AD7863:  Simultaneous Sampling Dual 175 kSPS 14-Bit A/D Converter

The AD7863 is a high speed, low power, dual 14-bit analog-to-digital converter that operates from a single 5 V supply.

The part contains two 5.2 μs successive approximation ADCs, two track/hold amplifiers, an internal 2.5 V reference and a high speed parallel interface. Four analog inputs are grouped into two channels (A and B) selected by the A0 input. Each channel has two inputs (V_A1 and V_A2 or V_B1 and V_B2) that can be sampled and converted simultaneously, thus preserving the relative phase information of the signals on both analog inputs. The part accepts an analog input range of ±10 V (AD7863-10), ±2.5 V (AD7863-3), and 0 V to 2.5 V (AD7863-2). Overvoltage protection on the analog inputs for the part allows the input voltage to go to ±17 V, ±7 V, or +7 V respectively, without causing damage.

A single conversion start signal (CONVST) simultaneously places both track/holds into hold and initiates conversion on both channels. The BUSY signal indicates the end of conversion and at this time the conversion results for both channels are available to be read. The first read after a conversion accesses the result from VA1 or VB1, and the second read accesses the result from VA2 or VB2, depending on whether the multiplexer select (A0) is low or high, respectively. Data is read from the part via a 14-bit parallel data bus with standard CS and RD signals. In addition to the traditional dc accuracy specifications such as linearity, gain, and offset errors, the part is also specified for dynamic performance parameters including harmonic distortion and signal-to-noise ratio.

The AD7863 is fabricated in the Analog Devices, Inc. linear compatible CMOS (LC²MOS) process, a mixed technology process that combines precision bipolar circuits with low power CMOS logic. It is available in 28-lead SOIC_W and SSOP.

Product Highlights

1. The AD7863 features two complete ADC functions allowing simultaneous sampling and conversion of two channels. Each ADC has a two-channel input mux. The conversion result for both channels is available 5.2 μs after initiating conversion.
2. The AD7863 operates from a single 5 V supply and consumes 70 mW typical. The automatic power-down mode, where the part goes into power-down once conversion is complete and wakes up before the next conversion cycle, makes the AD7863 ideal for battery-powered or portable applications.
3. The part offers a high speed parallel interface for easy connection to microprocessors, microcontrollers, and digital signal processors.
4. The part is offered in three versions with different analog input ranges. The AD7863-10 offers the standard industrial input range of ±10 V; the AD7863-3 offers the common signal processing input range of ±2.5 V, while the AD7863-2 can be used in unipolar 0 V to 2.5 V applications.
5. The part features very tight aperture delay matching between the two input sample and hold amplifiers.