9

TUSB211, TUSB211I

www.ti.com

SLLSEO0D – MAY 2015 – REVISED OCTOBER 2017

Product Folder Links: TUSB211

Submit Documentation Feedback

Copyright © 2015–2017, Texas Instruments Incorporated

Typical Application (continued)

8.2.1 Design Requirements

TUSB211 requires a valid reset signal as described in the power supply recommendations section. The capacitor

C4 is not required if a microcontroller drives the RSTN pin according to recommendations.

Pin 11 VREG is an internal LDO output that requires a 0.1 μF external capacitor to GND to stabilize the core.

Pin 6 EQ requires an external pulldown resistor if EQ levels 0-2 are needed. If EQ level 3 is needed, then the EQ

pin can be left floating.

8.2.2 Detailed Design Procedure

The ideal EQ setting is dependent upon the signal chain loss characteristics of the target platform. The general

recommendation is to start with EQ level 0, and then increment to EQ level 1, and so on. if permissible.

In order for the TUSB211 to recognize any change to the EQ setting, the RSTN pin must be toggled. This is

because the EQ pin is latched on power up and the pin is ignored thereafter.

In addition, TUSB211 does not compensate for any DC attenuation in the signal path. Therefore, minimizing DC

loss (that is, resistance) in the system design, is suggested. As a consequence, this might lead to increased line

capacitance. This is acceptable because the TUSB211 can compensate for the additional capacitive load.

Placement of the device is also dependent on the application goal. Table 1 summarizes the recommendations.

Table 1. TUSB211 Platform Placement Guideline

PLATFORM GOAL

SUGGESTED TUSB211 PLACEMENT

Pass USB Near End Mask

Close to measurement point

Pass USB Far End Eye Mask

Close to USB PHY

Cascade multiple 211s to improve device enumeration

Midway between each USB interconnect

NOTE

USB-IF certification tests for High Speed eye masks require the mandated use of the

USB-IF developed test fixtures. These test fixtures do not require the use of oscilloscope

probes. Instead they use SMA cables. More information can be found at the USB-IF

Compliance Updates Page. It is located under the ‘Electricals’ section, ID 86 dated March

2013.

The following procedure must be followed before using any oscilloscope compliance software to construct a USB

High Speed Eye Mask:

8.2.2.1 For a Host Side Application

1. Configure the TUSB211 to the desired EQ setting

2. Power on (or toggle the RSTN pin if already powered on) the TUSB211

3. Using SMA cables, connect the oscilloscope and the USB-IF host-side test fixture to the TUSB211

4. Enable the host to transmit USB TEST_PACKET

5. Execute the oscilloscope’s USB compliance software.

6. Repeat the above steps in order to re-test TUSB211 with a different EQ setting