TUSB551

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SLLSEJ1A – MARCH 2014 – REVISED MARCH 2014

The output swing setting can also be configured based on the amplitude needed to pass the compliance test.

This setting will also be based on the length of interconnect or cable the TUSB551 is driving. This terminal

should be pulled low through a resistor to ground or left floating. The application schematic above shows the

implementation. See Device Functional Modes section for OS values.

9.2.1.3 Application Performance Plot

Figure 14. TX Compliance Test with TUSB551 EQ = 3dB OS = 1050mV DE = 0dB

10 Power Supply Recommendations

This device is designed to operate with a 1.8V supply. If using a higher voltage system power supply such as

VBUS, a voltage regulator can be used to step down to 1.8V. Decoupling capacitors may be used to reduce

noise and improve power supply integrity.

11 Layout

11.1 Layout Guidelines

•

The 100nF capacitors on the TXP and SSTXN nets should be placed close to the USB connector (Type A,

Type B, and so forth).

•

The ESD and EMI protection devices (if used) should also be placed as close as possible to the USB

connector.

•

Place voltage regulators as far away as possible from the differential pairs.

•

In general, the large bulk capacitors associated with each power rail should be placed as close as possible to

the voltage regulators.

•

It is recommended that small decoupling capacitors for the 1.8V power rail be placed close to the TUSB551

as shown below.

•

The SuperSpeed differential pair traces for RXP/N and TXP/N must be designed with a characteristic

impedance of 90

Ω ±10%. The PCB stack-up and materials will determine the width and spacing needed for a

characteristic impedance of 90

Ω.

•

The SuperSpeed differential pair traces should be routed parallel to each other as much as possible. It is

recommended the traces be symmetrical.

•

In order to minimize cross talk, it is recommended to keep high speed signals away from each other. Each

pair should be separated by at least 5 times the signal trace width. Separating with ground will also help

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Product Folder Links: TUSB551