3 V/5 V, ±10 V Input Range, 1 mW 3-Channel 16-Bit, Sigma-Delta ADC
The AD7707 is a complete analog front end for low frequency measurement applications. This 3-channel device can accept either low level input signals directly from a transducer or high level (±10 V) signals and produce a serial digital output. It employs a Σ-Δ conversion technique to realize up to 16 bits of no missing codes performance. The selected input signal is applied to a proprietary programmable gain front end based around an analog modulator. The modulator output is processed by an on-chip digital filter. The first notch of this digital filter can be programmed via an on-chip control register allowing adjustment of the filter cutoff and output update rate.
The AD7707 operates from a single 2.7 V to 3.3 V or 4.75 V to 5.25 V supply. The AD7707 features two low level pseudo differential analog input channels, one high level input channel and a differential reference input. Input signal ranges of 0 mV to 20 mV through 0 V to 2.5 V can be accommodated on both low level input channels when operating with a VDD of 5 V and a reference of 2.5 V. They can also handle bipolar input signal ranges of ±20 mV through ±2.5 V, which are referenced to the LCOM input. The AD7707, with a 3 V supply and a 1.225 V reference, can handle unipolar input signal ranges of 0 mV to 10 mV through 0 V to 1.225 V. Its bipolar input signal ranges are ±10 mV through ±1.225 V. The high level input channel can accept input signal ranges of ±10 V, ±5 V, 0 V to 10 V and 0 V to 5 V. The AD7707 thus performs all signal conditioning and conversion for a 3-channel system.
The AD7707 is ideal for use in smart, microcontroller or DSP- based systems. It features a serial interface that can be configured for 3-wire operation. Gain settings, signal polarity and update rate selection can be configured in software using the input serial port. The part contains self-calibration and system calibration options to eliminate gain and offset errors on the part itself or in the system.
CMOS construction ensures very low power dissipation, and the power-down mode reduces the standby power consumption to 20 μW typical. This part is available in a 20-lead wide body (0.3 inch) small outline (SOIC) package and a low profile 20-lead TSSOP.
- The AD7707 consumes less than 1 mW at 3 V supplies and 1 MHz master clock, making it ideal for use in low power systems. Standby current is less than 8 μA.
- On-chip thin-film resistors allow ±10 V, ±5 V, 0 V to 10 V, and 0 V to 5 V high level input signals to be directly accom- modated on the analog inputs without requiring split supplies or charge-pumps.
- The low level input channels allow the AD7707 to accept input signals directly from a strain gage or transducer removing a considerable amount of signal conditioning.
- The part features excellent static performance specifications with 16 bits, no missing codes, ±0.003% accuracy, and low rms noise. Endpoint errors and the effects of temperature drift are eliminated by on-chip calibration options, which remove zero-scale and full-scale errors.
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.
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ADI has always placed the highest emphasis on delivering products that meet the maximum levels of quality and reliability. We achieve this by incorporating quality and reliability checks in every scope of product and process design, and in the manufacturing process as well. "Zero defects" for shipped products is always our goal.
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