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Analog Devices Introduces Industry's Smallest 18-Bit Analog-To-Digital Converter

Analog Devices » AD7690, AD7691

3 mm x 5 mm package means space- and power-constrained instrumentation applications no longer sacrifice signal conversion performance.

Analog Devices introduced the industry’s first 18-bit analog-to-digital converter (ADC) to deliver 400-kSPS (kilo-samples-per-second) data rates in a 3 mm × 5 mm MSOP (mini-small-outline package) package and also a 3 mm x 3 mm LFCSP (lead frame, chip scale package), the world’s smallest leadless package. Targeted at applications – such as battery operated medical equipment, remote and isolated data acquisition systems and industrial smart sensors – that can take advantage of its unique combination of speed, performance, low power and small package, the AD7690 is designed for applications where board space is at a premium but speed and accuracy cannot be sacrificed. In addition to doubling speed and enabling a 40 percent reduction in board space, the  has an SNR (signal-to-noise ratio) of 102 dB, making the 18-bit device 6 dB more accurate than the closest competing ADC.


Low Power SAR Ideal for Battery-Powered Devices
In addition to its increased precision, higher speed, and smaller package, the AD7690 consumes 80 percent less power than competing devices, making it a natural fit for battery-powered portable and handheld instrumentation applications. At its highest throughput rate of 400kSPS, the AD7690 dissipates 20 mW compared to 110 mW for the closest competing ADC. The device powers down automatically at the end of each conversion, so the power scales linearly with the sampling rate, making the part ideal for low-battery powered applications.

18-Bit Sampling with No Missing Codes
The AD7690 is a member of the Analog Devices’ PulSAR® family of successive approximation ADCs, the most cost-effective technology for applications that require precise digital modeling of analog signals. The device’s DNL (differential linearity) of +/-1 LSB (least significant bit) makes it the first ADC to offer true 18-bit linearity in an MSOP package with zero data latency. The AD7690 also achieves a typical INL (integral nonlinearity) specification of +/– 1LSB (least significant bit), a critical specification for engineers designing instrumentation devices capable of providing more accurate test measurements.

The AD7690 provides an on-chip track-and-hold, and exhibits no pipeline delay or latency, making it ideal for multiple multiplexed-channel applications. It operates from a single 5-V power supply; an optional I/O supply ensures compatibility with 1.8-, 2.5-, 3- and 5-V logic using the SPI-compatible serial interface. The serial interface also enables designers to “daisy chain” multiple ADCs using a single wire interface – reducing external component count and wiring connections – and provides an optional BUSY indicator for added flexibility. The device also includes an internal conversion clock, eliminating the need for an external clocking device.

In addition to the AD7690, Analog Devices is introducing the AD7691, which also delivers 18 bit linearity for applications that don’t have the same speed requirements or board space limitations. The AD7691 provides throughput of 250kSPS and operates on a 2.7- or 5-V single power supply. The devices work well with the ADA4941-1, a 16- and 18-bit single-ended to differential ADC driver from Analog Devices.

Pricing and Availability
The AD7690 and AD7691 are sampling now with production quantities available in February 2006. Both devices are available in the 3 mm x 3 mm MSOP package, as well as the 3 mm x 3 mm LFCSP package. The AD7690 and AD7691 are priced at $19.50 and $14.50, respectively, in 1,000-unit quantities.

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