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MCP16251 Datasheet(PDF) 14 Page  Microchip Technology 

MCP16251 Datasheet(HTML) 14 Page  Microchip Technology 
14 / 32 page MCP16251/2 DS20005173Bpage 14 2013  2016 Microchip Technology Inc. 5.0 APPLICATION INFORMATION 5.1 Typical Applications The MCP16251/2 synchronous boost regulator operates over a wide input and output voltage range. The power efficiency is high for several decades of load range. Output current capability increases with the input voltage and decreases with the 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 MCP16251/2, use Equation 51, where RTOP is connected to VOUT, RBOT is connected to GND and both are connected to the VFB input pin. EQUATION 51: EXAMPLE 1: EXAMPLE 2: EXAMPLE 3: The internal error amplifier is a transconductance type, i.e., its gain is not related to the resistors’ value. There are some potential issues with higher value resistors. For small surface mount resistors, environment con tamination can create leakage paths that significantly change the resistor divider ratio and change the output voltage tolerance. Designers should use resistors that are larger than 1 M with precaution; they can be used on limited temperature range (20 to +85oC). For a lower temperature (down to 40oC), resistors from Examples 1 or 2 should be calculated as follows: EXAMPLE 4: EXAMPLE 5: Smaller feedback resistor values will increase the quiescent current drained from the battery by a few µA, but will result in good regulation over the entire temperature range. For boost converters, the removal of the feedback resistors during operation must be avoided. In this case, the output voltage will increase above the absolute maximum output limits of the MCP16251/2 and damage the device (for additional information, see Application Note AN1337, “Optimizing Battery Life in DC Boost Converters Using MCP1640”, DS01337. 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 highpower applications that have highsource 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. Refer to Table 51 for the recommended range of the input capacitor value. VOUT = 2.0V VFB = 1.23V RBOT = 1 M RTOP = 626.01 kwith a standard value of 620 k , V OUT is 1.992V) VOUT = 3.3V VFB = 1.23V RBOT = 1 M RTOP = 1.68 Mwith a standard value of 1.69 M V OUT is 3.308V) VOUT = 5.0V VFB = 1.23V RBOT = 1 M RTOP = 3.065 M (with a standard value of 3.09 M V OUT is 5.03V) R TOP R BOT V OUT V FB 1 – = VOUT = 2.0V VFB = 1.23V RBOT = 309 k RTOP = 193.44 kwith a standard value of 191 k V OUT is 1.99V) VOUT = 3.3V VFB = 1.23V RBOT = 309 k RTOP = 520.024 kwith a standard value of 523 k V OUT is 3.311V) 
Similar Part No.  MCP16251_16 

Similar Description  MCP16251_16 


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