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Linear Tech ADC features variable resolution modes

Posted: 13 Aug 2002 ?? ?Print Version ?Bookmark and Share

Keywords:linear technology? ltc2440? delta sigma adc? analog digital converter? digital signal conversion?

Targeting precision industrial measurement applications, Linear Technology Corp. has released a 24-bit, no-latency delta-sigma ADC based on a patented variable-speed/resolution architecture. The LTC2440 is said to offer low-noise and high-resolution in each of 10 speed/resolution modes.

In its 6.9Hz output-rate mode, for example, with 0.25V noise and 24.6 effective number of bits, the converter offers simultaneous 50Hz/60Hz rejection, 25 million counts at a 12.5V input range and 500,000 counts at 150mV input range.

Product-marketing engineer Pat Sheehan said the device eliminates the complexities of programmable-gain amplifiers and is independent of sensor offset and tare voltages, benefiting precision instrumentation applications.

An 880Hz output rate mode achieves 25Vrms noise, enabling higher-accuracy control loops and precise tracking of rapidly changing input signals. The maximum output rate is 3.5kHz. All of the converter's speed and resolution modes are selectable through a serial interface.

Sheehan said the converter combines very low noise and high speed with ease of use and low cost. Transparent autocalibration ensures stable output codes independent of time, temperature, supply, and speed selection.

Because the LTC2440 is a no-latency converter, its digital filter always settles in one conversion cycle, even if there is a change in speed or resolution or a change in an external MUX input channel.

Its absolute accuracy (5ppm integral nonlinearity, 1ppm offset, 10ppm full scale) is independent of changes in the output rate. A wide common-mode input range simplifies AFE circuitry.

"This device will reduce customers' design time and allow them to get their products to market faster," said Sheehan. "It also provides a lot of flexibility in measurement."

The LTC2440 operates with a single 5V supply. It is offered in a 16-pin SSOP and screened for industrial and commercial temperature ranges. It is priced from $5.75 in 1,000-piece quantities.

EE Times

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