TPS7A4501-SP: HV regulation by elevating the ground potential

Lloyd,

I am uncertain what your intended circuit looks like for the TPS7A4501.  Could you post a snippet of schematic so I can understand your use case?

You mention high voltage.  The TPS7A4501 supports up to 20V Vin.

Regards,

Wade

The "PR_TINA.docx link should work.  Let know if it does not.  Thanks.

The idea came from snva583, a TI Appnote.

The LM117 is a much different part than the TPS7A4501 with a ground connection.

I cannot infer what you intend to do with the 4501 by looking at the LM117 schematic.

If you have your TINA schematic where you attempted to sim this, then that may help.

Regards,

Wade

I flipped the TL1431 (TLHV431 on schematic) and elevated the ground.  The TPS7A4501 references the ground instead of OUT.  It will take a few minutes on the schematic.  I tried some other things that didn't help.  Thanks.

The idea came from snva583, a TI Appnote.

I am having trouble understanding how this circuit will work.

Can you give me your intended operation?

220 Vin, with Vout of ? Iout ?

If you provide that, I will spend some time reviewing the application note.

Thanks,

Wade

220 vdc in, 200 vdc with 500ua load.  Thanks. The LM117 circuit works but our customer wants better thermal performance.  We ran a couple of thermal cycles on just the regulator (TPS7A4501) and had a 32 mv swing between -33°C and 65°C. About 10 times less than the LM117 design.

The LM117 had a minimum load of 5 milliamperes.  It was not very efficient.

Lloyd,

I am fairly certain this will not work. If you examine the node voltages relative to GND and Vout, it does not make sense.

For example, Vout to its psuedo GND node (top side of R10)

From that node to Vout is ~8V.

From GND to Top of C2 is also 8V.  Thus R7 will have to have a large voltage drop across it to balance out voltages.

I am not 100% certain on this, and will see if one of the designers can comment.

Where is the load intended to be in this schematic?   Is it R9?

Regards,

Wade

R9 is the intended load.

The "TINA/DC Analysis/Calculate Nodal Voltages" shows non-sense results.  I found the model for the TPS7A4501 in a reference design on the TI site.  I assumed it was a complete model and could support the "Calculate Nodal Voltages" function; however, I have not found any models for regulators (including shunt regulators) that are not "Transient" models.  I haven't tried any of those on a DC Analysis but I suspect that won't work.

I have been blaming the model.  

I found the model on the TPS7A4501-SP page.

The zip file is slvmda5.zip.

I have run the reference design and it appears to work with the DC Analysis.

I found the model on the TPS7A4501-SP page.

The zip file is slvmda5.zip.

I have run the reference design and it appears to work with the DC Analysis.

Lloyd,

The models should support DC analysis.   I will attempt to recreate your schematic in pspice as well as try to get a designers input.

I should be able to get this on Monday.

Regards,

Wade