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555 help

555 help

555 help

(OP)
I Bought some zsct1555 timer chips from Digi-key and can't seem to get them to work properly. They are made by Zetex for single cell opperation(down to .9v I believe). They are basically the same as the 555 but lower voltages and have a slightly different timing formula. I can't get the output to ever go high. I supply 1.5 volts and have the following component values. Ra=220, Rb=3200, and Ct=100uf. I also tried values of Ra=2200, Rb=22000, and Ct=22uf.  I get the same results either way. The voltage on Ct stays around 1.1 to 1.2 volts. All my components are surface mount and are quite close together, however I have checked for shorted traces often and have changed the 1555 and rechecked for shorts. I've tried running it from a single cell and a power supply plus I've disconnected all output circuitry. Could a 22uf capacitor have too much leakage current to allow the 1555 to switch states? Are my resistor values too low? Any insight would be greatly appreciated, Thanks!

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