• State TI Thinks Resolved
  • Locked Locked
  • Replies 5 replies
  • Answers 1 answer
  • Subscribers 53 subscribers
  • Views 676 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

CC1120: CC1120 - PA analog output damaged?

Jan Krchnak
Prodigy 140 points
Part Number: CC1120
Other Parts Discussed in Thread: TPD1E0B04

Hi,

i have a big problem since 1 year. We use CC1120 in our outdoor products, whereby we transmit data from sensor nodes to main station. We had many cases, when all nodes were lost at once. The problem appeared on main station apparently. After investigations we found this followed issue:

- The signal from the main station is hardly to catch and if we have signal, only very poor -110 to -120 dBm (only if we are 1-2 meter  far from main station)

- The signal from sensor node at main station is very good (I suppose, the receiver is working well).

- cc1120 is heating up during TX transmitting and current goes up to about 170 mA.

After that I found this curiosity: The resistance between PA and Ground is only 8 - 9 Ohm. Uff. Normally i would expected High-Z or very high resistance. I compared it with new CC1120 module, and really the new one has about 2 MOhm on PA to Ground. That is the reason of high current consumption during tx mode and too low output performance. LNA_P and LNA_N inputs seem to be ok.

Has anybody met such similar issue? The only solution for this issue we had, was main station changing. After we had much more problems we have investigated in last time and found this problem. If it would help you, i can provide my schematic using CC1120 and layouts of th board.

The question is, what happened, what could cause this issue?

Thanks

Best regards,

Jan

  • 0
    TI__Guru**** 317180 points
    This sounds like ESD damage.

    - Do your station have a different design than the nodes?
    - Is any ESD protection included?
  • 0 in reply to TER
    Prodigy 140 points

    Hi,

    Thank you for your fast answering.

    1. Yes, sensor node has only this difference: There is used internal PCB antenna inside the housing of sensor node (main station has an external antenna connected through MMCX connector). But the design of circuit around the RF CC1120 module is basically the same.

    2. No. There is no additional ESD protection on antenna path. I relied on only the internal ESD protection circuit of CC1120 and the recommend schematic design and parts from your documents. Maybe i missed something.

    Now i see that internal ESD protection of CC1120 is mentioned only for human body model (+- 2kV). Maybe in real world (outside) it is not enough. I checked out many sensors from our stations and i found, the damage occurred mostly at time when there was raining in the region. I assume there could be also lightning storm. Could it be this reason?

    How could I make additional ESD protection for antenna? Do you mean something like protection zener diode?

    May i send you also my layouts, and schematic of RF circuit. Could you take a look, if there is something wrong? We have 4-layer PCB: 1. Top Layer (Side with RF CC1120 module), 2. Internal Layer 1 - Ground, 3. Internal Layer - Ground + RF-VDD Plane, 4. Bottom Layer.

    Thanks

    Jan

  • 0 in reply to Jan Krchnak
    Prodigy 140 points

    Here is attached schematic of circuit with RF CC1120 module and layouts of the whole PCB board:

    PCBoard with CC1120 - Layouts_Components_3DView.PDF

    CC1120 Module - Schematic.pdf

  • 0 in reply to Jan Krchnak
    TI__Guru**** 317180 points

    We don't do recommendations on how to do ESD protection on the board since this is a system level task. A design using a PCB antenna where no part of the PCB is exposed will require less ESD protection than a design where "everyone" can touch the design. Making generic recommendations would therefore be difficult since it's a wide range of system implementations where they would have different needs.

    A design with an antenna that is possible to touch for "everybody" require extra ESD protection since the RF pins typically is more exposed for ESD. Typically a ESD diode should be placed as close to the antenna as possible ensuring that if a ESD pulse enters the antenna the energy goes through the diode and to ground and is not "seen" by the RF pins. The ESD diode should present a low cap load to the pin. http://www.ti.com/lit/ds/symlink/tpd1e0b04.pdf is one option.

  • 0 in reply to TER
    Prodigy 140 points

    Hi,

    Thank you very much. It can be as you said. I must admit we haven't done any ESD tests with that board. We will put additional ESD protection to antenna and try to do some ESD tests. I will inform you if something changed.

    Thanks

    Best regards,

    Jan