Linduino  1.3.0
Linear Technology Arduino-Compatible Demonstration Board

LTC2756: Serial 18-Bit SoftSpan IOUT DAC. More...

Detailed Description

LTC2756: Serial 18-Bit SoftSpan IOUT DAC.

The LTC2756 is an 18-bit multiplying serial-input,
current-output digital-to-analog converter. LTC2756A
provides full 18-bit performance-INL and DNL of +/-1LSB
maximum-over temperature without any adjustments. 18-bit
monotonicity is guaranteed in all performance grades. This
SoftSpan(TM) DAC operates from a single 3V to 5V supply
and offers six output ranges (up to +/-10V) that can be
programmed through the 3-wire SPI serial interface or
pin-strapped for operation in a single range.

SPI DATA FORMAT (MSB First):

Transfer Sequence:
      Byte #1                    Byte #2
MOSI: C3 C2 C1 C0 0  0  0  0   D17 D16 D15 D14 D13 D12 D11 D10
MISO: 0  0  0  0  0  0  0  0   D17 D16 D15 D14 D13 D12 D11 D10

      Byte #3                    Byte #4
MOSI: D9 D8 D7 D6 D5 D4 D3 D2   D1  D0  X  X  X  X  X  X
MISO: D9 D8 D7 D6 D5 D4 D3 D2   D1  D0  0  0  0  0  0  0

Write SPAN Sequence:
      Byte #1                    Byte #2
MOSI: C3 C2 C1 C0 0  0  0  0   X  X  X  X  X  X  X  X
MISO: 0  0  0  0  0  0  0  0   0  0  0  0  0  0  0  0

      Byte #3                    Byte #4
MOSI: X  X  X  X  S3 S2 S1 S0   X  X  X  X  X  X  X  X
MISO: 0  0  0  0  S3 S2 S1 S0   0  0  0  0  0  0  0  0


Cx   : DAC Command bits
Sx   : SPAN bits
Dx   : DAC Data Bits
X    : Don't care

Example Code:

Set DAC to -5v to +5v  and set output to 2.5v

uint8_t tx[4],rx[4];

// Set DAC to -5v to +5v
tx[3] = LTC2756_WRITE_SPAN;
tx[2] = 0x00;
tx[1] = LTC2756_BIPOLAR_N5_P5;
tx[0] = 0x00;

LTC2756_transfer_4bytes(LTC2756_CS, tx, rx);

float voltage = 2.5;
float LTC2756_lsb = 3.8146972656e-5;            // Typical lsb for -5V to +5v bipolar mode only
int32_t LTC2756_offset = 0x20000;               // Typical offset for -5V to +5v bipolar mode only

// Convert voltage to code
uint32_t code;
code = LTC2756_voltage_to_code(voltage, LTC2756_lsb, LTC2756_offset);

uint8_t tx[4],rx[4];
union
{
    uint8_t byte[4];
    uint32_t code;
} data;

// Load tx array with write command and code
data.code = code<<6;
tx[3] = LTC2756_WRITE_CODE;
tx[2] = data.byte[2];
tx[1] = data.byte[1];
tx[0] = data.byte[0];

LTC2756_transfer_4bytes(LTC2756_CS, tx, rx);

// Load tx arra with update DAC command
tx[3] = LTC2756_UPDATE;
tx[2] = 0x00;
tx[1] = 0x00;
tx[0] = 0x00;

LTC2756_transfer_4bytes(LTC2756_CS, tx, rx);

http://www.linear.com/product/LTC2756

http://www.linear.com/product/LTC2756#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.

Library Header File for LTC2756: Serial 18-Bit SoftSpan IOUT DAC

Definition in file LTC2756.h.

Go to the source code of this file.

Functions

void LTC2756_transfer_4bytes (uint8_t cs, uint8_t *tx, uint8_t *rx)
 Transfers four bytes to the LTC2756. More...
 
uint32_t LTC2756_voltage_to_code (float dac_voltage, float LTC2756_lsb, int32_t LTC2756_offset)
 Converts voltage to code. More...
 
void LTC2756_calibrate (uint32_t zero_code, uint32_t fs_code, float zero_voltage, float fs_voltage, float *LTC2756_lsb, int32_t *LTC2756_offset)
 Calculate the LTC2756 offset and LSB voltage given two measured voltages and their corresponding codes. More...
 

Macros

#define LTC2756_CS   QUIKEVAL_CS
 Define the CS pin. More...
 
LTC2756 DAC Cammands
#define LTC2756_WRITE_SPAN   0x20
 
#define LTC2756_WRITE_CODE   0x30
 
#define LTC2756_UPDATE   0x40
 
#define LTC2756_WRITE_SPAN_UPDATE   0x60
 
#define LTC2756_WRITE_CODE_UPDATE   0x70
 
#define LTC2756_READ_INPUTE_SPAN_REG   0xA0
 
#define LTC2756_READ_INPUT_CODE_REG   0xB0
 
#define LTC2756_READ_DAC_SPAN_REG   0xC0
 
#define LTC2756_READ_DAC_CODE_REG   0xD0
 
LTC2756 SPAN Options
#define LTC2756_UNIPOLAR_0_P5   0x00
 
#define LTC2756_UNIPOLAR_0_P10   0x01
 
#define LTC2756_BIPOLAR_N5_P5   0x02
 
#define LTC2756_BIPOLAR_N10_P10   0x03
 
#define LTC2756_BIPOLAR_N2_5_P2_5   0x04
 
#define LTC2756_BIPOLAR_N2_5_P7_5   0x05
 

Function Documentation

◆ LTC2756_calibrate()

void LTC2756_calibrate ( uint32_t  zero_code,
uint32_t  fs_code,
float  zero_voltage,
float  fs_voltage,
float *  LTC2756_lsb,
int32_t *  LTC2756_offset 
)

Calculate the LTC2756 offset and LSB voltage given two measured voltages and their corresponding codes.

Returns
void

Definition at line 97 of file LTC2756.cpp.

◆ LTC2756_transfer_4bytes()

void LTC2756_transfer_4bytes ( uint8_t  cs,
uint8_t *  tx,
uint8_t *  rx 
)

Transfers four bytes to the LTC2756.

Returns
void

Definition at line 74 of file LTC2756.cpp.

◆ LTC2756_voltage_to_code()

uint32_t LTC2756_voltage_to_code ( float  dac_voltage,
float  LTC2756_lsb,
int32_t  LTC2756_offset 
)

Converts voltage to code.

Returns
the calculated code

Definition at line 81 of file LTC2756.cpp.

Macro Definition Documentation

◆ LTC2756_BIPOLAR_N10_P10

#define LTC2756_BIPOLAR_N10_P10   0x03

Definition at line 161 of file LTC2756.h.

◆ LTC2756_BIPOLAR_N2_5_P2_5

#define LTC2756_BIPOLAR_N2_5_P2_5   0x04

Definition at line 162 of file LTC2756.h.

◆ LTC2756_BIPOLAR_N2_5_P7_5

#define LTC2756_BIPOLAR_N2_5_P7_5   0x05

Definition at line 163 of file LTC2756.h.

◆ LTC2756_BIPOLAR_N5_P5

#define LTC2756_BIPOLAR_N5_P5   0x02

Definition at line 160 of file LTC2756.h.

◆ LTC2756_CS

#define LTC2756_CS   QUIKEVAL_CS

Define the CS pin.

Definition at line 138 of file LTC2756.h.

◆ LTC2756_READ_DAC_CODE_REG

#define LTC2756_READ_DAC_CODE_REG   0xD0

Definition at line 153 of file LTC2756.h.

◆ LTC2756_READ_DAC_SPAN_REG

#define LTC2756_READ_DAC_SPAN_REG   0xC0

Definition at line 152 of file LTC2756.h.

◆ LTC2756_READ_INPUT_CODE_REG

#define LTC2756_READ_INPUT_CODE_REG   0xB0

Definition at line 151 of file LTC2756.h.

◆ LTC2756_READ_INPUTE_SPAN_REG

#define LTC2756_READ_INPUTE_SPAN_REG   0xA0

Definition at line 150 of file LTC2756.h.

◆ LTC2756_UNIPOLAR_0_P10

#define LTC2756_UNIPOLAR_0_P10   0x01

Definition at line 159 of file LTC2756.h.

◆ LTC2756_UNIPOLAR_0_P5

#define LTC2756_UNIPOLAR_0_P5   0x00

Definition at line 158 of file LTC2756.h.

◆ LTC2756_UPDATE

#define LTC2756_UPDATE   0x40

Definition at line 147 of file LTC2756.h.

◆ LTC2756_WRITE_CODE

#define LTC2756_WRITE_CODE   0x30

Definition at line 146 of file LTC2756.h.

◆ LTC2756_WRITE_CODE_UPDATE

#define LTC2756_WRITE_CODE_UPDATE   0x70

Definition at line 149 of file LTC2756.h.

◆ LTC2756_WRITE_SPAN

#define LTC2756_WRITE_SPAN   0x20

Definition at line 145 of file LTC2756.h.

◆ LTC2756_WRITE_SPAN_UPDATE

#define LTC2756_WRITE_SPAN_UPDATE   0x60

Definition at line 148 of file LTC2756.h.