PI0256HSN, PI0512HSN, PI1024HSN

Engineering Data Sheet

Page 2 of 8

March 13, 2002

Figure2. Geometry and layout of photodiode pixels.

During normal operation, the photons incident in or

near the NP photodiode junction generate free charges

that are collected and stored on the junction's depletion

capacitance. The number of collected charges is

proportional to the light exposure. Figure 3 shows the

stored signal charge as function of light exposure at a

wavelength of 575 nm. The exposure is the product of

the light intensity in nW/cm

seconds. The charge accumulates linearly until reach-

ing the saturation charge, and the corresponding

exposure is the saturation exposure.

There are two

saturation limits which are described in the Selectable

Charge Capacity section below.

The responsivity may be calculated as the saturation

charge divided by saturation exposure. The predicted

typical responsivity of a photodiode is 1.5

at 575 nm. Figure 4 shows the predicted responsivity

of the photodiodes as a function of wavelength.

Figure 3. Stored signal charge as function of exposure at

a wavelength of 575 nm.

2 Dummy

Pixels

Active Pixels

25µm

2 Dummy

Pixels

2500µm

0

10

20

30

40

50

60

70

80

0

100

200

300

400

500

Exposure (nJ/cm

saturation

w/o cap

saturation with cap