TPS74901KTWR LDO Linear Regulator's Power Efficiency

Joselito Parguian

Other Parts Discussed in Thread: TPS74901, PTH04T240W

I have 12V and 5V supplies only coming from my VME chassis that I can use to feed the TPS74901. I need to generate 1V output for my FPGA and I have to use the TPS74901 because I already have plenty of this part available from our inventory. The problem is the power efficiency becomes an issue at 20% if I use 5V supply and becomes even worse if I used 12V. I'm thinking of using a zener that is rated for 1.2V or less but these types of zener don't seem to exist. I thought about using a simple voltage divider circuit but using resistor to dump voltage and current doesn't appear to be a viable solution due to the excessive heat dissipation.

Does anybody have a better solution to improve the power efficiency of the TPS74901 using the supply inputs mentioned previously?

Thanks,

Jojo

over 12 years ago

0 Darwin Fernandez over 12 years ago

TI__Mastermind 41760 points

Hi Jojo,

Without decreasing the supply voltage, the overall efficiency cannot be improved. You can only hope to divert the power dissipation away from the TPS749 to avoid thermal shutdown. I recommend either having resistors in series to drop the input voltage at the LDO or paralleling the TPS749 so that the outputted currents divide down (as shown here http://www.ti.com/lit/an/slva250/slva250.pdf).

The most efficient way for your application is to use a buck converter down to about 1.4-1.5V and follow it with the TPS74901. The 5V rail can be used as the BIAS pin.

Regards,

Darwin

0 Joselito Parguian over 12 years ago in reply to Darwin Fernandez

Prodigy 150 points

Darwin,

Thanks for your response. I guess there is no simple solution to this but to replace the LDO Linear Regulator to Switching Regulator. Paralleling the TPS74901 or adding a buck converter increases the cost and complexity of the design. Do you have a suggestion or does TI have a recommended power supply implementation for a Virtex-5 FPGA. Can you please forward me these information if they exists?

Thanks,

Jojo

0 Darwin Fernandez over 12 years ago in reply to Joselito Parguian

TI__Mastermind 41760 points

Hi Jojo,

Please see the link below. Under "Choose processor family" you will find the Virtex-5 family and coresponding power solutions.

http://www.ti.com/analog/docs/analogsplash.tsp?contentId=135387&DCMP=pmp_p4p&HQS=NotApplicable%2bOT%2bprocessorpower

Regards,

Darwin

0 Joselito Parguian over 12 years ago in reply to Darwin Fernandez

Prodigy 150 points

Hi Darwin,

Sorry it me so long to respond, but I was tied up with other priorities. Thanks for these references. I think the PTH04T240WAD and the PTH08T230WAD are the parts I am looking to use. Do you have schematic and PCB layout symbols for these parts available for Altium Designer 10?

Thanks,

Jojo

0 Darwin Fernandez over 12 years ago in reply to Joselito Parguian

TI__Mastermind 41760 points

Hi Jojo,

Please see the link below to the product page.

http://www.ti.com/product/pth04t240w

At the bottom there is a section on CAD/CAE symbols and a instructions to acquire the desired symbols and footprints.

Regards,

Darwin

0 Joselito Parguian over 12 years ago in reply to Darwin Fernandez

Prodigy 150 points

David,

I finally had the chance to download Ultra Librarian and the bsl file and attempted to generate the Altium Designer footprint for the PTH04T240W. I followed the instructions on how to convert the files but the conversion process did not produce anything in the end. Below is the initial report that was generated by the Ultra Librarian tool:

Symbol "PTH04T240W_EAY_11" renamed to "PTH04T240W_EAY_1"
Component "PTH04T240W_EAY_11" renamed to "PTH04T240W_EAY_1"

Ultra Librarian Lite 5.3.163 Process Report

Message - Component PTH04T240W_EAY_1 has illegal symbol to pattern pin mappings.
Two pins refer to the same footprint pin. Component will be skipped.
Message - Component "PTH04T240W_EAY_1" has invalid pin data to footprint pin mapping.
This components footprint mapping "EAY11" will be undone.

TextStyle count: 20
Padstack count: 1
Pattern count: 1
Symbol count: 1
Component count: 0

Export

I noticed that the message contained errors which I am interpreting as the reason why the equivalent Altium Design footprint was not generated? Can you please explain what is going on?

Thanks,

Jojo