Linduino  1.3.0
Linear Technology Arduino-Compatible Demonstration Board

LTC2449: 24-Bit, 16-Channel Delta Sigma ADCs with Selectable Speed/Resolution. More...

Detailed Description

LTC2449: 24-Bit, 16-Channel Delta Sigma ADCs with Selectable Speed/Resolution.

LTC2442: 24-Bit, 4-Channel Delta Sigma ADC with Integrated Amplifier LTC2448: 24-Bit, 8-/16-Channel Delta Sigma ADCs with Selectable Speed/Resolution

The LTC2444/LTC2445/LTC2448/LTC2449 are 8-/16-channel (4-/8-differential)
high speed 24-bit No Latency Delta Sigma ADCs. They use a proprietary
delta-sigma architecture enabling variable speed/resolution. Through a
simple 4-wire serial interface, ten speed/resolution combinations
6.9Hz/280nVRMS to 3.5kHz/25uVRMS (4kHz with external oscillator) can be
selected with no latency between conversion results or shift in DC accuracy
(offset, full-scale, linearity, drift). Additionally, a 2X speed mode can
be selected enabling output rates up to 7kHz (8kHz if an external
oscillator is used) with one cycle latency.


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  :  1    0   EN  SGL OS  S2  S1  S0    OSR3 OSR2 OSR1 OSR1 SPD 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
*Dx  : Data Bits Below lsb
EN   : Enable Bit (0-keep previous mode, 1-change mode)
SGL  : Enable Single-Ended Bit (0-differential, 1-single-ended)
OS   : ODD/Sign Bit
Sx   : Address Select Bit
0SRX : Over Sampling Rate Bits
SPD  : Double Output Rate Select Bit (0-Normal rate, auto-calibration on, 2x rate, auto_calibration off)

Command Byte #1
1    0    EN   SGL  OS   S2   S1   S0   Comments
1    0    0    X    X    X    X    X    Keep Previous Mode
1    0    1    0    X    X    X    X    Differential Mode
1    0    1    1    X    X    X    X    Single-Ended Mode

|  Coversion Rate    |  RMS  | ENOB | OSR  | Latency
Command Byte #2          |Internal | External | Noise |      |      |
|  9MHz   | 10.24MHz |       |      |      |
OSR3 OSR2 OSR1 OSR1 SPD  | Clock   |  Clock   |       |      |      |
0    0    0    0    0      Keep Previous Speed/Resolution
0    0    0    1    0      3.52kHz   4kHz       23uV    17     64     none
0    0    1    0    0      1.76kHz   2kHz       3.5uV   20.1   128    none
0    0    1    1    0      880Hz     1kHz       2uV     21.3   256    none
0    1    0    0    0      440Hz     500Hz      1.4uV   21.8   512    none
0    1    0    1    0      220Hz     250Hz      1uV     22.4   1024   none
0    1    1    0    0      110Hz     125Hz      750nV   22.9   2048   none
0    1    1    1    0      55Hz      62.5Hz     510nV   23.4   4096   none
1    0    0    0    0      27.5Hz    31.25Hz    375nV   24     8192   none
1    0    0    1    0      13.75Hz   15.625Hz   250nV   24.4   16384  none
1    1    1    1    0      6.87kHz   7.8125Hz   200nV   24.6   32768  none
0    0    0    0    1      Keep Previous Speed/Resolution
OSR3 OSR2 OSR1 OSR1 1      2X Mode  *all clock speeds double

Example Code:

Read Channel 0 in Single-Ended with OSR of 65536

    uint16_t miso_timeout = 1000;
    adc_command = LTC2449_CH0 | LTC2449_OSR_32768 | LTC2449_SPEED_2X;   // Build ADC command for channel 0
                                                                        // OSR = 32768*2 = 65536

    if(LTC2449_EOC_timeout(LTC2449_CS, miso_timeout))    // Check for EOC
        return;                                          // Exit if timeout is reached
    LTC2449_read(LTC2449_CS, adc_command, &adc_code);    // Throws out last reading

    if(LTC2449_EOC_timeout(LTC2449_CS, miso_timeout))    // Check for EOC
        return;                                          // Exit if timeout is reached
    LTC2449_read(LTC2449_CS, adc_command, &adc_code);    // Obtains the current reading and stores to adc_code variable

    // Convert adc_code to voltage
    adc_voltage = LTC2449_code_to_voltage(adc_code, LTC2449_lsb, LTC2449_offset_code);

http://www.linear.com/product/LTC2449 http://www.linear.com/product/LTC2442 http://www.linear.com/product/LTC2448

http://www.linear.com/product/LTC2449#demoboards http://www.linear.com/product/LTC2442#demoboards http://www.linear.com/product/LTC2448#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 LTC2449: 24-Bit, 16-Channel Delta Sigma ADCs with Selectable Speed/Resolution

Definition in file LTC2449.h.

Go to the source code of this file.

Functions

int8_t LTC2449_EOC_timeout (uint8_t cs, uint16_t miso_timeout)
 Checks for EOC with a specified timeout. More...
 
void LTC2449_read (uint8_t cs, uint16_t adc_command, uint32_t *adc_code)
 Reads from LTC2449. More...
 
float LTC2449_code_to_voltage (int32_t adc_code, float LTC2449_lsb, int32_t LTC2449_offset_code)
 Calculates the voltage corresponding to an adc code, given lsb weight (in volts) and the calibrated ADC offset code (zero code that is subtracted from adc_code). More...
 
void LTC2449_cal_voltage (int32_t zero_code, int32_t fs_code, float zero_voltage, float fs_voltage, float *LTC2449_lsb, int32_t *LTC2449_offset_code)
 Calculate the lsb weight and offset code given a full-scale code and a measured zero-code. More...
 

Macros

#define LTC2449_CS   QUIKEVAL_CS
 Define the SPI CS pin. More...
 
Mode Configuration
#define LTC2449_KEEP_PREVIOUS_MODE   0x8000
 
#define LTC2449_KEEP_PREVIOUS_SPEED_RESOLUTION   0x0000
 
#define LTC2449_SPEED_1X   0x0000
 
#define LTC2449_SPEED_2X   0x0008
 
Single-Ended Channels Configuration
#define LTC2449_CH0   0xB000
 
#define LTC2449_CH1   0xB800
 
#define LTC2449_CH2   0xB100
 
#define LTC2449_CH3   0xB900
 
#define LTC2449_CH4   0xB200
 
#define LTC2449_CH5   0xBA00
 
#define LTC2449_CH6   0xB300
 
#define LTC2449_CH7   0xBB00
 
#define LTC2449_CH8   0xB400
 
#define LTC2449_CH9   0xBC00
 
#define LTC2449_CH10   0xB500
 
#define LTC2449_CH11   0xBD00
 
#define LTC2449_CH12   0xB600
 
#define LTC2449_CH13   0xBE00
 
#define LTC2449_CH14   0xB700
 
#define LTC2449_CH15   0xBF00
 
Differential Channel Configuration
#define LTC2449_P0_N1   0xA000
 
#define LTC2449_P1_N0   0xA800
 
#define LTC2449_P2_N3   0xA100
 
#define LTC2449_P3_N2   0xA900
 
#define LTC2449_P4_N5   0xA200
 
#define LTC2449_P5_N4   0xAA00
 
#define LTC2449_P6_N7   0xA300
 
#define LTC2449_P7_N6   0xAB00
 
#define LTC2449_P8_N9   0xA400
 
#define LTC2449_P9_N8   0xAC00
 
#define LTC2449_P10_N11   0xA500
 
#define LTC2449_P11_N10   0xAD00
 
#define LTC2449_P12_N13   0xA600
 
#define LTC2449_P13_N12   0xAE00
 
#define LTC2449_P14_N15   0xA700
 
#define LTC2449_P15_N14   0xAF00
 
Oversample Ratio (OSR) Commands
#define LTC2449_OSR_64   0xA010
 
#define LTC2449_OSR_128   0xA020
 
#define LTC2449_OSR_256   0xA030
 
#define LTC2449_OSR_512   0xA040
 
#define LTC2449_OSR_1024   0xA050
 
#define LTC2449_OSR_2048   0xA060
 
#define LTC2449_OSR_4096   0xA070
 
#define LTC2449_OSR_8192   0xA080
 
#define LTC2449_OSR_16384   0xA090
 
#define LTC2449_OSR_32768   0xA0F0
 

Function Documentation

◆ LTC2449_cal_voltage()

void LTC2449_cal_voltage ( int32_t  zero_code,
int32_t  fs_code,
float  zero_voltage,
float  fs_voltage,
float *  LTC2449_lsb,
int32_t *  LTC2449_offset_code 
)

Calculate the lsb weight and offset code given a full-scale code and a measured zero-code.

Returns
Void
Parameters
zero_codeMeasured code with the inputs shorted to ground
fs_codeMeasured code at nearly full-scale
zero_voltageMeasured zero voltage
fs_voltageVoltage measured at input (with voltmeter) when fs_code was read from adc
LTC2449_lsbOverwritten with lsb weight (in volts)
LTC2449_offset_codeOverwritten with offset code (zero code)

Definition at line 136 of file LTC2449.cpp.

◆ LTC2449_code_to_voltage()

float LTC2449_code_to_voltage ( int32_t  adc_code,
float  LTC2449_lsb,
int32_t  LTC2449_offset_code 
)

Calculates the voltage corresponding to an adc code, given lsb weight (in volts) and the calibrated ADC offset code (zero code that is subtracted from adc_code).

Returns
Returns voltage calculated from ADC code.
Parameters
adc_codeCode read from adc
LTC2449_lsbLSB weight (in volts)
LTC2449_offset_codeThe calibrated offset code (This is the adc code zero code that will be subtraced from adc_code)

Definition at line 127 of file LTC2449.cpp.

◆ LTC2449_EOC_timeout()

int8_t LTC2449_EOC_timeout ( uint8_t  cs,
uint16_t  miso_timeout 
)

Checks for EOC with a specified timeout.

Returns
Returns 0=successful, 1=unsuccessful (exceeded timeout)

Checks for EOC with a specified timeout.

Parameters
csChip Select pin
miso_timeoutTimeout (in milliseconds)

Definition at line 86 of file LTC2449.cpp.

◆ LTC2449_read()

void LTC2449_read ( uint8_t  cs,
uint16_t  adc_command,
uint32_t *  adc_code 
)

Reads from LTC2449.

Returns
void
Parameters
csChip Select pin
adc_command2 byte command written to LTC2449
adc_code4 byte conversion code read from LTC2449

Definition at line 107 of file LTC2449.cpp.

Macro Definition Documentation

◆ LTC2449_CH0

#define LTC2449_CH0   0xB000

Definition at line 156 of file LTC2449.h.

◆ LTC2449_CH1

#define LTC2449_CH1   0xB800

Definition at line 157 of file LTC2449.h.

◆ LTC2449_CH10

#define LTC2449_CH10   0xB500

Definition at line 166 of file LTC2449.h.

◆ LTC2449_CH11

#define LTC2449_CH11   0xBD00

Definition at line 167 of file LTC2449.h.

◆ LTC2449_CH12

#define LTC2449_CH12   0xB600

Definition at line 168 of file LTC2449.h.

◆ LTC2449_CH13

#define LTC2449_CH13   0xBE00

Definition at line 169 of file LTC2449.h.

◆ LTC2449_CH14

#define LTC2449_CH14   0xB700

Definition at line 170 of file LTC2449.h.

◆ LTC2449_CH15

#define LTC2449_CH15   0xBF00

Definition at line 171 of file LTC2449.h.

◆ LTC2449_CH2

#define LTC2449_CH2   0xB100

Definition at line 158 of file LTC2449.h.

◆ LTC2449_CH3

#define LTC2449_CH3   0xB900

Definition at line 159 of file LTC2449.h.

◆ LTC2449_CH4

#define LTC2449_CH4   0xB200

Definition at line 160 of file LTC2449.h.

◆ LTC2449_CH5

#define LTC2449_CH5   0xBA00

Definition at line 161 of file LTC2449.h.

◆ LTC2449_CH6

#define LTC2449_CH6   0xB300

Definition at line 162 of file LTC2449.h.

◆ LTC2449_CH7

#define LTC2449_CH7   0xBB00

Definition at line 163 of file LTC2449.h.

◆ LTC2449_CH8

#define LTC2449_CH8   0xB400

Definition at line 164 of file LTC2449.h.

◆ LTC2449_CH9

#define LTC2449_CH9   0xBC00

Definition at line 165 of file LTC2449.h.

◆ LTC2449_CS

#define LTC2449_CS   QUIKEVAL_CS

Define the SPI CS pin.

Definition at line 140 of file LTC2449.h.

◆ LTC2449_KEEP_PREVIOUS_MODE

#define LTC2449_KEEP_PREVIOUS_MODE   0x8000

Definition at line 146 of file LTC2449.h.

◆ LTC2449_KEEP_PREVIOUS_SPEED_RESOLUTION

#define LTC2449_KEEP_PREVIOUS_SPEED_RESOLUTION   0x0000

Definition at line 147 of file LTC2449.h.

◆ LTC2449_OSR_1024

#define LTC2449_OSR_1024   0xA050

Definition at line 216 of file LTC2449.h.

◆ LTC2449_OSR_128

#define LTC2449_OSR_128   0xA020

Definition at line 213 of file LTC2449.h.

◆ LTC2449_OSR_16384

#define LTC2449_OSR_16384   0xA090

Definition at line 220 of file LTC2449.h.

◆ LTC2449_OSR_2048

#define LTC2449_OSR_2048   0xA060

Definition at line 217 of file LTC2449.h.

◆ LTC2449_OSR_256

#define LTC2449_OSR_256   0xA030

Definition at line 214 of file LTC2449.h.

◆ LTC2449_OSR_32768

#define LTC2449_OSR_32768   0xA0F0

Definition at line 221 of file LTC2449.h.

◆ LTC2449_OSR_4096

#define LTC2449_OSR_4096   0xA070

Definition at line 218 of file LTC2449.h.

◆ LTC2449_OSR_512

#define LTC2449_OSR_512   0xA040

Definition at line 215 of file LTC2449.h.

◆ LTC2449_OSR_64

#define LTC2449_OSR_64   0xA010

Definition at line 212 of file LTC2449.h.

◆ LTC2449_OSR_8192

#define LTC2449_OSR_8192   0xA080

Definition at line 219 of file LTC2449.h.

◆ LTC2449_P0_N1

#define LTC2449_P0_N1   0xA000

Definition at line 176 of file LTC2449.h.

◆ LTC2449_P10_N11

#define LTC2449_P10_N11   0xA500

Definition at line 191 of file LTC2449.h.

◆ LTC2449_P11_N10

#define LTC2449_P11_N10   0xAD00

Definition at line 192 of file LTC2449.h.

◆ LTC2449_P12_N13

#define LTC2449_P12_N13   0xA600

Definition at line 194 of file LTC2449.h.

◆ LTC2449_P13_N12

#define LTC2449_P13_N12   0xAE00

Definition at line 195 of file LTC2449.h.

◆ LTC2449_P14_N15

#define LTC2449_P14_N15   0xA700

Definition at line 197 of file LTC2449.h.

◆ LTC2449_P15_N14

#define LTC2449_P15_N14   0xAF00

Definition at line 198 of file LTC2449.h.

◆ LTC2449_P1_N0

#define LTC2449_P1_N0   0xA800

Definition at line 177 of file LTC2449.h.

◆ LTC2449_P2_N3

#define LTC2449_P2_N3   0xA100

Definition at line 179 of file LTC2449.h.

◆ LTC2449_P3_N2

#define LTC2449_P3_N2   0xA900

Definition at line 180 of file LTC2449.h.

◆ LTC2449_P4_N5

#define LTC2449_P4_N5   0xA200

Definition at line 182 of file LTC2449.h.

◆ LTC2449_P5_N4

#define LTC2449_P5_N4   0xAA00

Definition at line 183 of file LTC2449.h.

◆ LTC2449_P6_N7

#define LTC2449_P6_N7   0xA300

Definition at line 185 of file LTC2449.h.

◆ LTC2449_P7_N6

#define LTC2449_P7_N6   0xAB00

Definition at line 186 of file LTC2449.h.

◆ LTC2449_P8_N9

#define LTC2449_P8_N9   0xA400

Definition at line 188 of file LTC2449.h.

◆ LTC2449_P9_N8

#define LTC2449_P9_N8   0xAC00

Definition at line 189 of file LTC2449.h.

◆ LTC2449_SPEED_1X

#define LTC2449_SPEED_1X   0x0000

Definition at line 148 of file LTC2449.h.

◆ LTC2449_SPEED_2X

#define LTC2449_SPEED_2X   0x0008

Definition at line 149 of file LTC2449.h.