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DS90C402: Ground connection and current consumption

May
Genius 9880 points
Part Number: DS90C402

Hi,

Customer have some confirmation regarding this IC.

- What happens if the ground pin of the DS90C402 is not connected to the ground pin of the corresponding LVDS driver? Not sure about the driver side since it is embedded in a COTS devices.

- Customer read a typical 3.5 mA current consumption with no load. How to evaluate the supply current in customer application ( Customer will use the DS90C402 with a 2 kHz LVDS incoming signal) ? The load capacitance of the DS90C402 will be about 15 pF

Thank you in advance.

Regards,
Maynard

  • 0
    TI__Guru* 93670 points

    Hi Maynard,

    1). We should try to provide the same GND potential for LVDS TX and RX. Else, there would be potential GND difference. If there is a possibility of GND potential difference, we should AC couple LVDS TX and RX.

    2). Maximum power consumption is with no load at 10mA. Therefor we should use max supply(5.5V) and 10mA to calculate maximum power consumption.

    Regards ,, Nasser

  • 0 in reply to Nasser Mohammadi
    TI__Genius 9880 points

    Hi Nasser,

    Customer is not clear with the number 2.

    Based from the information, customer want to know more information/explanation on how they can evaluate the current consumption in their application. 

    Regards,
    Maynard

  • 0 in reply to May
    TI__Guru* 93670 points

    Hi Maynard,

    Customer can put ammeter in series with device power supply to measure current in their application. 

    Regards ,Nasser

  • 0 in reply to Nasser Mohammadi
    TI__Genius 9880 points

    Hi Nasser,

    Thank you for the information, just want to confirm also, is there a way the customer can priori evaluate the current consumption? Customer did not want to do tests and just want to use the datasheet data.

    Regards,
    Maynard

  • 0 in reply to May
    TI__Genius 9880 points

    Hi Nasser,

    Is there a way the customer can priori evaluate the current consumption? Customer did not want to do tests and just want to use the datasheet data.

    Regards,
    Maynard

  • 0 in reply to May
    TI__Guru* 93670 points

    Hi Maynard,

    Customer can use data sheet provided data. Data sheet specifies - as noted earlier - 10mA with open input. We can multiply this by 5.5 - 55mW power consumption.

    Regards,,Nasser

  • 0 in reply to Nasser Mohammadi
    TI__Genius 9880 points

    Hi Nasser,

    Customer have follow up questions, details below.

    "However something is still unclear for me.
    The expert keeps answering that I should use 10 mA*5.5 V that is the maximum value.

    But I asked how I can evaluate a priori the current consumption in a certain case, is this the same of the no load input case reported in the datasheet?
    Will the current consumption be the same regardless the operating frequency and the load capacitance? Is there a reference graph for this?
    With the data about the frequency and the load capacitance stated in my previous message is the current consumption closer to the typical or to the maximum?
    That is what I would like to know.
    "    Regards,
    Maynard

  • 0 in reply to May
    TI__Guru* 93670 points

    Hi Maynard,

    1). Maximum power consumption is 10mA*5.5V as noted earlier.

    2). Power consumption is independent of the frequency or the data rate.

    3). Device power consumption has not been characterized using different loading capacitance such as 15pF. Also, switching parameters have been characterized using 5pF loading capacitance only.

    Regards ,Nasser

  • 0 in reply to Nasser Mohammadi
    TI__Genius 9880 points

    Hi Nasser,

    Customer have follow up confirmation.

    Does the current consumption depends only upon the temperature or are there others factor to consider?

    I am seeing that current definitely changes when temperature also changes. If load changes is there a big factor changes also?

    Thank you in advance.

    Regards,
    Maynard

  • 0 in reply to May
    TI__Guru* 93670 points

    Hi Maynard,

    Yes power consumption changes based on temperature. note 10mA noted in the data sheet is across the operating temperature.

    Please note figure 4 through 7 of the data sheet. Output voltage is a function of the power supply voltage. Given output load changes, based on power supply voltage, current/power consumption would change as well. 

    Regards ,,Nasser

  • 0 in reply to Nasser Mohammadi
    TI__Genius 9880 points

    Hi Nasser,

    Thank you for the information.

    Customer have additional question: Why the PSRR is not reported? How can I evaluate if the ripple of my power supply is to high?

    Regards,
    Maynard

  • 0 in reply to May
    TI__Guru* 93670 points

    Hi Maynard,

    Please use internal E2E for proprietary information. 

    Regards ,, Nasser