Analog front ends set sights on improved digital-camera/camcorder image

-- EDN, 1/20/2000

As digital camcorders and still cameras capture an increasing share of the video market, OEMs and consumers want improved image quality along with longer life from batteries. The AD9840 analog front end from Analog Devices, a correlated, double-sampling, 10-bit A/D-converter subsystem for CCD imagers, converts at 36M samples/sec and reduces power consumption to 140 mW (Picture).

The 2.7 to 3.6V IC's A/D accepts signals with a 2V p-p range and has an input capacitance of 5 pF. Its internal automatic gain control supports gain values of 2 to 36 dB via a 10-bit analog gain control. Typical differential nonlinearity is ±0.5 LSB, and SNR is less than 0.2 dB rms. Noise is 0.2 LSB rms at minimum gain, increasing to 3.75 LSB at maximum gain. The CMOS converter, which includes its own reference, uses a three- or four-wire serial interface to the camera's image processor and can slash its power consumption to less than 1 mW in shutdown mode. The AD-9840 costs $5.66 (1000), and the company has also introduced a compatible, half-speed, one-third-power version based on a modified AD9840 design (not just a slower clock) and plans in the next few months to introduce a higher resolution, low-noise, lower power version.

Analog Devices Inc, 1-781-937-1428, www.analog.com.

-by Bill Schweber