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How to create a decreasing Vout as control voltage say 1.16 down to 1.10V out of a measured increased current of say 0 to 2 A, by a Singel chanel LDO LP2985-N or by..

Subject: To regulate down voltage by the current over a small resister the voltage out from an Singel chanel LDO par example LP 2985-N , 5V,SOT 23-5

Hallo..I am stucked in my thoughts. I thought I could decrease the voltage out of the measured current by putting a current resistor to the ground, but it works in the opposite way. How do I decrease the voltage by increased current?

My case is:

I want to regulate by a change in current of 2A a decrease in Vout from 1.16 V to  1.10 V , par example Vout from  a voltage divider of 1.3 ΩkΩ/4.3 kΩ when you vary the voltage over the voltage divider  from  a LDO which gives a fix 5.0V down to 4.75V over the voltage divider created by an extra resistor 0.125 Ω in the voltage divider where the current up to 2 A pass through.. The 5.0V is chosen from the LM29858-5 because I need it in more places and I have the PCB made for it, it’s small, endure high temperature…perhaps I need an op instead but how and what? .  

  • I have solved it, very simple I don't know what was wrong before. ..You just put the extra resistor which all the current pass through before the 1.3 kΩ resistor at the bottom down to ground and . It will will compress the whole lot and that means a decrece in voltage measured between the two 1.3 ΩkΩ/4.3 kΩ resistors.
  • Christer,

    Glad you were able to figure it out. My apologies for a delay in response. I believe this had been posted as LM2985 before and our teams did not recognize this part number initially. Additionally, we had our Thanksgiving Holiday recently, so that delayed the response further.

    Again, I apologize for the delay. Typically our turnaround is within 1 business day, so please continue to post your questions on the E2E forums, and we will be sure to get to them as soon as well can.

    Best,
    Michael