The TPS65235-1 device has a 1-MHz nonsynchronous boost converter integrated and the boost converter features the internal compensation network. The TPS65235-1 device works well with both ceramic capacitor and electrolytic capacitor.

The recommended ceramic capacitors for the TPS65235-1 application are, at the minimum, rated as X7R/X5R, with a 35-V rating, and a 1206 size for the achieving lower LNB output ripple. Table 7-1 lists the recommended ceramic capacitors list for both 4.7-µH and 10-µH boost inductors.

If more cost-effictive design is needed, use a 100-µF electrolytic (low ESR) and a 10-µF or 35-V ceramic capacitor.

Figure 7-6 and Figure 7-7 show a bode plot of boost loop with 4.7-µH and 10-µH inductance and 4 µF, 5 µF, 7.5 µF, 10 µF, 15 µF, and 20 µF of boost capacitance after degrading. As the boost capacitance increases, the phase margin increases.

Figure 7-6 Gain and Phase Margin of the Boost Loop With Different Boost Capacitance (V_IN = 12 V, V_OUT = 18.2 V, I_LOAD = 1 A, f_SW = 1 MHz, 4.7 µH, Typical Bode Plot)

Figure 7-7 Gain and Phase Margin of the Boost Loop With Different Boost Capacitance (V_IN = 12 V, V_OUT = 18.2 V, I_LOAD = 1 A, f_SW = 1 MHz, 10 µH, Typical Bode Plot)