SNVS801B April   2012  – January 2016 DAC101C081 , DAC101C081Q , DAC101C085

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Description (continued)
  6. 6 Device Comparison Table
  7. 7 Pin Configuration and Functions
  8. 8 Specifications
    1. 8.1 Absolute Maximum Ratings
    2. 8.2 ESD Ratings
    3. 8.3 Recommended Operating Conditions
    4. 8.4 Thermal Information
    5. 8.5 Electrical Characteristics
    6. 8.6 AC and Timing Characteristics
    7. 8.7 Typical Characteristics
  9. 9 Detailed Description
    1. 9.1 Overview
    2. 9.2 Functional Block Diagram
    3. 9.3 Feature Description
      1. 9.3.1 DAC Section
      2. 9.3.2 Output Amplifier
      3. 9.3.3 Reference Voltage
      4. 9.3.4 Power-On Reset
      5. 9.3.5 Simultaneous Reset
      6. 9.3.6 Additional Timing Information: toutz
    4. 9.4 Device Functional Modes
      1. 9.4.1 Power-Down Modes
    5. 9.5 Programming
      1. 9.5.1 Serial Interface
      2. 9.5.2 Basic I2C™ Protocol
      3. 9.5.3 Standard-Fast Mode
      4. 9.5.4 High-Speed (Hs) Mode
      5. 9.5.5 I2C Slave (Hardware) Address
      6. 9.5.6 Writing to the DAC Register
      7. 9.5.7 Reading from the DAC Register
    6. 9.6 Registers
      1. 9.6.1 DAC Register
  10. 10Application and Implementation
    1. 10.1 Application Information
      1. 10.1.1 Bipolar Operation
      2. 10.1.2 DSP/Microprocessor Interfacing
        1. 10.1.2.1 Interfacing to the 2-wire Bus
        2. 10.1.2.2 Interfacing to a Hs-mode Bus
    2. 10.2 Typical Application
      1. 10.2.1 Design Requirements
      2. 10.2.2 Detailed Design Procedure
      3. 10.2.3 Application Curve
  11. 11Power Supply Recommendations
    1. 11.1 Using References as Power Supplies
      1. 11.1.1 LM4132
      2. 11.1.2 LM4050
      3. 11.1.3 LP3985
      4. 11.1.4 LP2980
  12. 12Layout
    1. 12.1 Layout Guidelines
    2. 12.2 Layout Example
  13. 13Device and Documentation Support
    1. 13.1 Device Support
      1. 13.1.1 Device Nomenclature
        1. 13.1.1.1 Specification Definitions
    2. 13.2 Related Links
    3. 13.3 Community Resources
    4. 13.4 Trademarks
    5. 13.5 Electrostatic Discharge Caution
    6. 13.6 Glossary
  14. 14Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

10 Application and Implementation

NOTE

Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality.

10.1 Application Information

10.1.1 Bipolar Operation

The DAC101C081 is designed for single supply operation and thus has a unipolar output. However, a bipolar output may be obtained with the circuit in Figure 27. This circuit will provide an output voltage range of ±5 Volts. A rail-to-rail amplifier should be used if the amplifier supplies are limited to ±5 V.

DAC101C081 DAC101C081Q DAC101C085 30052217.gif Figure 27. Bipolar Operation

The output voltage of this circuit for any code is found to be:

Equation 2. VO = (VA × (D / 1024) × ((R1 + R2) / R1) – VA × R2 / R1)

where

With VA = 5 V and R1 = R2,

Equation 3. VO = (10 × D / 1024) – 5 V

A list of rail-to-rail amplifiers suitable for this application are indicated in Table 2.

Table 2. Some Rail-to-Rail Amplifiers

AMP PKGS  Typ VOS Typ ISUPPLY
LMP7701 SOT-23-5 37 uV 0.79 mA
LMV841 SC70-5 50 uV 1 mA
LMC7111 SOT-23-5 0.9 mV 25 µA
LM7301 SO-8
SOT-23-5		 0.03 mV 620 µA
LM8261 SOT-23-5 0.7 mV 1 mA

10.1.2 DSP/Microprocessor Interfacing

Interfacing the DAC101C081 to microprocessors and DSPs is quite simple. The following guidelines are offered to simplify the design process.

10.1.2.1 Interfacing to the 2-wire Bus

Figure 28 shows a microcontroller interfacing to the DAC101C081 via the 2-wire bus. Pullup resistors (Rp) should be chosen to create an appropriate bus rise time and to limit the current that will be sunk by the open-drain outputs of the devices on the bus. Please refer to the I2C™ Specification for further details. Typical pullup values to use in Standard-Fast mode bus applications are 2kΩ to 10kΩ. SCL and SDA series resisters (RS) near the DAC101C081 are optional. If high-voltage spikes are expected on the 2-wire bus, series resistors should be used to filter the voltage on SDA and SCL. The value of the series resistance must be picked to ensure the VIL threshold can be achieved. If used, RS is typically 51Ω.

DAC101C081 DAC101C081Q DAC101C085 30052209.gif Figure 28. Serial Interface Connection Diagram

10.1.2.2 Interfacing to a Hs-mode Bus

Interfacing to a Hs-mode bus is very similar to interfacing to a standard-fast mode bus. In Hs-mode, the specified rise time of SCL is shortened. To create a faster rise time, the master device (microcontroller) can drive the SCL bus high and low. In other words, the microcontroller can drive the line high rather than leaving it to the pullup resistor. It is also possible to decrease the value of the pullup resistors or increase the pullup current to meet the tighter timing specs. Please refer to the I2C Specification for further details.

10.2 Typical Application

DAC101C081 DAC101C081Q DAC101C085 typ_app_SNVS801.gif Figure 29. Pressure Sensor Gain Adjust

10.2.1 Design Requirements

A positive supply only data acquisition system capable of digitizing a pressure sensor output. In addition to digitizing the pressure sensor output, the system designer can use the DAC101C081 to correct for gain errors in the pressure sensor output by adjusting the bias voltage to the bridge pressure sensor.

10.2.2 Detailed Design Procedure

As shown in Equation 4, the output of the pressure sensor is relative to the imbalance of the resistive bridge times the output of the DAC101C081, thus providing the desired gain correction.

Equation 4. Pressure Sensor Output = (DAC_Output × [(R2 / (R1 + R2) – (R4 / (R3 + R4)]

Likewise for the ADC161S626, Equation 5 shows that the ADC output is function of the Pressure Sensor Output times relative to the ratio of the ADC input divided by the DAC101C081 output voltage.

Equation 5. ADC161S626 Output = (Pressure Sensor Output × 100 /(2 × VREF) ) × 216

10.2.3 Application Curve

DAC101C081 DAC101C081Q DAC101C085 30052220.png Figure 30. INL vs Input Code