Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Register Log in

TL431 in SMPS feedback replaced with LT1009?

Status
Not open for further replies.
E

eem2am

Banned
Joined
Jun 22, 2008
Messages
1,179
Helped
37
Reputation
74
Reaction score
24
Trophy points
1,318
Activity points
0

Why are you sure it can not be used? Did you try it or is it just an assumption?

Maybe the difference is mainly the small signal frequency response of the regulator (just based on the two pulse response charts in the data sheets), and you need to adapt the control loop compensation.

Stefaan
 
  • Like
Reactions: treez

    T

    Points: 2
    Helpful Answer Positive Rating
So I assume you didn't try it yet. If you have a working system with the TL431, it should be not too difficult to test a LT1009.

If you assume there is virtual no current in the "ref" input, and the cathode-current versus cathode voltage (in the case the cathode is connected directly to the reference) behaves the same, you should be able to swap them.

On a larger scale , it doesn't matter how the component is made internally, if the behavior on the pins is more-or-less the same.

I've put the characteristics next to each other in following pdf. Be careful, the scale of the LT1009 is logarithmic.
 

Attachments

  • comp.pdf
    51.6 KB · Views: 152

I think, it's pretty obvious, that LT1009 can't be used in a similar circuit as TL431, because the low impedance internal voltage divider and other internal circuit details don't allow the "cathode" terminal to act independant of the reference voltage. You need a shunt regulator with high impedance output terminal and suffcient output voltage range.
 
  • Like
Reactions: treez

    T

    Points: 2
    Helpful Answer Positive Rating
FvM,

Indeed, I overlooked the input impedance, you can not do the voltage divider at the input to set the desired output voltage of your power supply if using the LT1009.

Stefaan
 

Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top