ADA4800

Rev. A | Page 11 of 16

APPLICATIONS INFORMATION

OPEN SOURCE CCD OUTPUT BUFFER

With low power, high slew rate, and fast settling time, the

ADA4800 is the ideal solution for an output buffer for CCD

sensors with an open source output configuration. Figure 21

shows a typical application circuit for the ADA4800 as a CCD

sensor output buffer.

The output of the CCD is connected directly to the IN pin

of the ADA4800, whose OUT pin is then ac-coupled into

the input of the analog front end.

IN

VEE

OUT

CCD

AFE

15V

ADA4800

+1

6

ISF

1

5

VCC

2

4

IDRV

3

120k

Ω

15V

249k

Ω

0.1µF

0.1µF

0.1µF

47µF

+

Figure 21. Typical Application Block Diagram

To help reduce the effects of power supply noise coupling into

the ISF and IDRV pins, use 0.1 μF ceramic bypass decoupling

capacitors. For best performance, place these capacitors as

close to each of these pins as is physically possible.

POWER SAVE MODE

The buffer of the ADA4800 consumes only 20 mW of static

power. To achieve even more power savings, the ADA4800

active load current can be switched off during standby mode

or reduced during monitoring mode. Figure 22 illustrates the

ADA4800 as an open source CCD buffer configured for using

be logically controlled by connecting the ISF pin to any general-

purpose output (GPO) pin of the system microcontroller through

an external resistor. A GPO logic high enables the flow of input

sink current, while a logic low disables the input sink current

and asserts the power save mode.

0V TO 3V

GPO PIN

IN

VEE

OUT

CCD

AFE

15V

ADA4800

+1

6

ISF

1

5

VCC

2

4

IDRV

3

10k

Ω

249k

Ω

0.1µF

0.1µF

0.1µF

47µF

+

Figure 22. Using GPO to Drive ISF Voltage

Figure 23 shows an example of the ADA4800 power save feature.

AFE

GPO1

GPO2

20k

Ω

20k

Ω

MAIN BOARD

FPC

ADA4800

ISF

Figure 23. Example Block Diagram for Sink Current Selection

Table 5. Input Sink Current Selection

Mode

GPO1

GPO2

Resistance (kΩ)

Standby

High-Z

High-Z

High-Z

0

0

0

N/A

Sleep

High-Z

1

20

1.90

1

High-Z

20

Active

1

1

10

3.36