Toshiba Develops CMOS Image Sensor for Small and Low Power Applications

  Toshiba Develops CMOS Image Sensor for Small and Low Power Applications

International Solid-State Circuits Conference 2013

Business Wire

TOKYO -- February 25, 2013

Toshiba Corporation (TOKYO:6502) today announced the development of a CMOS
image sensor with a small area and low power pixel readout circuits. A sample
sensor embedded with the readout circuits shows double the performance of a
conventional one.^(1) Toshiba presented this development at ISSCC 2013 in San
Francisco, CA on Feb. 20.

As demand for commodity mobile phones takes off in emerging markets, CMOS
image sensor need to be smaller, consume less power and offer low noise
performance. The pixel readout circuits of CMOS image sensors are largely
noise reducing correlated double sampling (CDS) circuits, along with a
programmable gain amplifier (PGA) and an analog to digital converter (ADC).
Serial signal processing architecture is best suited for securing conventional
CMOS image sensors with a small area and low power pixel readout circuits,
because a PGA and ADC can be shared by many CDS circuits placed in each column
area of the sensor. However, smaller size and lower power are still
challenges, since noise reduction circuits occupy a large area in the readout
circuits, and PGA and ADC have high power consumption.

Toshiba has developed three key technologies to overcome these challenges:
1) Column CDS circuits primarily made up of aria-efficient PMOS capacitors.
The area of the CDS circuits is reduced to about half that of conventional
circuits.
2) In the readout circuits, a level shift function is simultaneously achieved
by a capacitive coupling through the PMOS capacitors, allowing adjustment of
the signal dynamic range between the column CDS circuits and the PGA and the
ADC. This achieves low power and low voltage implementation of the PGA and
ADC, reducing their power consumption by 40%.
3) Implementation of a low power switching procedure in the ADC suited to
processing the pixel signals of CMOS image sensors. This reduces the switching
power consumption of the ADC by 80%.
Toshiba has integrated the three technologies in a sample sensor and confirmed
that they double the overall performance of the sensor core. The company now
plans to apply CMOS image sensors with the readout circuits to low cost mobile
phones and medical cameras in fiscal year 2013.

(1) Compared using Figure of Merit; FOM = power x noise / (pixels x frame
rate)

About Toshiba

Toshiba is a world-leading diversified manufacturer, solutions provider and
marketer of advanced electronic and electrical products and systems. Toshiba
Group brings innovation and imagination to a wide range of businesses: digital
products, including LCD TVs, notebook PCs, retail solutions and MFPs;
electronic devices, including semiconductors, storage products and materials;
industrial and social infrastructure systems, including power generation
systems, smart community solutions, medical systems and escalators &
elevators; and home appliances.

Contact:

Toshiba Semiconductor & Storage Products Company
Megumi Genchi / Kunio Noguchi, +81-3-3457-3367
semicon-NR-mailbox@ml.toshiba.co.jp
 
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