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Chemical battery boost-buck charge control scheme based on TI's BQ25703A I2C

The program is mainly developed based on TI BQ25703A. The article will mainly introduce the related attributes of BQ25703A and evaluation module bq2570x EVM. An in-depth understanding of the BQ25703A and its related components will help us understand the use of the program.
Solution Introduction

1.The  introduction of BQ25703A 

The BQ25703A is a synchronous NVDC battery buck-boost charge controller, offering low component count, high efficiency solution for space-constraint, multi-chemistry battery charging applications.

The NVDC-1 configuration allows the system to be regulated at battery voltage, but not drop below system minimum voltage. The system keeps operating even when the battery is completely discharged or removed. 

When load power exceeds input source rating, the battery goes into supplement mode and prevents the input source from being overloaded.

The BQ25703A charges battery from a wide range of input sources including USB adapter, high voltage USB PD sources and traditional adapters.During power up, the charger sets converter to buck, boost or buck-boost configuration based on input source and battery conditions. 

The charger automatically transits among buck, boost and buck-boost configuration without host control.

In the absence of an input source, the BQ25703A supports On-the-Go (OTG) function from 1- to 4-cell battery to generate 4.48 V to 20.8 V on VBUS. During OTG mode, the charger regulates output voltage and output current.

The BQ25703A monitors adapter current, battery current and system power. The flexibly programmed PROCHOT output goes directly to CPU for throttle back when needed.


BQ25703A typical application circuit diagram

BQ25703A typical application circuit diagram



FEATURES OF BQ25703A

Charge 1- to 4-Cell Battery From Wide Range of Input Sources

.3.5-V to 24-V Input Operating Voltage

.Supports USB2.0, USB 3.0, USB 3.1 (Type C), and USB_PD Input Current Settings

.Seamless Transition Between Buck and Boost Operation

.Input Current and Voltage Regulation (IDPM and VDPM) Against Source Overload

.Power/Current Monitor for CPU Throttling

.Comprehensive PROCHOT Profile, IMVP8 Compliant

.Input and Battery Current Monitor

.System Power Monitor, IMVP8 Compliant

.Narrow-VDC (NVDC) Power Path Management

.Instant-On With No Battery or Deeply Discharged Battery
.Battery Supplements System When Adapter is Fully-Loaded
.Ideal Diode Operation in Supplement Mode
.Power Up USB Port From Battery (USB OTG)
.Output 4.48-V to 20.8-V Compatible With USB PD
.Output Current Limit up to 6.35 A
.800-kHz or 1.2-MHz Programmable Switching frequency for 1-µH to 2.2-µH Low Profile Inductor
.Host Control Interface for Flexible System Configuration
.I2C (bq25703A) Port for Optimal System Performance and Status Reporting
.Hardware Pin to Set Input Current Limit Without EC Control
.High Accuracy Regulation and Monitor
.±0.5% Charge Voltage Regulation ±5% Power Monitor
.±2% Input/Charge Current Regulation
.±2% Input/Charge Current Monitor  
.Input, System, Battery Overvoltage Protection
.MOSFET Inductor Overcurrent Protection
.Low Battery Quiescent Current
.Input Current Optimizer (ICO) to Extract Max Input Power
.Charge Any Battery Chemistry: Li+, LiFePO4, NiCd, NiMH, Lead Acid
.Package: 32-Pin 4 × 4 WQFN
BQ25703A Applications
.Drones, Bluetooth® speakers, IP cameras, detachable and tablet PCs, and power banks
.Industrial and medical equipment
.Portable equipment with rechargeable batteries

Introduction of the BQ25700AEVM-732 and BQ25703AEVM-732 evaluation modules (EVM)

The BQ25700AEVM-732 and BQ25703AEVM-732 evaluation modules (EVM)are SMBus or I2C-controlledNVDC-1 buck boost charger. 

The input voltage range is between 3.5 V and 24 V, with a programmableoutput of 1–4 cells and a charge output current range of 64 mA to 8.128 A. 

This EVM does not include theEV2400 interface device; the EV2400 must be ordered separately to evaluate the BQ2570X EVM.

The BQ2570X evaluation modules are complete charger modules for evaluating an SMBUS or I2Ccontrolledbuck boost charge using the BQ2570X devices.

The BQ2570X EVM does not include the EV2400 interface board. To evaluate the BQ2570X EVM, order anEV2400 interface board separately.

The BQ2570X is a synchronous NVDC-1 battery buck boost charge controller, offering a low componentcount, high efficiency solution for space-constrained, multi-chemistry battery charging applications.

The NVDC-1 configuration allows the system to be regulated at the battery voltage, but not drop below thesystem minimum voltage. The system keeps operating even when the battery is completely discharged orremoved. When load power exceeds the input source rating, the battery supplement mode prevents theinput source from being overloaded.The BQ2570X charges the battery from a wide range of input sources including a 5-V USB adapter to ahigh-voltage USB PD source and traditional adapters.

During power up, the charger sets the converter to buck, boost, or buck-boost configuration based on theinput source and battery conditions. During the charging cycle, the charger automatically transits amongbuck, boost, and buck-boost configuration without host control.

The BQ2570X monitors adapter current, battery current, and system power. 


FEATURES 
• Evaluation module for the BQ2570X devices
• Supports 3.5- to 24-V input source
  – 3.5- to 24-V, 0- to 6-A input operating range and 1–4 cell battery configuration
  – Supports USB2.0, USB 3.0, USB 3.1 (USB Type-C™) and USB_PD
  – Supports USB OTG with 4.48- to 20.8-V adjustable output
  – Maximum Power Tracking by Input Voltage and Current Regulation

• Narrow VDC (NVDC) power path management

  – Instant-on works with no battery or deeply discharged battery (PG1.0 needs charge-enablecommand)
  – Battery supplements system when adapter is fully-loaded

• 800-kHz or 1.2-MHz switching frequency for low profile inductor

• SMBus (bq25700A) or I2C (bq25703A) port for optimal system performance and status reporting
• Power and Current Monitor for CPU Throttling
• Safety
  – Thermal shutdown
  – Input and system overvoltage protection
  – MOSFET overcurrent protection
• Accelerate charge time by battery path impedance compensation
• Charge status outputs for LED or host processor
• Maximum power tracking capability by input voltage regulation
• Test points for key signals available for testing purposes. Easy probe hook-up.

• Jumpers available. Easy-to-change connections.



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Key Components
No. Part Number Manufacturer
1 BQ25703ARSNT TI
2 BQ25703AEVM-732 TI
3 WP92420L1 TI
4 WP92420 TI