JAJSSK4A December 2023 – June 2024 TPSM64404 , TPSM64406 , TPSM64406E
PRODUCTION DATA
To increase phase margin when using an output capacitance close to the minimum in Table 7-4, a feedforward capacitor, designated as CFF can be placed across the upper feedback resistor. Place the zero created by CFF and RFBT higher than one fifth the switching to boost the phase without significantly increasing the crossover frequency. Because this CFF capacitor can conduct noise from the output of the circuit directly to the FB node of the IC, a 4.99-kΩ resistor, RFF, must be placed in series with CFF. If the ESR zero of the output capacitor is below 200 kHz, do not use CFF.
Additionally, for a dual output voltage output of 5 V for VOUT1 and 3.3 V for VOUT2, a fixed-frequency configuration can be used. Connect FB to VCC through a 10 kΩ resistor for a 5-V output or connect FB to AGND for a 3.3-V output. With the use of internal fixed feedback resistors, higher efficiency can be observed.