Low Quiescent Current 4011?

Hi

I am looking for a NAND gate 4011 that will draw the minimum current.
Can someone please point me in the right direction?

Also what are the lowest quiescent current V regulators- I am using the MAX666- is there anything better than this?

Thank you in advance.
arrow

A 4011 gate draws next to nothing if you:
1) Keep its inputs near Vcc and Vss.
2) Use a very high impedance load.
3) Operate it at as low a frequency as you can.
4) Use as low a supply voltage as you can.
5) Keep it cool.

An ordinary 4011 doesn't need a voltage regulator. They work with 3V to 18V. Old one were rated to 15V. :lol:

Hi

Thank you for your reply.

Something in the circuit I have is drawing current- of the order of 30uA. I want to identify what it is, so that I can reduce its current draw.

I have a MAX666 regulator and a 4011 Phillips chip.
Can you suggest
(a) how to measure the exact current consumption of each chip
(b) any V regulator that will draw less current than the MAX666

Thank you once again
Regards
arrow

Hi Arrow,
The datasheets indicate a max quiescent current of only 16uA.
What are you doing with them to draw more?

Hi Audioguru

Thank you for your reply.
I will measure the current more accurately a bit later.
Could you please tell me if there are other chips that use lower voltages than 3V minimum for operation?
and draw as little or less current than the 4011?

I am assumign that the outputs of the 4011 can be left to "float" and this will not effect my current draw? (I have tied all unused inputs to High)

Thank you once again.
arrow

Hi AudioGuru

I have just measured my current draw to be approximately 4uA.
I would like to get it below 1uA.

The CMOS is drawing 0.1uA or so my ammeter says.
The rest must be drawn by the MAX666.
Can you recommend a voltage regulator that will draw less than 3uA?
Also can I use a voltage reference?- do these have lower current consumptions? (I have never used a V reference before).

Thank you and
Regards
arrow

Hi Arrow,
Your floating outputs represent the required high impedance load and therefore reduce supply current.

Your current draw is extremely low and bordering on pcb and capacitor leakage currents.

The 74HCxx high speed Cmos series is guaranteed to work with a 2V supply, and circuits I built work fine with the lowest from my LM317 supply: 1.24V. A 74HC00 has the same logic gates as the 4011 but the pinout is different.

I haven't looked for nor seen a regulator or voltage reference with as low an operating current as the one you are using.
Why does your circuit need a voltage regulator? Please post it.
Maybe you can pulse its power for short on periods followed by long off periods. :lol:

Hi AudioGuru

Thank you very much for the information.

I am trying to build a low power switch.
When a certain voltage is reached it turns on. It remains on even if the voltage falls. Once another voltage is reached the switch must turn off.

This is readily doable if there is an unlimited amount of power, however we are running the entire circuit off a charged capacitor.

I have managed to get this to work using a NAND latch (flip flop). With the 4011 chip the "Low" state is proportional to the Vsupply to the chip. (That is the way I understand it). i.e. if Vss= 5V then the "ON" will be > 2.5V
and off will be < 2.5V.
For this reason I need a V regulator (I think). With the V reg I know that my "on" will be at >Vreg/2.

I believe that the system would also work if the "ON" was at a fixed value say >0.5V no matter the Vss.
Are there any logic chips that have a preset value for the "ON" state?

Thank you once again, and
Regards
arrow

Hi Arrow,
The input switching threshold voltage for Cmos logic is near half its supply voltage. Each IC is different and their guaranteed limit is from 0.3 to 0.7 of the supply voltage.
A Cmos gate draws a very low supply current when its inputs are at Vcc or Vss. If the input voltage ramps slowly then the gate draws supply current while the input voltage is near its threshold voltage.
A Cmos gate with Schmitt-trigger inputs can be used to "square-up" a slowly ramping voltage but their threshold voltage is fairly low and is very different for each one. Again, the gate draws supply current while its input voltage is near its theshold voltage.
74HCxx high speed Cmos is not recommended to have slowly ramping input voltages except those with Schmitt-trigger inputs. I used a 74HC14 Schmitt-trigger hex inverter in a low power circuit. When the supply voltage was 2V to 3V the max supply current was 100uA when the input voltage was near its threshold. With a 5V to 6V supply, the supply current was near 1mA. With the 5V to 6V supply, I used a regular Cmos 4584 instead and the max supply current was about 100uA.

Cmos gates have an extremely high input resistance when the input voltage is between Vss and Vcc. Maybe your voltage regulator is not needed or can be replaced by a couple of 22M resistors as a voltage divider. 3V across 44M is only 68nA.
Please post your schematic. :lol:

Hi CodeGuru

I do have a slowly increaseing Voltage on the capacitor.
The attached file contains the schematic.
My aim is to get the switch to use as little current as possible. (Right now its using approximately 3.4uA in the "off" state).

I do not have any other power supply besides this 3.3uF cap.
Would you have any suggestions to improve this?

I was thinking of dropping the 3V to say 2V- but CMOS 4011 does not operate to that voltage.

Also I am not quite sure why, but the circuit only seems to work with the 1.5k R between the 3V supply from the V regulator and the 4011. Would you know why this is the case?

Thank you for all your suggestions.
Regards
arrow

I don't know what you are doing with the gates without a schematic for them, or without all pins of the 4011 identified and labeled so I can translate its layout into a schematic.

Does the 1.5k resistor connect to pin 14 of the 4011? That's its positive supply pin, it won't work very well without a supply. :lol:

EDIT: I also don't know what you are doing with the MAX666 without all its pins identified and labeled so I can translate its layout into a schematic.

Hi AudioGuru

I am posting all the pins.
Basically I have a "NOT" gate (on the right hand side of the 4011), and a latch (I think its an RS latch) on the left side of the 4011.
The 1.5k resistor does connect the 4011 to the power of 3V (if I dont inclue it, the circuit does not work).

I am not quite sure why I need that 1.5k.

Now I have measured the current draw to be approximately 4.3uA using this circuit, and am not sure if its correct or not.

All the best
arrow

Hi Arrow,
I sketched a schematic of your flip-flop circuit and revised it with improvements:
1) The entire circuit could be done with a single Cmos MC14584 or 74C14 hex Schmitt trigger inverter or a CD4093 quad Schmitt trigger Nand gate.
2) You have both inputs at pins 12 and 13 being driven by a changing voltage, therefore their input transistors are both drawing supply current.
If you drive a single input and disable the other one then the supply current will be less, but the input threshold voltage will be different: it will be closer to half the supply voltage, therefore you must change the resistors if you want switching to occur at the same voltage as before.
3) Any current drawn by your load reduces the output voltage at pin 3, and also at input pin 6. Therefore the input transistors at pin 6 will draw some supply current.
If you use the spare gate as a buffer then the supply current will be less. :lol:

Hi AudioGuru

Thank you very much for your schematic- I have tried it and it did reduce the current slightly.
I suspect that my main current sink though is in the V regulator (MAX666). I have been looking for lower Iq V regulators with little success.

I know that what I am trying to do (recreate the MAX6433 with no time delay) is doable; I just dont know how to do it. The MAX6433 uses a comparator (without a regulator?)- I am not sure that that will save me something like 2uA.

Any thoughts on this?

Once again, I appreciate all your help.
Regards
arrow

arrow said:

I know that what I am trying to do (recreate the MAX6433 with no time delay) is doable; I just dont know how to do it. The MAX6433 uses a comparator (without a regulator?)- I am not sure that that will save me something like 2uA.

Any thoughts on this?

Click to expand...

I don't really see the problem with the short time delay?, presumably it's a design feature of the MAX6433?, it's certainly something that would usually be important in a low battery indicator.

Why is it a problem to you?.

Hi Nigel

I am using the circuit to do (relatively) accurate measurements. A time delay, that makes sense in a low battery indicator, gives a lot of variability in my results. This lack of reproducability is making me design a circuit that will work similarly to the MAX6433 but with no time delay to switch on. (The MAX6433 dealy itself is not repeatable from experiment to experiment).

Regards
arrow