8.2.1 Design Requirements

For this design example, use the parameters provided in Table 8-1.

Table 8-1. Design Parameters

PARAMETER

VALUE

Pre-channel A to B PCB trace length(1), LAB.

1 inches ≤ LAB ≤ 20 inches

Post-channel C to D PCB trace length(1), LCD.

≤ 6 inches

Minimum distance of the AC capacitors from TUSB522P, LAC-CAP

0.25 inches

Maximum distance of ESD component from the USB receptacle, LESD

0.6 inches

Maximum distance of series resistor (RESD) from ESD component, LR_ESD.

0.25 inches

CAC-USB1 AC-coupling capacitor (75 nF to 265 nF)

100 nF

CAC-USB2 AC-coupling capacitor (297 nF to 363 nF)

Options:

•

RX1 or RX2 are DC-coupled to USB receptacle

•

330 nF AC-couple with RRX resistor

Optional RRX resistor (220-kΩ ± 5%)

Not used

Optional RESD (0-Ω to 2.2-Ω)

Not used

VCC supply (3-V to 3.6-V)

3.3-V

EQ1 for RX1P/N (3, 6, or 9dB)

9 dB (EQ1 = High)

De-Emphasis 2 for TX2P/N (0, -3.5, and - 6.2 dB)

-6.2 dB (OS2 = Low, DE2 = High)

EQ2 for RX2P/N (3, 6, or 9 dB)

6 dB (EQ2 = Floating)

De-Emphasis 1 for TX1P/N (0, -3.5, and -6.2 dB)

-3.5 dB (OS1 = Low, DE1 = Floating)

Output Swing 1 (0.9 or 1.1 Vppd)

900 mV (OS1 = Low)

Output Swing 2 (0.9 or 1.1 Vppd)

900 mV (OS2 = Low)

(1)

Maximum trace length assumes an insertion loss of 0.2 dB/inch/GHz. If insertion loss is more than 0.2 dB/inch/GHz, then maximum

trace length must be reduced accordingly.

8.2.2 Detailed Design Procedure

The TUSB522P differential receivers and transmitters have internal BIAS and termination. Due to this, the

TUSB522P must be connected to the USB Host and receptacle through ac-coupling capacitors. In this example,

as depicted in Figure 8-2, 100 nF capacitors are placed on TX2P, TX2N, RX1P, RX1N, TX1P and TX1N. No

ac-coupling capacitors are placed on the RX2P and RX2N pins because it is assumed the device downstream of

the TUSB522P will have ac-coupling capacitors on its transmitter as defined by the USB 3.1 specification. The

system designer may desire to support short to VBUS protection. If this is the case, then a 330 nF ac-coupling

capacitor should be placed on RX2P/N pins.

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TUSB522P

SLLSEV9E – JULY 2016 – REVISED NOVEMBER 2023

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