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Please let me know about the measuring method of DCP020505.

Guru 18010 points
Other Parts Discussed in Thread: DCP020505, TPS2024

Please let me know the three following affairs about the measuring method of DCP020505.

1) Connection of ISO_AGND(Output GND) to AGND or GND will generate heat and damage DCP020505U.
(Grade which it is hot and cannot be touched if it touches by a fingertip)
Please let me know this cause.
In addition, when not connecting with GND, there is no generation of heat.

2) DCP020505U will be generated heat and damaged if GND of an FET probe is connected to ISO_AGND(Output GND).
(Grade which it is hot and cannot be touched if it touches by a fingertip)
It becomes the same phenomenon even if it makes it not connect AC_GND of an oscilloscope.
Please let me know this cause.

3) Please teach me how to measure ISO_+5V and ISO_AGND with an FET probe.
Since DCP020505U heats as mentioned above now, it cannot observe.

In addition, the customer is inquiring by 5Vin / 5 Vout/128 mA.

Thank you for your consideration.

  • Satoshi:

    Send schematic of this application  including all converter pin connections .

    The sync. pin, pin 28 must never have a scope probe attached to it or any finger or stray capacitance ( >3pf) or resistors connected to any other source. Any stray  capacitance, including scope probe capacitance  will decrease the internal switching frequency and over heat the converter.

    1.What is the  polarity  and voltage on the following:

    a. ISO_agnd  what is the relation ship to the converter pins?

    a1. What is the pin number of the converter  and schematic of what you are measuring?

    a2. Is there any voltage AC or DC on any ground ?

    a3. What is the application , motor drive or AC floating secondary bus?

     

    Tom

  • Dear TOM san

    Thank you for advising instantly.

    I following-do the contents checked with the customer.

    ---------------------------------------------------------------------------------------------------------------------------------------------------------------

    1.What is the polarity and voltage on the following:

    a. ISO_agnd what is the relation ship to the converter pins?

    =>Under a check

    a1. What is the pin number of the converter and schematic of what you are measuring?

     => circuit diagram is attached.

          Since I think whether a part part number is hard to see, I supplement.

           - A chip bead is BLM21P221SN1D of Murata.

            - Impedance is 220ohms in 100 MHz. An error is ±25%.

          In addition, for your information

          ---------------------------------------------------------------------------------------------------------------------------------

            - Oscilloscope(Tektronix) : TDS754C / probe :P If it measures by 6243 DCP020505U has heat.

            - Oscilloscope(Tektronix) : TPS2024/probe :P If it measures by 2220 DCP020505U does not have heat.

            ---------------------------------------------------------------------------------------------------------------------------------

    a2. Is there any voltage AC or DC on any ground ?

    =>yes

    a3. What is the application , motor drive or AC floating secondary bus?

    =>AC floating secondary bus, Application is Smart Grid.

    ---------------------------------------------------------------------------------------------------------------------------------------------------------------

    Moreover, I received the following question about DCP02050 in the addition.

    ----------------------------------------------------------------------------------------------

    - Please teach me processing of the non-connect pin of DCP020505U.

     (Open or ground)

    - Has the output 0V of DCP020505U floated completely the input side?

       Has not it connected by the capacitor etc. the input side?

    ----------------------------------------------------------------------------------------------

    Moreover, sorry, there was a clerical error in writing the other day.

    He was not 128-mA output specification but 16 mA x eight-piece usage (Total: 128 mA).

     

    As mentioned above, I need your help well.

    Satoshi

  • Satoshi:

    Thanks for the information and schematic  on the  SMART grid design.I assume the smart grid Isolated ground AC voltage is > 60VAC.

    1. First and most important limitation on the  DCPXXXX isolated converters is :

    a. The converter is UL 1950 recognized component. The UL 1950  maximum secondary SELV voltage is limited by design to 60VAC or 42VDC continuous operating voltage. The converter  is designed for ground fault elimination .

    c. There must be no resistor , 10 k (R211) or any other low resistance connected between Vin (5V) and pin 28 sync. pin. The unit will be electrically   stressed and will be  thermally overstressed. This low value  resistor reduces the normal internal switching frequency of 800KHz   to < 200KHZ.

    The only time a resistor (5Vinbus) of > 150kΩ is used is to compensate for capacitive loading (> 3pF) on the sync. pin  to Vin (5V).

    You can contact me by direct e-mail for additional information  and discussion on this application

     tguerin@ti.com

    Tom