Linear Battery Charger IC + Boost Converter for Wearable Applications

MP2703 - 26V Input, 1A, Linear Charger with Battery Diagnostics for 1 Cell or 2 Cells
MP28600 - Ultra-Low Quiescent Current, Synchronous Boost Converter

Given that wearables require tiny, low-power chargers, MPS has been working toward ways to deliver this power most effectively. Its design engineers have developed the MP2703, a state-of-the-art, ultra-low power linear charger with power path management. Not only does the MP2703 provide all the benefits of a typical linear charger, but it was designed for ultra-low power products, meaning it can be used for Bluetooth headphones, wearables, and even earbuds. Linear chargers are recommended for wearables because they are cost-effective and boast a simple design. Because linear chargers require fewer components, they enable more straightforward designs with lower manufacturing costs and increased reliability. The disadvantage of linear chargers for some applications is that they dissipate a relatively larger amount of power and thus excess heat. For low-power applications, however, this is not an issue, making linear chargers a well-suited option. The MP2703 was designed to meet the increasing power demands of wearables For example, the European Union’s e-call initiative has required all new cars to have automatic emergency call features. This is a trend that smart devices are starting to include as well; however, this feature can require up to a 12V operating input voltage (VIN). The MP2703 operates with up to 14.4V VIN — this is significantly higher than the standard 6V VIN, making the MP2703 a standout design choice. Its tiny QFN-10 (2mmx2.5mm) package means it can be implemented even for smart rings, versus the larger (3mmx3mm) footprint of competing products.

Another power solution that works well with the MP2703 for wearables applications is the MP28600, a DC/DC synchronous boost converter. The MP28600 steps up, or boosts, VIN to the target output voltage (VOUT), and can be set to down mode when VIN exceeds VOUT. Its tiny SOT563 (1.6mmx1.6mm) package makes it ideal for wearables. It is designed to meet wearables’ growing power demands, where the battery’s output may be below the VIN required to run applications such as GPS or e-call. In these systems, a step-up converter steps up the voltage from a battery output to ensure that there is sufficient power for the receiving device. Even if a wearable is not being actively used, it should be able to turn on and be responsive as soon as it is needed by the user. The MP28600 is ideal for these applications due to its ultra-low quiescent current (IQ); that is, when the product is not actively operating and in standby mode, it consumes very little power. It is important to consider IQ for battery-powered devices such as wearables since a lower IQ correspond with longer times between charges.

Features

• MP2703
  • Up to 26V of Sustainable Voltage
  • Up to 1A of Configurable Charge Current via the ISET Pin
  • ISET Pin Short-Circuit Protection (SCP)
  • Configurable Pre-Charge Current
  • Configurable Termination Current Threshold
  • Memory Selection for 3 Minimum Input Voltage Limit (VIN_LIM) Levels
  • Memory Selection for Battery Regulation Voltage from 2.4V to 4.5V Per Cell
  • 0.5% Battery Regulation Voltage Accuracy
  • Memory Selection for 1-Cell or 2-Cell Batteries
  • Battery Voltage Monitoring Pin
  • Battery Impedance Diagnostics
  • Integrated Chip Junction Temperature (TJ) Regulation
  • Battery Temperature Protection Compliant with JEITA Standard
  • 100nA Battery Leakage Current in Shutdown Mode
  • Down to 3mA Termination Current
  • Charge Status and Fault Indication
  • Input Power Indication
  • Integrated Charge Safety Timer
  • Memory for Miscellaneous Parameters
  • Provides Option to Charge 2-Cell to 6-Cell NiMH Batteries
  • Compatible with LiFePO4 Batteries
  • Available in a Compact QFN-10 (2mmx2.5mm) Package                                                                                                                
• MP28600
  • 0.7V to 5.25V Start-Up Voltage (VST) Range
  • 0.1V to 5.25V Operating Input Voltage (VIN) Range
  • 2.5V to 5.25V Output Voltage (VOUT) Range
  • Constant-Off-Time (COT) Control Mode
  • 600nA Quiescent Current (IQ)
  • 1A Fixed Switching Current Limit
  • 86% Efficiency for 1.5V to 5V/1mA
  • Automatic Switching between Boost Mode and Down Mode
  • True Disconnect during Shutdown
  • 150°C Thermal Shutdown Protection
  • Available in an SOT563 (1.6mmx1.6mm) Package
  • Optimized Performance with MPS Inductor MPL-AT Serie                                                                                                               
• Built-In Memory to Store Custom Configurations.
• Monitoring for Input Voltage (VIN), Output Voltage (VOUT), Output Current (IOUT), Output Power (POUT), and Temperature.
• Protections Including VIN Under-Voltage Lockout (UVLO), Output Over-Voltage Protection (OVP) and Under-Voltage Protection (UVP), OCP_TDC, OCP_SPIKE, and Over-Temperature Protection (OTP).
• Available in a Surface-Mount (27mmx18mmx6mm) Package.

Applications

• Smart wearables