PI0256HSN, PI0512HSN, PI1024HSN

Engineering Data Sheet

Page 4 of 8

March 13, 2002

I/O Pins

Besides the VSS and VDD supply pins, there are 9

functionally active I/O pins. Only two clocks, CLK and

START, are required for controlling the timing of the

sensor's video readout. One additional digital input,

ADDCAP controls the bank of capacitors as described

in the Selectable Charge Capacity section above. The

digital output, EOS, marks the end of the line-scan.

The charge output pin, QOUT, is typically connected to

a charge-integrating amplifier that is biased to Vbias

(see Recommended Operating Conditions section

below). For normal anti-blooming operation, the ABG

requires a 0.1-µF capacitor connected to VSS and the

ABD is also biased to Vbias. Each temperature diode

is operated with a small constant current that forward-

biases its PN junction. By measuring the forward-bias

voltage, one can track the silicon die temperature. The

temperature diodes may be disabled by connecting

their anodes to VSS. These I/Os are listed with their

acronym designators and functional descriptions in the

following Table 1.

Table 1. Symbols and functions and I/O pins.

Symbol

Function and Description

VSS

Ground.

VDD

+5.0 Volts.

START

Start Pulse: Input to start the line scan.

CLK

Clock Pulse: Input to clock the shift register.

ADDCAP

Add Capacitors: Input that selects the bank of capacitors to increase charge capacity.

EOS

End Of Scan: Output from the shift register to indicate the completion of one line scan.

QOUT

Video Charge Output: Output from the photodiodes pixels.

ABG

Anti-Blooming Gate: Self-biased gate for setting anti-blooming level. Requires 0.1-µF

connected to VSS.

ABD

Anti-Blooming Drain: Bias for anti-blooming drain. Set to Vbias.

TD1

Temperature Diode 1: Anode of temperature diode 1.

TD2

Temperature Diode 2: Anode of temperature diode 2.

NC

No Connection

Figure 5. Simplified circuit diagram of a HSN photodiode array. The diagram does not include the capacitor bank

and the anti-blooming circuitry.

CLK

ART

TD1

SHIFT REGISTER

EOS

QOUT

TD2

VSS