I have created a design for a low power pulse generator that can be seen here: http://siliconventures.net/images/Pulse%20Generator.PNG I tried several different chips for design purposes for the U1 comparator, and settled on the TLV3701 / TLV3702, which works very well in my simulator (Micro-Cap V12). The problem is all the sources I have found for the TLV370x want quite a bit for the chip, which is a real problem. I have tried numerous different nano power comparators, but every one I have tried is either too expensive in moderate quantities (100 - 200), or else the simulator croaks on the chip. It usually gives a singular matrix error. For example, the MCP6542 is only $0.46 in lots of 100 from Mouser, but when I insert the chip into the sim, it doesn't work. (Yes, I know the MCP6542 is a dual chip. The overall design incorporates several comparators.) Does anyone have a simulator that won't croak on the MCP6541 / MCP6542? Does anyone have a recommendation for a drop-in replacement for the TLV3702 or the MCP6541 that is even less expensive (and maybe will work with my sim)? If it helps, the circuit design can be found here: http://siliconventures.net/docs/Power%20Switch.CIR
Inexpensive nano power comparator needed
Started by ●April 8, 2021
Reply by ●April 8, 20212021-04-08
On Wed, 7 Apr 2021 20:16:03 -0700 (PDT), "rhor...@gmail.com" <rhorerles@gmail.com> wrote:>I have created a design for a low power pulse generator that can be seen here: > >http://siliconventures.net/images/Pulse%20Generator.PNG > >I tried several different chips for design purposes for the U1 comparator, and settled on the TLV3701 / TLV3702, which works very well in my simulator (Micro-Cap V12). The problem is all the sources I have found for the TLV370x want quite a bit for the chip, which is a real problem. I have tried numerous different nano power comparators, but every one I have tried is either too expensive in moderate quantities (100 - 200), or else the simulator croaks on the chip. It usually gives a singular matrix error. For example, the MCP6542 is only $0.46 in lots of 100 from Mouser, but when I insert the chip into the sim, it doesn't work. (Yes, I know the MCP6542 is a dual chip. The overall design incorporates several comparators.) > >Does anyone have a simulator that won't croak on the MCP6541 / MCP6542? Does anyone have a recommendation for a drop-in replacement for the TLV3702 or the MCP6541 that is even less expensive (and maybe will work with my sim)? > >If it helps, the circuit design can be found here: > >http://siliconventures.net/docs/Power%20Switch.CIRWhy not sim it with the TI part and build it with something else? Comparators aren't complex. Why bypass a voltage source? What is R8 for? R17? C2? -- John Larkin Highland Technology, Inc The best designs are necessarily accidental.
Reply by ●April 8, 20212021-04-08
On Wednesday, April 7, 2021 at 10:49:19 PM UTC-5, jla...@highlandsniptechnology.com wrote:> On Wed, 7 Apr 2021 20:16:03 -0700 (PDT), "rhor...@gmail.com"> Why not sim it with the TI part and build it with something else?Did you not read my post? Apparently not: "...and settled on the TLV3701 / TLV3702, which works very well in my simulator (Micro-Cap V12)."> Comparators aren't complex.'Not terribly so, but when working with microvolt differentials and microampere currents, a very small change in input capacitance, input bias currents, input impedance, common mode rejection, etc, can make a big difference in the behavior of the circuit. I did try some that plainly will not work as required. If this were TTL, or even ordinary CMOS, then your response would have some merit. The fact this entire circuit (including numerous daughter circuits) must use considerably less than 1mA, with commensurately large resistors and commensurately tiny capacitors, relatively small differences between two analog components can make a big difference. Since the various pinouts are quite different, designing a board for a part that won't work produces a serious impact to both cost and time, especially for a tiny start-up company like mine.> Why bypass a voltage source?Do you mean R3? Without R3 the pulse width is far too narrow and the period far, far too short. Without R3, the period is only 51 microseconds, and the pulse width is 3 microseconds. The output is also not very stable, at all. With R3, the output is very stable, the period is 57ms (more than ten times longer), and the pulse width is 1.7ms (568 times longer). A 3 microsecond pulse is not enough time for the daughter circuit to reliably produce any pulses, let alone a train of 7 pulses.> What is R8 for? R17? C2?R8 Reduces the negative feedback just a little, making the output just a little more square and just a few hundred microseconds wider. This helps make the daughter circuits more stable without increasing the current significantly. R17 prevents Q1 from triggering erratically and produces an even sharper edge to the output pulse leading edge. Again, this provides for greater stability with no significant increase in current. C2 allows for a very low ESR using less expensive components. Now, do you have anything constructive to add, such as a SPICE trace using the MCP6542, or a suggestion for a low cost 3.3V nano power comparator?
Reply by ●April 8, 20212021-04-08
On Thu, 8 Apr 2021 01:25:49 -0700 (PDT), "rhor...@gmail.com" <rhorerles@gmail.com> wrote:>On Wednesday, April 7, 2021 at 10:49:19 PM UTC-5, jla...@highlandsniptechnology.com wrote: >> On Wed, 7 Apr 2021 20:16:03 -0700 (PDT), "rhor...@gmail.com" > >> Why not sim it with the TI part and build it with something else? > >Did you not read my post? Apparently not: "...and settled on the TLV3701 / TLV3702, which works very well in my simulator (Micro-Cap V12)." > >> Comparators aren't complex. > >'Not terribly so, but when working with microvolt differentials and microampere currents, a very small change in input capacitance, input bias currents, input impedance, common mode rejection, etc, can make a big difference in the behavior of the circuit. I did try some that plainly will not work as required. If this were TTL, or even ordinary CMOS, then your response would have some merit. The fact this entire circuit (including numerous daughter circuits) must use considerably less than 1mA, with commensurately large resistors and commensurately tiny capacitors, relatively small differences between two analog components can make a big difference. Since the various pinouts are quite different, designing a board for a part that won't work produces a serious impact to both cost and time, especially for a tiny start-up company like mine. > >> Why bypass a voltage source? > >Do you mean R3? Without R3 the pulse width is far too narrow and the period far, far too short. Without R3, the period is only 51 microseconds, and the pulse width is 3 microseconds. The output is also not very stable, at all. With R3, the output is very stable, the period is 57ms (more than ten times longer), and the pulse width is 1.7ms (568 times longer). A 3 microsecond pulse is not enough time for the daughter circuit to reliably produce any pulses, let alone a train of 7 pulses. > >> What is R8 for? R17? C2? > >R8 Reduces the negative feedback just a little, making the output just a little more square and just a few hundred microseconds wider. This helps make the daughter circuits more stable without increasing the current significantly. R17 prevents Q1 from triggering erratically and produces an even sharper edge to the output pulse leading edge. Again, this provides for greater stability with no significant increase in current. C2 allows for a very low ESR using less expensive components. > >Now, do you have anything constructive to add, such as a SPICE trace using the MCP6542, or a suggestion for a low cost 3.3V nano power comparator?Nope. You're on your own. -- John Larkin Highland Technology, Inc The best designs are necessarily accidental.
Reply by ●April 9, 20212021-04-09
On Thursday, April 8, 2021 at 1:16:06 PM UTC+10, rhor...@gmail.com wrote:> I have created a design for a low power pulse generator that can be seen here: > > http://siliconventures.net/images/Pulse%20Generator.PNG > > I tried several different chips for design purposes for the U1 comparator, and settled on the TLV3701 / TLV3702, which works very well in my simulator (Micro-Cap V12). The problem is all the sources I have found for the TLV370x want quite a bit for the chip, which is a real problem. I have tried numerous different nano power comparators, but every one I have tried is either too expensive in moderate quantities (100 - 200), or else the simulator croaks on the chip. It usually gives a singular matrix error. For example, the MCP6542 is only $0.46 in lots of 100 from Mouser, but when I insert the chip into the sim, it doesn't work. (Yes, I know the MCP6542 is a dual chip. The overall design incorporates several comparators.) > > Does anyone have a simulator that won't croak on the MCP6541 / MCP6542? Does anyone have a recommendation for a drop-in replacement for the TLV3702 or the MCP6541 that is even less expensive (and maybe will work with my sim)? > > If it helps, the circuit design can be found here: > > http://siliconventures.net/docs/Power%20Switch.CIRhttps://www.microchip.com/wwwproducts/en/MCP6542 does offer a spice model for the part. You have to click on the link "SPICE Model for MCP6541/1R/1U/2/3/4 Devices" on the page, and it lets you download a zip file, which Windows Explorer will open up to let you read a text file for the Spice model for the device, which you should be able to cut and paste into a simulator like LTspice. You will probably have to edit the file to get it to work, those Spice models don't always work too well, and they take up a lot space in the circuit diagram. -- Bill Sloman, Sydney
Reply by ●April 9, 20212021-04-09
On Thursday, April 8, 2021 at 10:55:21 PM UTC-5, Bill Sloman wrote:> > http://siliconventures.net/docs/Power%20Switch.CIR > https://www.microchip.com/wwwproducts/en/MCP6542 > > does offer a spice model for the part. You have to click on the link "SPICE Model for MCP6541/1R/1U/2/3/4 Devices" on the page, and it lets you download a zip file, which Windows Explorer will open up to let you read a text file for the Spice model for the device, which you should be able to cut and paste into a simulator like LTspice. > > You will probably have to edit the file to get it to work, those Spice models don't always work too well, and they take up a lot space in the circuit diagram. > > -- > Bill Sloman, SydneyThanks! I will give it a whirl.
Reply by ●April 9, 20212021-04-09
On Wednesday, April 7, 2021 at 11:16:06 PM UTC-4, rhor...@gmail.com wrote:> I have created a design for a low power pulse generator that can be seen here: > > http://siliconventures.net/images/Pulse%20Generator.PNG > > I tried several different chips for design purposes for the U1 comparator, and settled on the TLV3701 / TLV3702, which works very well in my simulator (Micro-Cap V12). The problem is all the sources I have found for the TLV370x want quite a bit for the chip, which is a real problem. I have tried numerous different nano power comparators, but every one I have tried is either too expensive in moderate quantities (100 - 200), or else the simulator croaks on the chip. It usually gives a singular matrix error. For example, the MCP6542 is only $0.46 in lots of 100 from Mouser, but when I insert the chip into the sim, it doesn't work. (Yes, I know the MCP6542 is a dual chip. The overall design incorporates several comparators.) > > Does anyone have a simulator that won't croak on the MCP6541 / MCP6542? Does anyone have a recommendation for a drop-in replacement for the TLV3702 or the MCP6541 that is even less expensive (and maybe will work with my sim)? > > If it helps, the circuit design can be found here: > > http://siliconventures.net/docs/Power%20Switch.CIRYou don't need to simulate that circuit. The TLV7031 is a superior low voltage comparator for your application. Not jelly bean cheap, but less than half the price of 3701, less quiescent current, higher speed, internal hysteresis ( a big plus) and flexible output options https://www.ti.com/lit/ds/symlink/tlv7044.pdf?ts=1617939985692
Reply by ●April 10, 20212021-04-10
On Thursday, April 8, 2021 at 7:41:02 AM UTC-7, jla...@highlandsniptechnology.com wrote:> Nope. You're on your own.I think he's trying to generate free energy through muon induction from the spinning corpse of Bob Pease... -- john, KE5FX
Reply by ●April 10, 20212021-04-10
On Fri, 9 Apr 2021 21:30:24 -0700 (PDT), "John Miles, KE5FX" <jmiles@gmail.com> wrote:>On Thursday, April 8, 2021 at 7:41:02 AM UTC-7, jla...@highlandsniptechnology.com wrote: >> Nope. You're on your own. > >I think he's trying to generate free energy through muon induction from the >spinning corpse of Bob Pease... > >-- john, KE5FXSomething like that. There is an infinite supply of no-name obnoxious amateur googlegroopers who want free engineering and, probably, free energy. I met Bob a few times. He had a fatal attraction for rusty Volkswagens. -- John Larkin Highland Technology, Inc The best designs are necessarily accidental.
Reply by ●April 10, 20212021-04-10
On Friday, April 9, 2021 at 12:21:11 PM UTC-5, Fred Bloggs wrote:> You don't need to simulate that circuit.I disagree. Test prototyping (as opposed to production prototyping) is very expensive in both time and money - especially for someone who hasn't had an income for more than 2 years.> The TLV7031 is a superior low voltage comparator for your application.Yes, it absolutely is, I would think. I have looked at both the 7031 and the 3701. Neither one is modeled in Micro-Cap> Not jelly bean cheap, but less than half the price of 3701No, and that is a problem. They are not less than half the price, either. 'Closer to 75%, in the sources I checked. Both are considerably more than the MCP6541.>less quiescent current, higher speed, internal hysteresis ( a big plus) and flexible output optionsLower current is certainly a plus, although most of the current draw is from other devices in the circuit. Speed is not an issue, at all. The highest speed device is the 555, and it is only a few KHz. The comparators are all operating at less than 30Hz. Internal hysteresis is very nice, but the circuit design handles that externally (costing less than $0.02). Unfortunately, the MCP6541R is not pin-compatible with the 7031 - the power pins are swapped. The 7032 is more economical per comparator, but I am using an odd number of comparators on the board. I suppose I could use a mix of 7032 and 6541 chips. That is another design cycle out the window. I guess I just have to cross my fingers on this design cycle.
