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BQ500212AEVM non listed resistors

Hector Solar
Prodigy 150 points
Other Parts Discussed in Thread: BQ500212A

Hello there,

We want to perform our own transmitter design based on the BQ500212A chip. We have found two resistors in the EVM of the BQ500212A transmitter board that are not listed in the BOM. These are R51 and R54.

Can be those resistors avoided or must be also included in our design?

Best regards,

Hector.

  • 0
    TI__Genius 14890 points
    Hector,

    R51 and R54 are not required. Please make sure that pin 45 on the bq500212A is tied to the 3.3V supply.

    Please recheck to make sure you have the most current version of the EVM. The BOM I can view does show the resistors and their values.

    Regards,

    Dick
  • 0 in reply to Dick Stacey
    Prodigy 150 points
    Dear Dick,

    We based on the "Schematic and Materials Application Package" (SLUUAP8A August 2013–Revised January 2014). Is this document the last version?
    I have checked that pin 45 is tied to 3.3V through a resistor is this document version. Thank you for telling me.

    Best regards,
    Hector.
  • 0 in reply to Hector Solar
    TI__Genius 14890 points

    Hector,

    Thank you for the clarification.  I was using the EVM User's Guide as my reference.  Since the EVM and the Reference Design shown in the SLUUAP8A document are similar, but not equal, that explains the differences.

    You are in good shape now.

    Regards,

    Dick

  • 0 in reply to Dick Stacey
    Prodigy 150 points

    Dear Dick,

    Having compared both documents: "Schematic and Materials Application Package" (SLUUAP8A August 2013–Revised January 2014) vs User's Guide (SLVU928A–September 2013–Revised October 2013), I find some discrepancies. Can you tell me what are the correct assumptions?

    1. Pin 3 of U7 is connected to 3V3 in SLVU928A but not in SLUUAP8A. What is correct?

    2. Capacitor C8 shows different value: 2.2uF in SLVU928A but 1uF in SLUUAP8A .

    3. Capacitor C31 is 0.1uF in SLVU928A but 1uF in SLUUAP8A.

    4. Capacitor C27-C29 are X7R in SLVU928A but NP0 in SLUUAP8A.

    5. Resistors R36 and R37 are 1Ohm  in SLVU928A but 10Ohm in SLUUAP8A.

    6. Resistor R45 is 1Mohm in SLVU928A  but 10Kohms in SLUUAP8A.

    7. Resistor R99 is 86.6Kohm n SLVU928A  but 53.6Kohm in SLUUAP8A.

    With regards,

    Hector.

  • 0 in reply to Hector Solar
    TI__Guru 68796 points

    Hi Hector

    SLUUAP8A is a good reference design to use.  It is optimized as a design vs evaluation board. 

    1.) Pin 3 of U7 is connected to 3V3 in SLVU928A but not in SLUUAP8A. What is correct?

    • Schematic has been corrected and pin 3 is tied to 3.3V, SLUUAPAB

    2.) Capacitor C8 shows different value: 2.2uF in SLVU928A but 1uF in SLUUAP8A .

    • 2.2uF is used on the EVM but 1uF is a better value to use

    3.) Capacitor C31 is 0.1uF in SLVU928A but 1uF in SLUUAP8A.

    • C31 is part of a low pass filter for the current sense amplifier.  Filter size has been increased to improve the AC performance of the circuit. Recommend using 1uF.

    4.) Capacitor C27-C29 are X7R in SLVU928A but NP0 in SLUUAP8A.

    • The circuit will work with both and UG points out the performance difference in figure 5. 

    5.) Resistors R36 and R37 are 1Ohm  in SLVU928A but 10Ohm in SLUUAP8A.

    • R36 & R37 are part of a low pass filter for the current sense amplifier.  Filter size has been increased to improve the AC performance of the circuit. Recommend using 10 ohms.

    6.) Resistor R45 is 1Mohm in SLVU928A  but 10Kohms in SLUUAP8A.

    • The Power Up ckt (R54, D8, C12, R51) is not needed and pin can be pulled to 3.3V with a 10k resistor.

    7.) Resistor R99 is 86.6Kohm n SLVU928A  but 53.6Kohm in SLUUAP8A.

    • Yes FOD_Cal R99 and FOD R24 are set slop and threshold.  FOD performance will change due to several factors as designs change.  In this case the resonant capacitors C27-C29 are X7R vs NPO so the FOD_Cal changed to compensate.  
  • 0 in reply to Bill Johns
    Prodigy 150 points

    Dear Bill,

    Thank you for your answer. It helped a lot.

    Best regards,

    Hector.