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High Efficiency Battery Boost Regulator using the MCP1640Author
Giorgos Lazaridis
February 8, 2012

PAGE 4 of 4 - MCP1640 PCB Design Considerations and Drawings


PCB Design Considerations
When designing SMPS circuits, there are some considerations that must be taken into account for the PCB layout.

- Prototyping on a breadboard is usually out of the questions, since the high frequency switching currents will meet the unwanted high capacitance of the breadboard and will radically alter the results.

- The PCB tracks must be as short as possible. This ensures less EMI interference (from and to the circuit) and lower resistance

- The input and output capacitors as well as the inductor must be as close as possible to the chip

- It is important to understand that the inductor will create an EMF around it. Therefore, it is prohibited to have any sort of wire track near or underneath the inductor (even at the opposite layer) because this wire will experience heavy EMI. Ground planes around and near the inductor ensures better stability

- Using shielded inductors is a good technique to avoid EMI

- The feedback resistors and feedback loop (pins 4-5) must be as far as possible from the switching loop (pins 1-6). It is a good practice to separate them with a grounding layer to avoid false feedback measurements from inducted current.

Microchip provides the following PCB layouts for the 2 different packages:

 
SOT23-6 package (click to enlarge)		 

 
DFN-8 Package (click to enlarge)		 




The PCB Layout
Following these design considerations and adapting them to my part packages, here is the PCB layout that i designed to evaluate this chip:



In this zip file you will find the sch and brd schematic and PCB for the EaglePCB 5.11

Download file
MCP1640 Evaluation board Schematic and PCB


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  • At 12 January 2015, 21:21:09 user 123 wrote:   [reply @ 123]
      • VFB is always 1.12V -> should be corrected to 1.21 V
      Data Sheet MCP 1640

  • At 9 July 2013, 16:29:40 user Angel G. wrote:   [reply @ Angel G.]
      • I experimented today with a MCp1640 and also got around 140ma over range of Vin=2.7 .. 4.5V.
      Divider is set so the output to be 5.5V, but it can't get over 4V.
      I think there's a bug in the chip, because: When I disconnected the load (a resistor) & powered up w/o load. It managed to hold 5.5V with over 200ma to the resistor. So...

  • At 15 February 2013, 22:11:29 user Giorgos Lazaridis wrote:   [reply @ Giorgos Lazaridis]
      • @Ben Choy It is designed for 3.3 and 5 volts, but i'm quite sure it can do well at 1.2 as well. Or you can use 2 diodes to drop with little power loss.

  • At 14 February 2013, 4:35:19 user Ben Choy wrote:   [reply @ Ben Choy]
      • Just wonder, can this be adopted as a laser LED PSU, since I have a need to drive an laser LED on/off with logic voltage. The laser should take about 200mA to 300mA @ 1.2V.



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