SLVSA75A July   2010  – August 2015 TPS386596

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
    5. 6.5 Electrical Characteristics
    6. 6.6 Timing Requirements
    7. 6.7 Switching Characteristics
    8. 6.8 Typical Characteristics
  7. 7 Parameter Measurement Information
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Voltage Monitoring
      2. 8.3.2 Manual Reset
      3. 8.3.3 Reset Output
    4. 8.4 Device Functional Modes
  9. 9 Application and Implementation
    1. 9.1 Application Information
      1. 9.1.1 Undervoltage Detection
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
      3. 9.2.3 Application Curves
  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 Development Support
        1. 12.1.1.1 Spice Models
      2. 12.1.2 Device Nomenclature
    2. 12.2 Community Resources
    3. 12.3 Trademarks
    4. 12.4 Electrostatic Discharge Caution
    5. 12.5 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

9.1.1 Undervoltage Detection

The SENSEn inputs provide terminals at which the system voltages can be monitored. If the voltage at any one of the SENSEn pins drops the respective VITn, then the RESET output is asserted. The comparators have a built-in hysteresis to ensure smooth RESET transitions.

It is good analog design practice to use a 1-nF to 10-nF bypass capacitor at the SENSEn input to ground, to reduce sensitivity to transients, layout parasitics, and interference between power rails monitored by this device.

A typical connection of resistor dividers is show in Figure 14. SENSE1 is used to monitor a 3.3-V nominal power-supply voltage with a trip point equal to 2.90 V, and the remaining SENSEn (n = 2, 3, 4) inputs can be used to monitor voltage rails down to 0.4 V. Threshold voltages can be calculated using the following equations.

Equation 1. VMON(2) = (1 + RS2H/RS2L) × 0.4 (V)
Equation 2. VMON(3) = (1 + RS3H/RS3L) × 0.4 (V)
Equation 3. VMON(4) = (1 + RS4H/RS4L) × 0.4 (V)

9.2 Typical Application

Figure 14 shows a typical application for the TPS386956.

TPS386596 AppSch_lvsa75.gifFigure 14. Typical Application Circuit

9.2.1 Design Requirements

This design is intended to monitor the voltage rails for an FPGA. Table 2 summarizes the design requirements.

Table 2. Design Requirements

PARAMETER DESIGN REQUIREMENT
VDD 5 V
VMON(1) 3.3 V –10%
VMON(2) 1.5 V –5%
VMON(3) 1.2 V –5%
VMON(4) 1 V –5%

9.2.2 Detailed Design Procedure

Select the pullup resistors to be 100 kΩ to ensure that VOL ≤ 0.4 V.

Select RSnL = 10 kΩ for all channels to ensure DC accuracy.

Use Equation 1 through Equation 3 to determine the values of RSnH and RS4M. Using standard 1% resistors, Table 3 shows the results:

Table 3. Design Results

RESISTOR VALUE (kΩ)
RS1H 32.4
RS2H 25.5
RS3H 18.7
RS4H 14.3
RS4M 1

9.2.3 Application Curves

TPS386596 D001_SLVSA75.gif
Figure 15. Supply Current vs Supply Voltage
TPS386596 D004_SLVSA75.gif
Figure 17. SENSE1 Threshold and Hysteresis vs Temperature
TPS386596 D006_SLVSA75.gif
Figure 19. SENSE3 Threshold and Hysteresis vs Temperature
TPS386596 D003_SLVSA75.gif
Figure 16. SENSEn Minimum Pulse Width vs SENSEn Threshold Overdrive Voltage
TPS386596 D005_SLVSA75.gif
Figure 18. SENSE2 Threshold and Hysteresis vs Temperature