TS1001 Enabled Low Power 555 Timer Design

Touchstone Semiconductor TS1001 Coolest Opamp Design Contest Entry

I thought it would be fun to redesign the 555 timer using two TS1001 Low Power Opamps as comparators. The goal was to make the 555 Timer run on supply voltages below 1V and less than 5uA, so I could use a “fruit” Battery or Solar Cell to power the 555 timer in astable mode.

I started out by running some quick simulations with LTSPICE to prove out my circuit and size the resistors accordingly, so I could meet my 5uA current draw limit.

At the time of this contest no SPICE file was available for the TS1001 Opamp, so I just used the “Universal”  Opamp in LTSPICE; the majority of the current draw in my circuit is from the charge/discharge of the capacitor anyway.

I quickly made up a breadboard version of my circuit and tested it out to prove the concept.

 

I have two TS1001’s as the comparators and a Texas Instruments SN74AUC2G02 Dual-Nor Gate for the SR Latch.

I used DesignSpark’s PCB CAD program to create a Schematic & PCB of the 555 timer.

 

 Below I have my Low Power discrete 555 Timer running off an orange at 0.87V @ 4.4uA. 

Below is the square wave output of the 555 timer and the charge/discharge of the capacitor. This circuit is running at 18.4Hz. 

 

That is one of the downsides with this circuit; I was able to get it to run at a max output frequency of 525Hz with a 1V supply voltage before it pooped out. That is the whole power vs. performance trade off. Diodes Inc. has a Low Power 555 (ZSCT1555) that runs up to 330KHz @ 75uA; mine runs at 18Hz at 4.4uA… trade-offs.

I was also able to get the 555 timer running off of a Solar Cell pulled from a Light up Lawn Ornament. 

I hope you enjoyed my project entry; I had a lot of fun and learned a few things along the way.

DesignSpark Schematic & PCB files: http://www.divshare.com/download/15412088-d84
Gerber files: http://www.divshare.com/download/15412090-835
LTSPICE files: http://www.divshare.com/download/15412094-1d6