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I am working on a circuit with a Sharp Memory display that requires a VCOM 50% duty cycle square wave signal at a frequency of approx 1Hz.

It was suggested to use a TS3005 (Datasheet)which looked perfect until I see that Silicon Labs has EOL (End of Life) its timers and I cannot seem to get hold of them anymore.

It looks like the whole family of TS3001->TS3006 are being discontinued.

The TS3005 looked perfect because it had an adjustable duty cycle frequency using just a simple Resistor and its Ultra Low Supply Current: 1.35μA at 49Hz. This is a nice chip because it runs all on its own without CPU intervention.

I looked at the TI TPL5x00 chips but they all seem to need an outside DONE signal, and I wanted my CPU to be completely asleep, while the timer chip refreshes the Memory Display.

I really need something with very low power consumption as it will be running from a coin-cell battery.

Does anyone know of a suitable replacement circuit that performs the same in both duty cycle of 50%, Frequency (1Hz) and very low supply current?

I looked at the 555 timer and the power consumption is way too large.

I am working on something similar to the Chronio watch project here.

Thanks Mark

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  • \$\begingroup\$ have you even looked at CMOS low power 555 timers? Texas Instruments has one that uses 100uA ti.com/lit/ds/symlink/lmc555.pdf \$\endgroup\$
    – KyranF
    Mar 3, 2017 at 21:50
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    \$\begingroup\$ you could also try a very low power CMOS oscillator circuit and an ultra-low power comparator to convert the sine wave oscillation into a square wave \$\endgroup\$
    – KyranF
    Mar 3, 2017 at 21:51
  • \$\begingroup\$ here ya go! discovercircuits.com/PDF-FILES/astable.pdf \$\endgroup\$
    – KyranF
    Mar 3, 2017 at 21:55
  • \$\begingroup\$ I am late to the party so you may have found a replacement. Have you looked at the SiT1569 from Si time? \$\endgroup\$
    – Stuart
    Nov 12, 2018 at 15:58

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You could use a DS1341/2 to generate a 1 Hz signal ...in addition it could be your main crystal controlled timepiece. It draws less than 500 nA @ 3 V.

You could even use the new DS2417 which draws less than 200 nA @ 3 V and the 1-Wire interface is much lower power than I2C.

Since I assume you are using an ATMega328P, the 1 Hz signal can be a wakeup interrupt along with any button presses. If you are doing something like Chronio you should make sure to read Gammon and Morissey on deep sleep with the ATMega328(P), they are very useful research.

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  • \$\begingroup\$ great idea with the RTC and the 1Hz output pulse. I've also seen GPS modules output 1Hz pulses before too \$\endgroup\$
    – KyranF
    Mar 4, 2017 at 5:25

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