SLVSGA9A March 2022 – August 2022 TPS55289
PRODUCTION DATA
The TPS55289 outputs a voltage at the CDC pin proportional to the sensed voltage across an output current sensing resistor between the ISP pin and the ISN pin. Equation 6 shows the exact voltage at the CDC pin related to the sensed output current.
To compensate the voltage droop across a cable from the output of the USB port to its powered device, the TPS55289 can lift its output voltage in proportion to the load current. There are two methods in the TPS55289 to implement the compensation: by setting internal register 05h or by placing a resistor between the CDC pin and AGND pin.
When using internal output voltage feedback, use the internal compensation setting. When using an external resistor divider at the FB/INT pin to set the output voltage, use the external compensation setting by placing a resistor at the CDC pin.
By default, the internal cable voltage droop compensation function is enabled with 0 V added to the output voltage. Write the value into the bit CDC [2:0] in register 05h to get the desired voltage compensation.
When using external output voltage feedback, external compensation is better than the internal register for its high accuracy. The output voltage rises in proportion to the current sourcing from the CDC pin through the resistor at the CDC pin. Use 100-kΩ resistance for the up resistor of the feedback resistor divider. Equation 7 shows the output voltage rise related to the sensed output current, the resistance at the CDC pin, and the up resistor of the output voltage feedback resistor divider.
where
Figure 7-6 shows the output voltage rise versus the sensed output current and the resistor at the CDC pin when RFB_UP is 100 kΩ.