AD7724ASTZ

ADCs/DACs - Special Purpose Overview

The AD7724ASTZ is a dual-channel, seventh-order sigma-delta modulator from Analog Devices Inc., housed in a 48-lead LQFP package. It operates with a master clock frequency up to 13 MHz and accepts differential analog inputs within a 0 V to +2.5 V or ±1.25 V range. The device features an on-chip 2.5 V reference and supports both unipolar and bipolar input modes. Key static performance metrics include an integral nonlinearity of ±0.003% FSR and a gain error of ±0.6% FSR. Dynamic specifications provide a typical signal-to-(noise + distortion) ratio of 90 dB in bipolar mode. Power supplies require AVDD and DVDD at 5 V ±5%, with DVDD1 configurable for 3 V or 5 V logic compatibility.

ADCs/DACs - Special Purpose Feature Summary

• Dual seventh-order sigma-delta modulators with single-bit output streams
• On-chip 2.5 V bandgap reference with external buffer capability
• Configurable unipolar (0 V to VREF) or bipolar (±VREF/2) input ranges
• Logic outputs compatible with 3 V or 5 V systems via DVDD1 selection

ADCs/DACs - Special Purpose Applications

• High-resolution data acquisition systems requiring continuous sampling
• Industrial process control instrumentation
• Medical equipment utilizing differential signal processing
• Precision measurement devices needing high dynamic range

ADCs/DACs - Special Purpose Procurement Notes

Verify the specific ordering suffix 'ASTZ' corresponds to the -40 °C to +85 °C temperature range and the ST-48 48-lead LQFP package option as defined in the manufacturer's ordering guide. Confirm that the required power supply voltages align with the specified 5 V ±5% for AVDD/DVDD and the selectable 3 V or 5 V for DVDD1. Ensure ESD precautions are observed during handling due to the sensitivity of the CMOS circuitry.

ADCs/DACs - Special Purpose Selection Notes

Select this component when a dual-channel, high-order sigma-delta modulation architecture is required for noise shaping without integrated digital filtering. The AD7724 provides raw bit streams intended for external digital filter implementation, such as the FIR filters described in the datasheet. Consider the 13 MHz maximum master clock frequency and the resulting output data rates when designing the downstream digital processing stage. Verify that the external reference voltage range of 2.32 V to 2.68 V matches the system requirements if bypassing the internal reference.

ADCs/DACs - Special Purpose Part Context

The AD7724 belongs to the AD7724 series of dual CMOS/H9018-/H9004 modulators. It is distinct from complete ADCs like the AD7710 or AD7712 as it outputs a continuous bit stream rather than a decimated digital word. The 'A' version denotes the industrial temperature range (-40 °C to +85 °C), while the 'ST' package option specifies the plastic thin quad flatpack form factor.

ADCs/DACs - Special Purpose Replacement Considerations

Publicly confirmed substitute part numbers are not available in the provided documentation. Designers should evaluate other dual-channel sigma-delta modulators from Analog Devices or third-party manufacturers based on pin compatibility, clock frequency limits, and input range specifications.

ADCs/DACs - Special Purpose FAQ

How is the analog input range configured?

The BIP pin selects the mode: a logic low enables unipolar mode (0 V to VREF), while a logic high enables bipolar mode (±VREF/2 centered about a common-mode bias).

What is the function of the REF1 and REF2 pins?

REF1 connects to the internal 2.5 V reference output. REF2 drives the switched-capacitor DAC. For lowest gain error with an external reference, ground REF1 and apply the external reference to REF2.

Can the device operate with an external clock source?

Yes. By tying XTAL_OFF high, an external clock can be applied directly to the XTAL2/MCLK pin. Alternatively, a sine wave can be AC coupled to XTAL1 with XTAL_OFF tied low.