TPS7A7300 LDOs in series

Robert Curtis

Other Parts Discussed in Thread: TPS7A7300

Hello,

I have an application with a Xilinx Spartan 6 LX9 and I need to convert a 5v input supply to 3.3v (I/O and Aux) and 1.2v for the core of the FPGA. The application must use LDOs as it is in proximity of noise sensitive devices. I am considering the TPS7A7300 for both the 3.3v and 1.2v conversion.

If I use the 3.3V output of one LDO as the input to the 1.2V LDO, is there anything area I need to be concerned about?

Thanks for any help,

Rob Curtis

over 11 years ago

0 Hisen Zhang over 11 years ago

TI__Prodigy 615 points

Hi Robert

I am appreciate that you could provide the maximum output current of the 3.3V and 1.2V power supply.

So we can figure out whether the TPS7A7300 is fit for your application.

If you use the 3.3V output of one LDO as the input to the 1.2V LDO, it may cause some ripples on 3.3V rail during the load transient on the 1.2V output.

If the output current is quite large, you may take the thermal issue into consideration.

You can use DC/DC+LDO solutions to increase efficiency and keep low noise if necessary.

Best Regards

Hisen

0 Robert Curtis over 11 years ago in reply to Hisen Zhang

Intellectual 430 points

Hello Hisen,

The current will be low. Estimate 250 mA @ 1.2V and 200 mA at 3.3V.

I can't use the DC/DC convertors as the switching may cause EMI problems with nearby components.

0 Hisen Zhang over 11 years ago in reply to Robert Curtis

TI__Prodigy 615 points

Hi Robert

TPS7A7300 is suitable for your applications, according to your output current.

As I mentioned above, I do not recommend you to use TPS7A7300 in series, because it may cause ripples on 3.3V rail during the load transient on the 1.2V output.

Best Regards

Hisen Zhang

Power management

Power management forum

TPS7A7300 LDOs in series

Hi Robert