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Texas Instruments TUSB2XX implementation Application notes
Application Report
SLLA392 – May 2018
TUSB2XX Implementation Guide
Michael Walker
ABSTRACT
This document is for platform designers implementing the TUSB2XX family of USB 2.0 redrivers. The
Family consists of the TUSB211, TUSB212, TUSB213, TUSB214, and TUSB215. Detailed information for
each device can be found in each devices separate datasheet.
This document gives the differences and similarities between the TUSB2XX devices. This document
provides board design recommendations for the various devices and features for designing with the
TUSB2XX devices. This document is intended for developers familiar with high-speed PCB design and
layout. Knowledge of the USB 2.0 protocol is recommended as well. The following layout
recommendations should not be considered the sole method of implementation, but rather as a guide. The
preferences of the individual developer, requirements of the design, number of components in the circuit,
as well as many other factors can influence each individual layout.
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Contents
Introduction ................................................................................................................... 2
Differences Between Devices .............................................................................................. 2
General Implantation Guidelines ........................................................................................... 4
Layout Differences and Examples ........................................................................................ 5
Testing ........................................................................................................................ 7
Frequently Asked Questions .............................................................................................. 10
References .................................................................................................................. 12
List of Figures
1
Simplified Schematic ........................................................................................................ 2
2
RGY Package 14 Pin (VQFN) Top view (TUSB213, TUSB215) ...................................................... 3
3
RWB Package 12 Pin (X2QFN) Top View for TUSB211, TUSB212, TUSB214 (no DC_BOOST on
TUSB211) ..................................................................................................................... 3
4
TUSB211, TUSB212 and TUSB214 Layout Example .................................................................. 5
5
TUSB213 and TUSB215 Layout Example
6
USB 2.0 High Speed Test Upstream Signal Quality Testing
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9
10
11
............................................................................... 6
.......................................................... 8
USB-IF HS Electrical Test Tool ............................................................................................ 8
USB 2.0 Device High-Speed Test Fixture with Embedded Host ...................................................... 9
Pre-Channel and Post-Channel .......................................................................................... 10
Falling Edge Eye Diagram ................................................................................................ 11
Leading and Trailing Edge ................................................................................................ 12
List of Tables
1
TUSB2XX EQ and Boost settings ......................................................................................... 4
Trademarks
All trademarks are the property of their respective owners.
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Introduction
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Introduction
The TUSB2XX family of devices is USB High-Speed (HS) signal conditioners, designed to compensate for
ISI signal loss in a transmission channel.
TUSB2XX devices have a patented design which is agnostic to USB Low Speed (LS) and Full Speed (FS)
signals. LS and FS signal characteristics are unaffected by the TUSB2XXs while HS signals are
compensated.
Programmable signal AC boost permits fine tuning device performance to optimize High Speed signals at
the connector. This helps to pass USB High Speed electrical compliance tests.
In addition, The TUSB2XXs are compatible with the USB On-The-Go (OTG) and Battery Charging (BC)
protocols.
1.1
Typical System Implementation
Figure 1. Simplified Schematic
2
Differences Between Devices
2.1
DC Boost
All the devices in the TUSB2XX family AC boost. This compensates for ISI loss. The TUSB212, TUSB213,
TUSB214 and TUSB215 all offer DC boost which helps to improve the signal quality for USB compliance.
2.2
Power Supply Differences
The TUSB211, TUSB212 and TUSB214 require a VCC of 3.3 V. The TUSB213 and TUSB215 require a
VCC of 5 V.
2.3
Package Differences
The TUSB2XX devices come in two different packages the TUSB213 and TUB215 come in a VQFN
package, the TUSB211, TUSB212, TUSB214 come in a X2QFN package.
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Differences Between Devices
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Figure 2. RGY Package 14 Pin (VQFN) Top view (TUSB213, TUSB215)
D1P D1M
3
SCL/CD
4
11 VREG
RSTN
5
10 GND
EQ
6
2
7
1
8
12
VCC
SDA
9
DC_BOOST
/ENA_HS
D2P D2M
Figure 3. RWB Package 12 Pin (X2QFN) Top View for
TUSB211, TUSB212, TUSB214 (no DC_BOOST on TUSB211)
2.4
Charging Downstream Port
All of the TUSB2XX devices are compatible with the USB On-The-Go (OTG) and Battery Charging (BC)
protocols. Only the TUSB214 and TUSB215 act as Charging Downstream Port(CDP) Controllers.
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General Implantation Guidelines
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General Implantation Guidelines
3.1
Selecting Equalization and Boost Level for the TUSB2XX
The primary purpose of the TUSB2XXs is to restore the signal integrity of a USB high-speed channel up to
the USB connector. The platform goal is to pass the USB Near-End or Far-End Eye Mask with the
TUSB2XX in the best location.
Typically, place the TUSB2XX close to the USB connector on a host platform in order to pass Near-End
Eye Mask testing. This includes systems where the USB connector may be placed at the far-end of an
internal cable.
Typical EQ and Boost recommendations for the TUSB211, TUSB212, TUSB213, TUSB214 and TUSB215.
Table 1. TUSB2XX EQ and Boost settings
Device
TUSB211
Approximate
Gain(dB)
Max Pre-Channel
loss to pass (near
end eye mask)
Max Post-Channel
Loss to Pass (near
end eye mask)
0
1
12 inches FR4
6 inches FR4
1
2
1 meter 28 AWG
0.5 meter 28 AWG
3
1.7 meter 28 AWG
1 meter 28 AWG
EQ Settings
2
DC Boost Settings
N/A
3(lowest gain)
TUSB212,
TUSB213,
TUSB214,
TUSB215
3.2
0.4
6 inches FR4
3 inches FR4
0
LOW
2
1 meter 28 AWG
0.5 meter 28 AWG
1
MID
3
2 meter 28 AWG
1 meter 28 AWG
2
MID
5
3 meter 28 AWG
2 meter 28 AWG
3(highest gain)
HIGH
9
5 meter 28 AWG
3 meter 28 AWG
Power Supply Recommendations
On power up, the interaction of the RSTN pin and power on ramp could result in digital circuits not being
set correctly. The device should not be enabled until the power on ramp has settled to VCC or higher to
ensure a correct power on reset of the digital circuitry. If RSTN cannot be held low by microcontroller or
other circuitry until the power on ramp has settled, then an external capacitor from the RSTN pin to GND
is required to hold the device in the low power reset state.
The RC time constant should be larger than five times of the power on ramp time (0 to VCC). With a
typical internal pull up resistance of 500 kΩ, the recommended minimum external capacitance is
calculated as:
(1)
4
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Layout Differences and Examples
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4
Layout Differences and Examples
4.1
Layout Differences
The TUSB211, TUSB212 and TUSB214 all share the same X2QFN package which require connecting the
D1P pin to the D2P pin and the D1M pin to the D2M pin below the device. The TUSB213 and TUSB215
use the VQFN package and do not have their P pins and M pins connected.
4.2
Example Layouts
Figure 4. TUSB211, TUSB212 and TUSB214 Layout Example
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Layout Differences and Examples
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Figure 5. TUSB213 and TUSB215 Layout Example
4.3
High Speed layout guidelines
Refer to the following application Report for general layout guidelines (High Speed Layout Guidelines).
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Testing
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5
Testing
5.1
USB 2.0 High Speed Downstream Signal Quality Testing
When performing USB 2.0 compliance eye-diagram testing with a host or the downstream port of a HUB
with the TUSB2XX, a scenario can occur where the TUSB2XX signal boosting is not enabled. This can
occur when the test packets are being transmitted before the USB test fixture is connected to the
TUSB2XX. This scenario does not occur during device compliance eye-diagram testing as the USB test
fixture must always be connected while testing a device. This scenario only occurs during the compliance
testing with the USB test fixtures and does not affect normal operation with a host, HUB, or device.
To avoid this scenario, follow the test procedures provided by the scope equipment vendor and USB-IF
(links provided in Section 5.2). Specifically, the USB HS test fixture should be connected prior to executing
the TEST PACKETS command using the HSETT test tool. Alternatively, if the test fixture is hot-plugged to
the host or downstream HUB port after the command to send test packets has already been entered using
the HSETT tool, it is necessary to select TEST PACKETS and click “Execute” again after the test fixture is
connected to ensure the TUSB2XX detects a compliance test set-up.
The following generic procedure can be used to take the USB 2.0 compliance eye-diagrams (refer to
Section 5.4 for details):
1. Connect the USB test fixture to the host, downstream HUB (+ TUSB2XX) port or device under test.
2. Configure the host, or HUB, or device using xHSETT or HSETT to send test packets using the
procedure detailed in the HSETT documentation.
3. Start sending test packets
4. Capture test packet on scope to display eye (running compliance software on the scope)
USB 2.0 compliance eye-diagrams can be taken on host, device, and HUB platform ports configured with
the TUSB2XX using the EHCI and xHCI High-speed Electrical Test Tool Setup Instruction document
provided by the USB Implementers Forum.
5.2
USB 2.0 Upstream Signal Quality Testing
When performing USB 2.0 Compliance Eye Diagram testing on an USB device, a mechanism is required
to place the device in the proper test mode. Then output the USB Test Packets. This is normally
accomplished by using the xHSETT or HSETT to send a TEST_PACKET command to the device. Once in
test mode, the device controller repeatedly sends the Test Packets on the Port under Test until the device
is reset or power cycled. The TUSB2XX is placed between the device controller and USB port in the
system and must remain powered on with no reset being asserted to the TUSB2XX. Once the device is
sending the High-Speed Test Packets, the TUSB2XX is active and remains active as long as the Host is
sending packets, power has not been removed and no reset has been asserted. If power is removed or
the TUSB2XX is reset after the device is in test mode sending Test Packets, the device is inactive, and no
longer condition the signal.
The following generic procedure can be used to take the USB 2.0 compliance eye-diagrams (refer to
Section 5.4 for details):
1. Use the USB-IF (Or Scope Vendor’s) USB 2.0 Device High-Speed Test Fixture (See Figure 6).
Connect the USB Test Fixture to the USB device to be tested.
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Testing
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Figure 6. USB 2.0 High Speed Test Upstream Signal Quality Testing
2. Connect the PC to the USB 2.0 Device High-Speed Test Fixture
3. Invoke the High-speed Electrical Test Tool software on the PC. The main menu appears and shows
the USB2.0 host controller.
Figure 7. USB-IF HS Electrical Test Tool
4. Select Device and click TEST to enter the HS Electrical Test Tool - Device Test menu. The device
under test should be enumerated with the device’s VID shown together with the root port in which it is
connected.
5. Select TEST_PACKET from the Device Command dropdown menu and click EXECUTE. This forces
the device under test to continuously transmit test packets.
6. Switch Test Fixture from “INIT” to “TEST” to Capture Test Packet on scope to display eye (Running
Compliance software on the scope)
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5.3
USB 2.0 High Speed Embedded Host Signal Quality Testing
When performing USB 2.0 Compliance Eye Diagram testing on an embedded USB Host, a mechanism is
needed to place the Controller in the Head unit in the proper test mode. Then output the USB Test
Packets. This is accomplished with the use of a USB device with a specific VID/PID which places the
Controller into a test mode. Once in test mode, the embedded Host repeatedly sends the Test Packets on
the Port under Test until the Host is reset or power cycled. The TUSB2XX is placed between the Host and
USB port in the system and must remain powered on with no reset being asserted to the TUSB2XX. Once
the Host is sending the High-Speed Test Packets, the TUSB2XX is active and remains active as long as
the Host is sending packets. Power has not been removed and no reset has been asserted. If power is
removed or the TUSB2XX is reset after the Host is in test mode sending Test Packets, the device is
inactive and no longer condition the signal.
The following generic procedure can be used to take the USB 2.0 compliance eye-diagrams (refer to
Section 5.4 for details):
1. Use the USB-IF (Or Scope Vendor’s) USB 2.0 Device High-Speed Test Fixture (See Figure 8).
Connect the USB Test Fixture to the Head Unit USB Port to be tested.
Figure 8. USB 2.0 Device High-Speed Test Fixture with Embedded Host
2. Connect the special test device with test VID/PID info to the Test fixture (Where the USB Host would
normally connect).
3. Use any specific steps or commands to enable the Host to send Test Packets (This step may be
specific to each platform).
4. Start sending Test Packets
5. Switch Test Fixture from “INIT” to “TEST” to Capture Test Packet on scope to display eye (Running
Compliance software on the scope)
5.4
Test Procedure Document Links
Details for setting up and running the application are contained in the EHCI and xHCI High-speed
Electrical Test Tool Setup Instruction document provided by the USB-IF at the following link:
http://www.usb.org/developers/tools/HSETT_Instruction_0_4_1.pdf
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Frequently Asked Questions
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xHCI (USB 3.0 Host) – XHSETT test application:
http://www.usb.org/developers/tools/
EHCI (USB 2.0 Host) – EHSETT test application:
http://www.usb.org/developers/tools/usb20_tools/
Vendor-Specific Test Procedures:
http://www.usb.org/developers/compliance/electrical_tests/
USBET:
http://www.usb.org/developers/tools/usb20_tools/#USBET20
6
Frequently Asked Questions
6.1
What is Pre-Channel and Post-Channel?
The pre-channel is the path the signal takes from the host to the TUSB2XX device. The post-channel is
the path the signal takes from the TUSB2XX device to the USB device.
Figure 9. Pre-Channel and Post-Channel
6.2
Can D1 and D2 be swapped?
It does not matter whether D1 or D2 is connected to the host or the device. It does matter that the DP is
connected to the data plus and that DM is connected to data minus.
6.3
Does the Thermal Pad need to be connected to GND?
No, the Thermal Pad on the TUS213 and TUSB215 are not connected to anything and do not need to be
connected to GND.
6.4
What are the near end and far end eye masks?
Near end eye masks are used to test the electrical compliance to the USB protocol for USB receptacles
while far end eye masks are used to test the electrical compliance of a USB plug.
6.5
Where to place the TUSB2XX in an active cable?
The TUSB2XX should be placed on the device side of an active cable. For USB 2.0 cables, this is the
type B side of the cable. This is because the TUSB2XX can over boost the Hosts USB 2.0 signal and
trigger a disconnect in the host device.
6.6
Why is the TUSB2XX is stuck in High speed mode upon startup?
Due to the lack of HS negotiation and subsequent enumeration during HOST downstream eye diagram
test the TUSB2XX detect the HOST downstream eye diagram test by detecting high speed test fixture to
get into high speed electrical compliance mode.
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Some host or hub downstream port has been observed to pull down DP/DM low during power up or when
it is in the process of initialization. During this time period, while DP/DM is being pulled down by the host ,
if TUSB2XX is powered on TUSB2XX could detect this low bus condition on DP/DM as a test fixture and
get into high speed electrical compliance mode.
While in this mode, ENA_HS remains high even if the device is disconnected or suspend. If ENA_HS is
high, low speed or full speed device could fail to enumerate. RSTN must be low to reset the device and
exit compliance mode.
The recommendation at power up is to hold TUSB2XX in reset by holding RSTN low until the host
initialization is completed.
6.7
is the DC Boost boosting both DP and DM lines and why is it needed?
Yes, the DC Boost boosts both the DP and DM lines. DC Boost is needed to compensate for the DC loss
that occurs in the transmission channel (Longer cables have more DC loss which can result in eyediagram mask hits).
6.8
Why does the TUSB2XX not boost the falling edge?
Figure 10. Falling Edge Eye Diagram
The eye diagram has two Edges. It has the leading edge and the trailing edge not rising edge and falling
edge. This is because every falling edge is also a raising edge and every raising is also a falling edge
(see Figure 11).
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References
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Figure 11. Leading and Trailing Edge
The way to improve the trailing edge to pass electrical compliance is to reduce the capacitance on the
data lines. One way to decrease capacitance on lines is to use layout techniques that reduce capacitance.
the user can also reduce capacitance by changing the thickness of the PCB and changing the material of
the PCB to reduce the capacitance on the data lines. Another way to reduce capacitance is to use lower
capacitance ESD devices on the data lines.
7
References
•
•
•
•
•
•
•
•
•
•
•
•
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TUSB211 Datasheet (SLLSEO0)
TUSB211 Schematic Checklist (SLLA389)
TUSB211 to TUSB212 Changes (SLLA376)
TUSB212 Datasheet (SLLSEX5)
TUSB212 Schematic Checklist (SLLA391)
TUSB213 Datasheet (SLLSEX6)
TUSB213 Schematic Checklist (SLLA393)
TUSB214 Datasheet (SLLSEX7)
TUSB214 Schematic Checklist (SLLA394)
TUSB215 Datasheet (SLLSEX8)
TUSB215 Schematic Checklist (SLLA395)
High-Speed Layout Guidelines (SCAA082)
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