24-08-2012, 03:38 PM
Single Chip 12-Bit Data Acquisition System
[attachment=32648]
DESCRIPTION
The LTC®1290 is a data acquisition component which
contains a serial I/O successive approximation A/D converter.
It uses LTCMOSTM switched capacitor technology
to perform either 12-bit unipolar or 11-bit plus sign bipolar
A/D conversions. The 8-channel input multiplexer can be
configured for either single-ended or differential inputs (or
combinations thereof). An on-chip sample-and-hold is
included for all single-ended input channels. When the
LTC1290 is idle it can be powered down with a serial word
in applications where low power consumption is desired.
The serial I/O is designed to be compatible with industry
standard full duplex serial interfaces. It allows either MSBor
LSB-first data and automatically provides 2's complement
output coding in the bipolar mode. The output data
word can be programmed for a length of 8, 12 or 16 bits.
This allows easy interface to shift registers and a variety of
processors.
DIGITAL CONSIDERATIONS
Serial Interface
The LTC1290 communicates with microprocessors and
other external circuitry via a synchronous, full duplex,
four-wire serial interface (see Operating Sequence). The
shift clock (SCLK) synchronizes the data transfer with
each bit being transmitted on the falling SCLK edge and
captured on the rising SCLK edge in both transmitting and
receiving systems. The data is transmitted and received
simultaneously (full duplex).
Data transfer is initiated by a falling chip select (CS) signal.
After the falling CS is recognized, an 8-bit input word is
shifted into the DIN input which configures the LTC1290
for the next conversion. Simultaneously, the result of the
previous conversion is output on the DOUT line. At the end
of the data exchange the requested conversion begins and
CS should be brought high. After tCONV, the conversion is
complete and the results will be available on the next data
transfer cycle. As shown below, the result of a conversion
is delayed by one CS cycle from the input word requesting it.
[attachment=32648]
DESCRIPTION
The LTC®1290 is a data acquisition component which
contains a serial I/O successive approximation A/D converter.
It uses LTCMOSTM switched capacitor technology
to perform either 12-bit unipolar or 11-bit plus sign bipolar
A/D conversions. The 8-channel input multiplexer can be
configured for either single-ended or differential inputs (or
combinations thereof). An on-chip sample-and-hold is
included for all single-ended input channels. When the
LTC1290 is idle it can be powered down with a serial word
in applications where low power consumption is desired.
The serial I/O is designed to be compatible with industry
standard full duplex serial interfaces. It allows either MSBor
LSB-first data and automatically provides 2's complement
output coding in the bipolar mode. The output data
word can be programmed for a length of 8, 12 or 16 bits.
This allows easy interface to shift registers and a variety of
processors.
DIGITAL CONSIDERATIONS
Serial Interface
The LTC1290 communicates with microprocessors and
other external circuitry via a synchronous, full duplex,
four-wire serial interface (see Operating Sequence). The
shift clock (SCLK) synchronizes the data transfer with
each bit being transmitted on the falling SCLK edge and
captured on the rising SCLK edge in both transmitting and
receiving systems. The data is transmitted and received
simultaneously (full duplex).
Data transfer is initiated by a falling chip select (CS) signal.
After the falling CS is recognized, an 8-bit input word is
shifted into the DIN input which configures the LTC1290
for the next conversion. Simultaneously, the result of the
previous conversion is output on the DOUT line. At the end
of the data exchange the requested conversion begins and
CS should be brought high. After tCONV, the conversion is
complete and the results will be available on the next data
transfer cycle. As shown below, the result of a conversion
is delayed by one CS cycle from the input word requesting it.