FEATURES

Integrated active load and gain of 1 buffer

Very low buffer power consumption

As low as 20 mW on chip

Power save feature to reduce active load current by GPO

control

High buffer speed

400 MHz, −3 dB bandwidth

415 V/μs slew rate

Fast settling time to 1%, 2 V step: 5 ns

Adjustable buffer bandwidth

Push-pull output stage

Adjustable active load current

Small package: 1.6 mm × 1.6 mm × 0.55 mm

 

ANWENDUNGEN

CCD image sensor output buffer

Digital still cameras

Camcorders

 

ALLGEMEINE BESCHREIBUNG

The ADA4800 is voltage buffer integrated with an active load. The buffer is a low power, high speed, low noise, high slew rate, fast settling, fixed gain of 1 monolithic amplifier for chargecoupled device (CCD) applications. For CCD applications, the active load current source (IAL) can load the open source CCD sensor outputs and the buffer can drive the AFE load. The active current load can also be switched off, to use the ADA4800 as just a unity gain buffer. The buffer consumes only 20 mW of static power. In applications where power savings is critical, the ADA4800 features a power save mode (see the Power Save Mode section), which further reduces the total current consumption. The bandwidth of the ADA4800 buffer is also fully adjustable through the IDRV pin. The buffer of the ADA4800 employs a push-pull output stage architecture, providing drive current and maximum slew capability for both rising and falling signal transitions. At a 5 mA quiescent current setting, it provides 400 MHz, −3 dB bandwidth, which makes this buffer well suited for CCD sensors from machine vision to digital still camera applications.The versatility of the ADA4800 allows for seamless interfacing with many CCD sensors from various manufacturers. The ADA4800 is designed to operate at supply voltages as low as 4 V and up to 17 V. It is available in a 1.6 mm × 1.6 mm × 0.55 mm, 6-lead LFCSP package and is rated to operate over the industrial temperature range of −40℃ to +85℃.The ADA4800 allows for additional power savings by reducing the active load current. The active load current can be logically controlled by connecting the ISF pin to any general-purpose output (GPO) pin of a system microcontroller through an external resistor. A GPO logic high enables the flow of the active load current. Appling –VS or connecting a high-Z to the ISF pin places the ADA4800 into power save mode by shutting down the active load current.

 

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.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.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.Power save mode allows IAL current to be logically controlled by connecting the ISF pin to any generalpurpose 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.