16-Bit, Isolated Sigma-Delta Modulator,
Data Sheet
FEATURES
5 MHz to 20 MHz external clock input rate
16 bits, no missing codes
Signal-to-noise ratio (SNR): 88 dB typical
Effective number of bits (ENOB): 14.2 bits typical
Typical offset drift vs. temperature: 1.6 µV/°C
Low voltage differential signaling (LVDS) interface
On-board digital isolator
On-board reference
Full-scale analog input voltage range: ±320 mV
−40°C to + 125°C operating temperature range
High common-mode transient immunity: >25 kV/µs
16-lead, wide-body SOIC_IC, with increased creepage
package
Safety and regulatory approvals
UL recognition
5000 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
Maximum working insulation voltage (V
IORM
): 1250 V
PEAK
APPLICATIONS
Shunt current monitoring
AC motor controls
Power and solar inverters
Wind turbine inverters
Data acquisition systems
Analog-to-digital and opto-isolator replacements
FUNCTIONAL BLOCK DIAGRAM
F
igure 1.
GENERAL DESCRIPTION
The AD7405
1
is a high performance, second-order, Σ-Δ modulator
that converts an analog input signal into a high speed, single-bit
LVDS data stream, with on-chip digital isolation based on
Analog Devices, Inc., iCoupler® technology. The AD7405 operates
from a 4.5 V to 5.5 V (V
DD1
) power supply and accepts a
differential input signal of ±250 mV (±320 mV full-scale). The
differential input is ideally suited to shunt voltage monitoring in
high voltage applications where galvanic isolation is required.
The analog input is continuously sampled by a high performance
analog modulator, and converted to a ones density digital output
stream with a data rate of up to 20 MHz. The original information
can be reconstructed with an appropriate digital filter to achieve
88 dB SNR at 78.1 kSPS. The LVDS input/output can use a 3 V
to 5.5 V supply (V
DD2
).
The LVDS interface is digitally isolated. The LVDS interface
technology, combined with monolithic transformer technology,
means the on-chip isolation provides outstanding performance
characteristics, superior to alternatives such as optocoupler
devices. The AD7405 device is offered in a 16-lead, wide-body
SOIC_IC package and has an operating temperature range of
−40°C to +125°C.
1
Protected by U.S. Patents 5,952,849; 6,873,065; and 7,075,329.
V
DD1
V
DD2
AD7405
BUF
REF
CLK
DECODER
GND
1
GND
2
MCLKIN+
(5MHz TO
20MHz)
MCLKIN–
MDAT+
MDAT–
V
IN+
V
IN–
CLK
ENCODER
DATA
ENCODER
DATA
DECODER
Σ-Δ ADC
12536-001
Rev. A Document Feedback
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