Compensation network with MLCC (multiple layer ceramic capacitor) at the output

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Compensation network with MLCC (multiple layer

ceramic capacitor) at the output

MLCCs with values in the range of 10 µF-22 µF and rated voltages in the range of 10 V-25 V

are available today at relatively low cost from many manufacturers.

These capacitors have very low ESR values (a few m

Ω) and thus are occasionally used for

the output filter in order to reduce the voltage ripple and the overall size of the application.

However, a very low ESR value affects the compensation of the loop (see Section 4: Closing

the loop) and in order to keep the system stable, a more complicated compensation network

may be required. Figure 29 shows an example of a compensation network that stabilizes the

system with ceramic capacitors at the output (the optimum component value depends on

the application).

Figure 29.

MLCC compensation network example

7.1

External SOFT_START network

At the start-up, the device can quickly increase the current up to the current limit in order to

charge the output capacitor. If a soft ramp-up of the output voltage is required, an external

soft-start network can be implemented as shown in Figure 30.

COMP pin.

This clamps the duty cycle, limiting the slew rate of the output voltage.