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Power up sequence of ADG452

We used ADG452 in dual power mode. Vss=-15V Vdd=+15V.

When i supply Vss=-15V first(befor supply Vdd), the D1 pin appeared voltage -100mV. This voltage is not what we expect

So,The power up sequence Vss,Vdd,VL is problem? what is the right power up sequence.

Thank you!

  • Hi Syu,

    Can you confirm what do you mean in this statement: "When i supply Vss=-15V first(befor supply Vdd), the D1 pin appeared voltage -100mV. This voltage is not what we expect"

    Do you mean Vss is already connected (no Gnd, Vdd, VL, and S1) and then you measure D1?

    Regards,
    Yoworex

  • Thank you for your replay.

    I am sorry and i mean Vss and Gnd  is already connected (no Vdd, VL, and S1) and then i measure D1.

  • Hi Syu,

    We can only guarantee the performance of our product if the operation condition in the datasheet is met.

    Follow-up questions:

    1. Why are you measuring D1 when Vdd is not yet connected? is this a limitation of your power source?
    2. During measuring D1, is there an input to S1?
    3. How long this condition last (Vss and Gnd already connected but no Vdd)

    Best Regards,

    Yoworex

  • Thank you for your replay.

    1.Why are you measuring D1 when Vdd is not yet connected? is this a limitation of your power source?

    A: On my environment Vdd and Vss can not be powered at the same time . When vss suplied first,we found that the current of vss is 40mA while normal situation is about 0mA.

    2.During measuring D1, is there an input to S1?

    A:Other circuits are not yet powered, so S1 is float.

    3.How long this condition last (Vss and Gnd already connected but no Vdd)

    A:Vss and Vddd are supplied by two power supply. So the time can by controlled,but more than 5s.

  • Hi Syu,

    1. "On my environment Vdd and Vss can not be powered at the same time . When vss supplied first, we found that the current of vss is 40mA while normal situation is about 0mA."
    Q: During your current measurement, does the ADG452 is completely isolated (no other circuit connected)? what is your load on D1?

    2. "Other circuits are not yet powered, so S1 is float"
    Q: How about logic input, VL? 

    3. "Vss and Vddd are supplied by two power supply. So the time can by controlled,but more than 5s."
    Q: can you try GND and VDD and measure D1 and Idd?

  • Thank you for your replay.

    1. Q: During your current measurement, does the ADG452 is completely isolated (no other circuit connected)? what is your load on D1?

     A: The D1 of ADG452 is connected with TPS65186RGZT(VCOM) which is not powered.

    2. Q: How about logic input, VL? 

     A: VL is low because it is not powered yet.

    3. Q: can you try GND and VDD and measure D1 and Idd?

      A: We tested the following case.

            case1: vss/gnd only power supply   Result:vss=40mA, D1=100mV

            case2: vdd/gnd only power supply  Result:vdd=0mA, D1=0mV

            case3: vdd/gnd power supply first,and then vss   Result:vdd=0mA, vss=0mA, D1=0mV

  • Hi Syu,

    Can you try the following setup (still with GND and Vss supply only):

    1.Un-connect the D1 to TPS65186RGZT(VCOM) then measure again the current and D1 voltage.

    2. Try using different channel (eg. S2/D2)? measure again the Iss and Drain voltage? 

    3. Do you have spare unit of ADG452? if yes, can you try using it and measure again the Iss and drain voltage?

    Regards,

    Yoworex

  • Hi Yoworex 

    Thank you for your replay.

    1 and 2. Sorry, There is no way to try this on our pcb condition.

    3.We have tested it on several pcb boards and the results are the same.

    There is no power-on sequence requirement on datashee. Do you have a recommended power-on sequence?

  • Hi Syu,


    "1 and 2. Sorry, There is no way to try this on our pcb condition."

    A: In this case I'll do a bench test of the device (same supply as yours Vss and Gnd only) and see if it's drawing 40mA and -100mV at D1. Get back to you soon.

    "There is no power-on sequence requirement on datashee. Do you have a recommended power-on sequence?"

    A: It's good to power it in this way: Gnd-Vdd-Vss-VL-Sx/Dx.

    Please ensure correction operation of the device and meet the minimum supply requirement before any measurements.

    Regards,

    Yoworex