CMOS Image sensor

[hjhjh]

Hello,

I do a project related cmos image sensor , and it need photodiode. I have a question about that: How can photodiode implement in CMOS technology?? And how can I find photodiode in cadence with PDK TSMC 180.
And how I can define the output voltage of photodiode for input ADC ?? (how can I find the specs of my photodiode & ADC)

Hjhjh

 

[dick_freebird]

You will be working with photocurrent, not voltage, and
likely a CTIA cell with integration-time controlled by a
host (to set "exposure"). Part of that would be to keep
any pixel output below ADC all-ones, above all-zeroes.

That then wants an idea of pixel output per spec input
given pixel detector area. That can vary within a process,
by device-species and by construction details. When you
have a good max number you can scale CTIA gain /
integration-window interval, with ADC input range, to set
max frame time (or the other way 'round, depending on
what's yours to define).

You will use a natural process diode, of which you have
a limited set of choices and probably only one that's a
good idea for your amplifier design. The PDK diode is
probably not ideal as a photodiode (attributes like noise
are likely not modeled or poorly so, and low illumination
losses would like you to do some field control, maybe
plate over the diode to drive collection away from the
oxide surface and its surface recombination.

There are many, many scholarly papers on ROIC design
and CMOS image sensors for you to seek out and pick
through. Optimizing integrated photodiodes has been an
area of robust research. Go look. You might even find
references which have to do with your target foundry tech.

 

[D.A.(Tony)Stewart]

For visible light-corrected CIE curves, look up Photo Sensors. Sharp and Panasonic excelled in these but transferred their old technology parts to Vishay.

 

[hjhjh]

You will be working with photocurrent, not voltage, and
likely a CTIA cell with integration-time controlled by a
host (to set "exposure"). Part of that would be to keep
any pixel output below ADC all-ones, above all-zeroes.

That then wants an idea of pixel output per spec input
given pixel detector area. That can vary within a process,
by device-species and by construction details. When you
have a good max number you can scale CTIA gain /
integration-window interval, with ADC input range, to set
max frame time (or the other way 'round, depending on
what's yours to define).

You will use a natural process diode, of which you have
a limited set of choices and probably only one that's a
good idea for your amplifier design. The PDK diode is
probably not ideal as a photodiode (attributes like noise
are likely not modeled or poorly so, and low illumination
losses would like you to do some field control, maybe
plate over the diode to drive collection away from the
oxide surface and its surface recombination.

There are many, many scholarly papers on ROIC design
and CMOS image sensors for you to seek out and pick
through. Optimizing integrated photodiodes has been an
area of robust research. Go look. You might even find
references which have to do with your target foundry tech.

Hmm
In my document I find cmos sensors have 2 main type : Passive pixel sensors(PPS) & Active pixel sensor(APS)
With PPS they used CTIA as you write to collect photocurrent off photodiode (PD). But with 3-T APS they used a buffer to collect the voltage of PD and then they apply an ADC to convert. I 'd like to understand why they use that buffer ??
And i 'd like to know the signal after readout, it go to the MUX and how to control the mux to readout to ADC in this document
CMOS Image Sensors

For visible light-corrected CIE curves, look up Photo Sensors. Sharp and Panasonic excelled in these but transferred their old technology parts to Vishay.

D.A
Thanks for your answer. But I want to implement it in CMOS technology to intergrate with other component.

 

[hjhjh]

Hmm
In my document I find cmos sensors have 2 main type : Passive pixel sensors(PPS) & Active pixel sensor(APS)
With PPS they used CTIA as you write to collect photocurrent off photodiode (PD). But with 3-T APS they used a buffer to collect the voltage of PD and then they apply an ADC to convert. I 'd like to understand why they use that buffer ??
And i 'd like to know the signal after readout, it go to the MUX and how to control the mux to readout to ADC in this document
CMOS Image Sensors

D.A
Thanks for your answer. But I want to implement it in CMOS technology to intergrate with other component.

And why the number of pixel is 16×16 or 4x4 but another number ???
Please help me
Thanks

 

[D.A.(Tony)Stewart]

> I 'd like to understand why they use that buffer ??

To detect lower light levels, the impedance must be raised to detect lower currents.

>16×16 or 4x4

Where did you see that?

 

[hjhjh]

Oh I have an another question about Single photon avalanche diode (SPAD)
It can be detect the first photon come to the SPAD ??? and with another photon ??

 

[D.A.(Tony)Stewart]

and another and another ... https://www.wikiwand.com/en/Single-photon_avalanche_diode

 

[dick_freebird]

You do not want to mess with APDs (that's avalanche photodiodes,
not the Active Pixel Detector) unless you must. There is more
art around keeping at the gain-point you want, of getting that point
to match across MxN channels and so on. Photon counting can't be
done cost effectively in another way, but an imager is not a photon
counter (unless you are talking "staring arrays" in deep space black
in a temperature-controlled box - APDs' junction leakage current is
as valid a "signal" as a photon wandering by, and must be dealt
with).

Don't come up with such questions until you have the "product" spec
in hand, to give you the "goalposts". Otherwise all you get is a sack o'
unvalidated possibilities. Get it specified, get approach picked, get it
done.