SLVSD65A March   2016  – May 2016 TPS3890

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Device Comparison Table
  6. 6 Pin Configuration and 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 Documentation Support
      1. 12.1.1 Related Documentation
    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

The following sections describe in detail how to properly use this device, depending on the requirements of the final application.

9.2 Typical Application

A typical application for the TPS389018 is shown in Figure 25. The TPS389018 can be used to monitor the 1.8-V VDD rail required by the TI Delfino™ microprocessor family. The open-drain RESET output of the TPS389018 is connected to the XRS input of the microprocessor. A reset event is initiated when the VDD voltage is less than VITN or when MR is driven low by an external source.

TPS3890 tc1_tps3808_slvsd65.gif Figure 25. TPS3890 Monitoring the Supply Voltage for a Delfino Microprocessor

9.2.1 Design Requirements

The TPS3890 RESET output can be used to drive the reset (XRS) input of a microprocessor. The RESET pin of the TPS3890 is pulled high with a 1-MΩ resistor; the reset delay time is controlled by the CT capacitor and is set depending on the reset requirement times of the microprocessor. During power-up, XRS must remain low for at least 1 ms after VDD reaches 1.5 V for the C2000™ Delfino family of microprocessors. For 100-MHz operation, the Delfino TMS320F2833x microcontroller uses a supply voltage of 1.8 V that must be monitored by the TPS3890.

9.2.2 Detailed Design Procedure

The primary constraint for this application is choosing the correct device to monitor the supply voltage of the microprocessor. The TPS389018 has a negative threshold of 1.73 V and a positive threshold of 1.74 V, making the device suitable for monitoring a 1.8-V rail. The secondary constraint for this application is the reset delay time that must be at least 1 ms to allow the Delfino microprocessor enough time to startup up correctly. Because a minimum time is required, the worst-case scenario is a supervisor with a high CT charging current (ICT) and a low CT comparator threshold (VCT). For applications with ambient temperatures ranging from –40°C to +125°C, CCT can be calculated using ICT(Max), VCT(MIN), and solving for CCT in Equation 1 such that the minimum capacitance required at the CT pin is 1.149 nF. If standard capacitors with ±20% tolerances are used, then the CT capacitor must be 1.5 nF or larger to ensure that the 1-ms delay time is met.

A 0.1-µF decoupling capacitor is connected to the VDD pin as a good analog design practice and a 1-MΩ resistor is used as the RESET pullup resistor to minimize the current consumption when RESET is asserted. The MR pin can be connected to an external signal if desired or connected to VDD if not used.

9.2.3 Application Curve

TPS3890 D008-SLVSD65-01_Startup_Delay.gif
Figure 26. Startup Delay vs Temperature