Hi,
How to trim LT8625SP-1, or any regulator with SET pin (usually from silent switcher 3 products family) using LTC2980-24 DAC, up to 3.3V or more?
The DAC maximum output up-to ~2.6V, and applying amplification at DAC output is not applicable since the Hi-Z output (or "DAC Disconnect" feature) will not result Hi-Z at opamp output.
Thanks,
Ita
Hi Charly,
My design uses LTC2980-24 as a power management for several power supplies to a single load. The output range of one the LT8625SP-1 should be trimmed between 1.0V to 3.4V.
It should looks like these schematic (taken from LT8625SP-1 datasheet).
I use the servo option in LTC2980-24 to compensate the IR drop between one of LT8625SP-1 to the point of load, and the DAC limit the output to ~2.6V.
Please notice that LT8625SP-1 does not have common voltage FB pin, it is connected to to SET pin which has 1:1 ratio to the output voltage.
I still defining this specific concept so the schematic is not ready yet, however, I'll explain better.
We use extensively with LTC2980-24 as a controller, monitor and sequencer for many power rails on others project and would like to re-use it.
One of LTC2980-24 features is a close-loop servo which use integrated DAC that can trim power supply output through FB pin while sensing the point-of-load voltage. Most (if not all) silent switcher 3 (SS3) power supplies have different feedback mechanism, where there is no reference voltage (FB pin0, rather a small current source through SET pin.
Regarding your questions, I will have placeholder for the 10k resistor, but it only in the example to have voltage divider from DAC output range 1.2V-4.8V to output voltage 1.0-4.0V.
The DAC in example requires external software and additional code to close-loop the IR drop, and LTC2980-24 will do it much better, but it can only output DAC up-to 2.6V.
