

+/- 100 ppm or better.

6.4.3

RESETN

After RESETN is pulsed low (during power up for example), the device shall start up in it’s

default condition. This will include reading the EEPROM, if fitted.

During startup, the RESETN line should be held low for between 100 µs and 50 ms after the

supplies are stable. On the reference design board, an RC circuit is used to delay the rise of

RESETN using values of 470 k

Ωand 100 nF. This gives a delay of approximately 20 ms

between VDD3IO reaching 3 V and the device coming out of reset.

6.4.4

I2C Interface

The VL6522 can be used as a I2C master. By writing to the video class extension units on

the device over usb, the SDA & SCL pins can be controlled. This allows the slaving of such

devices as servos, EEPROMs or any device with an I2C interface. More detail on this

interface can be found in section

4.3.2.

VL6522 データシート(PDF) 28 Page - STMicroelectronics