Datasheet

AIN0
AIN1
AIN2
AIN3
AIN4
AIN5
AIN6
AIN7
AIN8
AIN9
AIN10
AIN11
AIN12
AIN13
AIN14
AIN15
AINCOM
Control
Logic
VREFPVREFN
AVSS
PLLCAP XTAL1XTAL2
DRDY
PWDN
RESET
START
SPI
Interface
CS
SCLK
DIN
DOUT
Digital Filter
Clock Control
16−Channel
MUX
AVDD
Sensor
Bias
M
UXOUTP
MUX
OUTN
ADCINP GND
AD
CINN
ADC Channel Control
Supply Monitor
GPIO
G
PIO[7:0]
DVDD
Temperature
Ext Ref Monitor
Internal Ref
ADC
CLKSELCLKIO
ADS1258-EP
SBAS445D –MARCH 2009– REVISED MARCH 2011 www.ti.com
OVERVIEW
The ADS1258 is a flexible, 24-bit, low-noise ADC V
IN
= (ADCINP – ADCINN), against the differential
optimized for fast multi-channel, high-resolution reference input, V
REF
= (VREFP – VREFN). The
measurement systems. The converter provides a digital filter receives the modulator signal and
maximum channel scan rate of 23.7kSPS, providing a provides a low-noise digital output. The ADC channel
complete 16-channel scan in less than 700μs. block controls the multiplexer Auto-Scan feature.
Channel Auto-Scan occurs at a maximum rate of
Figure 34 shows the block diagram of the ADS1258.
23.7kSPS. Slower scan rates can be used with
The input multiplexer selects the analog input pins
corresponding increases in resolution.
connected to the multiplexer output pins
(MUXOUTP/MUXOUTN). External signal conditioning Communication is handled over an SPI-compatible
can be used between the multiplexer output pins and serial interface with a set of simple commands
the ADC input pins (ADCINP/ADCINN) or the providing control of the ADS1258. Onboard registers
multiplexer output can be routed internally to the ADC store the various settings for the input multiplexer,
inputs without external circuitry. Selectable current sensor detect bias, data rate selection, etc. Either an
sources within the input multiplexer can be used to external 32.768kHz crystal, connected to pins XTAL1
bias sensors or detect for a failed sensor. On-chip and XTAL2, or an external clock applied to pin CLKIO
system function readings provide readback of can be used as the clock source. When using the
temperature, supply voltage, gain, offset, and external external crystal oscillator, the system clock is
reference. available as an output for driving other devices or
controllers. General-purpose digital I/Os (GPIO)
The ADS1258 converter comprises a fourth-order,
provide input and output control of eight pins.
delta-sigma modulator followed by a programmable
digital filter. The modulator
measures the differential input signal,
Figure 34. ADS1258 Block Diagram
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