The AD7938/AD7939 are 12-bit and 10-bit, high speed, low power, successive approximation (SAR) analog-to-digital converters (ADCs). The parts operate from a single 2.7 V to 5.25 V power supply and feature throughput rates up to 1.5 MSPS. The parts contain a low noise, wide bandwidth, differential track-and-hold amplifier that can handle input frequencies up to 50 MHz.
The AD7938/AD7939 feature eight analog input channels with a channel sequencer that allows a preprogrammed selection of channels to be converted sequentially. These parts can operate with either single-ended, fully differential, or pseudo differential analog inputs.
The conversion process and data acquisition are controlled using standard control inputs that allow easy interfacing with microprocessors and DSPs. The input signal is sampled on the falling edge of CONVST and the conversion is also initiated at this point.
The AD7938/AD7939 have an accurate on-chip 2.5 V reference that can be used as the reference source for the analog-to-digital conversion. Alternatively, this pin can be overdriven to provide an external reference.
These parts use advanced design techniques to achieve very low power dissipation at high throughput rates. They also feature flexible power management options. An on-chip control register allows the user to set up different operating conditions, including analog input range and configuration, output coding, power management, and channel sequencing.
- High throughput with low power consumption.
- Eight analog inputs with a channel sequencer.
- Accurate on-chip 2.5 V reference.
- Single-ended, pseudo differential, or fully differential analog inputs that are software selectable.
- Single-supply operation with VDRIVE function. The VDRIVE function allows the parallel interface to connect directly to 3 V or 5 V processor systems independent of VDD.
- No pipeline delay.
- Accurate control of the sampling instant via a CONVST input and once-off conversion control.
At least one model within this product family is in production and available for purchase. The product is appropriate for new designs but newer alternatives may exist.
The EVAL-AD7938CBZ is a fully featured evaluation kit for the AD7938. This board operates in stand alone mode or in conjunction with the Evaluation Controller board . When operated with the Evaluation Controller board, software is provided enabling the user to perform detailed analysis of the ADC's performance. This software includes the technical note describing the operation and set up of the evaluation board in standalone operation or when operated with the Evaluation Controller board.
Recommended External Voltage References
MS-2210: Designing Power Supplies for High Speed ADC
Maximize Performance When Driving Differential ADCs
... Converting a single-ended signal to a differential signal before the analog-to-digital conversion can improve the...
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