TLV3501: Problem simulating in LTspice, when shutdown is pulled to 5V, output does not go Hi-Z

Hi ScottC,

Thank you for your post. Let me take a look at the model and get back to you by the end of business Friday.

Best Regards,

Joe

Applications Engineer

Linear Amplifiers Business Unit | Comparators Product Line (CMPS)

All information in this correspondence and in any related correspondence is provided “as is” and “with all faults”, and is subject to TI’s Important Notice (http://www.ti.com/corp/docs/legal/important-notice.shtml)

Hi ScottC,

Can you provide me with the LTSpice simulation file? This way, I can take a look at what you are seeing more directly.

Best Regards,

Joe

Applications Engineer

Linear Amplifiers Business Unit | Comparators Product Line (CMPS)

All information in this correspondence and in any related correspondence is provided “as is” and “with all faults”, and is subject to TI’s Important Notice (http://www.ti.com/corp/docs/legal/important-notice.shtml)

Hi Scott,

works for me in TINA-TI:

scott_tlv3501.TSC

Hhm, in your shown schematic "V5" is disconnected from the TLV3501?

Kai

PS: Your LTspice simulation file should be zipped before publishing here

Thanks again Kai for your support.

Scott

Thanks for your post.  I too am a little concerned about the connections in your schematic snapshot.  Other than that, I am not really seeing any problem with the proposed circuit to simulate.  It looks like it should work as Kai has shown.

Chuck

Actually from your own simulation you also show the part not working properly!  Note on page 11 of the data sheet when the shutdown (SD) pin is pulled (5V) the output of the TLV3501 should be in a Hi-Z configuration.  Your simulations shows exactly what I am seeing.  When VG2 is at 5V VF1 should also be at 5V because you have a 1k Pull  up on it!  Please see the attached picture showing another TI part TLV1805Q1 which also has a SD pin when pulled hi goes Hi-Z.  You will see in my pictured simulation it is working properly.  The TLV1805 is a 450nS part, I would like to use the TLV3501 which is a 4.5nS part.  Note I have the TLV1805 part in and actual board and it does go Hi-Z when pulled Hi.  So as can be seen from my LTSpice simulations under the same exact configurations one part the other part does not. FYI in my original simulation V5 is not connected true, but the SD is connected directly to 5 volts.  I don't get it both parts should work the same ... may be am missing something!! ... or maybe I am correct!!  Please let me know i would like to simulate it before i put the funds to an actual baord.

Actually from your own simulation you also show the part not working properly!  Note on page 11 of the data sheet when the shutdown (SD) pin is pulled (5V) the output of the TLV3501 should be in a Hi-Z configuration.  Your simulations shows exactly what I am seeing.  When VG2 is at 5V VF1 should also be at 5V because you have a 1k Pull  up on it!  Please see the attached picture showing another TI part TLV1805Q1 which also has a SD pin when pulled hi goes Hi-Z.  You will see in my pictured simulation it is working properly.  The TLV1805 is a 450nS part, I would like to use the TLV3501 which is a 4.5nS part.  Note I have the TLV1805 part in and actual board and it does go Hi-Z when pulled Hi.  So as can be seen from my LTSpice simulations under the same exact configurations one part the other part does not. FYI in my original simulation V5 is not connected true, but the SD is connected directly to 5 volts.  I don't get it both parts should work the same ... may be am missing something!! ... or maybe I am correct!!  Please let me know i would like to simulate it before i put the funds to an actual baord.

Here is zipped LTSpice simulations of both your parts

ScottC

8176.Comp-2 test.zip

Hi Scott,

Thank you for your response and sim files. I will look into this and get back to you by the end of the week. 

Can you also take a look at the Error Log (under VIEW->SPICE ERROR LOG) and see if it chokes up any warnings or errors?

If LTSpice does not recognize something, it ignores it.

You can also use a switch on the output controlled by the SHUTDOWN signal to mimic the HIGH-Z response.

Best Regards,

Joe

Applications Engineer

Linear Amplifiers Business Unit | Comparators Product Line (CMPS)

All information in this correspondence and in any related correspondence is provided “as is” and “with all faults”, and is subject to TI’s Important Notice (http://www.ti.com/corp/docs/legal/important-notice.shtml)

Hi Scott,

yes, you are absolutely right. I'm sorry. I had the simulation tested with a pull-down resistor at the output first, and then changed from a pull-down to a pull-up. And then I haven't noticed that the TLV3501 is still emitting low level.

So, yes, you are right, the model seems to show an error.

Having said this, when you look into the macro model you will find the section "Notes":

It seems that the model is only modelling the disabling itself, in a sense that the output does not toggle any longer when being disabled. Also the shutdown current -or by other words- the decrease of supply current is modelled, when being disabled. But I don't see any mentioning in the "Notes" that the output going to high impedance is modelled, when being disabled.

Kai