ADS8885_14 Datasheet, PDF (17/49 Pages) Texas Instruments – 18-Bit, 400-kSPS, Serial Interface, microPower, Miniature, True-Differential Input, SAR Analog-to-Digital Converter

ADS8885
www.ti.com
OVERVIEW
SBAS568A – MAY 2013 – REVISED DECEMBER 2013
The ADS8885 is a high-speed, successive approximation register (SAR), analog-to-digital converter (ADC) from
a 16- and 18-bit product family. This compact device features high performance. Power consumption is
inherently low and scales linearly with sampling speed. The architecture is based on charge redistribution, which
inherently includes a sample-and-hold (S/H) function.
The ADS8885 supports a true-differential analog input across two pins (INP and INN). When a conversion is
initiated, the differential input on these pins is sampled on the internal capacitor array. While a conversion is in
progress, both the INP and INN inputs are disconnected from the internal circuit.
The ADS8885 uses an internal clock to perform conversions. The device reconnects the sampling capacitors to
the INP and INN pins after conversion and then enters an acquisition phase. During the acquisition phase, the
device is powered down and the conversion result can be read.
The device digital output is available in SPI-compatible format, which makes interfacing with microprocessors,
digital signal processors (DSPs), or field-programmable gate arrays (FPGAs) easy.
ANALOG INPUT
As shown in Figure 45, the device features a differential analog input. Both positive and negative inputs are
individually sampled on 55-pF sampling capacitors and the device converts for the voltage difference between
the two sampled values: V_INP – V_INN.
AVDD
REF
DVDD
REF
AINP
AINN
GND
Sample
and
Hold
AGND
A^SD^AC^R
SPI
ADC
REFM
DGND
CONVST
SCLK
DOUT
DIN
GND
Figure 45. Detailed Block Diagram
Copyright © 2013, Texas Instruments Incorporated
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