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LM4F230H5QR

eli
Guru 13485 points
  1. Do I need to connect GNDA to the GND? (I only need the UART ports and the USB)
  2. Do I need to connect VDDc to 1.2V?
  3. I noticed from the schematics of the EVL board capacitors of 0.01uF, 0.1uF and 1uF before the VDD and VDDA. Do I need to connect them?
  • 0
    TI__Expert 4705 points

    Eli,

    1. Yes. You also need to supply VDDA with +3.3V, check datasheet page 219:

    VDDA must be supplied with 3.3 V, or the microcontroller does not function properly. VDDA
    is the supply for all of the analog circuitry on the device, including the clock circuitry.

    http://www.ti.com/lit/ds/symlink/lm4f230h5qr.pdf 

    2. No, VDDc is supplied via an internal LDO. Check Figure 5-4. in the datasheet.

    3. While the device might function properly without the bypass capacitors it is highly recommended to connect them. It is good design practice to always have bypass capacitors on your power supply pins. Place the capacitors so that the 0.01uF is closest to the MCU, then the 0.1uF and finally the 1uF.

    best regards,

    Aslan Abioqa

  • 0
    Guru 117855 points

    eli said:
    Do I need to connect GNDA to the GND?

    Did not see this explicitly addressed - to achieve the best analog performance it's best to minimize the flow of digital currents through GND-A.  If yours is a 2-sided pcb - use of a "star ground" with a short, wide & direct path between GND-A and your central ground point is advised.

    While you don't believe that you need analog at this time - requirements change - best that you design well now - so that a redesign is not forced upon you in the future.  To that end - suggest that you add similar caps close to VDD-A.  (we also use an 06-03 ferrite bead - helps to further quiet the ADC)

    As always - study (and model) the schematic & layout of the EVM board - even if your target design is (for now) greatly restricted...