a FEATURES 16-Bit Monotonicity over Temperature ؎2 LSBs Integral Linearity Error Microprocessor Compatible with Readback Capability Unipolar or Bipolar Output Multiplying Capability Low Power (100 mW typical)
LC2MOS 16-Bit Voltage Output DAC AD7846 FUNCTIONAL BLOCK DIAGRAM
The AD7846 is a 16-bit DAC constructed with Analog Devices’ LC2MOS process. It has VREF+ and VREF– reference inputs and an on-chip output amplifier. These can be configured to give a unipooutput range (0 V to +5 V, 0 V to +10 V) or bipolar output ranges (± 5 V, ± 10 V).
1. 16-Bit Monotonicity The guaranteed 16-bit monotonicity over temperature makes the AD7846 ideal for closed-loop applications.
The DAC uses a segmented architecture. The 4 MSBs in the DAC latch select one of the segments in a 16-resistor string. Both taps of the segment are buffered by amplifiers and fed to a 12-bit DAC, which provides a further 12 bits of resolution. This architecture ensures 16-bit monotonicity. Excellent integral linearity results from tight matching between the input offset voltages of the two buffer amplifiers.
2. Readback The ability to read back the DAC register contents minimizes software routines when the AD7846 is used in ATE systems. 3. Power Dissipation Power dissipation of 100 mW makes the AD7846 the lowest power, high accuracy DAC on the market.
In addition to the excellent accuracy specifications, the AD7846 also offers a comprehensive microprocessor interface. There are 16 data I/O pins, plus control lines (CS, R/W, LDAC and CLR). R/W and CS allow writing to and reading from the I/O latch. This is the readback function which is useful in ATE applications. LDAC allows simultaneous updating of DACs in a multi-DAC system and the CLR line will reset the contents the DAC latch to 00 . . . 000 or 10 . . . 000 depending on the state of R/W. This means that the DAC output can be reset to 0 V in both the unipolar and bipolar configurations. The AD7846 is available in 28-pin plastic, ceramic, LCCC and PLCC packages.
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