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MP2145 数据表(PDF) 17 Page - Monolithic Power Systems |
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MP2145 数据表(HTML) 17 Page - Monolithic Power Systems |
17 / 19 page MP2145 – 5.5V, 6A, 1.2MHz, COT, BUCK SWITCHER MP2145 Rev. 1.11 www.MonolithicPower.com 17 12/20/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. Selecting the Output Capacitor The output capacitor stabilizes the DC output voltage. Ceramic capacitors are recommended. Low ESR capacitors are preferred to limit the output voltage ripple. Estimate the output voltage ripple as: OUT OUT OUT ESR S 1 IN S VV 1 V 1 R f L V 8 f C2 Where L1 is the inductor value and RESR is the equivalent series resistance (ESR) value of the output capacitor. When using ceramic capacitors, the capacitance dominates the impedance at the switching frequency, and causes most of the output voltage ripple. For simplification, the output voltage ripple can be estimated as: OUT OUT OUT 2 S 1 IN VV ΔV1 8 f L C2 V For tantalum or electrolytic capacitors, the ESR dominates the impedance at the switching frequency. For simplification, the output ripple can be approximated as: OUT OUT OUT ESR IN S1 VV ΔV 1 R f L V The characteristics of the output capacitor also affect the stability of the regulation system. For MP2145, 2pcs 22uF Co can satisfy the most application. Add Co can reduce DCM and CCM output ripple effectively. However, a very large Co may cause light group pulse in sleep mode. Load Transient Optimization MP2145 can add a capacitor (Cc) between ramp pin and output sense pin to improve load transient. The larger Cc value is, the faster load transient respond speed is. A typical Cc 22pF trades off load transient and loop stability, maximum Cc is less than 200pF in case of SW instability issue. Further, MP2145 internally has optimized compensate block to cover most application. Ramp pin can be floated in normal application. PCB Layout Recommendation Proper layout of the switching power supplies is very important, and sometimes critical to make it work properly. Especially, for the high switching converter, if the layout is not carefully done, the regulator could show poor line or load regulation, stability issues. For MP2145, the high speed step-down regulator, the input capacitor should be placed as close as possible to the IC pins. As shown in Figure 7, the 0805 size ceramic capacitor is used, please make sure the two ends of the ceramic capacitor be directly connected to PIN 8 (the Power Input Pin) and PIN 10/11/12 (the Power GND Pin). 1 4 10 9 3 7 6 12 SW OUT RAMP FB VIN SW VIN PG EN MODE/ VCON GNDGNDGND 5 2 8 11 Cin Cout R1 R2 GND Pin10,11,12 (PGND) Pin8 (VIN) Lout Figure 7: Two ends of Input decoupling Capacitor close to Pin 8 and Pin 10/11/12 |
类似零件编号 - MP2145 |
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类似说明 - MP2145 |
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