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Hello, I am working on a USB powered audio device that needs phantom power (48v @ 4mA total).
1. Phantom Power
I'm using an the phantom example in the TPS61170 datasheet adapted for use with the a TPS61040. It's working very nicely at 48v, but I would welcome any criticism, watch-outs, or suggestions for the following design:
Variable Voltage
In order to offer a low-power mode, I'd like to be able to switch to a lower voltage Phantom spec, and I was wondering if anybody's had any experience with this. Would it be safe to switch in a resistor in parallel with R2 using a FET or a 4066-type switch?
I would appreciate any advice on this matter. Thank you!
the circuit is good. but the input voltage of tps61040 should be 1.8~6V. make sure that Vout is lower than max voltage during transient, such as startup, load transient and Vout switching using FB pin. thanks
boost converter solution team
jasper li
Thanks Jasper, you're right, I was adapting the schematic for a picture and forgot to fix the input voltage. It will be getting 5v from USB.
Can you clarify "load transient and Vout switching using FB pin," I'm not sure I understand what you mean here. Is there an Application Note that I could read to get a greater understanding?
Load transient : the load change from 0mA to 100mA for example.
Vout switching: because you mentioned that you want to change the Vout using a mosfet and a resistor in parallel with R2
Jasper li
Ah! I believe I understand now, that helps me to parse the sentence better.
So you think the mosfet switching could work reasonably as long as I do not let Vout exceed spec in the process? That was what I was hoping.
According to the datasheet, the part is not spec'd for 48v, but if I keep Vout within wattage specifications and hold the part in SHUTDOWN when switching R2, would you say this is a reasonably safe approach for preserving the life of the TPS61040?
Thanks again Jasper, I'll post again here if anything comes up. Your advice is much appreciated!