LTC6904 - 1kHz - 68MHz Serial Port Programmable Oscillator

Features

  • 1kHz to 68MHz Square Wave Output
  • 0.5% (Typ) Initial Frequency Accuracy
  • Frequency Error <1.1% Over All Settings
  • 10ppm/°C Typical Frequency Drift Over Temperature
  • 0.1% Resolution
  • 1.7mA Typical Supply Current (f < 1MHz, VS = 2.7V)
  • 2.7V to 5.5V Single Supply Operation
  • Jitter <0.4% Typical 1kHz to 8MHz
  • Easy to Use SPI (LTC6903) or I2C (LTC6904) Serial Interface
  • Output Enable Pin
  • –55°C to 125°C Operation
  • MS8 Package
Designed for Automotive and Transportation Applications
AEC-Q100 data available for specific packages


Typical Application

LTC6904 Typical Application
LTC6904 Typical Application

Description

The LTC6903/LTC6904 are low power self contained digital frequency sources providing a precision frequency from 1kHz to 68MHz, set through a serial port. The LTC6903/ LTC6904 require no external components other than a power supply bypass capacitor, and they operate over a single wide supply range of 2.7V to 5.5V.

The LTC6903/LTC6904 feature a proprietary feedback loop that linearizes the relationship between digital control setting and frequency, resulting in a very simple frequency setting equation:

Packaging

CAD Symbols and Footprints: The downloadable Zip file below contains the schematic symbol and PCB footprints.

For complete and up to date package information and drawings, please refer to our packaging page

Part Number Package Code Temp Package
Drawing
RoHS
LTC6904CMS8#PBF MS-8 MS8 C 05-08-1660 Yes
LTC6904CMS8#TRPBF MS-8 MS8 C 05-08-1660 Yes
LTC6904HMS8#PBF MS-8 MS8 H 05-08-1660 Yes
LTC6904HMS8#TRPBF MS-8 MS8 H 05-08-1660 Yes
LTC6904IMS8#PBF MS-8 MS8 I 05-08-1660 Yes
LTC6904IMS8#TRPBF MS-8 MS8 I 05-08-1660 Yes
LTC6904MPMS8#PBF MS-8 MS8 MP 05-08-1660 Yes
LTC6904MPMS8#TRPBF MS-8 MS8 MP 05-08-1660 Yes


LTC6904 Package Drawing

Order Info

  • Part numbers ending in PBF are lead free. Solder plated terminal finish (SnPb) versions are non-standard and special terms and conditions and pricing applies if available. Please contact LTC marketing for information.
  • Part numbers containing TR or TRM are shipped in tape and reel or 500 unit mini tape and reel, respectively
  • Please refer to our general ordering information or the product datasheet for more details

Package Variations and Pricing

Part Number Package Temp Price
(1-99)
Price
(1k)*
RoHS
LTC6904CMS8#PBF MS-8 C $2.60 $2.10 Yes
LTC6904CMS8#TRPBF MS-8 C $2.16 Yes
LTC6904HMS8#PBF MS-8 H $2.99 $2.42 Yes
LTC6904HMS8#TRPBF MS-8 H $2.48 Yes
LTC6904IMS8#PBF MS-8 I $2.99 $2.42 Yes
LTC6904IMS8#TRPBF MS-8 I $2.48 Yes
LTC6904MPMS8#PBF MS-8 MP $8.78 $6.30 Yes
LTC6904MPMS8#TRPBF MS-8 MP $8.84 $6.36 Yes
Buy NowRequest Samples
* The USA list pricing shown is for BUDGETARY USE ONLY, shown in United States dollars (FOB USA per unit for the stated volume), and is subject to change. International prices may differ due to local duties, taxes, fees and exchange rates. For volume-specific price or delivery quotes, please contact your local Linear Technology sales office or authorized distributor.

Demo Boards

Linear Technology offers many demo boards free of charge to qualified customers. Contact your local sales office or distributor to inquire about a demo board. Certain demo boards are also available for sale via credit card on this website. Demo boards are for evaluation purposes only. It remains the customer’s responsibility to verify proper and reliable operation in the actual end application.

Part Number Description Price Documentation
DC726B-B LTC6904 Demo Board | 1kHz to 68MHz Serial Port Programmable Oscillator (req DC2026) $100.00
Buy Now

Companion Boards

Part Number Description Price Documentation
DC2026C Linduino One Isolated USB Demo Board: An Arduino- and QuikEval-Compatible Code Development Platform $75.00
DC590B Isolated USB Serial Controller for Linear Technology QuikEval-Compatible Demo Boards $50.00
Buy Now
Click here to view our complete list of demo boards

Designed for Automotive and Transportation Applications

AEC-Q100 data is available for these specific part numbers. Please contact your local sales representative for more information regarding reliability reports or to inquire about parts that are not included. For more information, view our Automotive and Transportation page

Part Number Package Temp Price
(1-99)
Price
(1k)*
RoHS
LTC6904HMS8#PBF MS-8 H $2.99 $2.42 Yes
LTC6904HMS8#TRPBF MS-8 H $2.48 Yes
LTC6904IMS8#PBF MS-8 I $2.99 $2.42 Yes
LTC6904IMS8#TRPBF MS-8 I $2.48 Yes
LTC6904MPMS8#PBF MS-8 MP $8.78 $6.30 Yes
LTC6904MPMS8#TRPBF MS-8 MP $8.84 $6.36 Yes
Buy NowRequest Samples
* The USA list pricing shown is for BUDGETARY USE ONLY, shown in United States dollars (FOB USA per unit for the stated volume), and is subject to change. International prices may differ due to local duties, taxes, fees and exchange rates. For volume-specific price or delivery quotes, please contact your local Linear Technology sales office or authorized distributor.

Applications

  • Precision Digitally Controlled Oscillator
  • Power Management
  • Direct Digital Frequency Synthesis (DDS) Replacement
  • Replacement for DAC and VCO
  • Switched Capacitor Filter Clock

Product Notifications

Please login to your MyLinear account for notifications of datasheet updates, new document releases and LTspice model announcements for your favorite products. If you do not have a MyLinear account you may Sign Up Now.

Forgot your password? Click here.
Need help? Email mylinear@linear.com with questions and comments.

Design Tools

Linduino

Linduino is an Arduino compatible platform for developing and distributing firmware libraries and code for SPI and I²C-compatible integrated circuits. The Linduino One board interfaces to more than 300 QuikEval demonstration cards, supporting a variety of product types including analog-to-digital converters (ADCs)digital-to-analog converters (DACs)power monitors, and more. Firmware libraries for individual devices are written in C and designed to be portable to a wide variety of processors and microcontrollers. Each library has a demonstration program that can be uploaded to the Linduino One platform to allow the circuit and software to be quickly and easily verified.

Click here for more information on Linduino

OscCalc, an Excel based selection and synthesis tool, allows you to choose and configure the Silicon Oscillator best suited for your application.

  • Download and open OscCalc
  • Enable Macros
  • Enter your desired switching frequency. Suitable silicon oscillators will be highlighted in green. Clicking on a part will show you the external component values and settings required to achieve your desired switching frequency.

Code

Linduino is Linear Technology's Arduino compatible system for developing and distributing firmware libraries and example code for Linear Technology’s integrated circuits. The code below can be downloaded or copied and pasted into your project. Please visit the Linduino Home Page for demo board, manual and setup information.

This part is Code Supported: There is example code available for this part. The code below may rely on other drivers available in the full library.

Download LTC6904 - DC726B_B Linduino.INO File

/*!
Linear Technology DC726B-B (or DC726A-B) Demonstration Board.
LTC6904: 1kHz to 68MHz Serial Port Programmable Oscillator

@verbatim

NOTES
  Setup:
   Set the terminal baud rate to 115200 and select the newline terminator. Equipment
   required is a precision voltage source and a precision voltmeter (to monitor 
   voltage source). No external power supply is required. Ensure JP1 is installed in
   the default position from the factory.
  
  Demo Board Configuration:
   To properly use this program with the DC726B-B demo board (or the DC726A-B), JMP 2 
   needs to be set to QuikEval.
   
USER INPUT DATA FORMAT:
 decimal : 1024
 hex     : 0x400
 octal   : 02000  (leading 0 "zero")
 binary  : B10000000000
 float   : 1024.0

@endverbatim

http://www.linear.com/product/LTC6904

http://www.linear.com/product/LTC6904#demoboards

REVISION HISTORY
$Revision: 3592 $
$Date: 2015-06-10 11:50:47 -0700 (Wed, 10 Jun 2015) $

Copyright (c) 2013, Linear Technology Corp.(LTC)
All rights reserved.

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

1. Redistributions of source code must retain the above copyright notice, this
   list of conditions and the following disclaimer.
2. 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.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
(INCLUDING, BUT NOT LIMITED TO, 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.

The views and conclusions contained in the software and documentation are those
of the authors and should not be interpreted as representing official policies,
either expressed or implied, of Linear Technology Corp.

The Linear Technology Linduino is not affiliated with the official Arduino team.
However, the Linduino is only possible because of the Arduino team's commitment
to the open-source community.  Please, visit http://www.arduino.cc and
http://store.arduino.cc , and consider a purchase that will help fund their
ongoing work.
*/

/*! @file
    @ingroup LTC6904
*/

#include <Arduino.h>
#include <stdint.h>
#include "Linduino.h"
#include "UserInterface.h"
#include "LT_I2C.h"
#include "QuikEval_EEPROM.h"
#include "LTC6904.h"
#include <Wire.h>

// Function Declaration 
void print_title(); 
void print_prompt();
void settings();
uint8_t set_frequency();
uint8_t manually_set_reg();


// Global variables
static uint8_t output_config = LTC6904_CLK_ON_CLK_INV_ON;  //!< Keeps track of output configuration.

//! Initialize Linduino
void setup()
{
  quikeval_I2C_init();           // Configure the EEPROM I2C port for 100kHz
  quikeval_I2C_connect();        // Connect I2C to main data port
  Serial.begin(115200);          // Initialize the serial port to the PC
  print_title();
  print_prompt();
}

//! Repeats Linduino loop
void loop()
{
  int16_t user_command;
  uint8_t ack = 0;

  user_command = read_int();

  Serial.println(user_command);

  switch(user_command)
  {
    case 1: 
      ack = set_frequency();
      break;
    case 2:
      ack = manually_set_reg();
      break;
    case 3:
      settings();
      break;
    default:
      Serial.println(F("Invalid command"));
      break;
  }

  // A buffer is used for SDA to the LTC6904.
  // This does not allow the Linduino to observe an
  // I2C ACK. Thus, the following code is not used
  // to ignore the NACK.
  /*
  if(ack == 1)
  {
    Serial.println();
    Serial.println(F("I2C ACK Error"));
  }
  */

  print_prompt();
}
        
//! Prints the title block when program first starts.
void print_title()
{
  Serial.println();
  Serial.println(F("*****************************************************************"));
  Serial.println(F("* DC726A Demonstration Program                                  *"));
  Serial.println(F("*                                                               *"));
  Serial.println(F("* This program demonstrates how to send data to the             *"));
  Serial.println(F("* programmable oscillator                                       *"));
  Serial.println(F("*                                                               *"));
  Serial.println(F("* Set the baud rate to 115200 and select the newline terminator.*"));
  Serial.println(F("*                                                               *"));
  Serial.println(F("*****************************************************************"));
}

//! Prints main menu.
void print_prompt()
{
  Serial.println();
  Serial.println(F("1-Set frequency out"));
  Serial.println(F("2-Manually set OCT and DAC code"));
  Serial.println(F("3-Settings"));
  Serial.println();
  Serial.print(F("Enter a command:"));
}

//! Sets the output frequency.
//! @return the ACK if 0, NACK if 1
uint8_t set_frequency()
{
  float freq;
  uint16_t clock_code;
  uint8_t ack;

  Serial.print(F("Enter the desired clock freq (KHz):"));

  freq = read_float();

  Serial.println(freq, 4);

  // Calculates the code necessary to create the clock frequency
  clock_code = LTC6904_frequency_to_code(freq/1000, output_config);

  ack = LTC6904_write(LTC6904_ADDRESS, (uint16_t)clock_code);
  return(ack);
}

//! Manually Sets OCT and DAC Code
//! @return ack
uint8_t manually_set_reg()
{
  uint8_t oct;
  uint8_t ack;
  uint16_t dac_code;

  Serial.print(F("Enter the OCT:"));

  oct = read_int();
  if(oct > 15)
    oct = 15;
  Serial.println(oct);
    
  Serial.println();
  Serial.print(F("Enter the DAC code:"));
    
  dac_code = read_int();
    
  Serial.println(dac_code);
  Serial.println();
   
  // Manually set registers
  ack = LTC6904_write(LTC6904_ADDRESS, (uint16_t)((oct<<12)|(dac_code<<2)|output_config));
  return(ack);
}

//! Configures the output
void settings()
{
  int16_t user_command;
 
  Serial.println();
  Serial.println(F("Output Configuration"));
  Serial.println(F("1-CLK On and CLK INV ON"));
  Serial.println(F("2-CLK Off and CLK INV ON"));
  Serial.println(F("3-CLK On and CLK INV Off"));
  Serial.println(F("4-Power Down"));
  Serial.println();
  Serial.print(F("Enter a command:"));

  user_command = read_int();

  Serial.println(user_command);

  switch(user_command)
  {
    case 1:
      output_config = LTC6904_CLK_ON_CLK_INV_ON;
      break;
    case 2:
      output_config = LTC6904_CLK_OFF_CLK_INV_ON;
      break;
    case 3:
      output_config = LTC6904_CLK_ON_CLK_INV_OFF;
      break;
    case 4:
      output_config = LTC6904_POWER_DOWN;
      break;
    default:
      Serial.println(F("Invalid command"));
  }
}

Download LTC6904 - Linduino Header File

/*!
LTC6904: 1kHz to 68MHz Serial Port Programmable Oscillator

@verbatim

The LTC6903/LTC6904 are low power self contained digital
frequency sources providing a precision frequency from 
1kHz to 68MHz, set through a serial port. The LTC6903/
LTC6904 require no external components other than a 
power supply bypass capacitor, and they operate over a 
single wide supply range of 2.7V to 5.5V.

@endverbatim

http://www.linear.com/product/LTC6904

http://www.linear.com/product/LTC6904#demoboards

REVISION HISTORY
$Revision: 2172 $
$Date: 2014-01-22 10:25:19 -0800 (Wed, 22 Jan 2014) $

Copyright (c) 2013, Linear Technology Corp.(LTC)
All rights reserved.

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

1. Redistributions of source code must retain the above copyright notice, this
   list of conditions and the following disclaimer.
2. 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.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
(INCLUDING, BUT NOT LIMITED TO, 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.

The views and conclusions contained in the software and documentation are those
of the authors and should not be interpreted as representing official policies,
either expressed or implied, of Linear Technology Corp.

The Linear Technology Linduino is not affiliated with the official Arduino team.
However, the Linduino is only possible because of the Arduino team's commitment
to the open-source community.  Please, visit http://www.arduino.cc and
http://store.arduino.cc , and consider a purchase that will help fund their
ongoing work.
*/

/*! @file
    @ingroup LTC6904
    Library Header File for LTC6904: 1kHz to 68MHz Serial Port Programmable Oscillator
*/

#ifndef LTC6904_H
#define LTC6904_H

// LT6904 address options
// Uncomment the desired address
#define LTC6904_ADDRESS 0x17     //!< ADR 0
//#define LTC6904_ADDRESS 0x16     //!< ADR 1

/*!
@{ 
|   OCT Options     |   f>=  (MHz)  |   f< (MHz)    |
|   :-----------    |   :--------:  |   :-------:   |
|   LTC6904_OCT_15  |   34.05       |   68.03       |
|   LTC6904_OCT_14  |   17.02       |   34.01       |
|   LTC6904_OCT_13  |   8.5111      |   17.01       |
|   LTC6904_OCT_12  |   4.256       |   8.503       |
|   LTC6904_OCT_11  |   2.128       |   4.252       |
|   LTC6904_OCT_10  |   1.064       |   2.126       |
|   LTC6904_OCT_9   |   0.532       |   1.063       |
|   LTC6904_OCT_8   |   0.266       |   0.5314      |
|   LTC6904_OCT_7   |   0.133       |   0.2657      |
|   LTC6904_OCT_6   |   0.0665      |   0.1329      |
|   LTC6904_OCT_5   |   0.03325     |   0.06643     |
|   LTC6904_OCT_4   |   0.01662     |   0.03322     |
|   LTC6904_OCT_3   |   0.008312    |   0.01661     |
|   LTC6904_OCT_2   |   0.004156    |   0.008304    |
|   LTC6904_OCT_1   |   0.002078    |   0.004152    |
|   LTC6904_OCT_0   |   0.001039    |   0.002076    |
*/
// OCT Options
                                // f>=  (MHz)       | f< (MHz)
#define LTC6904_OCT_15  0x0F    // 34.05            | 68.03
#define LTC6904_OCT_14  0x0E    // 17.02            | 34.01
#define LTC6904_OCT_13  0x0D    // 8.5111           | 17.01
#define LTC6904_OCT_12  0x0C    // 4.256            | 8.503
#define LTC6904_OCT_11  0x0B    // 2.128            | 4.252
#define LTC6904_OCT_10  0x0A    // 1.064            | 2.126
#define LTC6904_OCT_9   0x09    // 0.532            | 1.063
#define LTC6904_OCT_8   0x08    // 0.266            | 0.5314
#define LTC6904_OCT_7   0x07    // 0.133            | 0.2657
#define LTC6904_OCT_6   0x06    // 0.0665           | 0.1329
#define LTC6904_OCT_5   0x05    // 0.03325          | 0.06643
#define LTC6904_OCT_4   0x04    // 0.01662          | 0.03322
#define LTC6904_OCT_3   0x03    // 0.008312         | 0.01661
#define LTC6904_OCT_2   0x02    // 0.004156         | 0.008304
#define LTC6904_OCT_1   0x01    // 0.002078         | 0.004152
#define LTC6904_OCT_0   0x00    // 0.001039         | 0.002076
//! @}

// Output Configuration
#define LTC6904_CLK_ON_CLK_INV_ON   0x00    //!< Clock on, inverted clock on
#define LTC6904_CLK_OFF_CLK_INV_ON  0x01    //!< Clock off, inverted clock on
#define LTC6904_CLK_ON_CLK_INV_OFF  0x02    //!< Clock on, inverted clock off
#define LTC6904_POWER_DOWN          0x03    //!< Powers down clocks

//! Writes 2 bytes
//! @return 1 if successful, 0 if failure
uint8_t LTC6904_write(uint8_t address,     //!< I2C address 
                      uint16_t code        //!< Code to be written
                      );

//! Calculates the code necessary to create the clock frequency
//! @return the code for the LTC6904 
uint16_t LTC6904_frequency_to_code(float frequency, //!< Clock frequency in MHz
                                  uint8_t clk       //!< Output configuration
                                  );

#endif

Download LTC6904 - Linduino.CPP File

/*!
LTC6904: 1kHz to 68MHz Serial Port Programmable Oscillator

@verbatim

The LTC6903/LTC6904 are low power self contained digital
frequency sources providing a precision frequency from 
1kHz to 68MHz, set through a serial port. The LTC6903/
LTC6904 require no external components other than a 
power supply bypass capacitor, and they operate over a 
single wide supply range of 2.7V to 5.5V.

@endverbatim

http://www.linear.com/product/LTC6904

http://www.linear.com/product/LTC6904#demoboards

REVISION HISTORY
$Revision: 2172 $
$Date: 2014-01-22 10:25:19 -0800 (Wed, 22 Jan 2014) $

Copyright (c) 2013, Linear Technology Corp.(LTC)
All rights reserved.

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

1. Redistributions of source code must retain the above copyright notice, this
   list of conditions and the following disclaimer.
2. 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.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
(INCLUDING, BUT NOT LIMITED TO, 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.

The views and conclusions contained in the software and documentation are those
of the authors and should not be interpreted as representing official policies,
either expressed or implied, of Linear Technology Corp.

The Linear Technology Linduino is not affiliated with the official Arduino team.
However, the Linduino is only possible because of the Arduino team's commitment
to the open-source community.  Please, visit http://www.arduino.cc and
http://store.arduino.cc , and consider a purchase that will help fund their
ongoing work.
*/

//! @defgroup LTC6904 LTC6904: 1kHz to 68MHz Serial Port Programmable Oscillator

/*! @file
    @ingroup LTC6904
    Library for LTC6904: 1kHz to 68MHz Serial Port Programmable Oscillator
*/

#include <stdint.h>
#include <Arduino.h>
#include "Linduino.h"
#include "LT_I2C.h"
#include "LTC6904.h"
#include <Wire.h>
#include "math.h"

// Writes 2 bytes
uint8_t LTC6904_write(uint8_t address, uint16_t code)
{
    uint8_t ack;
    ack = i2c_write_byte_data(address, (0x0FF00 & code)>>8, 0x0FF & code);
    return(ack);
}

// Calculates the code necessary to create the clock frequency
// Returns the Code for the LTC6904 
uint16_t LTC6904_frequency_to_code(float frequency, uint8_t clk)
{
    uint8_t oct;
    double oct_double;
    float float_dac;
    uint16_t dac;

    // Calculate OCT
    oct_double = log10((double)((frequency*1000000)/1039));
    oct_double *= 3.322;
    
    // Keep OCT within range
    if(oct_double>15)
        oct = 15;
    if(oct_double<0)
        oct = 0;
    oct = (uint8_t)oct_double;  // Cast as uint8_t , round down

    // Calculate DAC code
    float_dac = 2048-(2078*pow(2, (10+ oct)))/(frequency*1000000);   // Calculate the dac code
    float_dac = (float_dac > (floor(float_dac) + 0.5)) ? ceil(float_dac) : floor(float_dac);  // Round

    // Keep DAC within range
    if(float_dac>1023)
        float_dac = 1023;
    if(float_dac<0)
        float_dac = 0;
    
    dac = (uint16_t)float_dac;  // Cast as uint16_t

    return((uint16_t)((oct<<12)| (dac<<2) | clk));
}

Technical Support