LT3080 0 to 3 V variable voltage regulator circuit

Hello all. I am having some trouble figuring out how to use the LT3080. I d idn'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 tha t I expect it to.

I want to supply a variable voltage from 0-3VDC with the highest stable cur rent 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 adjustabl e regulator circuit on page 10 of the data sheet.

Any help would be appreciated.

Reply to
steveandaugie
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didn't see any circuit examples that looked like what I wanted to do. I ha ve simulated a circuit in LTSpice but I can't quite get it to act the way t hat I expect it to.

urrent possible. I don't know what voltages to use for IN and ctrl and I do n't know what resistance value to use for SET. I am using the basic adjusta ble regulator circuit on page 10 of the data sheet.

Iset is 10uA so 3V would be Rset=3V/10uA=300kOhm adjustable resistor. T hen depending on your maximum load current, the Vctrl droput could be as mu ch 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, a 3

00k adjustable rheostat on RSET to GND and a 2.2uF capacitor between the ou tput 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. Be s ure and check the thermal resistance spec for your package, to be multiplie d by the power dissipation (Vin-Vout) x Iload, for computing temperature ri se, keeping TJ < 150oC or whatever it is.
Reply to
bloggs.fredbloggs.fred

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 simple st connection 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 lo w currents, then there may a problem with meeting the minimum output curren t requirements. If your situation is really small load currents at reasonab le output 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 multipl ied 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 1 k on the output.

Reply to
steveandaugie

r. Then depending on your maximum load current, the Vctrl droput could be a s much as 1.6V, so the Vctrl has to be at least 3V + 1.6V =4.6V. The simp lest connection 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 th e 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 curr ent requirements. If your situation is really small load currents at reason able output 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 multi plied by the power dissipation (Vin-Vout) x Iload, for computing temperatur e rise, keeping TJ < 150oC or whatever it is.

1k on the output.

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

George H.

Reply to
George Herold

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