SNVSBZ2E March   2021  – December 2023 TPS3704

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Device Nomenclature
  6. 5 Pin Configuration and Functions
  7. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 Timing Requirements
    7. 6.7 Timing Diagrams
    8. 6.8 Typical Characteristics
  8. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 VDD
      2. 7.3.2 SENSEx Input
        1. 7.3.2.1 Immunity to SENSEx Pins Voltage Transients
          1. 7.3.2.1.1 SENSEx Hysteresis
      3. 7.3.3 RESETx/RESETx
    4. 7.4 Device Functional Modes
      1. 7.4.1 Normal Operation (VDD > VDD(MIN))
      2. 7.4.2 Undervoltage Lockout (VPOR < VDD < UVLO)
      3. 7.4.3 Power-On Reset (VDD < VPOR)
  9. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Voltage Threshold Accuracy
      2. 8.1.2 Adjustable Voltage Thresholds
    2. 8.2 Typical Application
      1. 8.2.1 Design 1: Multi-Rail Window Monitoring for Microcontroller Power Rails
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
      2. 8.2.2 Design 2: Manual Self-Test Option for Enhanced Functional Safety Use Cases
        1. 8.2.2.1 Design Requirements
        2. 8.2.2.2 Detailed Design Procedure
      3. 8.2.3 Application Curves
    3. 8.3 Power Supply Recommendations
      1. 8.3.1 Power Supply Guidelines
    4. 8.4 Layout
      1. 8.4.1 Layout Guidelines
      2. 8.4.2 Layout Example
  10. 9 Device and Documentation Support
    1. 9.1 Device Nomenclature
    2. 9.2 Receiving Notification of Documentation Updates
    3. 9.3 Support Resources
    4. 9.4 Trademarks
    5. 9.5 Electrostatic Discharge Caution
    6. 9.6 Glossary
  11. 10Revision History
  12. 11Mechanical, Packaging, and Orderable Information

Package Options

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

8.1.2 Adjustable Voltage Thresholds

The TPS3704x maximum accuracy (1%) allows for adjustable voltage thresholds using external resistors without adding major inaccuracies to the device. In case that the desired monitored voltage is not available, external resistor dividers can be used to set the desired voltage thresholds. Figure 8-2 illustrates an example of how to adjust the voltage threshold with external resistor dividers. For assistance in calulating the external resistors access the TPS3704 adjustable threshold voltage resistor calculator in the Design Tools and Simulation section of the TPS3704 product page. The resistors can be calculated depending on the desired voltage threshold and device part number. TI recommends using an adjustable voltage threshold device variant because of the bypass mode of internal resistor ladder.

For example, consider a 2.0 V rail being monitored (VMON) using the TPS3704 0.8 V adjustable variant. Using Equation 2, R1 = 15 kΩ given that R2 = 10 kΩ, VMON = 2 V, and VSENSE1 = 0.8 V. This device is typically meant to monitor a 0.8 V rail with ±4% voltage thresholds. This means that the device undervoltage threshold (VIT-(UV)) and overvoltage threshold (VIT+(OV)) is 0.768 V and 0.832 V respectively. Using Equation 2, VMON = 1.92 V when VSENSE1 = VIT-(UV). This can be denoted as VMON-, the monitored undervoltage threshold where the device will assert a reset signal. Using Equation 2 again, the monitored overvoltage threshold (VMON+) = 2.08 V when VSENSE1 = VIT+(OV). If a wider tolerance or UV only threshold is desired, use a device variant shown on
Table 9-3 to determine what device part number matches your application.

Equation 2. VSENSE1 = VMON × (R2 / (R1 + R2))

There are inaccuracies that must be taken into consideration while adjusting voltage thresholds. Aside from the tolerance of the resistor divider, there is an internal resistance of the SENSE1 pin that may affect the accuracy of the resistor divider. Although expected to be very high impedance, users are recommended to calculate the values for design specifications. The internal sense resistance RSENSE1 can be calculated by the sense voltage VSENSE1 divided by the sense current ISENSE1 as shown in Equation 4. VSENSE1 can be calculated using
Equation 2 depending on the resistor divider and monitored voltage. ISENSE1 can be calculated using Equation 3.

Equation 3. ISENSE1 = [(VMON – VSENSE1) / R1] – (VSENSE1 / R2)
Equation 4. RSENSE1 = VSENSE1 / ISENSE1
GUID-20210202-CA0I-LZZW-M3HV-HZ4F32L211J5-low.svg Figure 8-2 Adjustable Voltage Threshold with External Resistor Dividers