LT3090
Recommended for New Designs
The LT3090 is a 600mA, low dropout negative linear regulator that is easily parallelable to increase output current or spread heat on surface mounted boards...
Datasheet
LT3090 on Analog.com
Dear Sir/Madam,
I used the TPS7A3301 in an application where i adjusted the feedback voltage using a DAC. Vin=-30 and Vout=-27 to -28. It worked nicely however i ran into a problem with this part at these voltages that made the solution non viable.
I would like to use the LT3090 in the same application where the output voltage can be changed by using a DAC or something similar. Vin = -30 and Vout=-27 to -28V.
Page 15 of the DS mentions the following:
For applications requiring higher accuracy
or an adjustable output voltage, the SET pin may
be actively driven by an external voltage source
capable of sourcing 50μA – the application limitations
are the creativity and ingenuity of the circuit designer.
Any thoughts how to achieve this without impacting on the noise performance of the LDO?
Regards Joe
Dear Arad,
Thank you for the reply. I was thinking about the arrangement you mention before posting. I had several concerns. Firstly, the op amp would be at -27V to -28V unless a secondary resistor is used. Secondly, the set input is high impedance and is susceptible to noise pickup. Lastly, the DS mentions not to drive SET more than 0V3 below VIN.
Regards Joe
The image below shows one way to vary the output voltage of the LT3090 between -27V and -28V using the output of a DAC:
The image below shows one way to vary the output voltage of the LT3090 between -27V and -28V using the output of a DAC:
Hi ARad,
Thank you.
I took a slightly different approach by using a active filter to reduce DAC noise.
The DAC is represented by a voltage source 0 to +2V048.
The output of the OPA376 swings 0 to -2V048.
The +-2V5 rails power up first and the DAC output powers up at 0V.
Do you see any issues with this circuit?
Regards Joe
