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TIC12400: Requirement of 24 Active high channel

Prashant Chavan6
Intellectual 320 points
Part Number: TIC12400

Dear All,

I have confusion of why TIC12400 has only ten channel comes with Vbat switch monitoring?, is it limitation of that part?. In our project active high signal is requirement.

otherwise please provide me details of why active low and why not active high. Which one is better?? So that we can convince our customer.

Best regards,

Prashant

  • 0
    TI__Mastermind 22965 points
    Prashant, TIC12400 has current sink option on 10-channels and hence these 10 can be used to monitor battery connected switches. All 24-channels have current-source option for use with ground connected switches.

    What type & how many switches does your customer need to support?
  • 0 in reply to Ravi Singh
    Intellectual 320 points

    Dear Sir,

    Good day and wishes,

    We have already used TIC12400 in our one of project, working fine. But according new project requirement we need to monitor high side switch i.e need of Active high signal (24V DC). Switchs will be push button type.

    Customer want to monitor 36 switches.

    I have one more question which you not answered, Normally TI digital input monitor IC used to monitor active low signal but not active high. what are technical things behind it??

    Best regards,

    Prashant

  • 0 in reply to Prashant Chavan6
    TI__Mastermind 22965 points
    Hi Prashant,

    If the customer needs to monitor 36 battery connected switches, one option is to use multiple MSDI devices (will need 4x devices to support 36 hi-side switches).

    Since it is only a ON/OFF push button type switch, another option (depending on their system flexibility) would be to include a fixed pull-down resistor for each of the 36 battery connected switch & use the TIC12400 in current-source mode with 0mA setting. This way all 24 channels of MSDI can be used to monitor the switch status.

    I did not follow your comment "normally TI digital input monitor IC used to monitor active low signal but not active high"........are you asking why the device supports 24 ground connected switch monitoring & only 10 supply connected switch monitoring? If, so the answer is the ground connected switches are the more commonly used.
  • 0 in reply to Ravi Singh
    Intellectual 320 points

    Dear Ravi,

    Thanks for your valuable input, According to datasheet of TIC12400

    The device monitors 24 direct switch inputs, with 10 inputs configurable to monitor switches connected to either ground or battery ( why not all 24 input configurable to monitor switches connected to either ground or battery???). Is there any other reason apart from one you have mentioned earlier, like related to power consumption (Pc) and power dissipation(Pd) of IC.

    I hope you understand my curiosity behind this question, and you will provide me more technical reason about the same.

    Looking forward to your reply,

    Thanks very much!

    Prashant

  • 0 in reply to Prashant Chavan6
    TI__Mastermind 22965 points
    Hi Prashant,
    Thanks for elaborating. The ground connected & battery connected switch support configuration (24 vs.10) is primarily driven by common system requirements. (ground connected switches are more prevalent in systems compared to battery connected switches). Supporting battery connected switches on all channels has trade-offs with chip area and package size.
  • 0 in reply to Ravi Singh
    Intellectual 320 points

    Hi Ravi,

    Good day and wishes!

    Thanks for helping me and make easier to understand logic behind such configuration which you provide. Could you please suggest any alternative part from TI except TIC12400 which will fulfill our requirement.

    Kind regards,

    Prashant

  • 0 in reply to Prashant Chavan6
    TI__Mastermind 22965 points
    Hi Prashant,
    TIC12400 is our best (and also industry leading) solution for automotive contact monitor currently.

    Did you have a chance to run the option I previously suggested (pull-down resistor on each switch) to enable using all 24-channels to detect the battery connected switch status using TIC12400?
  • 0 in reply to Ravi Singh
    Intellectual 320 points

    Dear Sir,

    I will consider your solution for 24 channel. But before that could you please provide block diagram for your solution for better understanding.

    Regards,

    Prashant

  • 0 in reply to Prashant Chavan6
    TI__Intellectual 2165 points

    Hi Prashant,

    As mentioned previously, we suggest using a solution that includes using TIC12400 and pull-down resistor on each switch.

    For each of the switch, the configuration we suggest is the following:

    Depending on the system voltage, including a fixed pull-down resistor for each of the 36 battery connected switch and use the TIC12400 in current-source mode with 0mA setting will enable the internal ADC to monitor the switch status.

    For example, if Vbat =24V, using R= 10k ohms and set 1V as the ON/OFF threshold, the ADC will be able to recognize if switch is closed or not.

    All 24 channels of TIC12400 can be used in this case, so only 2 TIC12400 will be needed for 36 switches.

    Thank you and please let me know if further questions.

    Regards,

    Helen