Texas Instruments TUSB8020BPHP REVA User Manual page 5

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The TUSB8020BEVM also implements optional isolation using two small noise filtering capacitors and a 1-
MΩ 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.
Please 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.
3 Optional Serial EEPROM
Each TUSB8020BEVM is equipped with an onboard EEPROM/socket placeholder, U1. A small I2C
EEPROM can be installed to set the configuration registers as defined in the TUSB8020B data sheet
(SLLSEF6). 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 TUSB8020B.
The EEPROM interface defaults to programmable (not write-protected) so that any installed EEPROM's
contents 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 TUSB8020B data sheet. In addition, a
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4 Power
The TUSB8020B EVM operates from the power provided by a 5-V wall power adapter, J5, not bus power
supplied by a USB host. TI recommends using a wall power adapter that is capable of sourcing 2 A to 3 A
because the hub must be able to source significant power on its downstream ports (900 mA per port).
The TUSB8020B 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 (SLVS720). The 1.1-V core voltage required by the
TUSB8020B is sourced by the 3.3-V rail to reduce unnecessary heat dissipation. The TPS74801, U5, is a
1.5-A output single channel LDO linear regulator (SBVS074). Both regulators require few external passive
components and are appropriately rated for heat dissipation.
5 Hub Configuration
The TUSB8020BEVM can be configured by setting several inputs to the TUSB8020B 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 pull-up or pull-down resistor for each
configuration input or override it with an external pull-up or pull-down resistor. The settings can be
modified using SW1 on the EVM. Descriptions of the possible configuration changes are included in the
Configuration Switches
6 Optional Circuitry
The TUSB8020B EVM design implements a variety of LEDs, none of which are required by the USB
specification. They are provided to make testing and debug easier.
• D1 – Indicates that the upstream USB port is connected at High-Speed.
• D2 - Indicates that the downstream USB port 2 is connected at SuperSpeed.
• D3 – Indicates that the downstream USB port 1 is connected at SuperSpeed.
• D4 – Indicates that the upstream USB port is connected at SuperSpeed.
• D5 – Indicates that 5 V is being applied to the TUSB8020B EVM.
• D6 – Indicates downstream USB port 1 power is on.
• D7 – Indicates downstream USB port 2 power is on.
• D8 – Indicates BOARD_3P3V is active
The switches (SW1 and SW3) and headers (J2, J7, J8, JP1) present on the TUSB8020B EVM are
intended for lab evaluation only and are not required for production designs.
SLLU196 – March 2014
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based EEPROM utility is available upon request.
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Optional Serial EEPROM
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