Linduino  1.3.0
Linear Technology Arduino-Compatible Demonstration Board

LTC2440: 24-Bit, Differential Delta Sigma ADCs with Selectable Speed/Resolution. More...

Detailed Description

LTC2440: 24-Bit, Differential Delta Sigma ADCs with Selectable Speed/Resolution.

The LTC2440 is a high speed 24-bit No Latency Delta Sigma TM ADC with 5ppm
INL and 5uV offset. It uses proprietary delta-sigma architecture enabling
variable speed and resolution with no latency. Ten speed/resolution
combinations (6.9Hz/200nVRMS to 3.5kHz/25uVRMS) are programmed through a
simple serial interface. Alternatively, by tying a single pin HIGH or
LOW, a fast (880Hz/2uVRMS) or ultralow noise (6.9Hz, 200nVRMS, 50/60Hz
rejection) speed/resolution combination can be easily selected. The
accuracy (offset, full-scale, linearity, drift) and power dissipation are
independent of the speed selected. Since there is no latency, a
speed/resolution change may be made between conversions with no
degradation in performance.


SPI DATA FORMAT (MSB First):

            Byte #1                            Byte #2

Data Out :  !EOC DMY SIG D28 D27 D26 D25 D24   D23 D22 D21 D20 D19 D18 D17 D16
Data In  :  OSR4 OSR3 OSR2 OSR1 OSR1 X X X     X    X  X   X   X  X  X  X

Byte #3                        Byte #4
D15 D14 D13 D12 D11 D10 D9 D8  D7 D6 D5 D4 *D3 *D2 *D1 *D0
X   X   X   X   X   X   X  X   X  X  X  X   X  X   X   X

!EOC : End of Conversion Bit (Active Low)
DMY  : Dummy Bit (Always 0)
SIG  : Sign Bit (1-data positive, 0-data negative)
Dx   : Data Bits
EN   : Enable Bit (0-keep previous mode, 1-change mode)
SGL  : Enable Single-Ended Bit (0-differential, 1-single-ended)
Sx   : Address Select Bit
0SRX : Over Sampling Rate Bits

                          |      CONVERSION RATE          |
                          |   INTERNAL   |   EXTERNAL     |
OSR4 OSR3 OSR2 OSR1 OSR1  |  9MHz CLOCK  |  10.24MHz CLOCK  |  RMS NOISE  |  ENOB  |  OSR
x    0    0    0    1        3.52kHz        4kHz               23uV          17       64
x    0    0    1    0        1.76kHz        2kHz               3.5uV         20       128
0    0    0    0    0        880Hz          1kHz               2uV           21.3     256*
x    0    0    1    1        880Hz          1kHz               2uV           21.3     256
x    0    1    0    0        440Hz          500Hz              1.4uV         21.8     512
x    0    1    0    1        220Hz          250Hz              1uV           22.4     1024
x    0    1    1    0        110Hz          125Hz              750nV         22.9     2048
x    0    1    1    1        55Hz           62.5Hz             510nV         23.4     4096
x    1    0    0    0        27.5Hz         31.25Hz            375nV         24       8192
X    1    0    0    1        13.75Hz        15.625Hz           250nV         24.4     16384
X    1    1    1    1        6.87kHz        7.8125Hz           200nV         24.6     32768**
** Address allows tying SDI HIGH  *Additional address to allow tying SDI LOW


Example Code:

Read ADC with OSR of 65536

    uint16_t miso_timeout = 1000;

    if(!LTC2440_EOC_timeout(LTC2440_CS, miso_timeout)) // Check for EOC
      LTC2440_read(LTC2440_CS, adc_command, &adc_code);     // Throws out reading
    else
    {
      return;
    }

    if(!LTC2440_EOC_timeout(LTC2440_CS, miso_timeout)) // Check for EOC
      LTC2440_read(LTC2440_CS, adc_command, &adc_code); // Take valid reading
    else
    {
      return;
    }

    // Convert adc_code to voltage
    adc_voltage = LTC2440_code_to_voltage(adc_code, LTC2440_vref);

http://www.linear.com/product/LTC2440

http://www.linear.com/product/LTC2440#demoboards

Copyright 2018(c) Analog Devices, Inc.

All rights reserved.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

  • Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
  • Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.
  • Neither the name of Analog Devices, Inc. nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission.
  • The use of this software may or may not infringe the patent rights of one or more patent holders. This license does not release you from the requirement that you obtain separate licenses from these patent holders to use this software.
  • Use of the software either in source or binary form, must be run on or directly connected to an Analog Devices Inc. component.

THIS SOFTWARE IS PROVIDED BY ANALOG DEVICES "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, NON-INFRINGEMENT, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL ANALOG DEVICES BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, INTELLECTUAL PROPERTY RIGHTS, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

Header for LTC2440: 24-Bit, Differential Delta Sigma ADCs with Selectable Speed/Resolution.

Definition in file LTC2440.h.

Go to the source code of this file.

Functions

int8_t LTC2440_EOC_timeout (uint8_t cs, uint16_t miso_timeout)
 Checks for EOC with a specified timeout. More...
 
void LTC2440_read (uint8_t cs, uint8_t adc_command, int32_t *adc_code)
 Reads from LTC2440. More...
 
float LTC2440_code_to_voltage (int32_t adc_code, float vref)
 Calculates the voltage corresponding to an adc code, given the reference (in volts) More...
 

Macros

#define LTC2440_CS   QUIKEVAL_CS
 Define the SPI CS pin. More...
 
Oversample Ratio (OSR) Commands
#define LTC2440_OSR_64   0x08
 
#define LTC2440_OSR_128   0x10
 
#define LTC2440_OSR_256_   0x00
 
#define LTC2440_OSR_256   0x18
 
#define LTC2440_OSR_512   0x20
 
#define LTC2440_OSR_1024   0x28
 
#define LTC2440_OSR_2048   0x30
 
#define LTC2440_OSR_4096   0x38
 
#define LTC2440_OSR_8192   0x40
 
#define LTC2440_OSR_16384   0x48
 
#define LTC2440_OSR_32768   0x78
 

Function Documentation

◆ LTC2440_code_to_voltage()

float LTC2440_code_to_voltage ( int32_t  adc_code,
float  vref 
)

Calculates the voltage corresponding to an adc code, given the reference (in volts)

Returns
Returns voltage calculated from ADC code.
Parameters
adc_codeCode read from adc
vrefVRef (in volts)

Definition at line 92 of file LTC2440.cpp.

◆ LTC2440_EOC_timeout()

int8_t LTC2440_EOC_timeout ( uint8_t  cs,
uint16_t  miso_timeout 
)

Checks for EOC with a specified timeout.

Returns
Returns 0=successful, 1=unsuccessful (exceeded timeout)
Parameters
csChip Select pin
miso_timeoutTimeout (in milliseconds)

Definition at line 80 of file LTC2440.cpp.

◆ LTC2440_read()

void LTC2440_read ( uint8_t  cs,
uint8_t  adc_command,
int32_t *  adc_code 
)

Reads from LTC2440.

Parameters
csChip select
adc_command1 byte command written to LTC2440
adc_code4 byte conversion code read from LTC2440

Definition at line 86 of file LTC2440.cpp.

Macro Definition Documentation

◆ LTC2440_CS

#define LTC2440_CS   QUIKEVAL_CS

Define the SPI CS pin.

Definition at line 130 of file LTC2440.h.

◆ LTC2440_OSR_1024

#define LTC2440_OSR_1024   0x28

Definition at line 140 of file LTC2440.h.

◆ LTC2440_OSR_128

#define LTC2440_OSR_128   0x10

Definition at line 136 of file LTC2440.h.

◆ LTC2440_OSR_16384

#define LTC2440_OSR_16384   0x48

Definition at line 144 of file LTC2440.h.

◆ LTC2440_OSR_2048

#define LTC2440_OSR_2048   0x30

Definition at line 141 of file LTC2440.h.

◆ LTC2440_OSR_256

#define LTC2440_OSR_256   0x18

Definition at line 138 of file LTC2440.h.

◆ LTC2440_OSR_256_

#define LTC2440_OSR_256_   0x00

Definition at line 137 of file LTC2440.h.

◆ LTC2440_OSR_32768

#define LTC2440_OSR_32768   0x78

Definition at line 145 of file LTC2440.h.

◆ LTC2440_OSR_4096

#define LTC2440_OSR_4096   0x38

Definition at line 142 of file LTC2440.h.

◆ LTC2440_OSR_512

#define LTC2440_OSR_512   0x20

Definition at line 139 of file LTC2440.h.

◆ LTC2440_OSR_64

#define LTC2440_OSR_64   0x08

Definition at line 135 of file LTC2440.h.

◆ LTC2440_OSR_8192

#define LTC2440_OSR_8192   0x40

Definition at line 143 of file LTC2440.h.