AD7715ANZ-5

FEATURES
Programmable gain front end Gains 2, 32 and 128 Differential input capability

Three-wire serial interface SPI-, QSPITM-, MICROWIRETM-, and DSP-compatible Ability to buffer the analog input V (AD7715-5) operation Low supply current: 450 µA maximum 3 V supplies Low-pass filter with programmable output update 16-lead SOIC/PDIP/TSSOP

The is a complete analog front end for low frequency measurement applications. The part can accept low level input signals directly from a transducer and outputs a serial digital word. It employs a - conversion technique to realize to 16 bits of no missing codes performance. The 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 the on-chip control register allowing adjustment of the filter cutoff and output update rate.

The AD7715 features a differential analog input as well as a differential reference input. It operates from a single supply or 5 V). It can handle unipolar input signal ranges to 20 mV, to 80 mV, 1.25 V and V. It can also handle bipolar input signal ranges of ±20 mV, ±80 mV, ±1.25 V and ±2.5 V. These bipolar ranges are referenced to the negative input of the differential analog input. The AD7715 thus performs all signal conditioning and conversion for a single channel system.

The AD7715 is ideal for use in smart, microcontroller, or DSPbased systems. It features a serial interface that can be configured for three-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 power-down mode reduces the standby power consumption 50 µW typical. The part is available 16-lead, 0.3 inch-wide, plastic dual-in-line package (PDIP) as well 16-lead 0.3 inch wide small outline (SOIC_W) package and a 16-lead TSSOP package.

1. The AD7715 consumes less than µA in total supply current 3 V supplies and 1 MHz master clock, making it ideal for use in low-power systems. Standby current is less than 10 µA.

2. The programmable gain input allows the AD7715 to accept input signals directly from a strain gage or transducer removing a considerable amount of signal conditioning.

3. The AD7715 is ideal for microcontroller or DSP processor applications with a three-wire serial interface reducing the number of interconnect lines and reducing the number of optocouplers required in isolated systems. The part contains on-chip registers which allow software control over output update rate, input gain, signal polarity, and calibration modes.

4. The part features excellent static performance specifications with 16-bits no missing codes, ±0.0015% accuracy, and low rms noise (<550 nV). Endpoint errors and the effects of temperature drift are eliminated by on-chip calibration options, which remove zero-scale and full-scale errors.

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D to Rev. E Changes to Table : 13 Changed : 33 Updated Outline Dimensions : 39 Changes to Ordering Guide C to Rev. D Updated Format : Universal Changes to Table : 9 Updated Outline Dimensions B to Rev. C

Digital Filtering : 21 Analog Filtering : 23 Calibration : 23 Using the : 26 Clocking and Oscillator Circuit : 26 System Synchronization : 26 Reset Input : 27 Standby Mode : 27 Accuracy : 27 Drift Considerations : 27 Power Supplies : 28 Digital Interface : 29 Configuring the : 31 Microcontroller/Microprocessor Interfacing to 68HC11 Interface to 8XC51 Interface ADSP-2184N/ADSP-2185N/ADSP-2186N/ ADSP-2187N/ADSP-2188N/ADSP-2189N Interface : 33 Code For Setting Up The 34 C Code for Interfacing : 34 Applications Information : 36 Pressure Measurement : 36 Temperature Measurement : 37 Smart Transmitters : 38 Outline Dimensions : 39 Ordering Guide : 40

SPECIFICATIONS

AVDD 5 V, DVDD 5 V, REF IN(+) 2.5 V; REF IN(-) = AGND; fCLK = 2.4576 MHz, unless otherwise noted. All specifications TMIN to TMAX, unless otherwise noted.

No Missing Codes Output Noise Integral Nonlinearity Unipolar Offset Error2 Unipolar Offset Drift3 Bipolar Zero Error2 Bipolar Zero Drift3 Positive Full-Scale Error2, 4 Full-Scale Drift3, 5 Gain Error2, 6 Gain Drift3, 7

Bipolar Negative Full-Scale Error2 Bipolar Negative Full-Scale Drift3

ANALOG INPUTS/REFERENCE INPUTS Input Common-Mode Rejection (CMR) Normal-Mode Hz Rejection8 Normal-Mode Hz Rejection8 Common-Mode Hz Rejection8 Common-Mode Hz Rejection8 Common-Mode Voltage Range9 Absolute AIN/REF IN Voltage8 Absolute/Common-Mode AIN Voltage9 AIN DC Input Current8 AIN Sampling Capacitance8 AIN Differential Voltage Range10

VINL, Input Low Voltage VINL, Input Low Voltage VINH, Input High Voltage VINH, Input High Voltage MCLK IN Only VINL, Input Low Voltage VINL, Input Low Voltage VINH, Input High Voltage VINH, Input High Voltage

Guaranteed by design; filter notch 60 Hz Depends on filter cutoffs and selected gain Filter notch 60 Hz

Typically ±0.0004% For gains of 1 and 2 For gains of 32 and 128 Specifications for AIN and REF IN unless noted At dc; typically 102 dB For filter notches of 25 Hz, 50 Hz, ±0.02 × fNOTCH For filter notches of 20 Hz, 60 Hz, ±0.02 × fNOTCH For filter notches of 25 Hz, 50 Hz, ±0.02 × fNOTCH For filter notches of 20 Hz, 60 Hz, ±0.02 × fNOTCH AIN for the BUF bit of setup register = 0 and REF IN AIN for the BUF bit of setup register = 0 and REF IN BUF bit of setup register = 1

Unipolar input range (B/U bit of setup register = 1) Bipolar input range (B/U bit of setup register = 0) For gains of 1 and 2 For gains of 32 and 128 ±1% for specified performance; functional with lower VREF