L5963 datasheet(32/49 Pages) STMICROELECTRONICS

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Application information

L5963

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DocID028553 Rev 3

Figure 14. Closed loop system with TYPE III network

The above figure shows the closed loop system with a TYPE III compensation network and

presents the closed loop transfer function. See the guidelines for calculation of TYPE III

network below:

Choose a value for R1, usually between 2 k and 5 kΩ.

Choose a gain (R2/R1) that shifts the Open Loop Gain up to give the desired

bandwidth. This allows the 0 dB crossover to occur in the frequency range where the

Type III network has its second plateau in the gain. The following equation calculates

an R2 that accomplishes this, given the system parameters and a chosen R1.

Equation 9

C2 is calculated by placing the zero at 50% of the output filter double pole frequency:

Equation 10

C1 can be calculated by placing the first pole at the ESR zero frequency:

Equation 11

Set the second pole at half the switching frequency and also set the second zero at the

output filter double pole. This combination brings the following equation:

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