Isolated Sigma-Delta Modulator
AD7401A
Rev. C
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FEATURES
20 MHz maximum external clock rate
Second-order modulator
16 bits, no missing codes
±2 LSB INL typical at 16 bits
1 μV/°C typical offset drift
On-board digital isolator
On-board reference
±250 mV analog input range
Low power operation: 17 mA typical at 5.5 V
−40°C to +125°C operating range
16-lead SOIC package
Internal clock version: AD7400A
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
V
IORM
= 891 V peak
APPLICATIONS
AC motor controls
Shunt current monitoring
Data acquisition systems
Analog-to-digital and opto-isolator replacements
GENERAL DESCRIPTION
The AD7401A
1
is a second-order, sigma-delta (Σ-Δ) 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 AD7401A operates from a 5 V
power supply and accepts a differential input signal of ±250 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 (V
DD2
).
The serial interface is digitally isolated. High speed CMOS,
combined with Analog Devices, Inc., iCoupler® 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 AD7401A
is offered in a 16-lead SOIC and has an operating temperature
range of −40°C to +125°C.
FUNCTIONAL BLOCK DIAGRAM
IN
+
DD1
DD2
V
IN
–
Σ-∆ ADC
CONTROL LOGIC
AD7401A
B
U
F
T
/
H
REF
WATCHDOG
GND
1
GND
2
MDAT
MCLKIN
DECODE
ENCODE DECODE
ENCODE
UPDATE
WATCHDOG
UPDATE
07332-001
Figure 1.
1
Protected by U.S. Patents 5,952,849; 6,873,065; and 7,075,329. Other patents pending.
