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MCP1640TIMC Datasheet(PDF) 15 Page  Microchip Technology 

MCP1640TIMC Datasheet(HTML) 15 Page  Microchip Technology 
15 / 32 page 2010 Microchip Technology Inc. DS22234Apage 15 MCP1640/B/C/D 5.0 APPLICATION INFORMATION 5.1 Typical Applications The MCP1640/B/C/D synchronous boost regulator operates over a wide input voltage and output voltage range. The power efficiency is high for several decades of load range. Output current capability increases with input voltage and decreases with increasing output voltage. The maximum output current is based on the NChannel peak current limit. Typical characterization curves in this data sheet are presented to display the typical output current capability. 5.2 Adjustable Output Voltage Calculations To calculate the resistor divider values for the MCP1640/B/C/D, the following equation can be used. Where RTOP is connected to VOUT, RBOT is connected to GND and both are connected to the FB input pin. EQUATION 51: Example A: VOUT = 3.3V VFB = 1.21V RBOT = 309 k RTOP = 533.7 k (Standard Value = 536 k) Example B: VOUT = 5.0V VFB = 1.21V RBOT = 309 k RTOP = 967.9 k (Standard Value = 976 k) There are some potential issues with higher value resistors. For small surface mount resistors, environment contamination can create leakage paths that significantly change the resistor divider that effect the output voltage. The FB input leakage current can also impact the divider and change the output voltage tolerance. 5.3 Input Capacitor Selection The boost input current is smoothed by the boost inductor reducing the amount of filtering necessary at the input. Some capacitance is recommended to provide decoupling from the source. Low ESR X5R or X7R are well suited since they have a low temperature coefficient and small size. For most applications, 4.7 µF of capacitance is sufficient at the input. For high power applications that have high source impedance or long leads, connecting the battery to the input 10 µF of capacitance is recommended. Additional input capacitance can be added to provide a stable input voltage. Table 51 contains the recommended range for the input capacitor value. 5.4 Output Capacitor Selection The output capacitor helps provide a stable output voltage during sudden load transients and reduces the output voltage ripple. As with the input capacitor, X5R and X7R ceramic capacitors are well suited for this application. The MCP1640/B/C/D is internally compensated so output capacitance range is limited. See Table 51 for the recommended output capacitor range. While the NChannel switch is on, the output current is supplied by the output capacitor COUT. The amount of output capacitance and equivalent series resistance will have a significant effect on the output ripple voltage. While COUT provides load current, a voltage drop also appears across its internal ESR that results in ripple voltage. EQUATION 52: Where dV represents the ripple voltage and dt represents the ON time of the NChannel switch (D * 1/ FSW). Table 51 contains the recommended range for the input and output capacitor value. R TOP R BOT V OUT V FB  1 – = TABLE 51: CAPACITOR VALUE RANGE CIN COUT Min 4.7 µF 10 µF Max none 100 µF I OUT C OUT dV dt  = 
Similar Part No.  MCP1640TIMC 

Similar Description  MCP1640TIMC 


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