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AD7720
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CMOS Sigma-Delta Modulator
FUNCTIONAL BLOCK DIAGRAM
FEATURES
12.5 MHz Master Clock Frequency
0 V to +2.5 V or 61.25 V Input Range
Single Bit Output Stream
90 dB Dynamic Range
Power Supplies: AVDD, DVDD: +5 V 6 5%
On-Chip 2.5 V Voltage Reference
28-Lead TSSOP
GENERAL DESCRIPTION
This device is a 7th order sigma-delta modulator that converts
the analog input signal into a high speed 1-bit data stream. The
part operates from a +5 V supply and accepts a differential input
range of 0 V to +2.5 V or ±1.25 V centered about a common-
mode bias. 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. The original information can be
reconstructed with an appropriate digital filter.
The part provides an accurate on-chip 2.5 V reference. A refer-
ence input/output function is provided to allow either the inter-
nal reference or an external system reference to be used as the
reference source for the part.
The device is offered in a 28-lead TSSOP package and designed
to operate from –40°C to +85°C.
2.5V
REFERENCE
SIGMA-DELTA
MODULATOR
CLOCK
CIRCUITRY
CONTROL
LOGIC
AVDD AGND DVDD DGND REF1
REF2
DATA
SCLK
XTAL1/MCLK
XTAL2
DVAL
RESETO
RESET
VIN(+)
VIN(–)
MZERO
GC
BIP
STBY
AD7720