AD7401| Datasheet

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Isolated Sigma-Delta Modulator AD7401
FEATURES
20 MHz maximum external clock rate Second-order modulator 16 bits no missing codes 2 LSB INL typical at 16 bits 3.5 V/ C maximum offset drift On-board digital isolator On-board reference Low power operation: 20 mA maximum at 5.25 V -40 C to +105 C operating range 16-lead SOIC package Safety and regulatory approvals UL recognition 3750 V rms for 1 minute per UL 1577 CSA Component Acceptance Notice #5A VDE Certificate of Conformity DIN V VDE V 0884-10 (VDE V 0884-10):2006-12 VIORM = 891 V peak

GENERAL DESCRIPTION
The AD7401 1 is a second-order, sigma-delta (-) modulator that converts an analog input signal into a high speed, 1-bit data stream with on-chip digital isolation based on Analog Devices, Inc. iCoupler technology. The AD7401 operates from a 5 V power supply and accepts a differential input signal of 200 mV ( 320 mV full scale). The analog input is continuously sampled by the analog modulator, eliminating the need for external sample-and-hold circuitry. The input information is contained in the output stream as a density of ones with a data rate up to 20 MHz. The original information can be reconstructed with an appropriate digital filter. The serial I/O can use a 5 V or a 3 V supply (VDD2). The serial interface is digitally isolated. High speed CMOS, combined with monolithic air core transformer technology, means the on-chip isolation provides outstanding performance characteristics, superior to alternatives such as optocoupler devices. The part contains an on-chip reference. The AD7401 is offered in a 16-
lead SOIC and has an operating temperature range of -40 C to +105 C. An internal clock version, AD7400, is also available.
1

APPLICATIONS
AC motor controls Data acquisition systems A/D + opto-isolator replacements

Protected by U.S. Patents 5,952,849; 6,873,065; and 7,075,329. Other patents pending.
VDD2

FUNCTIONAL BLOCK DIAGRAM
VDD1

AD7401
VIN+ VIN
T/H

- ADC UPDATE WATCHDOG

BUF

ENCODE

DECODE

MDAT

REF

CONTROL LOGIC

WATCHDOG

UPDATE

DECODE

ENCODE

MCLKIN

GND1

GND2

Figure 1.

Rev. B
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05851-001