SBOS785B April   2016  – August 2017 TLV2379 , TLV379 , TLV4379

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Device Comparison Table
  6. 6 Pin Configuration and Functions
  7. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information: TLV379
    5. 7.5 Thermal Information: TLV2379
    6. 7.6 Thermal Information: TLV4379
    7. 7.7 Electrical Characteristics: VS = 1.8 V to 5.5 V
    8. 7.8 Typical Characteristics
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Operating Voltage
      2. 8.3.2 Rail-to-Rail Input
      3. 8.3.3 Rail-to-Rail Output
      4. 8.3.4 Capacitive Load and Stability
    4. 8.4 Device Functional Modes
  9. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
      3. 9.2.3 Application Curve
    3. 9.3 System Examples
  10. 10Power Supply Recommendations
    1. 10.1 Input and ESD Protection
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Documentation Support
      1. 12.1.1 Related Documentation
    2. 12.2 Related Links
    3. 12.3 Receiving Notification of Documentation Updates
    4. 12.4 Community Resources
    5. 12.5 Trademarks
    6. 12.6 Electrostatic Discharge Caution
    7. 12.7 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

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

9 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.

9.1 Application Information

When designing for ultra-low power, choose system components carefully. To minimize current consumption, select large-value resistors. Any resistors can react with stray capacitance in the circuit and the input capacitance of the operational amplifier. These parasitic RC combinations can affect the stability of the overall system. Use of a feedback capacitor assures stability and limits overshoot or gain peaking.

9.2 Typical Application

A typical application for an operational amplifier is an inverting amplifier, as shown in Figure 16. An inverting amplifier takes a positive voltage on the input and outputs a signal inverted to the input, making a negative voltage of the same magnitude. In the same manner, the amplifier also makes negative input voltages positive on the output. In addition, amplification can be added by selecting the input resistor RI and the feedback resistor RF.

TLV379 TLV2379 TLV4379 app_sch_sbos785.gif Figure 16. Application Schematic

9.2.1 Design Requirements

The supply voltage must be chosen to be larger than the input voltage range and the desired output range. The limits of the input common-mode range (VCM) and the output voltage swing to the rails (VO) must also be considered. For instance, this application scales a signal of ±0.5 V (1 V) to ±1.8 V (3.6 V). Setting the supply at ±2.5 V is sufficient to accommodate this application.

9.2.2 Detailed Design Procedure

Determine the gain required by the inverting amplifier using Equation 1 and Equation 2:

Equation 1. TLV379 TLV2379 TLV4379 app_eq1_sbos754.gif
Equation 2. TLV379 TLV2379 TLV4379 app_eq2_sbos754.gif

When the desired gain is determined, choose a value for RI or RF. Choosing a value in the kilohm range is desirable for general-purpose applications because the amplifier circuit uses currents in the milliamp range. This milliamp current range ensures the device does not draw too much current. The trade-off is that very large resistors (100s of kilohms) draw the smallest current but generate the highest noise. Very small resistors (100s of ohms) generate low noise but draw high current. This example uses 10 kΩ for RI, meaning 36 kΩ is used for RF. These values are determined by Equation 3:

Equation 3. TLV379 TLV2379 TLV4379 app_eq3_sbos754.gif

9.2.3 Application Curve

TLV379 TLV2379 TLV4379 D125_SBOS754.gif Figure 17. Inverting Amplifier Input and Output

9.3 System Examples

Figure 18 shows the basic configuration for a bridge amplifier using the TLV379.

TLV379 TLV2379 TLV4379 ai_single_amp_bridge_bos785.gif Figure 18. Single Op Amp Bridge Amplifier

Figure 19 shows the TLV2379 used as a window comparator. The threshold limits are set by VH and VL, with VH > VL. When VIN < VH, the output of A1 is low. When VIN > VL, the output of A2 is low. Therefore, both op amp outputs are at 0 V as long as VIN is between VH and VL. This architecture results in no current flowing through either diode, Q1 in cutoff, with the base voltage at 0 V, and VOUT forced high.

If VIN falls below VL, the output of A2 is high, current flows through D2, and VOUT is low. Likewise, if VIN rises above VH, the output of A1 is high, current flows through D1, and VOUT is low.

The window comparator threshold voltages are set using Equation 4 and Equation 5.

Equation 4. TLV379 TLV2379 TLV4379 q_vh_bos785.gif
Equation 5. TLV379 TLV2379 TLV4379 q_vl_bos785.gif
TLV379 TLV2379 TLV4379 ai_window_comp_bos785.gif
1. RIN protects A1 and A2 from possible excess current flow.
2. IN4446 or equivalent diodes.
3. 2N2222 or equivalent NPN transistor.
Figure 19. TLV2379 as a Window Comparator