Design ultralow power, narrow band ADC

[anhnha]

Hi,
I want to design an ADC with these specifications:
Fin = 20MHz
BW= 20MHz
ENOB > 4
Power consumption P < 1mW
Could anyone suggest me some ADC for this kind? I have searched a lot in
IEEE but there are only two ADC with SAR ADC and time-interleaved ADC.
The ultralow power consumption makes it hard for me to find a
architecture. I have little experience about this. Kindly help me.

 

[Baluncore]

You like a challenge don't you !

To convert a 20MHz signal Nyquist says you will need one converter at 40Msps or two at 20Msps.
The best commercial unit would be 8 bits at about 50mW. But you only want 4 bits.

A resistive divider with 15 comparators might be possible but 15 comparators at 40MHz (= 25ns) will draw about 15ma at 3 volts = 45mW. You might minimise the power slightly by using 15 AC coupled single transistors as your comparators. A sample pulse switches AC inputs from reference to signal at 40Msps.

Maybe some knowledge of your signal characteristics could reduce power by pre-processing. Can you tell me how the signal is modulated ?

Take a look at;
http://www.ti.com/lsds/ti/analog/dataconverters/data_converter.page
http://www.linear.com/products/Analog-to-Digital_Converters_(ADC)
http://www.linear.com/products/Comparators

 

[carlgrace]

Hi,
I want to design an ADC with these specifications:
Fin = 20MHz
BW= 20MHz
ENOB > 4
Power consumption P < 1mW
Could anyone suggest me some ADC for this kind? I have searched a lot in
IEEE but there are only two ADC with SAR ADC and time-interleaved ADC.
The ultralow power consumption makes it hard for me to find a
architecture. I have little experience about this. Kindly help me.

By design an ADC do you mean design an IC? If so, you didn't look that hard in IEEE.

Harpe, P.J.A., Zhou, C., Bi, Y., Meijs, N.P. van der, Wang, X., Philips, K.J.P., Dolmans, G. & Groot, H. de (2011). A 26μ W 8 bit 10 MS/s asynchronous SAR ADC for low energy radios. IEEE Journal of Solid-State Circuits, 46(7), 1585-1595.

http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=05771068

Reduce the 8-bits to 4 and you can get the power no problem.

For a four-bit ADC though, maybe a straight flash is the way to go since you only need 15 comparators. Depends on the process you're using, of course.

 

[Baluncore]

This is slow but includes discussion of different methods including switched capacitors.
Very Low Power SAR ADC

 

[alphy]

As a fellow scientist, I understand your desire to design an ADC with these specific requirements. The first step in designing an ultralow power, narrow band ADC is to understand the trade-offs between power consumption, speed, and resolution. In this case, your desired power consumption of less than 1mW narrows down your options significantly, as most high-speed ADCs consume more power.

One possible option for your design could be a successive approximation register (SAR) ADC. SAR ADCs are known for their low power consumption and high resolution, making them suitable for your requirements. However, they may not be the best choice for high-speed applications.

Another option could be a delta-sigma ADC. These ADCs are known for their high resolution and low power consumption, but they also have a slower conversion rate compared to other ADC architectures. This may not be an issue for your specific application, as your desired input frequency and bandwidth are both 20MHz.

In addition, you may want to consider using a time-interleaved ADC. While there may only be two options currently available in IEEE, this architecture has shown promise for achieving both high speed and low power consumption. However, it may require more complex circuitry and careful design to meet your desired specifications.

Ultimately, the best approach for your design will depend on your specific application and trade-offs between power consumption, speed, and resolution. I suggest conducting further research and consulting with other experts in the field to determine the most suitable ADC architecture for your needs. Best of luck in your design process!