SBOS321E March   2005  – April 2016 TLV3501 , TLV3502

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
  6. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information: TLV3501
    5. 6.5 Thermal Information: TLV3502
    6. 6.6 Electrical Characteristics
    7. 6.7 Switching Characteristics
    8. 6.8 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Operating Voltage
      2. 7.3.2 Input Overvoltage Protection
    4. 7.4 Device Functional Modes
      1. 7.4.1 Shutdown
  8. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Adding External Hysteresis
    2. 8.2 Typical Application
      1. 8.2.1 Relaxation Oscillator
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
        3. 8.2.1.3 Application Curve
      2. 8.2.2 High-Speed Window Comparator
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Examples
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Development Support
        1. 11.1.1.1 TI Precision Designs
    2. 11.2 Documentation Support
      1. 11.2.1 Related Documentation
    3. 11.3 Related Links
    4. 11.4 Community Resource
    5. 11.5 Trademarks
    6. 11.6 Electrostatic Discharge Caution
    7. 11.7 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

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8 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.

8.1 Application Information

8.1.1 Adding External Hysteresis

The TLV350x has a robust performance when used with a good layout. However, comparator inputs have little noise immunity within the range of a specified offset voltage (±5 mV). For slow-moving or noisy input signals, the comparator output can cause an undesirable switch state as input signals move through the switching threshold. In such applications, the 6 mV of internal hysteresis of the TLV350x might not be sufficient. For greater noise immunity, external hysteresis can be added by connecting a small amount of feedback to the positive input. Figure 17 shows a typical topology used to introduce 25 mV of additional hysteresis, for a total of 31-mV hysteresis when operating from a single 5-V supply. Use Equation 1 to calculate the approximate total hysteresis.

Equation 1. TLV3501 TLV3502 sbos321_eq1.gif

The total hysteresis, VHYST, sets the value of the transition voltage required to switch the comparator output, by enlarging the threshold region, thereby reducing sensitivity to noise.

TLV3501 TLV3502 adding_hyst.gif Figure 17. Adding Hysteresis to the TLV350x

8.2 Typical Application

8.2.1 Relaxation Oscillator

The TLV350x can easily be configured as a simple and inexpensive relaxation oscillator. In Figure 18, the R2 network sets the trip threshold at 1/3 and 2/3 of the supply. Because this circuit is a high-speed circuit, the resistor values are low to minimize the effects of parasitic capacitance. The positive input alternates between 1/3 of V+ and 2/3 of V+, depending on whether the output is low or high. The time to charge (or discharge) is 0.69 × R1C. Therefore, the period is 1.38 × R1C. For 62 pF and 1 kΩ as shown in Figure 18, the output is calculated to 10.9 MHz. An implementation of this circuit oscillated at 9.6 MHz. Parasitic capacitance and component tolerances explain the difference between theory and actual performance.

TLV3501 TLV3502 relaxation_oscillator.gif Figure 18. Relaxation Oscillator

8.2.1.1 Design Requirements

For hysteresis of 1/3 of V+ and threshold levels between 1/3 of V+ and 2/3 of V+, the resistors connected to the comparator positive input must be equal in value. The resistor value must be kept low enough so it does not create additional time constant because of the input capacitor and board parasitic capacitor. The value of the charging resistor, R1, must be relatively low for high-frequency switching without drawing high current and affecting the output high and low level. The value of the charging capacitor must be high enough to avoid errors cause by parasitic capacitance.

8.2.1.2 Detailed Design Procedure

For the positive input, +IN = 1/3 VOUT + 1/3 V+ = 1/3 V+ if VOUT is low and assuming VOL is very close to GND. Or, +IN = 1/3 VOUT + 1/3 V+ = 1/3 V+ = 2/3 V+ if VOUT is high and assuming VOH is very close to V+.

For the negative input, the capacitor charges to 2/3 V+ and discharges to 1/3 V+ exponentially at the same rate with a time constant of R1C.

8.2.1.3 Application Curve

TLV3501 TLV3502 typ_cur_sbos507.gif Figure 19. TLV3501 Device With Upper and Lower Thresholds With 1-V Hysteresis

8.2.2 High-Speed Window Comparator

A window comparator circuit determines when a signal is between two voltages. The TLV3502 can readily be used to create a high-speed window comparator. VHI is the upper voltage threshold, and VLO is the lower voltage threshold. When VIN is between these two thresholds, the output in Figure 20 is high. Figure 21 shows a simple means of obtaining an active low output. The reference levels are connected differently between Figure 20 and Figure 21. The operating voltage range of either circuit is 2.7 V to 5.5 V.

TLV3501 TLV3502 window_comparator_active_high.gif Figure 20. Window Comparator—Active High
TLV3501 TLV3502 window_comparator_active_low.gif Figure 21. Window Comparator—Active Low