Electronic Design

16 Bits, Buffers, And Voltage References All Squeeze Into SOT-23-Packaged DACs

Homing in on industrial-control and T&M applications, Analog Devices has extended its portfolio of small-footprint nanoDACs. Eight pin-compatible 12- to 16-bit digital-to-analog converters (DACs) now enter the fray, some for closed-loop control systems and others for open loop.

The latest family members come in SOT-23 packages and micro small-outline packages (MSOPs) that provide about a 45% smaller footprint than roughly equivalent competing chips. The new nanoDACs embody several other innovations as well.

Three of the four optimized for closed-loop control incorporate an internal self-calibrating 10-ppm/°C (max) internal voltage reference. (A tight voltage-reference temperature coefficient affects integral and differential nonlinearity and total unadjusted error.) They also use two tricks that let them fit 16 bits of resolution into SOT-23 packages. One, ADI's patented segmented resistor-string architecture, reduces the number of resistors needed for the DAC ladder. The other is a larger package cavity.

In the chips optimized for open-loop control, where absolute accuracy is all-important, a digital calibration engine removes integral nonlinearity (INL) errors for real 1-LSB INL. Each chip guarantees monotonic differential nonlinearity by design.

The final new feature is a low-noise, stable, rail-to-rail output amplifier built with bipolar technology on a new biCMOS process. Also, a three-wire serial interface operates at clock rates up to 30 MHz. It's compatible with standard serial-peripheral-interface (SPI), queued-SPI, Microwire, and DSP interface standards. Both lines come with power-on-reset circuit options to automatically power up to mid- or zero-scale for generating both bipolar or unipolar outputs.

The AD5660 nanoDACs for closed-loop apps comprise the 16-bit AD5660, the 14-bit AD5640, and the 12-bit AD5620, all with the on-chip voltage reference, and the 16-bit AD5662 without a reference. ADI's AD5060 nanoDACs for open-loop control include the 16-bit AD5060 and 14-bit AD5040. The unbuffered AD5062 and AD5063 provide 16-bit resolution in an SOT-23 for applications requiring customized output buffers or generation of bipolar outputs from a unipolar source.

Every device's power-down feature reduces the current consumption of the device to 1 mA at 5 V. Each new DAC operates from a single 2.7- to 5.5-V power supply. Power consumption is 400 µA maximum at 5 V (excluding internal reference), dropping to 1 mA in power-down mode.

The AD5660 family is available now in an eight-lead SOT-23 package and MSOP, with 1000-unit prices starting from $1.70 per unit. Unit pricing for the AD5060 family, also in an eight-lead SOT-23 package and 10-lead MSOP, starts at $5.95.

Analog Devices

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