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2022-09-15 14:32:14
LED7706 6 -row 30mAh LED driver for LCD panels with 6 rows of lift regulators (2)
Among them, vin, min is the minimum input voltage, and iOUT is the total output current.
Note: The lower the value of the inductor (the lower the switch frequency), the bandwidth can be achieved. The output capacitor must directly participate in the voltage circuit converter to avoid large enough line conversion from the maximum input voltage to the minimum input voltage ( #8710; VOUT should not exceed 50-100 millival):
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Once the output capacitor is selected, the RCOMP can be calculated as:
Among them, GM u003d 2.7S, GEA u003d 375μs formula 10 will set the ring bandwidth to FU. Then, determine that the CCOMP capacitor sets the frequency of the zero point to 5 times the loop bandwidth:
A simple way to optimize different applications is to use 20K instead of RCOMP fine -tuning and fine -tuning and fine -tuning and fine adjustment of RCOMP. Adjust their values u200bu200bto properly damch output transient response. Insufficient damping will lead to excessive ringing of the output end and poor phase margin. Figure 10A10B gives an example of compensation adjustment for typical applications.
Slope compensation
The topology structure of constant frequency and peak current mode has the advantages of easy realization of the loop. Compensation output ceramic lid (reduced cost and application scale) and rapid transient response. In addition, this peak current current measurement simplifies current limit protection to avoid saturated inductors that do not want. On the other hand, there is a disadvantage of this topological structure: when there is an inherently open -loop instability, when the duty cycle is greater than 0.5. This phenomenon is called ""secondary harmonic instability"