SNVS088F May   2004  – April 2016 LM3704

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Pin Configuration and Functions
  5. 5 Specifications
    1. 5.1 Absolute Maximum Ratings
    2. 5.2 ESD Ratings
    3. 5.3 Recommended Operating Conditions
    4. 5.4 Thermal Information
    5. 5.5 Electrical Characteristics
    6. 5.6 Typical Characteristics
  6. 6 Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
      1. 6.3.1 Reset Output
      2. 6.3.2 Reset Threshold
      3. 6.3.3 Manual Reset Input (MR)
      4. 6.3.4 Power-Fail Comparator (PFI/PFO)
      5. 6.3.5 Low-Line Output (LLO)
    4. 6.4 Device Functional Modes
      1. 6.4.1 RESET Output Low
      2. 6.4.2 RESET Output High
  7. 7 Application and Implementation
    1. 7.1 Application Information
    2. 7.2 Typical Application
      1. 7.2.1 Design Requirements
      2. 7.2.2 Detailed Design Procedure
      3. 7.2.3 Application Curves
    3. 7.3 System Examples
  8. 8 Power Supply Recommendations
  9. 9 Layout
    1. 9.1 Layout Guidelines
    2. 9.2 Layout Example
  10. 10Device and Documentation Support
    1. 10.1 Device Support
      1. 10.1.1 Device Nomenclature
    2. 10.2 Community Resources
    3. 10.3 Trademarks
    4. 10.4 Electrostatic Discharge Caution
    5. 10.5 Glossary
  11. 11Mechanical, Packaging, and Orderable Information

Package Options

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

7 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.

7.1 Application Information

The LM3704 is a microprocessor supervisory circuit that provides the maximum flexibility for monitoring power supplies and battery-controlled functions. The reset threshold is typically 3.08 V but can be customized for voltages between 2.2 V and 5 V in 10-mV increments by contacting Texas Instruments. The power-fail input, which is a 1.225-V threshold detector for power-fail warning, can be adjusted using a resistor divider as shown in Figure 11. This section shows various application circuits to provide different monitoring solutions.

7.2 Typical Application

LM3704 10136918.gif Figure 11. Monitoring Two Critical Supplies

7.2.1 Design Requirements

The component count is minimal; employing two resistors as part of a voltage-divider circuit is all that is needed for the typical application of monitoring two critical supplies shown in Figure 11.

7.2.2 Detailed Design Procedure

The voltage-divider circuit that connects to the power-fail reset pin is chosen such that the reset threshold at the device is 1.225 V as shown in Figure 11.

7.2.3 Application Curves

LM3704 monitoring_vin1_reset_snvs088.gif
Standard reset threshold is 3.08 V. Custom reset voltages are available between 2.2 V and 5 V in 10-mV increments by contacting Texas Instruments.
Figure 12. Monitoring VIN1 for Reset Condition
LM3704 monitoring_vin2_reset_snvs088.gif
See Electrical Characteristics for high and low levels of this specific application.
Figure 13. Monitoring VIN2 for Reset Condition

7.3 System Examples

The LM3704 voltage supervisor has various features such as power-fail input detection, low-line output, and manual reset while requiring few to no additional components making it versatile and easy-to-use. See Figure 14 through Figure 18 for a variety of circuit applications.

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LM3704 10136919.gif Figure 14. Monitoring Two Supplies Plus Manual Reset
LM3704 10136921.gif
MR input with its 1.225-V nominal threshold, may monitor an additional supply voltage. An internal 56-kΩ pullup resistor is included on this input.
Figure 16. Microprocessor Supervisor
With Early Warning Detector
LM3704 10136920.gif Figure 15. Monitoring Dual Supplies
Plus External Fault Input
LM3704 10136922.gif Figure 17. Regulator/Switch With Long-Term Overvoltage Lockout
Prevents Overdissipation in Linear Regulator
LM3704 10136931.gif Figure 18. Switch Debouncer