Tech Briefs Magazine - September 2024 - PIT-2
Analysis and
Simulation of
Low-Light INL
in CMOS Image
Sensors
W
ith the increase in demand for higher resolution
image sensors, pixel pitch has been reduced
to fit a larger number of pixels within
the same sensor size. In order to read at the
same frame rate, multiple rows must be read concurrently.
This requires multiple analog to data converters (ADCs) per
pixel pitch. ADC pitch has been reduced even further as a result,
requiring a tighter layout. The likelihood of parasitic
coupling increases, which manifests as electrical crosstalk. In
single-slope ADC architecture, ADCs have some shared common
nets, including supplies, grounds, biases and ramp. A
larger number of ADCs converting at the same time can cause
kickback on these shared nets. This can lead to non-idealities,
one of which is nonlinearity.
In addition to traditional sources of nonlinearity, array-level
effects become more visible due to the larger and denser array
size of the ADCs. These can cause dips in the linearity plot
which are tedious to correct and require multiple correction
curves. Traditionally, optically black columns are used for row
noise correction and offset cancellation. Since they all have
similar signal levels, they convert at the same time and introduce
a disturbance on shared nets. This can create nonlinearity
in the darker regions of an image, which is more apparent
to the human eye. In addition, the number of ADC conversions
in the dark can change depending on the scene. As a
result, the magnitude of the disturbance varies and makes it
more difficult to correct. It is therefore better to eliminate the
problem at the source.
Single-Slope ADC and Linearity
Column-parallel ADC architecture and a single-slope ADC
schematic are shown in Figure 1 and Figure 2 respectively.
The ADCs use correlated double sampling (CDS) to read
the pixel voltage. Auto-zeroing (AZ) is completed with respect
to the pixel reset level. The ramp is held at a fixed ref2
Figure
1: Column-parallel readout architecture. (Image: Forza Silicon)
Photonics & Imaging Technology, September 2024
Lead Image: Forza Silicon
Tech Briefs Magazine - September 2024
Table of Contents for the Digital Edition of Tech Briefs Magazine - September 2024
Tech Briefs Magazine - September 2024 - Intro
Tech Briefs Magazine - September 2024 - Sponsor
Tech Briefs Magazine - September 2024 - Cov1
Tech Briefs Magazine - September 2024 - Cov2
Tech Briefs Magazine - September 2024 - 1
Tech Briefs Magazine - September 2024 - 2
Tech Briefs Magazine - September 2024 - 3
Tech Briefs Magazine - September 2024 - 4
Tech Briefs Magazine - September 2024 - 5
Tech Briefs Magazine - September 2024 - 6
Tech Briefs Magazine - September 2024 - 7
Tech Briefs Magazine - September 2024 - 8
Tech Briefs Magazine - September 2024 - 9
Tech Briefs Magazine - September 2024 - 10
Tech Briefs Magazine - September 2024 - 11
Tech Briefs Magazine - September 2024 - 12
Tech Briefs Magazine - September 2024 - 13
Tech Briefs Magazine - September 2024 - 14
Tech Briefs Magazine - September 2024 - 15
Tech Briefs Magazine - September 2024 - 16
Tech Briefs Magazine - September 2024 - 16A
Tech Briefs Magazine - September 2024 - 16B
Tech Briefs Magazine - September 2024 - 16C
Tech Briefs Magazine - September 2024 - 16D
Tech Briefs Magazine - September 2024 - 17
Tech Briefs Magazine - September 2024 - 18
Tech Briefs Magazine - September 2024 - 19
Tech Briefs Magazine - September 2024 - 20
Tech Briefs Magazine - September 2024 - 21
Tech Briefs Magazine - September 2024 - 22
Tech Briefs Magazine - September 2024 - 23
Tech Briefs Magazine - September 2024 - 24
Tech Briefs Magazine - September 2024 - 25
Tech Briefs Magazine - September 2024 - 26
Tech Briefs Magazine - September 2024 - 27
Tech Briefs Magazine - September 2024 - 28
Tech Briefs Magazine - September 2024 - 29
Tech Briefs Magazine - September 2024 - 30
Tech Briefs Magazine - September 2024 - 31
Tech Briefs Magazine - September 2024 - 32
Tech Briefs Magazine - September 2024 - 33
Tech Briefs Magazine - September 2024 - 34
Tech Briefs Magazine - September 2024 - 35
Tech Briefs Magazine - September 2024 - 36
Tech Briefs Magazine - September 2024 - 37
Tech Briefs Magazine - September 2024 - 38
Tech Briefs Magazine - September 2024 - 39
Tech Briefs Magazine - September 2024 - 40
Tech Briefs Magazine - September 2024 - 41
Tech Briefs Magazine - September 2024 - 42
Tech Briefs Magazine - September 2024 - 43
Tech Briefs Magazine - September 2024 - 44
Tech Briefs Magazine - September 2024 - 45
Tech Briefs Magazine - September 2024 - 46
Tech Briefs Magazine - September 2024 - 47
Tech Briefs Magazine - September 2024 - 48
Tech Briefs Magazine - September 2024 - Cov3
Tech Briefs Magazine - September 2024 - Cov4
Tech Briefs Magazine - September 2024 - PIT-Cov1
Tech Briefs Magazine - September 2024 - PIT-Cov2
Tech Briefs Magazine - September 2024 - PIT-1
Tech Briefs Magazine - September 2024 - PIT-2
Tech Briefs Magazine - September 2024 - PIT-3
Tech Briefs Magazine - September 2024 - PIT-4
Tech Briefs Magazine - September 2024 - PIT-5
Tech Briefs Magazine - September 2024 - PIT-6
Tech Briefs Magazine - September 2024 - PIT-7
Tech Briefs Magazine - September 2024 - PIT-8
Tech Briefs Magazine - September 2024 - PIT-9
Tech Briefs Magazine - September 2024 - PIT-10
Tech Briefs Magazine - September 2024 - PIT-11
Tech Briefs Magazine - September 2024 - PIT-12
Tech Briefs Magazine - September 2024 - PIT-13
Tech Briefs Magazine - September 2024 - PIT-14
Tech Briefs Magazine - September 2024 - PIT-15
Tech Briefs Magazine - September 2024 - PIT-16
Tech Briefs Magazine - September 2024 - PIT-17
Tech Briefs Magazine - September 2024 - PIT-18
Tech Briefs Magazine - September 2024 - PIT-19
Tech Briefs Magazine - September 2024 - PIT-20
Tech Briefs Magazine - September 2024 - PIT-21
Tech Briefs Magazine - September 2024 - PIT-22
Tech Briefs Magazine - September 2024 - PIT-23
Tech Briefs Magazine - September 2024 - PIT-24
Tech Briefs Magazine - September 2024 - PIT-25
Tech Briefs Magazine - September 2024 - PIT-Cov4
https://www.nxtbook.com/smg/techbriefs/24TB10
https://www.nxtbook.com/smg/techbriefs/24TB09B
https://www.nxtbook.com/smg/techbriefs/24TB09
https://www.nxtbook.com/smg/techbriefs/24TB08
https://www.nxtbook.com/smg/techbriefs/24TB07
https://www.nxtbook.com/smg/techbriefs/24TB06
https://www.nxtbook.com/smg/techbriefs/24TB05B
https://www.nxtbook.com/smg/techbriefs/24TB05
https://www.nxtbook.com/smg/techbriefs/24TB04
https://www.nxtbook.com/smg/techbriefs/24TB03
https://www.nxtbook.com/smg/techbriefs/24TB02
https://www.nxtbook.com/smg/techbriefs/24TB01
https://www.nxtbook.com/smg/techbriefs/23TB12
https://www.nxtbook.com/smg/techbriefs/23TB11
https://www.nxtbook.com/smg/techbriefs/23TB10
https://www.nxtbook.com/smg/techbriefs/23TB09
https://www.nxtbook.com/smg/techbriefs/23TB08
https://www.nxtbook.com/smg/techbriefs/23TB07
https://www.nxtbook.com/smg/techbriefs/23TB06
https://www.nxtbook.com/smg/techbriefs/23TB05
https://www.nxtbook.com/smg/techbriefs/23TB04
https://www.nxtbook.com/smg/techbriefs/23TB03
https://www.nxtbook.com/smg/techbriefs/23TB02
https://www.nxtbook.com/smg/techbriefs/23TB01
https://www.nxtbook.com/smg/Testing/22TB12
https://www.nxtbook.com/smg/techbriefs/22TB12
https://www.nxtbook.com/smg/techbriefs/22TB11
https://www.nxtbook.com/smg/techbriefs/22TB10
https://www.nxtbook.com/smg/techbriefs/22TB09
https://www.nxtbook.com/smg/techbriefs/22TB08
https://www.nxtbook.com/smg/techbriefs/22TB07
https://www.nxtbook.com/smg/techbriefs/22TB06
https://www.nxtbook.com/smg/techbriefs/22TB05-P
https://www.nxtbook.com/smg/techbriefs/22TB05-D
https://www.nxtbook.com/smg/techbriefs/22TB04
https://www.nxtbook.com/smg/techbriefs/22TB03
https://www.nxtbook.com/smg/techbriefs/22TB02
https://www.nxtbook.com/smg/techbriefs/22TB01
https://www.nxtbook.com/smg/techbriefs/21TB12
https://www.nxtbook.com/smg/techbriefs/21TB11
https://www.nxtbook.com/smg/techbriefs/21TB10
https://www.nxtbook.com/smg/techbriefs/21TB09
https://www.nxtbook.com/smg/techbriefs/21TB08
https://www.nxtbook.com/smg/techbriefs/21TB07
https://www.nxtbook.com/smg/techbriefs/21TB06
https://www.nxtbook.com/smg/techbriefs/21TB05
https://www.nxtbook.com/smg/techbriefs/21TB04
https://www.nxtbook.com/smg/techbriefs/21BT03
https://www.nxtbook.com/smg/techbriefs/21TB02
https://www.nxtbookmedia.com