SLUSG46 March   2026 BQ25785

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Device Comparison Table
  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 Typical Characteristics BQ2578X
  8. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1  Power-Up Sequence
      2. 7.3.2  MODE Pin Detection
      3. 7.3.3  REGN Regulator (REGN LDO)
      4. 7.3.4  Independent Comparator Function
      5. 7.3.5  Battery Charging Management
        1. 7.3.5.1 Autonomous Charging Cycle
        2. 7.3.5.2 Battery Charging Profile
        3. 7.3.5.3 Charging Termination
        4. 7.3.5.4 Charging Safety Timer
      6. 7.3.6  Temperature Regulation (TREG)
      7. 7.3.7  Vmin Active Protection (VAP) When Battery Only Mode
      8. 7.3.8  Two Level Battery Discharge Current Limit
      9. 7.3.9  Fast Role Swap Feature
      10. 7.3.10 CHRG_OK Indicator
      11. 7.3.11 Input and Charge Current Sensing
      12. 7.3.12 Input Current and Voltage Limit Setup
      13. 7.3.13 Battery Cell Configuration
      14. 7.3.14 Device HIZ State
      15. 7.3.15 USB On-The-Go (OTG)
      16. 7.3.16 Quasi-dual Phase Converter Operation
      17. 7.3.17 Continuous Conduction Mode (CCM)
      18. 7.3.18 Pulse Frequency Modulation (PFM)
      19. 7.3.19 Switching Frequency and Dithering Feature
      20. 7.3.20 Current and Power Monitor
        1. 7.3.20.1 High-Accuracy Current Sense Amplifier (IADPT and IBAT)
        2. 7.3.20.2 High-Accuracy Power Sense Amplifier (PSYS)
      21. 7.3.21 Input Source Dynamic Power Management
      22. 7.3.22 Integrated 16-Bit ADC for Monitoring
      23. 7.3.23 Input Current Optimizer (ICO)
      24. 7.3.24 Two-Level Adapter Current Limit (Peak Power Mode)
      25. 7.3.25 Processor Hot Indication
        1. 7.3.25.1 PROCHOT During Low Power Mode
        2. 7.3.25.2 PROCHOT Status
      26. 7.3.26 Device Protection
        1. 7.3.26.1  Watchdog Timer (WD)
        2. 7.3.26.2  Input Overvoltage Protection (ACOV)
        3. 7.3.26.3  Input Overcurrent Protection (ACOC)
        4. 7.3.26.4  System Overvoltage Protection (SYSOVP)
        5. 7.3.26.5  System Voltage Maximum Regulation (SYS_MAX)
        6. 7.3.26.6  Battery Overvoltage Protection (BATOVP)
        7. 7.3.26.7  Battery Charge Overcurrent Protection (BATCOC)
        8. 7.3.26.8  Battery Discharge Overcurrent Protection (BATDOC)
        9. 7.3.26.9  BATFET Charge Current Clamp Protection Under LDO Regulation Mode
        10. 7.3.26.10 Sleep Comparator Protection Between VBUS and ACP_A (SC_VBUSACP)
        11. 7.3.26.11 REGN Power Good Protection (REGN_PG)
        12. 7.3.26.12 System Under Voltage Lockout (VSYS_UVP) and Hiccup Mode
        13. 7.3.26.13 OTG Mode Over Voltage Protection (OTG_OVP)
        14. 7.3.26.14 OTG Mode Under Voltage Protection (OTG_UVP)
        15. 7.3.26.15 Thermal Shutdown (TSHUT)
    4. 7.4 Device Functional Modes
      1. 7.4.1 Forward Mode
        1. 7.4.1.1 System Voltage Regulation with Narrow VDC Architecture
        2. 7.4.1.2 Battery Charging
      2. 7.4.2 USB On-The-Go Mode
      3. 7.4.3 Pass Through Mode (PTM)-Patented Technology
      4. 7.4.4 Learn Mode
    5. 7.5 Programming
      1. 7.5.1 SMBus Interface
        1. 7.5.1.1 SMBus Write-Word and Read-Word Protocols
        2. 7.5.1.2 Timing Diagrams
    6. 7.6 BQ25785 Register Map
    7. 7.7 BQ25785 Registers
  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 Input Snubber and Filter for Voltage Spike Damping
        2. 8.2.2.2 ACP-ACN Input Filter
        3. 8.2.2.3 Inductor Selection
        4. 8.2.2.4 Input Capacitor
        5. 8.2.2.5 Output Capacitor
        6. 8.2.2.6 Power MOSFETs Selection
      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
        1. 8.4.2.1 Layout Example Reference Top View
  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 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

7.1 Overview

The BQ25785 is a Narrow VDC buck-boost charger controller for portable electronics such as notebook, detachable, ultrabook, tablet, and other mobile devices with rechargeable batteries. The device provides a seamless transition between different converter operation modes (buck, boost, or buck-boost), fast transient response, and high light load efficiency.

The BQ25785 supports a wide range of power sources, including USB-C PD EPR ports, legacy USB ports, traditional AC-DC adapters, and so forth. The device takes an input voltage from 3.5V to 40V and charges a battery of 2cell to 5cell in series. In the absence of an input source, the BQ25785 supports the USB On-the-Go (OTG) function from a 2cell to 5cell battery to generate an adjustable 3V to 38V at the USB port with 20mV resolution.

When only the battery powers the system and no external load is connected to the USB OTG port, the BQ25785 provides the Vmin Active Protection (VAP) feature. In VAP operation, the BQ25785 first charges up the voltage of the input decoupling capacitors at VBUS to store a certain amount of energy. During the system peak power spike, the huge current drawn from the battery introduces a larger voltage drop across the impedance from the battery to the system. The energy stored in the input capacitors supplement the system, to prevent the system voltage from dropping below the minimum system voltage and leading the system to a black screen. This VAP is designed to absorb system power peaks during the periods of high demand to improve system turbo performance, which is highly recommended by Intel for the platforms with a 2S battery.

The BQ25785 features Dynamic Power Management (DPM) to limit input power and avoid AC adapter overloading. During battery charging, as system power increases, charging current is reduced to maintain total input current below adapter rating. If system power demand temporarily exceeds adapter rating, the BQ25785 supports the NVDC architecture to allow battery discharge energy to supplement system power.

The BQ25785 monitors adapter current, battery current, and system power. The flexibility of the programmable PROCHOT output goes directly to the CPU for throttling back when needed.

The latest version of the USB-C PD specification includes Fast Role Swap (FRS) to verify that power role swapping occurs in a timely fashion so that the device or devices connected to the dock never experience momentary power loss or glitching. The device integrates FRS with compliance to the USB-C PD specification.

The TI-patented switching frequency dithering pattern can significantly reduce EMI noise over the entire conductive EMI frequency range (150kHz to 30Mhz). Multiple dithering scale options are available to provide flexibility for different applications to simplify EMI noise filter design.

To be compliant with Intel IMVP8 / IMVP9, the BQ25785 includes a PSYS function to monitor the total platform power from the adapter and battery. Besides PSYS, the device provides both an independent input current buffer (IADPT) and a battery current buffer (IBAT) with highly accurate current sense amplifiers. If the platform power exceeds the available power from the adapter and battery, a PROCHOT signal is asserted to the CPU so that the CPU optimizes the performance for the power available to the system.

The SMBus host controls input current, charge current, and charge voltage registers with high resolution, high accuracy regulation limits. The interface also sets the PROCHOT timing and threshold profile to meet system requirements.