SBVS303B March   2017  – February 2018 TPS3890-Q1

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Typical Application Circuit
      2.      VITN Accuracy vs Temperature
  4. 4 Revision History
  5. 5 Device Comparison Table
  6. 6 Pin Configuration and Functions
    1.     Pin 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
    5. 7.5 Electrical Characteristics
    6. 7.6 Timing Requirements
    7. 7.7 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 User-Configurable RESET Delay Time
      2. 8.3.2 Manual Reset (MR) Input
      3. 8.3.3 RESET Output
      4. 8.3.4 SENSE Input
        1. 8.3.4.1 Immunity to SENSE Pin Voltage Transients
    4. 8.4 Device Functional Modes
      1. 8.4.1 Normal Operation (VDD > VDD(min))
      2. 8.4.2 Above Power-On-Reset But Less Than VDD(min) (VPOR < VDD < VDD(min))
      3. 8.4.3 Below Power-On-Reset (VDD < VPOR)
  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
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Device Support
      1. 12.1.1 Device Nomenclature
    2. 12.2 Documentation Support
      1. 12.2.1 Related Documentation
    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

8.3.4 SENSE Input

The SENSE input can vary from ground to 5.5 V (7.0 V, absolute maximum), regardless of the device supply voltage used. The SENSE pin is used to monitor the critical voltage rail. If the voltage on this pin drops below VITN, then RESET is asserted. When the voltage on the SENSE pin exceeds the positive threshold voltage, RESET deasserts after the user-defined RESET delay time.

The internal comparator has built-in hysteresis to ensure well-defined RESET assertions and deassertions even when there are small changes on the voltage rail being monitored.

The TPS3890-Q1 device is relatively immune to short transients on the SENSE pin. Glitch immunity is dependent on threshold overdrive, as illustrated in Figure 19 for VITN and Figure 18 for VITP. Although not required in most cases, for noisy applications good analog design practice is to place a 1-nF to 10-nF bypass capacitor at the SENSE input to reduce sensitivity to transient voltages on the monitored signal.

The adjustable version (TPS389001-Q1) can be used to monitor any voltage rail down to 1.15 V using the circuit shown in Figure 24.

TPS3890-Q1 ai_threshold_sbvs303.gifFigure 24. Using the TPS389001-Q1 to Monitor a User-Defined Threshold Voltage

The target threshold voltage for the monitored supply (VITx(MON)) and the resistor divider values can be calculated by using Equation 2 and Equation 3, respectively:

Equation 2. VITx(MON)= VITx × (1 + R1 ÷ R2)

Equation 3 can be used to calculate either the negative threshold or the positive threshold by replacing VITx with either VITN or VITP, respectively.

Equation 3. RTOTAL = R1 + R2

Resistors with high values minimize current consumption; however, the input bias current of the device degrades accuracy if the current through the resistors is too low. Therefore, choosing an RTOTAL value so that the current through the resistor divider is at least 100 times larger than the SENSE input current is simplest. See the Optimizing Resistor Dividers at a Comparator Input application report for more details on sizing input resistors.