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Tps70148 dual output regulator

vinoth pandiyan
Prodigy 105 points

hello sir

            we are using Tps70148 dual output regulator of 3.3v vout1  and 1.5v vout2 for cmos sensor (OV7962) based camera application,Here problem is  our cmos sensor have four input rail of  3.3v and one 1.5 core voltage  so here we utilize this single 3.3v output of  Tps70148 to those four separate inputs of cmos sensor  ,

In no load condition the regulator IC maintain 3.27v in vout1 measured in multimeter and 1.49 in vout2 but we connect to those four output it regulate 3.43v in vout1 and 2.22v in vout2 this the problem , we don't know why it regulate above than determined

But we input the sensor as different rail have separate decoupling cap as recommenced by cmos vendor 

for your reference here i attach our schematic4048.camera_or9_SCH.pdf

in our schematic there is one controller (CY7C68013) we check with cmos sensor only , we use the controller as DNI so pls consider this

Thank you

vinoth pandiyan

  • 0
    TI__Expert 3300 points

    Hi Vinoth,

    Thanks for your post. We are currently looking into this. 

    Regards,

    Kartik

  • 0 in reply to Kartik Sinha
    TI__Guru 55940 points

    Hi Vinoth,

    I have a few questions to help me better understand the problem you are having.

    Could you tell me more about the load condition?  How much current are you drawing?  Is the load constant?  Does the LDO regulate incorrectly when the Camera Sensor draws more current or in all states (power up, stand by, sleep, ect)?

    Are the higher regulations continuous or is there a slow transient where the regulated outputs decrease?

    On your PCB, is there anything that could be adding extra output voltage?

    Very Respectfully,

    Ryan

  • 0 in reply to Ryan Eslinger
    Prodigy 105 points

    Hi Ryan

                                               Thanks  for your Reply,   Independently  cmos sensor only posses 60 mA constant current without controller and we utilize the regulator only for sensor and controller .

    And both 3.3v and 1.8 outputs have 33uf  tantalum capacitors  for stability ,we select the capacitor as recommended ESR level as per data sheet ,

    Here Pls explain me why and what are reasons it regulate undetermined level .

    Thanks Regards

    vinoth pandiyan

  • 0 in reply to vinoth pandiyan
    TI__Guru 55940 points

    Hi Vinoth,

    I apologize if I am mistaken, but I thought you were using TPS70148 which has a 3.3V and a 1.5V output.  Your last response indicates a 1.8V output.  Could you please verify which part you are using?

    Could you also clarify what the conditions are where you are experiencing the 2.22V output on vout2?  What are the conditions with the controller and cmos sensor when you see the higher outputs?

    Very Respectfully,

    Ryan

  • 0 in reply to Ryan Eslinger
    Prodigy 105 points

    Hi Ryan

                         sorry ,that is 1.5v only and no load condition it regulate as 3.3V and 1.5v  as normal ,when it connect to cmos load  it regulate 3.3 as 3.46 and 1.5 as 2.22  at 60 mA current flow , this is problem.

  • 0 in reply to vinoth pandiyan
    TI__Guru 55940 points

    Hi Vinoth,

    This is unusual behavior!  Have you tried replacing the TPS70148 with another part?  If so, is the behavior the same on every TPS70148?

    To help me better understand the conditions, could you please send me your PCB layout and a waveform containing input, output and load current from startup to the 60mA load?

    Very Respectfully,

    Ryan