LT3080 0 to 3 V variable voltage regulator circuit

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Hello all. I am having some trouble figuring out how to use the LT3080. I didn't see any circuit examples that looked like what I wanted to do. I havesimulated a circuit in LTSpice but I can't quite get it to act the way that I expect it to.

I want to supply a variable voltage from 0-3VDC with the highest stable current possible. I don't know what voltages to use for IN and ctrl and I don't know what resistance value to use for SET. I am using the basic adjustable regulator circuit on page 10 of the data sheet.

Any help would be appreciated.

 

[[email protected]]

Hello all. I am having some trouble figuring out how to use the LT3080. Ididn't see any circuit examples that looked like what I wanted to do. I have simulated a circuit in LTSpice but I can't quite get it to act the way that I expect it to.



I want to supply a variable voltage from 0-3VDC with the highest stable current possible. I don't know what voltages to use for IN and ctrl and I don't know what resistance value to use for SET. I am using the basic adjustable regulator circuit on page 10 of the data sheet.



Any help would be appreciated.

Iset is 10uA so 3V would be Rset=3V/10uA=300kOhm adjustable resistor. Then depending on your maximum load current, the Vctrl droput could be as much as 1.6V, so the Vctrl has to be at least 3V + 1.6V =4.6V. The simplestconnection would then be a 5V supply powering IN & CTRL tied together, a 300k adjustable rheostat on RSET to GND and a 2.2uF capacitor between the output and GND. If you're going for really small output voltages at very low currents, then there may a problem with meeting the minimum output current requirements. If your situation is really small load currents at reasonableoutput voltages then you need to add something like 1k on the output. Be sure and check the thermal resistance spec for your package, to be multiplied by the power dissipation (Vin-Vout) x Iload, for computing temperature rise, keeping TJ < 150oC or whatever it is.

 

[[email protected]]

Iset is 10uA so 3V would be Rset=3V/10uA=300kOhm adjustable resistor.Then depending on your maximum load current, the Vctrl droput could be as much as 1.6V, so the Vctrl has to be at least 3V + 1.6V =4.6V. The simplest connection would then be a 5V supply powering IN & CTRL tied together, a300k adjustable rheostat on RSET to GND and a 2.2uF capacitor between the output and GND. If you're going for really small output voltages at very low currents, then there may a problem with meeting the minimum output current requirements. If your situation is really small load currents at reasonable output voltages then you need to add something like 1k on the output. Besure and check the thermal resistance spec for your package, to be multiplied by the power dissipation (Vin-Vout) x Iload, for computing temperature rise, keeping TJ < 150oC or whatever it is.

Thank you. That worked perfectly. Especially your advice about adding the 1k on the output.

 

[George Herold]

Thank you. That worked perfectly. Especially your advice about adding the1k on the output.

Glad it's working. If this is for production then be careful about the output cap ESR. (see page 10 of data sheet.) It burned me....

George H.