10

FN6649.0

September 23, 2009

Application Information

The ISL55112 2+2 CCD device provides four drivers for

horizontal inputs of CCD arrays. It comprises two high

capacitance drivers (H1/H2) and two low capacitive

drivers for handling Reset Gate (RG)/Last H (HL) inputs

of a CCD device.

From an applications and physical routing standpoint, the

H1/H2 (high current drivers) have identical circuitry.

Likewise, the HL/RG (low current drivers) circuitry is the

same internally. In dual device applications, the user is

free to swap driver outputs to accommodate layout

requirements.

The ISL55112 H1/H2 have fast rise / fall times into large

capacitive loads. H1/H2 are designed with short

propagation delays and tightly controlled skew, allowing

the device to be used on large, fast CCD arrays, used in

image processing applications

Supply Voltages

The ISL55112 has three types of pins when it comes to

supply voltages: Logic, driver rails and device bias

connections.

VDD and Ground Supply Connections

the operating thresholds for the digital inputs

digital logic connections. Typically they are logic

connections coming from the master CCD timing

generator. PD should have fast transitions, but should not

run at frequencies above 1Hz.

CCD Driver Rails

Each of the four driver outputs has its own set of high

and low rail supply connections. The positive rail

connections for the drivers are RG_VP, HL_VP, H1_VP,

H2_VP. The negative driver rail connections are RG_VN,

HL_VN, H1_VN, H2_VN. (Note H1_VN = H2_VN and

should always be at the same voltage).

Once the user has defined the “Driver” amplitudes

voltage required.

Device Bias connections

determined once the CCD device driver output amplitude

requirements have been determined.

Dual Video CCD Connection Considerations

Physical placement that keeps series inductance to a

minimum is important. The ISL55112 design

accommodates dual device placement close to a CCD

device.

H1 / H2 and RG / HL drivers are internally identical. The

user can rotate the device for PCB placement close to a

single CCD with dual-video requirements.

Power Supply Sequencing

The ISL55112 substrate is connected to the VSUB Pin.

Positive Protection is connected to the VPLUS pin.

The system supply GND connection will always be

present, and is the reference to all other supply voltages.

VN busses. Digital inputs should be driven as soon as all

CCD Array

with Dual

Video Outputs

19

18

17

15

14

13

1

2

3

4

5

6

7

RGIN

H1IN

H2IN

HLIN

RGOUT

HLOUT

H1OUT

H2OUT

RGIN

H1IN

H2IN

HLIN

HLOUT

RGOUT

H1OUT

H2OUT

7

6

5

4

3

2

1

13

14

15

17

18

19

RG_VP

RG_VN

RG_VP

RG_VN

HL_VP

HL_VN

HL_VN

HL_VP

HXVP

HXVP

3.3V

3.3V

PIN 12 (VSUB)

PIN 12 (VSUB)

FIGURE 4. SYMMETRY ACCOMMODATES DUAL DEVICE UTILIZATION WITH A DUAL VIDEO CCD DEVICE

ISL55112