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LMZ34002: GND sense connection for Rset

Part Number: LMZ34002

Hi,

It says in the datasheet to connect a GND sense from the Rset to the GND closest to the load as shown in Fig 48. I don't see this trace/route in that figure. Can you provide more explanation? Is it just that we should route a trace on from the GND via on Rset to a load component tied to GND at Vout? Or can you explain it graphically some way?

Thanks,

Uttara

  • They did not follow their own recommendation. The Rset resistor is terminated to ground right at the resistor to the main PWR GND right by the IC. Typically you would want to connect it near C04 or C03. The copper GND connection is very wide copper pour area. Probably not much loss in it. Maybe someone from the module group can elaborate.
  • You are correct, the layout shows the Rset connected to GND near the module, not near the load. See the attached for an example.

     LMZ34002Sense.docx

  • Thank you the pictures you sent make sense to me and we are implementing it this way in layout. I had two more questions. For the A_Vout and Vout connection data sheet shows that they need to be connected at pins 8 and 9 only. Can you let me know whether a solid plane connecting A_Vout and Vout would be sufficient? I am not sure how to achieve this connection the way it is shown on page22 because we use larger PCB vias and the finger connecting A_Vout and Vout is much larger than shown in the datasheet. I am guessing a larger plane flood will also work the same way?

    Can you also explain the function of the A_Vout on this chip? I see that is mostly connects to Vout or can be used to control the switching frequency on the RT pin is that the case or it has a different function as well?

    Thanks,
    Uttara
  • Can you contact me directly at jarrigo@ti.com ?