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LME49810 sink pin current

Andreas Vogel
Prodigy 10 points

Hello,

anybody an idea, if the current thru the sink pin is limited internally ?

In case of traditional output current limiting, this pin will be coonnected to GND in case of short circuit via 2 BE diodes..... would this harm the sink pin ?

  • 0
    Prodigy 30 points

    I've thought about pulling the COMP pin low (to Vee) via a transistor in case of negative Overcurrent and pull down the BiasPos to OUT in case of positive overcurrent... in "simulation" it works, but whats about real world ?

    Any suggestions or comments ?

    How do you solved the problem/issue with overcurrent limiting ?

    Andreas

  • 0
    TI__Intellectual 1240 points

    Hello Vogel-san,

    I'll make some comment on your question about sink pin current limit. LME49810 has output current limit ckt on both source and sink pin. Figure-2 is showing simplified schematic though actual output of source pin is configured with durlington connection and has resistor for current sensing by Vbe and back to base of duarlington Trs. The typical current limit value is around 60mA on both source and sink pin.

    I hope this comment will be helpful for your question.

    Best regards

    T NAOKAWA 

  • 0 in reply to Andreas-Claudius Vogel
    TI__Intellectual 1240 points

    Hello Vogel-san,

    I'll make a comment about LME49810 simulation schematic you downloaded. This schematic is very specific condition to look at sink side output current becuse comp pin is connected to GND. To work amplifier mode, you need to change the connection as follow. 1) Remove comp pin connection to GND and put 10pF cap between comp pin and sink pin, 2)short BiasP and BiasM or short R8 resistor, 3) remove OSENSE connection to GND and OSENSE pin connect to R9, 4) Change R9 value to 1k or higher value. Incase of 1k ohms, you will have output voltage clamp around +/-60V because of current limit on both source and sink pin. If you want higher voltage, you will use maybe 2k ohms. This connection is similar to Figure 3 test ckt schematic in datasheet.

    I hope this help for your problem and issue.

    Best regards

    T NAOKAWA

     

  • 0 in reply to Toyojiro Naokawa
    Prodigy 30 points

    Sorry, but  wich shematic do you mean ? The one in the datasheet ?

    And, if I understood it right, there are current limit circuits inside the LME49810 chip for the source and sink pins ?

    Best regards and thanks for the help,

    Andreas

  • 0 in reply to Andreas-Claudius Vogel
    TI__Intellectual 1240 points

    Hello Vogel-san,

    The connection I mentioned for your simulation for just LME49810 is Fig 4 in the datsheet.

    The simulation schematic you down loaded is not good to check device behaivior as amplifier. to check amplifier behavior you need to change the connection as fig-4 in the datasheet.

    Yes, your understanding is correct that LME49810 has internal current limit ckt.

    Best regards

    T NAOKAWA