- Ask a related questionWhat is a related question?A related question is a question created from another question. When the related question is created, it will be automatically linked to the original question.
Hi,
I'm planning to use TMS320F28375S DSP in my project. Considering TI LaunchXL evaluation board design( http://www.ti.com/lit/ug/sprui77a/sprui77a.pdf), 1.2V is derived from a switching regulator to power up DSP core.But as per my previous knowledge on TMS320F28335, I used a dual output LDO to derive core and supply voltages to DSP.
Is it OK if I use similar LDO to derive 3.3V and 1.2V. I have selected LDO from Texas ie TPS70345PWP. Please help me by answering what will be the implication on DSP performance if I go with LDO (TMS320F28335) or Switcher (TPS62420QDRCRQ1).
Naveen,
Generally speaking, you can use any power supply for TMS320F28375S as long as the power source satisfies the following three aspects:
1) Recommended Operating Conditions
2) Power Capacity
3) Power Sequencing
----
Looking at the TPS70345 datasheet, it appears that this dual output LDO can satisfy all three aspects of voltage range, power capacity, and ramp sequence (SEQ=0).
Additionally, the TPS70345 uses a RESET signal that is open-drain, which is recommended for use with TMS320F28375S XRSn. The only issue that I see is that the RESET buffer appears to be a little weaker than what is recommended for TMS320F28375S. I would not expect this to be a major issue as long as the pull-up resistor is sized appropriately. You may need to experiment with some different values to find one that is reliable and close to the recommended pull-up values from the TMS320F28375S datasheet.
-Tommy
Hi Tommy,
Thank you so much for detailed explanation and support. I have a doubt in TP70345 datasheet. As i understand it is a fixed dual output LDO with 3.3V & 1.2V. Below figure is from datasheet.
But in graphs, it shows that it generates an output of 1.8V instead of 1.2V. It made me confused while referring the data. Below figure is for quick reference.
Could you please explain why is it 1.8V.
One last question, Is there any power on and power sequence for TMS320F2837XS. As I understand it is mentioned only about voltage level to be maintained. But are there any specific timing consideration like which supply to be ON first while powering ON, What is time gap to be maintained between two power supplies.
Thank you
Naveen Devara said:Could you please explain why is it 1.8V.
I believe that you are looking at the enhanced, high-reliability (EP) version of the TPS70345 device. Information in EP datasheets is often sourced from the non-enhanced versions of the devices.
The TPS703xx datasheet has multiple device offerings with various fixed output voltages:
Naveen Devara said:One last question, Is there any power on and power sequence for TMS320F2837XS. As I understand it is mentioned only about voltage level to be maintained. But are there any specific timing consideration like which supply to be ON first while powering ON, What is time gap to be maintained between two power supplies.
The power sequencing requirement from the F2837x datasheet recommends that the 3.3V supply always be greater than the 1.2V supply. This condition is most easily satisfied by powering on 3.3V before 1.2V. There is no dead time requirement.
