Datasheet AD7714 (Analog Devices)

a
3 V/5 V, CMOS, 500
␮
A Signal Conditioning ADC AD7714 FEATURES FUNCTIONAL BLOCK DIAGRAM Charge Balancing ADC 24 Bits No Missing Codes AV DV REF IN(–) DD DD REF IN(+) 0.0015% Nonlinearity AVDD CHARGE Five-Channel Programmable Gain Front End BALANCING 1
m
A Gains from 1 to 128 A/D CONVERTER AIN1
Σ
STANDBY -
∆
Can Be Configured as Three Fully Differential MODULATOR AIN2 Inputs or Five Pseudo-Differential Inputs SYNC AIN3 BUFFER PGA DIGITAL FILTER AIN4 Three-Wire Serial Interface AIN5 MATRIX SPI™, QSPI™, MICROWIRE™ and DSP Compatible A = 1–128 AIN6 SWITCHING 3 V (AD7714-3) or 5 V (AD7714-5) Operation 1
m
A SERIAL INTERFACE Low Noise (<150 nV rms) AGND REGISTER BANK SCLK Low Current (350␣
␮
A typ) with Power-Down (5
␮
A typ) BUFFER CS AD7714Y Grade: MCLK IN CLOCK DIN +2.7 V to 3.3 V or +4.75 V to +5.25 V Operation MCLK OUT GENERATION DOUT 0.0010% Linearity Error AD7714 –40
ⴗ
C to +105
ⴗ
C Temperature Range Schmitt Trigger on SCLK and DIN AGND DGND POL DRDY RESET Low Current (226␣
␮
A typ) with Power-Down (4
␮
A typ)
for three-wire operation. Gain settings, signal polarity and channel
Lower Power Dissipation than Standard AD7714
selection can be configured in software using the serial port. The
Available in 24-Lead TSSOP Package
AD7714 provides self-calibration, system calibration and back-
Low-Pass Filter with Programmable Filter Cutoffs
ground calibration options and also allows the user to read and
Ability to Read/Write Calibration Coefficients
write the on-chip calibration registers.
APPLICATIONS
CMOS construction ensures very low power dissipation, and the
Portable Industrial Instruments
power-down mode reduces the standby power consumption to
Portable Weigh Scales
15␣ µW typ. The part is available in a 24-pin, 0.3 inch-wide, plastic
Loop-Powered Systems
dual-in-line package (DIP); a 24-lead small outline (SOIC)
Pressure Transducers
package, a 28-lead shrink small outline package (SSOP) and a 24-lead thin shrink small outline package (TSSOP).
GENERAL DESCRIPTION†
The AD7714 is a complete analog front end for low-frequency
PRODUCT HIGHLIGHTS
measurement applications. The device accepts low level signals 1. The AD7714Y offers the following features in addition to the directly from a transducer and outputs a serial digital word. It standard AD7714: wider temperature range, Schmitt trigger employs a sigma-delta conversion technique to realize up to 24 on SCLK and DIN, operation down to 2.7 V, lower power bits of no missing codes performance. The input signal is applied consumption, better linearity, and availability in 24-lead to a proprietary programmable gain front end based around an TSSOP package. analog modulator. The modulator output is processed by an on- 2. The AD7714 consumes less than 500 µA (fCLK IN = 1␣ MHz) chip digital filter. The first notch of this digital filter can be or 1 mA (fCLK IN = 2.5␣ MHz) in total supply current, making programmed via the on-chip control register allowing adjust- it ideal for use in loop-powered systems. ment of the filter cutoff and settling time. 3. The programmable gain channels allow the AD7714 to ac- The part features three differential analog inputs (which can also cept input signals directly from a strain gage or transducer be configured as five pseudo-differential analog inputs) as well as a removing a considerable amount of signal conditioning. differential reference input. It operates from a single supply (+3␣ V 4. The AD7714 is ideal for microcontroller or DSP processor or +5␣ V). The AD7714 thus performs all signal conditioning and applications with a three-wire serial interface reducing the num- conversion for a system consisting of up to five channels. ber of interconnect lines and reducing the number of opto- The AD7714 is ideal for use in smart, microcontroller- or DSP- couplers required in isolated systems. The part contains based systems. It features a serial interface that can be configured on-chip registers that allow control over filter cutoff, input gain, channel selection, signal polarity and calibration modes. †See page 39 for data sheet index. 5. The part features excellent static performance specifications SPI and QSPI are trademarks of Motorola, Inc. with 24-bit no missing codes, ±0.0015% accuracy and low MICROWIRE is a trademark of National Semiconductor Corporation. rms noise (140 nV). Endpoint errors and the effects of tem- REV. C perature drift are eliminated by on-chip self-calibration, Information furnished by Analog Devices is believed to be accurate and which removes zero-scale and full-scale errors. reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties
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