SLVSES4D September 2019 – June 2024 TPS54J060
PRODUCTION DATA
The output voltage is programmed by the voltage-divider resistors, RFB_T and RFB_B, shown in Equation 25. Connect RFB_T between the FB pin and the output, and connect RFB_B between the FB pin and AGND. The recommended RFB_B value is from 499 Ω to 20 kΩ. Determine RFB_T using Equation 25.
In most applications, a feedforward capacitor (CFF) in parallel with RFB_T is recommended. CFF can improve the transient response and increase the phase margin. CFF can be required for sufficient phase margin if the output voltage is greater than 1.8 V or if the LC double pole frequency is below fSW / 60. The frequency of the LC double pole for this application is calculated with Equation 26 to be 12.1 kHz. This is less than fSW / 60 so CFF is used.
The recommended value for CFF is calculated with Equation 27. This equation selects CFF to put a zero at fLC × 3. In this example, the calculated value is 434 pF and a standard value of 470 pF is used. For higher output voltages, the zero from CFF must be closer to the LC double pole. For example, for a 5-V application, the zero from CFF must be placed at or even below the LC double pole.