Homework 6: Printed Circuit Board Layout Design Narrative

Transcription

1 Homework 6: Printed Circuit Board Layout Design Narrative Team Code Name: Treasure Chess Group No. 2 Team Member Completing This Homework: Sidharth Malik Address of Team Member: purdue.edu Evaluation: SEC DESCRIPTION MAX SCORE 1.0 Introduction PCB Layout Design Considerations - Overall PCB Layout Design Considerations - Microcontroller PCB Layout Design Considerations - Power Supply Summary List of References 10 App A PCB Layout Top & Bottom Copper Screenshot 20 App B PCB Layout To-Scale Component Side Layout 20 TOTAL 100 Comments: Comments from the grader will be inserted here.

2 1.0 Introduction Our project is a voice-controlled digital chess board. The board and the pieces will be displayed on two 16x32 RGB LED matrices, resulting in a 32x32 grid. The chess players will be able to speak their moves trough analog microphones provided at each end of the board. Keypads will also be available for the players to use as an alternate way of moving pieces. Each player will also have an OLED display to show game information and to confirm moves submitted via voice control. The major components of the PCB will be the three microcontrollers. Since all microcontrollers are on the PCB, the unused pins will have to be mapped to headers in case we need any to use any pins later. 2.0 PCB Layout Design Considerations Overall 2.1 PCB Components The PCB will contain the following components: Power Supply Units x 2 One for 5V and the other for 3.3V. Microcontrollers x 3 dspic33fj64gs606 [1], PIC24FJ128GA006 [2], and PIC24EP512GU810 [3] (Surface Mount) Keypad Encoders x 2 EDE1144 [4] (Through Holes) Shift Registers x 2 SN74LV164APWPR [5] (Surface Mount) 8-bit Level Translators x 2 TXB0108PWPR [6] (Surface Mount) Mini Push Button Switch x 3 [7] (Through Holes) RJ 11 Connectors x 3 [8] (Through Holes) 4-bit Level Translators x 2 TXB0104PWPR [9] (Surface Mount) 2.2 PCB Trace Sizes The wall wart will give voltage between 9V and 12V. Most of the components run on 3.3V except for the RGB LED Matrix, the keypads, the OLED displays, the shift registers, and the keypad encoders which work at 5V. The RGB LED Matrices draw a maximum of 2A current when all LED s are white. To account for that and to meet the temperature requirements, the 5V power rails will be 40 mils wide. The 3.3V power rail will be 20 mils wide since the current requirements is not that high. All other remaining traces will be 12 mils wide. -1-

3 2.3 EMI/Noise Reduction For noise reduction, ground and power rails will run parallel to each other; the power rail will be on the top and the ground layer will be on the bottom. The two microphones will be the only two sources of analog signals in the design. There will be a few PWM signals which will be generated by the display logic microcontroller (for the RGB LED matrices) and the game logic microcontroller (for providing a clock to the keypad encoders). 2.4 PCB Component Placement As shown in Fig. 1, the keypad encoders and shift registers are getting input from the game logic microcontroller. Hence, these components are being placed close to the game logic microcontroller to reduce routing. There will be an LCD display, a keypad, a microphone, and a RGB LED matrix on either side of the PCB. Fig. 1: Placement of Components on the PCB 3.0 PCB Layout Design Considerations - Microcontroller The dspic33fj64gs606 microcontroller will have 6 decoupling capacitors, the PIC24FJ128GA006 microcontroller will have 5 decoupling capacitors, and the PIC24EP512GU810 will have 6 decoupling capacitors. All decoupling capacitors will be placed very close to the Vdd and Vss pins on the microcontrollers. All microcontrollers will be using internal clocks. Only two other components need a clock: the RGB LED matrices and keypad -2-

4 encoders. The clock for the RGB LED matrices will be supplied by the display logic microcontroller. The clock for the keypad encoder will be supplied by the game logic microcontroller. There is one RJ-11 connector for each microcontroller. There will be a reset switch (mini push button) connected to each microcontroller as well. 4.0 PCB Layout Design Considerations - Power Supply 4.1 5V Power Supply This power supply was generated with the help of Texas Instruments WEBENCH Software. As shown in Fig. 2, the inductor L1 is a non standard inductor with specific requirements (L = 4.7µH; DCR = 15.5mΩ). As a result, the specific inductor (SRR1260-4R7Y) had to be used. This power supply is used to power the keypad encoders, RGB LED Matrices, and shift registers. As shown in Fig. 1, these components are placed closer to the 5V power supply so that the power rails for the 5V supply do not run all over the PCB. Fig. 2: 5V Power Supply Schematic V Power Supply This power supply was generated with the help of Texas Instruments WEBENCH Software. As shown in Fig. 3, the inductor L1 is a non standard inductor with specific requirements (L = 5.6µH; DCR = 100mΩ). As a result, the specific inductor (SDR0403-5R6ML) -3-

5 had to be used. This power supply is used to power all the microcontrollers and pulling the microphone output high. The power rail for this supply runs all over the board in approximately the shape of a W. Fig. 3: 3.3V Power Supply Schematic 5.0 Summary This report highlights the major considerations gone into designing the PCB. The considerations from this report were used carefully to come up with a successful PCB. Trace sizing, EMI reduction, and component placement were two of the major factors for determining how the PCB was designed. Two different power supplies were used for meeting the different voltage requirements. The 5 V power supply was used to draw high currents. As a result, the 5V rail had a greater width. -4-

6 6.0 List of References [1] Microchip, "dspic33fj64gs406/606/608/610," Microchip, 29 November [Online]. Available: [Accessed 31 January 2013]. [2] Microchip, "PIC24FJ128GA010 FAMILY," Microchip, 11 Nov [Online]. Available: [Accessed 29 Jan. 2013]. [3] Microchip, "PIC24EPXXX(GP/GU)810/814," Microchip, 29 Nov [Online]. Available: [Accessed 4 Feb. 2013]. [4] E-Lab Digital Engineering, Inc., "EDE1144 Keypad Encoder IC," Jameco, [Online]. Available: [Accessed 6 Feb. 2013]. [5] Texas Instruments, "SN74LV164A," Texas Instruments, Apr [Online]. Available: [Accessed 19 Feb. 2013]. [6] Texas Instruments, "TXB0108," Texas Instruments, May [Online]. Available: [Accessed 19 Feb. 2013]. [7] Sparkfun, "Mini Push Button Switch," Sparkfun, [Online]. Available: [Accessed 21 Feb. 2013]. [8] Assmann Electronics, Inc., "A R," Assmann Electronics, Inc., [Online]. Available: [Accessed 19 Feb. 2013]. [9] Texas Instruments, "TXB0104," Texas Instruments, May [Online]. Available: [Accessed 18 Feb. 2013]. -5-

7 Appendix A: PCB Layout Top & Bottom Copper Fig 4: Top layout Fig 5: Bottom layout -6-

8 Appendix B: PCB Layout To-Scale Component Side Layout -7-

9 Fig 6: Parts Layout -8-