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ZHCSKZ8B March 2020 – June 2021 LM61435-Q1

PRODUCTION DATA

封裝選項

請參考 PDF 數據表獲取器件具體的封裝圖。

機械數據 (封裝 | 引腳)

RJR|14

散熱焊盤機械數據 (封裝 | 引腳)

訂購信息

9.2.2.4 Output Capacitor Selection

The value of the output capacitor and its ESR determine the output voltage ripple and load transient performance. The output capacitor is usually determined by the load transient requirements rather than the output voltage ripple. Table 9-3 can be used to find the output capacitor and C_FF selection for a few common applications. Note that a 1-kΩ R_FF can be used in series with C_FF to further improve noise performance. In this example, improved transient performance is desired giving 2 x 47-μF ceramic as the output capacitor and 22 pF as C_FF.

Table 9-3 Recommended Output Ceramic Capacitors and C_FF Values

FREQUENCY	TRANSIENT PERFORMANCE	3.3-V OUTPUT		5-V OUTPUT
FREQUENCY	TRANSIENT PERFORMANCE	CERAMIC OUTPUT CAPACITANCE	C_FF	CERAMIC OUTPUT CAPACITANCE	C_FF
2.1 MHz	Minimum	3 x 22 μF	10 pF	2 x 22 μF	22 pF
2.1 MHz	Better Transient	2 x 47 μF	33 pF	3 x 22 μF	33 pF
400 kHz	Minimum	4 x 22 μF	4.7 pF	3 x 22 μF	10 pF
400 kHz	Better Transient	5 x 22 μF	33 pF	4 x 22 μF	33 pF

To minimize ceramic capacitance, a low-ESR electrolytic capacitor can be used in parallel with minimal ceramic capacitance. As a starting point for designing with an output electrolytic capacitor, Table 9-4 shows the recommended output ceramic capacitance C_FF values when using an electrolytic capacitor.

Table 9-4 Recommended Electrolytic and Ceramic Capacitor and C_FF Values

FREQUENCY	TRANSIENT PERFORMANCE	3.3-V OUTPUT		5-V OUTPUT
FREQUENCY	TRANSIENT PERFORMANCE	C_OUT	C_FF	C_OUT	C_FF
400 kHz	Minimum	2 x 22 μF ceramic + 1 x 470 μF, 100-mΩ electrolytic	10 pF	2 x 22 μF ceramic + 1 x 470 μF, 100-mΩ electrolytic	10 pF
400 kHz	Better Transient	4 x 22 μF ceramic + 2 x 280 μF,100-mΩ electrolytic	33 pF	3 x 22 μF ceramic + 1 x 560 μF, 100-mΩ electrolytic	22 pF

Most ceramic capacitors deliver far less capacitance than the rating of the capacitor indicates. Be sure to check any capacitor selected for initial accuracy, temperature derating, and voltage derating. Table 9-3 and Table 9-4 have been generated assuming typical derating for 16-V, X7R, automotive grade capacitors. If lower voltage, non-automotive grade, or lower temperature rated capacitors are used, more capacitors than listed are likely to be needed.