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Original question:

TIDA-01387: Inductor Selection

TIDA-01387: Zener Diode Selection

Karan Aggarwal
Prodigy 230 points
Part Number: TIDA-01387
Other Parts Discussed in Thread: TPS61021A

Can I use this zener diode: MMSZ4689T1 instead of the original one - 1SMB5918BT3G used in the design?

Also Ive created a gsm supply using reference design. Could you please review the layout and suggest improvements

if any?

Schematic:

BOM:

Layout (VGSM trace is routed, though not visible below)

  • 0
    Prodigy 230 points
    the bottom layer is ground plane
  • 0 in reply to Karan Aggarwal
    TI__Mastermind 40080 points

    Hi Sir,

    You can use the Zener your chosen in your application.

    What is the Io and Io max in your application? Suggest you add  two vias under the IC, so that the GND of the top layer and the bottom layer connected together!

  • 0 in reply to Helen chen
    Prodigy 230 points

    Hey Helen

    Thanks for your reply.

    By Io and Io max, I hope you are referring to the load current, right?

    Usually its in the 20mA to 100mA range with the pulse current that be as high as 2 A and last as long as 577 µs within a 4.615-ms period.

    Since it powers a SIMCOM800C gprs module the avg current comes out to be 250mA.

    Also, there is a solder pad below the IC. Are you saying that I need to bury a via

    below that? Wouldn't it be enough if I include more vias very close to the

    IC at the output side or will below the IC be a must?

    Also, I had read in a TI application note for power supplies that the 

    Analog ground and Digital ground must be connected at only one point.

    Since the lower ground is feeding the rest of the pcb also which is mostly

    serving digital signals, I've added vias

    only at the output side, to ensure a single connection point between the two.

    Rgds

    Karan

  • 0 in reply to Karan Aggarwal
    TI__Mastermind 40080 points

    Hi Sir,

    For the layout, please refer to the section 10.2 in the datasheet on page 18. or please refer to the TPS61021 user guide.

  • 0 in reply to Helen chen
    TI__Mastermind 40080 points

    Hi Sir,

    Yes, what I mean is the load current.

    Yes, bury vias. Please check the TPS61021A EVM layout in the below picture.

    top layer:

    Bottom layer: