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DCR021205

Daniel H.
Prodigy 20 points
Other Parts Discussed in Thread: DCR021205

Hello,

I am using the DCR021205 isolated switching regulator for a custom PCB and am receiving some weird results. Currently, I cannot get the 5V rail to come online when the input voltage is around 12V. Dropping the input voltage to around 5V allows the output voltage to switch on at around 3V. The input voltage can then steadily by raised to around 12.2V before the 5V rail cuts out. A schematic for the regulator is attached as well. The circuit looks nearly identical to the datasheet, except I forgot to hook up to error pin. 

switching_reg.pdf

  • 0
    TI__Mastermind 38230 points

    Daniel:

    The schematic  R43 and C22 are incorrectly located. is one possible reason for the in correct power up.

    Short out R43  with (0) ohm jumper i.e.  C22 1uf Ceramic  filter  must directly connected to Vrec with no  resistor at R43 position. .

    In addition to above  is the input power supply (12V), is may be also at time is in current limit during power up .

    Tom

  • 0 in reply to Tom Guerin
    Prodigy 20 points

    Thank you, shorting R43 fixed my issue. 

    Also, could you take a look at my output filter. I am trying to reduce output ripple and so I have placed L1 and C20 to work in combination with C21 to form a pi filter. I see in the datasheet that C21 can be increased to 2.2uF to decrease ripple even further. Would you recommend increase C20 and C21? What value of L1 would you recommend for this switching regulator? Thank you.

  • 0 in reply to Daniel H.
    TI__Mastermind 38230 points

    Daniel:

    L1 is a high frequency100MHz filter. I recommend change C21 from 100nF to Ceramic 2.2uf. Leave C20 as 100nf for now.

    Tom