ADS7864YB/250

The ADS7864 is a dual 12-bit, 500kHz analog-to-digital (A/D) converter with 6 fully differential input channels grouped into three pairs for high speed simultaneous signal acquisition. Inputs to the sample-and-hold amplifiers are fully differential and are maintained differential to the input of the A/D converter. This provides excellent common-mode rejection of 80dB at 50kHz which is important in high noise environments. The ADS7864 offers a parallel interface and control inputs to minimize software overhead. The output data for each channel is available as a 16-bit word (address and data). The ADS7864 is offered in a TQFP-48 package and is fully specified over the -40°C to +85°C operating range. The ADS7864 is a high speed, low power, dual 12-bit analog-to-digital converter (ADC) that operates from a single +5V supply. The input channels are fully differential with a typical common-mode rejection of 80dB. The part contains dual 2µs successive approximation ADCs, six differential sample-and-hold amplifiers, an internal +2.5V reference with REFIN and REFOUT pins and a high speed parallel interface. There are six analog inputs that are grouped into three channels (A, B and C). Each A/D converter has three inputs (A0/A1, B0/B1 and C0/C1) that can be sampled and converted simultaneously, thus preserving the relative phase information of the signals on both analog inputs. Each pair of channels has a hold signal (HOLDA, HOLDB, HOLDC) to allow simultaneous sampling on all six channels. The part accepts an analog input voltage in the range of -VREF to +VREF, centered around the internal +2.5V reference. The part will also accept bipolar input ranges when a level shift circuit is used at the front end. A conversion is initiated on the ADS7864 by bringing the HOLDX pin low for a minimum of 15ns. HOLDX low places both sample-and-hold amplifiers of the X channels in the hold state simultaneously and the conversion process is started on both channels. The BUSY output will then go low and remain low for the duration of the conversion cycle. The data can be read from the parallel output bus following the conversion by bringing both RD and CS low. Conversion time for the ADS7864 is 1.75µs when an 8MHz external clock is used. The corresponding acquisition time is 0.25µs. To achieve maximum output rate (500kHz), the read function can be performed during at the start of the next conversion.

Applications

• Motor Control
• Multi-Axis Positioning Systems
• 3-Phase Power Control

Key features

• 6 Simultaneous Sampling Channels
• Fully Differential Inputs
• 2µs Total Throughput per Channel
• No Missing Codes
• Parallel Interface
• 1MHz Effective Sampling Rate
• Low Power: 50mW 6X FIFO