SLVSHK6A March   2025  – March 2026 TPS61381-Q1

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Pin Configuration and Functions
  6. 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 I2C Timing Characteristics
    7. 5.7 Typical Characteristics
  7. 6 Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
      1. 6.3.1 VCC Power Supply and UVLO Logic
      2. 6.3.2 Enable or Shutdown
      3. 6.3.3 Device Operating Modes and Control Logic
      4. 6.3.4 Status Indicator IO (STATUS Pin)
      5. 6.3.5 Thermal Shutdown
    4. 6.4 Charger Feature Description
      1. 6.4.1 Charger Enable
      2. 6.4.2 LDO Charger
      3. 6.4.3 NiMH Battery Charging Profile
      4. 6.4.4 Lithium Battery Charging Profile
      5. 6.4.5 Super Capacitor Charging Profile
      6. 6.4.6 Battery Cold, Hot Temperature (TS Pin)
      7. 6.4.7 Charger Protection and Fault Condition Indication
    5. 6.5 Boost Feature Description
      1. 6.5.1 Enable and Start up
        1. 6.5.1.1 Automatic Transition into Boost Mode
        2. 6.5.1.2 Manual Transition into Boost Mode
      2. 6.5.2 Down Mode
      3. 6.5.3 Output Short- to-Ground Protection
      4. 6.5.4 Boost Control Loop
      5. 6.5.5 Current Limit Operation
      6. 6.5.6 Functional Modes at Light Load
        1. 6.5.6.1 Auto PFM Mode
        2. 6.5.6.2 Forced PWM Mode
      7. 6.5.7 Duty Cycle Limitation
      8. 6.5.8 BUB Voltage Loop
      9. 6.5.9 Spread Spectrum
    6. 6.6 Battery State-of-Health (SOH) Detection Feature Description
      1. 6.6.1 SOH Mode Operation
      2. 6.6.2 Multi-Signal Output in AVI Pin
      3. 6.6.3 Calculate Impedance of BUB
    7. 6.7 I2C Serial Interface
      1. 6.7.1 Data Validity
      2. 6.7.2 START and STOP Conditions
      3. 6.7.3 Byte Format
      4. 6.7.4 Acknowledge (ACK) and Not Acknowledge (NACK)
      5. 6.7.5 Slave Address and Data Direction Bit
      6. 6.7.6 Single Read and Write
      7. 6.7.7 Multi-Read and Multi-Write
  8. 7 Register Maps
    1. 7.1  Register 00H: CHIP_ID
    2. 7.2  Register 01H: BOOST_SET1
    3. 7.3  Register 02H: BOOST_SET2
    4. 7.4  Register 03H: BOOST_SET3
    5. 7.5  Register 04H: CHGR_SET1
    6. 7.6  Register 05H: CHGR_SET2
    7. 7.7  Register 06H: CHGR_SET3
    8. 7.8  Register 07H: CHGR_SET4
    9. 7.9  Register 08H: CHGR_STATUS
    10. 7.10 Register 09H: SOH_SET1
    11. 7.11 Register 0AH: SOH_SET2
    12. 7.12 Register 0BH: CONTROL_STATUS
    13. 7.13 Register 0CH: FAULT_CONDITION
    14. 7.14 Register 0DH: STATUS_PIN_SET
    15. 7.15 Register 0EH: SW_RST
  9. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1 Selecting the External MOSFET
        2. 8.2.2.2 Inductor Selection
        3. 8.2.2.3 Capacitor in Back-Up Battery Side
        4. 8.2.2.4 Selecting the Output Capacitor
        5. 8.2.2.5 Loop Stability and Compensation Design
          1. 8.2.2.5.1 Small Signal Analysis
          2. 8.2.2.5.2 Loop Compensation Design
      3. 8.2.3 Application Curves
    3. 8.3 Power Supply Recommendations
    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 Support
      1. 9.1.1 Third-Party Products Disclaimer
    2. 9.2 Documentation Support
      1. 9.2.1 Related Documentation
    3. 9.3 Receiving Notification of Documentation Updates
    4. 9.4 Support Resources
    5. 9.5 Trademarks
    6. 9.6 Electrostatic Discharge Caution
    7. 9.7 Glossary
  11. 10Revision History
  12. 11Mechanical, Packaging, and Orderable Information

8.2.2.4 Selecting the Output Capacitor

Main consideration for designing the output capacitor is the requirements for the output voltage drop when main battery fails and the device transition into boost mode. The minimum Cout can be calculated by:

Equation 11. C o u t > I o u t m a x × 20 u s Δ V o u t m a x

Where

• COUT is the output capacitance

• IOUTMAX is the maximum output current

• ΔVOUTMAX is the maximum output voltage drop allowed when transition into boost mode

20us is the maximum transition time for the device to enter boost mode and start switching

The output ripple voltage another factor that affects the Cout selection. Assuming a capacitor with zero ESR, the minimum capacitance needed for a given ripple can be calculated by

Equation 12. C o u t > I o u t m a x × ( V o u t - V B U B ) f s w × Δ V × V o u t

Where

• IOUT is the output current

• VOUT is the output DC voltage

• VBUB is the backup battery voltage

• ΔV is the output voltage ripple required

• fswis the switching frequency

Typically, a combination of ceramic capacitors and bulk electrolytic capacitors is needed to provide low ESR, high ripple current, and small output voltage ripple.

Ceramic capacitors has DC-bias derating that significantly reduce the effective capacitance when a DC-voltage is applied. So please check the DC-bias curve at Boost Vout target voltage when calculating the capacitance.

Electrolytic capacitors has large ESR and the ESR of electrolytic capacitor can increase by over 10 times under low temperature condition and seriously affect loop stability. So please make sure low temperature ESR is considered when calculating loop stability. Poly-hybrid capacitors usually has smaller ESR under low temperature and is therefore more recommended.

Based on the application requirement, this application choose 100uF electrolytic capacitor with four 10uF ceramic capacitors in parallel.