Hardware Overview
3
SLLU261A – April 2017 – Revised February 2019
Copyright © 2017–2019, Texas Instruments Incorporated
TUSB8044RGC Evaluation Module
2
Hardware Overview
The TUSB8044RGCEVM board hardware can be divided into the following functional areas:
2.1
TUSB8044RGC
The TUSB8044 on the TUSB8044 EVM (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 TUSB8044 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 TUSB8044RGCEVM limits the downstream
connections to that speed (SS, HS, and FS), or lower.
The TUSB8044 enumerates a
Billboard
device on a virtual downstream port for USB Type-C applications
with alternate mode support. It also has an
I
2
C Master
controllable through an HID compliant device
enumerated on a virtual downstream port.
The TUSB8044 requires a 24-MHz low-ESR crystal, Y1, with a 1-M
Ω
feedback resistor. The crystal should
be in fundamental mode with a load capacitance of 12 to 24 pF and a frequency stability rating of ±100
PPM or better. To ensure a proper startup oscillation condition, TI recommends a maximum crystal
equivalent series resistance (ESR) of 50
Ω
.
The TUSB8044 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.
2.2
USB Port Connectors
The TUSB8044 EVM is equipped with five standard 9-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, J3, J4, and 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.
The USB ports can be attached through a standard USB cable to any USB 3.0 or legacy USB host, hub,
or device. The TUSB8044 will automatically connect to any upstream USB 3.0 host or hub at both SS and
HS. Using a legacy USB cable between the TUSB8044 EVM and a USB 3.0 host or hub forces it to HS
operation. The same is true if a legacy USB cable is used between the TUSB8044 EVM and a
downstream SS-capable device; operation will be limited to USB 2.0 HS.
2.3
USB Port Connector – Power
VBUS is received from the upstream host or hub on J1. The TUSB8044 is configured as a self-powered
hub, so there is not any significant current draw by the EVM from VBUS. The TUSB8044 does monitor the
VBUS input after filtering through a resistor divider network of a 90.9-k
Ω
, 1% resistor, R2, and a 10-k
Ω
,
1% resistor, R3. VBUS cannot be directly connected to the TUSB8044 device. A bulk capacitor of at least
1
μ
F is required on the upstream port VBUS input to comply with the USB specification. The
TUSB8044EVM uses a 10-
μ
F capacitor, C35.
VBUS, sourced by the 5-V wall power input, J6, is provided to the downstream port connectors. The USB
3.0 specification limits the current consumption of a USB 3.0 device to 900 mA at 5 V. The current limiting
parameter of the TPS2001C devices, U7, U8, U9, and U10, is 2 A to avoid any spurious overcurrent
events due to bus-powered HDD spin-up power fluctuations or unnecessary limiting during USB charging.
A production implementation could place stricter limits on this power consumption. An overcurrent event
on any of the downstream port connectors will be reported to the TUSB8044 through the OVERCURxZ
inputs.
