Study on 12-/14-/16-Bit,  Octal-Channel, DAC <ul><li>Source: Texas Instruments </li></ul>
Introduction <ul><li>Purpose </li></ul><ul><ul><li>An Overview study on 12-/14-/16-Bit, Octal-Channel DAC </li></ul></ul><...
Features <ul><li>Relative Accuracy:  </li></ul><ul><li>–  DAC7568 (12-Bit): 0.3 LSB INL  </li></ul><ul><li>–  DAC8168 (14-...
Applications <ul><li>Portable Instrumentation 234 ·  </li></ul><ul><li>Closed-Loop Servo-Control/Process  </li></ul><ul><l...
Digital-to-Analog Converter (DAC) Resistor String Device Architecture <ul><li>The DAC architecture consists of eight strin...
Internal Reference Bandgap Reference Simplified Schematic <ul><li>The internal reference is externally available at the VR...
Serial Interface <ul><li>The DAC have a 3-wire serial interface SYNC, SCLK, and Din compatible with SPI, QSPI, and Microwi...
Power-Down Modes <ul><li>The DAC have two separate sets of power-down commands. One set is for the DAC channels and the ot...
Load Regulation Accurate Load Regulation of the DAC <ul><li>Load regulation is defined as the change in reference output v...
Application Diagram of DAC  Connecting to MCU <ul><li>The MSP430F449 mC will interface with the DAC8564 using the SPI seri...
Microprocessor Interfacing DAC to an 8051 Interface DAC to an   Microwire Interface DAC to an   68HC11 Interface <ul><li>I...
Application Information <ul><li>Internal Reference: </li></ul><ul><li>The internal reference of the DAC7568 does not requi...
Additional Resource <ul><li>For ordering DAC7568, please click the part list or </li></ul><ul><li>Call our sales hotline <...
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Study on 12-/14-/16-Bit, Octal-Channel, DAC

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An Overview study on 12-/14-/16-Bit, Octal-Channel DAC

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  • This is a study on the Texas Instruments 12/14/16 bit octal channel DAC.
  • Welcome to the training module on the 12-bit resolution DAC7568. This training module covers how to interface the DAC to an MCU and application information.
  • The 16-bit DAC8568, 14-bit DAC8168, and 12-bit DAC7568 digital-to-analog converters (DACs) from Texas Instruments target data-acquisition systems, industrial process control, and portable instrumentation. Their internal reference provides temperature drift performance of 2 ppm/°C (typical) up to 5 ppm/°C (maximum) across the entire operating range for twice the accuracy of competitive devices, according to TI. The internal reference, which saves space and cost compared to external references, also offers a high initial accuracy of ±0.004% (typical) and ±0.002% to help eliminate the need for full-scale system calibration.
  • This device Targeting applications such as industrial process control and portable instrumentation, the DAC8568 (16-bit), DAC8168 (14-bit) and DAC7568 (12-bit) digital-to-analog converters (DACs) from TI integrate eight channels in a TSSOP-14 or TSSOP-16 package. Features include a power of 0.56 mW per channel (including internal reference current) and a temperature drift of 2 ppm/°C (typ) up to 5 ppm/ °C (max). The internal reference offers an initial accuracy of ±0.004% (typ); ±0.02% and the output glitch energy is 0.1nV-s.
  • The DAC architecture consists of eight string DACs each followed by an output buffer amplifier The resistor string is simply a string of resistors, each of value R . The code loaded into the DAC register determines at which node on the string the voltage is tapped off to be fed into the output amplifier by closing one of the switches connecting the string to the amplifier. It is monotonic because it is a string of resistors. The output buffer amplifier is capable of generating. rail-to-rail voltages on its output, giving a maximum output range of 0V to AVDD.
  • To enable the internal reference, write the 32-bit serial command When performing a power cycle to reset the device, the internal reference is switched off (default mode). In the default mode, the internal reference is powered down until a valid write sequence is applied to power up the internal reference. If the internal reference is powered up, it automatically powers down when all DACs power down in any of the power-down modes
  • This page gives you serial interface feature that exist in this device. It has 3- wire serial interface Sync, Sclk, Din which are compatible with SPI, Qspi and microwire standards. It has 32-bit shift register which consist of four prefix bits, four control bits, 16 data bits and four feature bits. The data format is straight binary with all &apos;0&apos;s corresponding to 0V output and all &apos;1&apos;s corresponding to full-scale output
  • This page gives information about the different power down modes present in the DAC. There are four power modes which exist here, these modes are selected using the PD1, PD2 bits. Power up selected DAC, Power down selected DAC 1Kohm to GND, 100Kohm to GND, Power down selected DAC High-Z to GND are the different modes.
  • Load regulation is defined as the change in reference output voltage as a result of changes in load current. The load regulation of the internal reference is measured using force and sense contacts The force and sense lines reduce the impact of contact and trace resistance, resulting in accurate measurement of the load regulation contributed solely by the internal reference.
  • The MSP430F449 mC will interface with the DAC8564 using the SPI serial data communication protocol via the MSP430 USART0 port. Only two pins are used from the four-pin SPI mode of configuration. It is implemented this way because there is no need for reading any data back from the DAC8564, or having the MSP430 microcontroller be enslaved by another host peripheral for SPI purposes. Therefore, the STE and the MISO functions in SPI mode of the USART0 port are not used. The DAC8564 receives a 24-bit digital input word serially Because the SPI only provides eight data clocks per transmission, three write cycles are required within the SYNC low period to complete one write cycle to the DAC8564.
  • Here we show the some of the interface between DAC and Microcontroller. In 8051 based MCU we use UART interface connection like TXD, RXD line and SYNC is derived from a programmable port pin. In Microwire connection the data are shifted out on every falling edge of serial clock.
  • This page gives some application information about this device like Internal Reference, Supply voltage, Noise Performance, Thermal Hysteresis.
  • Thank you for taking the time to view this presentation on “ DAC7568 ” . If you would like to learn more or go on to purchase some of these devices, you may either click on the part list link, or simply call our sales hotline. For more technical information you may either visit the Texas Instruments site, or if you would prefer to speak to someone live, please call our hotline number, or even use our ‘live chat’ online facility. You may visit Element 14 e-community to post your questions.
  • Study on 12-/14-/16-Bit, Octal-Channel, DAC

    1. 1. Study on 12-/14-/16-Bit, Octal-Channel, DAC <ul><li>Source: Texas Instruments </li></ul>
    2. 2. Introduction <ul><li>Purpose </li></ul><ul><ul><li>An Overview study on 12-/14-/16-Bit, Octal-Channel DAC </li></ul></ul><ul><li>Outline </li></ul><ul><ul><li>Features and application </li></ul></ul><ul><ul><li>DAC concept, Internal reference </li></ul></ul><ul><ul><li>Serial Interface, power down modes, load regulation, </li></ul></ul><ul><ul><li>MCU Interfacing, Application Diagram. </li></ul></ul><ul><li>Content </li></ul><ul><ul><li>13 pages </li></ul></ul>
    3. 3. Features <ul><li>Relative Accuracy: </li></ul><ul><li>– DAC7568 (12-Bit): 0.3 LSB INL </li></ul><ul><li>– DAC8168 (14-Bit): 1 LSB INL </li></ul><ul><li>– DAC8568 (16-Bit): 4 LSB INL </li></ul><ul><li>Glitch Energy: 0.1nV-s </li></ul><ul><li>Internal Reference: </li></ul><ul><ul><li>2.5V Reference Voltage (disabled by default) </li></ul></ul><ul><ul><li>0.004% Initial Accuracy (typ) </li></ul></ul><ul><ul><li>2ppm/°C Temperature Drift (typ) </li></ul></ul><ul><ul><li>5ppm/°C Temperature Drift (max) </li></ul></ul><ul><ul><li>20mA Sink/Source Capability </li></ul></ul><ul><li>Power-On Reset to Zero Scale or Midscale </li></ul><ul><li>Ultra-Low Power Operation: 1.25mA at 5V Including Internal Reference Current </li></ul><ul><li>Wide Power-Supply Range: +2.7V to +5.5V </li></ul><ul><li>Monotonic Over Entire Temperature Range </li></ul><ul><li>Low-Power Serial Interface with Schmitt-Triggered Inputs: Up to 50MHz </li></ul><ul><li>On-Chip Output Buffer Amplifier with Rail-to-Rail Operation </li></ul><ul><li>Temperature Range: -40°C to +125°C </li></ul>
    4. 4. Applications <ul><li>Portable Instrumentation 234 · </li></ul><ul><li>Closed-Loop Servo-Control/Process </li></ul><ul><li>Control </li></ul><ul><li>Data Acquisition Systems </li></ul><ul><li>Programmable Attenuation, Digital Gain, and Offset Adjustment </li></ul><ul><li>Programmable Voltage and Current Sources </li></ul>
    5. 5. Digital-to-Analog Converter (DAC) Resistor String Device Architecture <ul><li>The DAC architecture consists of eight string DACs each followed by an output buffer amplifier. </li></ul><ul><li>The devices include an internal 2.5V reference with 2ppm/°C temperature drift performance, and offer either 5V or 2.5V full scale output voltage. </li></ul><ul><li>The input coding to the DAC is straight binary, so the ideal output voltage is given by: </li></ul>
    6. 6. Internal Reference Bandgap Reference Simplified Schematic <ul><li>The internal reference is externally available at the VREFIN/VREFOUT pin. </li></ul><ul><li>A minimum 100nF capacitor is recommended between the reference output and GND for noise filtering. </li></ul><ul><li>The internal reference of the DAC is a bipolar, transistor-based, precision bandgap voltage reference. </li></ul><ul><li>The short-circuit current is limited by design to approximately 100mA. </li></ul><ul><li>There are two modes that allow communication with the internal reference: Static and Flexible. In Flexible mode, DB19 must be set to '1'. </li></ul>
    7. 7. Serial Interface <ul><li>The DAC have a 3-wire serial interface SYNC, SCLK, and Din compatible with SPI, QSPI, and Microwire interface standards. </li></ul><ul><li>The DAC input shift register is 32-bits wide, consisting of four prefix bits DB31 to DB28 four control bits (DB27 to DB24), 16 data bits (DB23 to DB4), and four feature bits </li></ul><ul><li>All 32 bits of data are loaded into the DAC under the control of the serial clock input, SCLK. </li></ul>Serial Write Operation timing diagram
    8. 8. Power-Down Modes <ul><li>The DAC have two separate sets of power-down commands. One set is for the DAC channels and the other set is for the internal reference. </li></ul><ul><li>The DAC uses four modes of operation. These modes are accessed by setting control bits C3, C2, C1, and C0, and power-down register bits DB8 and DB9. </li></ul><ul><li>The DAC treats power-down condition as data. All analog channel circuits are shut down when the power-down mode is exercised. </li></ul><ul><li>The contents of the DAC register are unaffected when in power down. </li></ul>DAC Operating Modes Output Stage During Power-Down
    9. 9. Load Regulation Accurate Load Regulation of the DAC <ul><li>Load regulation is defined as the change in reference output voltage as a result of changes in load current </li></ul><ul><li>The load regulation of the internal reference is measured using force and sense contacts </li></ul><ul><li>Force and sense lines should be used for applications that require improved load </li></ul>
    10. 10. Application Diagram of DAC Connecting to MCU <ul><li>The MSP430F449 mC will interface with the DAC8564 using the SPI serial data communication protocol. Only two pins are used from the four-pin SPI mode of configuration. </li></ul><ul><li>The SYNC function is a level-triggered signal that indicates the start of a serial data frame transfer through the SPI bus. </li></ul>
    11. 11. Microprocessor Interfacing DAC to an 8051 Interface DAC to an Microwire Interface DAC to an 68HC11 Interface <ul><li>In Serial interface between 8051MCU and DAC: </li></ul><ul><li>TXD of the 8051 drives SCLK of the DAC. </li></ul><ul><li>RXD drives the serial data line of the device. </li></ul><ul><li>The SYNC signal is derived from a bit-programmable pin on the port of 8051. </li></ul><ul><li>In Microwire Interface Serial data are shifted out on the falling edge of the serial clock and are clocked into the DAC on the rising edge of the SK signal. </li></ul><ul><li>In 68HC11 Interface SCK of the 68HC11 drives the SCLK of the DAC. </li></ul><ul><li>MOSI output drives the serial data line of the DAC. </li></ul><ul><li>The SYNC signal derives from a port line PC7 </li></ul>
    12. 12. Application Information <ul><li>Internal Reference: </li></ul><ul><li>The internal reference of the DAC7568 does not require an external load capacitor for stability because it is stable with any capacitive load. </li></ul><ul><li>For improved noise performance, an external load capacitor of 150nF or larger connected to the V REFH /V REFOUT output is recommended. </li></ul><ul><li>Supply Voltage: </li></ul><ul><li>The internal reference features an extremely low dropout voltage. It can be operated with a supply of only 5mV above the reference output voltage in an unloaded condition. </li></ul><ul><li>Noise Performance: </li></ul><ul><li>Typical 0.1Hz to 10Hz voltage noise can be seen in Internal Reference Noise </li></ul><ul><li>Additional filtering can be used to improve output noise levels. </li></ul><ul><li>The typical noise density for midscale code is 120nV/√Hz at 1kHz and 100nV/√Hz at 1MHz. </li></ul><ul><li>Thermal Hysteresis: </li></ul><ul><li>Thermal hysteresis for a reference is defined as the change in output voltage after operating the device at +25°C. </li></ul>
    13. 13. Additional Resource <ul><li>For ordering DAC7568, please click the part list or </li></ul><ul><li>Call our sales hotline </li></ul><ul><li>For more product information go to </li></ul><ul><ul><li>http://focus.ti.com/docs/prod/folders/print/dac7568.html </li></ul></ul><ul><li>Visit Element 14 to post your question </li></ul><ul><ul><li> www.element-14.com </li></ul></ul><ul><li>For additional inquires contact our technical service hotline or even use our “Live Technical Chat” online facility </li></ul>

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