Hardware Overview
4
SLLU261A – April 2017 – Revised February 2019
Copyright © 2017–2019, Texas Instruments Incorporated
TUSB8044RGC Evaluation Module
2.4
USB Port Connector – Noise Filtering
Each downstream VBUS output has a 150-
μ
F bulk capacitor (C70, C71, C76, C79) as recommended by
the TPS2001C data manual (
) to prevent in-rush current events on the downstream devices. In
addition, there are ferrite beads and small capacitors on the VBUS lines to reduce noise and address ESD
and EMI concerns.
The TUSB8044EVM also implements optional isolation using two small noise-filtering capacitors and a 1-
M
Ω
resistor between the earth ground of each connector and the digital ground of the EVM; this is not a
requirement, but should be used if ground isolation is desired.
NOTE:
Note that the series capacitors implemented on the SS TX pairs are incorporated to satisfy
the USB 3.0 requirement that differential links be AC coupled on the transmit pair.
2.5
Optional Serial EEPROM
Each TUSB8044EVM is equipped with an onboard EEPROM or socket placeholder, U2. A small I
2
C
EEPROM can be installed to set the configuration registers as defined in the TUSB8044 data manual
(
). In its default setting, the EVM does not have an EEPROM installed and instead uses the
configuration inputs to determine any optional settings of the TUSB8044.
The EEPROM interface defaults to programmable (not write-protected) so that any installed contents on
the EEPROM may be modified to test various settings. If an EEPROM data change is required, the values
may be changed using the register access methods outlined in the TUSB8044 data sheet. In addition, a
Microsoft
®
Windows
®
based EEPROM utility is available upon request.
2.6
Power
The TUSB8044 EVM operates from the power provided by a 5-V wall power adapter, J6, not bus power
supplied by a USB host. TI recommends to use a wall power adapter that is capable of sourcing 2 to 3 A
because the hub must be able to source significant power on its downstream ports (900 mA per port).
The TUSB8044 EVM uses a single-channel LDO voltage regulator to drop 5 V to 3.3 V. The TPS7A4533,
U4, is a 1.5-A output linear regulator (
). The 1.1-V core voltage required by the TUSB8044 is
sourced by the 3.3-V rail to reduce unnecessary heat dissipation. The TPS74801, U6, is a 1.5-A output
single channel LDO linear regulator (
). Both regulators require few external passive components
and are appropriately rated for heat dissipation.
2.7
Hub Configuration
The TUSB8044EVM can be configured by setting several inputs to the TUSB8044 that are sampled at
power-on reset or using an optional serial EEPROM or SMBUS host. A production implementation without
EEPROM or SMBUS could either rely on the default internal pullup or pulldown resistor for each
configuration input or override it with an external pullup or pulldown resistor. The settings can be modified
using SW1 and SW2 on the EVM. Descriptions of the possible configuration changes are included in
.
2.8
Optional Circuitry
The TUSB8044 EVM design implements a variety of LEDs, none of which are required by the USB
specification. They are provided to make testing and debugging easier.
•
D1 – indicates that the upstream USB port power is on
•
D4 – indicates that 3.3 V is being applied to the TUSB8044 EVM
•
D5 – indicates downstream USB port 1 power is on
•
D6 – indicates downstream USB port 2 power is on
•
D7 – indicates downstream USB port 3 power is on
•
D8 – indicates downstream USB port 4 power is on
The switches (SW1, SW2, and SW3) and headers (J7, J8, J9) present on the TUSB8044 EVM are
intended only for lab evaluation and are not required for production designs.
