Rainbow Electronics TH7899M - Manual (Page 6)

6
TH7899M
2201A–IMAGE–02/02
Output Amplifiers The TH7899M sensor has four output amplifiers. These are located in each corner of
the device at the ends of the readout register. Charge packets are clocked to a pre-
charge capacitor (floating diffusion) whose potential varies linearly with the quantity of
charge in each packet. This potential is applied to the input gate of a two stage source
follower amplifier and the output signal is read. Then, the reset clock
Φ
R removes the
charge from the floating diffusion via the reset drain VDR which imposes its reference
level.
Figure 5. On-chip Output Amplifier Structure
Multi-Pinned-Phase
(MPP) Mode
The TH7899M sensor operates in the MPP mode in order to substantially decrease dark
current (typically from 0.6 nA/cm
2 to 25 pA/cm 2 at 25°C). Compared to standard technol-
ogy, the MPP mode allows, while keeping all other performances unchanged, either to
increase exposure time, or to operate at higher temperature.
Dark current is due to thermal generation in the substrate of the CCD. The different gen-
eration sources are as follows:
• surface states at the Si-SiO
2
interface which is the main contribution
• generation and diffusion in the bulk
• generation in the depleted zone
If the gates are biased with adequate negative biases, holes appear at the Si-SiO
2
inter-
face and fill in the interface states suppressing their dark current contribution. As a
result, only the minor bulk and depleted zone contributions remain.
Absolute Maximum Ratings*
Storage temperature..................................... -55°C to + 150°C
Operating temperature ................................... -40°C to + 85°C
Temperature cycling ...................................................15°C/mn
*NOTICE: Stresses above those listed under ABSOLUTE
MAXIMUM RATINGS may cause permanent
device failure. Functionally at or above these lim-
its is not implied. Exposure to absolute maximum
ratings for extended periods may affect reliability.