TPS25751AS datasheet(30/85 Pages) TI2

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that has minimal impact on adjacent higher speed lanes. The TX inner mask enforces the maximum limits on the

rise and fall times. Refer to the USB-PD Specifications for more details.

8.3.1.4 USB-PD BMC Transmitter

The TPS25751A transmits and receives USB-PD data over one of the CCy pins for a given CC pin pair (one

pair per USB Type-C port). The CCy pins are also used to determine the cable orientation and maintain the

cable/device attach detection. Thus, a DC bias exists on the CCy pins. The transmitter driver overdrives the CCy

DC bias while transmitting, but returns to a Hi-Z state, allowing the DC voltage to return to the CCy pin when not

transmitting. While either CC1 or CC2 can be used for transmitting and receiving, during a given connection only,

the one that mates with the CC pin of the plug is used, so there is no dynamic switching between CC1 and CC2.

USB-PD BMC TX/RX Block Diagram shows the USB-PD BMC TX and RX driver block diagram.

Digitally

Adjustable

VREF (VRXHI, VRXLO)

Level Shifter

Driver

PD_TX

PD_RX

LDO_3V3

CC2

CC1

USB-PD Modem

Figure 8-7. USB-PD BMC TX/RX Block Diagram

Figure 8-8 shows the transmission of the BMC data on top of the DC bias. Note that the DC bias can be

anywhere between the minimum and maximum threshold for detecting a Sink attach. This note means that the

DC bias can be above or below the VOH of the transmitter driver.

DC Bias

VOH

VOL

DC Bias

VOH

VOL

Figure 8-8. TX Driver Transmission with DC Bias

The transmitter drives a digital signal onto the CCy lines. The signal peak, VTXHI, is set to meet the TX masks

defined in the USB-PD Specifications. Note that the TX mask is measured at the far-end of the cable.

TPS25751A

SLVSJG7 – MAY 2026

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