AFAIK, most LDOs work well when Vi > Vdrop + Vo,
some LDOs would work Vi <= Vdrop + Vo
I'd like adopt TPS7A2050 as system regulator where Vin of TPA7A20 is Vbus of USB(5V)
My load would about 200mA~250mA.
As the title,is it okay to use Vbus to directly feed the Vin of TPS7A20?
Hello,
Putting in a Vbus on the input of the TPS7A2050 would work (see section 7.3.3 below). However, whether it will work in your application depends on what your tolerance for the output voltage is. A typical USB Vbus voltage can range from 4.75V to 5.5V (for certain OTG applications, it can be as low as 4.4V). When looking at the Dropout Voltage specification in the Electrical Specifications table, it says that the maximum dropout voltage with an output between 2.5V and 5.5V is 145mV. If your application will not work with an output voltage of ~4.6V (4.75V - 150mV), then I would not recommend using this solution. Is there a reason why you are wanting to use an LDO to convert a 5V input to a 5V output instead of just sending the Vbus supply directly to your load?
Hi @Eric Smith & @Nick Butts
My brief of design as this picture:
Since minimum Vs rail of OPA2810 is 4.75V, I should select TPS7A2050 rather than TPS7A2045.
I'd like to supply above circuit with USB.
I also found TPS7A20 datasheet mentioned:
5V-USB-in and 5V LDO out may enter Dropout Operation, PSRR would be degraded.
OK! maybe I would abandon supplied with USB.
I would find others PSU which can provide >5.2V.
Thanks!
