Part Number:TPS82740A
Tool/software: WEBENCH® Design Tools
Starting here:
www.ti.com/product/TPS82740A/toolssoftware
in the panel : WEBENCH® Designer TPS82740A
I make a change to the basic design parameters, within the datasheet values allowed for this device:
change Vout to 2.5 V
Change Iout to 0.1 A
and, click 'Open Design'
I get message 'Design Cannot be Created'
Why?? !!
When I click 'OK' to select different parts... there are NO PARTS in the list
So, hit 'Recalculate, and get a list... but, no modules in the list!
SO, back to the datasheet pages
change back to the default values of 1.8 V and 0.2 A, click 'Open Design', and, lo and behold, up comes a TPS82740A design
BUT, if I change to 2.5 Vvout, it comes back with another message that it can't find a part... meantime, there is a little panel 'Selected Vout:' which seems to show 'allowed' Vout selection, BUT, there is no indication to the user that the Vin(minimum) is linked to the choice of Vout!!
I noted that he schematic now shows the correct connections of VSEL lines to reflect the selected voltage! Bravo!
With a little experimentation, Webench REQUIRES 300 mV of headroom in Vin(minimum) before it will accept the design, but the error messages do not give the user any idea why it is rejecting the design...it takes a careful look at the datasheet to see that this 300 mV seems to be derived from the Vth_100+ and Vth_100- threshold voltages.
And, I changed the input voltage in one design control panel, but Webench decided that Vin should be 4.1 V
So, I finally got a startup simulation to run, with 2.5 Vin and 2.5 Vout, by setting the input startup voltage to 0 V and 2.5 V... then, it plotted the IC input current(WEBENCH® Designer TPS82740A) with a 20 A max, and -10 A minimum, for what is a 500 mA signal...then, adding the waveform Iin , it also plotted that to +20 / -10 A scale! And, as well, re-plotted the Iic that I had manually-reset to plot -100 mA to 1 A scale
It INSISTS on having a scale factor or -1 to +4 V for Vin and Vout, no matter what I set in the Waveform Controls panel.
I'll insert the Tina-TI export of this design, here, and maybe you can tell me/us how many, and what kind of, errors, I've made??
Even better, after hand-rescaling the input current to some reasonable value, Webench rescales it to +20 and -6 A whenever I try to zoom in!!!
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