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CXW8508 View Datasheet(PDF) - Unspecified

 Part Name Description Manufacturer CXW8508 CXW8508 - SOP8 PIN Unspecified
CXW8508 Datasheet PDF : 9 Pages
 1 2 3 4 5 6 7 8 9 深圳市诚芯微科技有限公司　　　　　　　　　　　　　　　　　　　　　　ＣＸ８５０８ The goal of compensation design is to shape the converter transfer function to get a desired loop gain. The system crossover frequency where the feedback loop has the unity gain is important. Lower crossover frequencies result in slower line and load transient responses, while higher crossover frequencies could cause system insta- bility. A good rule of thumb is to set the cross- over frequency below one-tenth of the switching frequency. To optimize the compensation components, the following procedure can be used. capacitor (C6) is required. It is required if the ESR zero of the output capacitor is located at less than half of the switching frequency, or the following rela- tionship is valid: If this is the case, then add the second compensation capacitor (C6) to set the pole fP3 at the location of the ESR zero. Determine the C6 value by the equation: 1. Choose the compensation resistor (R3) to set the desired crossover frequency. Determine the R3 value by the following equation: Where fC is the desired crossover frequency which is typically below one tenth of the switch- ing frequency. 2. Choose the compensation capacitor (C3) to achieve the desired phase margin. For applica- tions with typical inductor values, setting the compensation zero, fZ1, below one-forth of the crossover frequency provides sufficient phase margin. Determine the C3 value by the following equa- tion: External Bootstrap Diode It is recommended that an external bootstrap diode be added when the system has a 5V fixed input or the power supply generates a 5V output. This helps im- prove the efficiency of the regulator. The bootstrap diode can be a low cost one such as IN4148 or BAT54. CX8508 Where R3 is the compensation resistor. 3. Determine if the second compensation Figure 2—External Bootstrap Diode This diode is also recommended for high duty cycle operation when output voltage (VOUT>12V) applications 7