counterdigital-logicintegrated-circuitmicrocontroller
I am currently looking at a 4017B Decade Counter Data Sheet.
As I look at the Logic Schematic for this IC (http://www.ti.com/lit/ds/symlink/cd4017b.pdf) I can see several sqaure boxes label D, C, Q(bar), Q.
Am I correct in assuming that these square boxes are a variant of the 'Flip Flop' in order to store the value that the counter is on and would I be right in assuming if I replicated this schematic with my own flip flop I could create my own Decade Counter?
Thanks.
The MM5450 may do what you want.
34 outputs, serial fed, chainable.
Notionally 3 pins to drive (clock, data, latch) but can be driven with 1 pin if needed. Digikey $4.39/1 This one in DIP-40 but also available in LCC.
if this does not suit your need you need to provide a more complete description of your requirement.
Outputs are open drain, ie either on = low or off = float or open circuit.
After looking at the datasheet, the part normally pulls 60-70mA at 5V, dissipates 350mW. This will be warm to the touch, not hot. Not sure why you're using an old TTL device, newer fast CMOS parts have standby currents in the 100uA range.
You mention adding a resistor to gnd, what's the other end of the resistor connected to?
You may float TTL inputs, hopefully there are no DC loads on the outputs, otherwise the chip will draw current unnecessarily.
Try this: connect a series resistor (5 ohms) inline with Vcc. If you get a voltage drop > 0.5V across the resistor, then either the chip is damaged or the outputs (including RCO) are driving heavy loads.
Best Answer
Correct, those are normal D flip-flops. The 4017B itself is just some D flip-flops behind a decoder, so just flip-flops wouldn't be enough to replicate the whole counter; you can use a 74xx42 or 74xx45 as the decoder after the flip-flops.