Hardware Overview; Tusb8040A; Usb Port Connectors; Usb Port Connector - Power - Texas Instruments TUSB8040AEVM User Manual

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Table Of Contents

Table of Contents

The TUSB8040AEVM board hardware can be divided into five functional areas:

TUSB8040A

The TUSB8040A on the TUSB8040AEVM (U1 on the schematic) operates as a functional interconnect

between an upstream connection to a USB host or hub and up to four directly connected downstream

devices or hubs. More devices and hubs can be supported if arranged in tiers. The TUSB8040A is

capable of supporting operation at USB SuperSpeed (SS), High-Speed (HS), Full Speed (FS) or Low

Speed (LS). In general, the speed of the upstream connection of the TUSB8040AEVM limits the

downstream connections to that speed (SS, HS, and FS) or lower.

The TUSB8040A requires a 24-MHz low ESR crystal, Y1 with a 1-MΩ feedback resistor. The crystal

should be fundamental mode with a load capacitance of 12 pF – 24 pF and a frequency stability rating of

±100 PPM or better. To ensure a proper startup oscillation condition, a maximum crystal equivalent series

resistance (ESR) of 50 Ω is recommended.

The TUSB8040A can also use an oscillator or other clock source. When using an external clock source

such as an oscillator, the reference clock should have ±100 PPM (or better) frequency stability and have

less than 50-ps absolute peak to peak jitter (or less) than 25-ps peak to peak jitter after applying the USB

3.0 jitter transfer function.

USB Port Connectors

The TUSB8040AEVM is equipped with 5 standard nine pin USB 3.0 port connectors. One of these five

connectors, J1, is a Type B connector designed to interface with an upstream USB host or hub. The

remaining connectors, J2-J5, are Type A connectors for connection to downstream devices or hubs.

Standard size connectors were used on the EVM design, but USB micro connectors can be used if

desired. It is also possible to implement a legacy USB connector on one or more of the downstream ports

if SuperSpeed operation is not desired.

The USB ports can be attached via a standard USB cable to any USB 3.0 or legacy USB host, hub or

device. The TUSB8040A will automatically connect to any upstream USB 3.0 host or hub at both

SuperSpeed and High-Speed. Using a legacy USB cable between the TUSB8040AEVM and a USB 3.0

host or hub will force it to High-Speed operation. The same is true if a legacy USB cable is used between

the TUSB8040A EVMand a downstream SuperSpeed capable device in that operation will be limited to

USB High-Speed.

2.1

USB Port Connector - Power

VBUS is received from the upstream host or hub on J1. The TUSB8040A is configured as a self-powered

hub, so there should not be any significant current draw by the EVM from VBUS. The TUSB8040A does

monitor the VBUS input after filtering through a resistor divider network of a 90.9-kΩ, 1% resistor, R1, and

a 10-kΩ, 1% resistor, R3. VBUS cannot be directly connected to the TUSB8040A device.

NOTE: The VBUS LED implemented on the EVM will cause a USB 2.0 compliance issue because it

draws greater than 2-mA of current while the USB connection is suspended. It is included for

lab evaluation purposes only.

A bulk capacitor of at least 1 µF is required on the upstream port VBUS input to comply with the USB

specification. The TUSB8040AEVM uses a 10-µF capacitor, C37.