TINA/Spice/TPS62740: The 4-bit pattern generator fails when 'start display' is set 'long' & It would be great to have a 'trigger' input to the generator, to allow it to start synchronously to a device...

Barry Rowland

Part Number: TPS62740
Other Parts Discussed in Thread: TINA-TI,

Tool/software: TINA-TI or Spice Models

I have a 4-bit pattern generator running a sequence, 'repeat pattern' to drive the VSEL pins on TPS62740... If I start the simulation display at close to 0 time, the generator runs continuously, as expected. If, however, I set the simulation to start display at 10 ms, after the start-up delay of the TPS62740, the pattern generator does not run, the outputs seem to be 'floating'.

It is also a waste of simulator cycles to have this generator running continuously, when I really want it to start after the DC/DC is finished start-up. Two functions would be great:

1) a 'hardware trigger' input

2) a start running time.

over 5 years ago

0 Somen Das over 5 years ago

TI__Intellectual 1040 points

Hi Barry,

Can you share the simulation testbench with us?

Thanks,
Somen

0 Barry Rowland over 5 years ago in reply to Somen Das

Intellectual 550 points

Sure can...let's see if I can remember how ;-) It also seems that it may depend on the step time, as I increased the step time to 100 us per step, and it now seems to be functioning as expected.

here's with 10 µs step time

62740 with VSEL stepper 10 us step.TSC

Here's the trace display, in 'Preview'

I tried with step time at 25 µs and 15 µs, it seems to work at those settings, also, but 10 µs, not.

Thanks!

0 Barry Rowland over 5 years ago in reply to Somen Das

Intellectual 550 points

It seems that I am a real 'bad guy', when it comes to finding corner cases :-{

0 Vivek Agarwal over 5 years ago in reply to Barry Rowland

TI__Intellectual 1595 points

Hi Barry,

I have simulated the schematic shared by you with 10us step time and observed the results shown below.

As per my understanding, the output looks fine to me.

Could you please clarify more about the issue you are facing with this setup?

Thanks,

Vivek Agarwal

0 Barry Rowland over 5 years ago in reply to Vivek Agarwal

Intellectual 550 points

Hello Vivek;

it seems to be rather dependent on some factor that I can not get a fix on... thanks for trying it out.... BTW, it takes 12-15 minutes to run these sim's on my Dell i5Core laptop. Kind of makes it a long progress to even check this problem at different settings.

Barry

0 Vivek Agarwal over 5 years ago in reply to Barry Rowland

TI__Intellectual 1595 points

Hi Barry,

In order to reduce simulation time you can try changing the Analysis parameters as shown below.

But reducing the simulation time might reduce the accuracy of the model.

Thanks,

Vivek Agarwal

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TINA/Spice/TPS62740: The 4-bit pattern generator fails when 'start display' is set 'long' & It would be great to have a 'trigger' input to the generator, to allow it to start synchronously to a device...