Low quiescent current comparator problem

[ytliang]

I need to design a cheap comparator that requires almost 0 quiescent current (0.3uA to be exact). Basically the output goes high when the input > 0.15v, otherwise it's a low.

Can somebody provide some ideas/suggestions?
Many thanks,

 

[mathsolvesit]

Make a discrete comparator (standard textbook back-to-back PNP's driving an NPN) using exptemely low collector curoff current devices. Here's a few:
MMBT5771, FMMTL618.
Your resistor values will have to be >30Meg.
Don't expect low quiescent current above 40C though.

 

[ytliang]

Make a discrete comparator (standard textbook back-to-back PNP's driving an NPN) using exptemely low collector curoff current devices. Here's a few:
MMBT5771, FMMTL618.
Your resistor values will have to be >30Meg.
Don't expect low quiescent current above 40C though.

Thanks for the reply.
If I were to use a comparator you mentioned, I would need a bandgap reference to generate the 0.15v. A normal comparator + a bandgap reference that operate under 0.3uA total quiescent current doesnt seem reasonable.
I was thinking more of an easier approach that probably doesnt require a "real" or "traditional" comparator because I dont need it to compare a range of values. The difficulty lies in that 0.15v is lower than the threshold voltage of an NMOS.

 

[JPR]

Are there any other specifications?

Input impedance?
How fast does the comparator need to transition?
What temperature range does the comparator need to operate over?
What is the tolerance on the 150mV?
What other circuits might be available? Reference voltages? Bias currents? Clock circuits?

If you can handle a current pull-up on the input when it is below 150mV, then you could use a common gate type amplifier, IF you have a way to bias the gate at 150mV above threshold.

If you have clock circuits, you might be able to make a switched capacitor circuit to multiply the voltage up to a useable level.

 

[ytliang]

Are there any other specifications?

Input impedance?
How fast does the comparator need to transition?
What temperature range does the comparator need to operate over?
What is the tolerance on the 150mV?
What other circuits might be available? Reference voltages? Bias currents? Clock circuits?

If you can handle a current pull-up on the input when it is below 150mV, then you could use a common gate type amplifier, IF you have a way to bias the gate at 150mV above threshold.

If you have clock circuits, you might be able to make a switched capacitor circuit to multiply the voltage up to a useable level.

There is no spec really. The threshold value can be between 100mV ~ 240mV. It needs to operate from -40 ~ 85 degree. It's supposed to be used as an enable detection device. When the enable signal is above 150mV, the IC turns on. As a result, no other circuits are available because the IC is turned off when we need the detection.

As for the common gate suggestion, I would think the input should be a high impedance node and does not drain current for this application, preferably the gate of a transistor.

Thanks a lot for the advices,