Power Management BQ24741 Multi-Cell Synchronous Switch-mode Charger With Low Iq and Accurate Trickle Charge

Features

• NMOS-NMOS Synchronous Buck Converter
• Resistor-Programmable Switching Frequency between 300 kHz and 800 kHz
• 8 V-24 V Input Voltage Operation Range
• Cells Pin Support Two to Four Li-Ion Cells up to 18 V Battery Voltage
• Analog Inputs with Ratiometric Programming via Resistors or DAC/GPIO
  • Charge Voltage (4-4.512 V/cell)
  • Charge Current (up to 10 A)
  • Adapter Current Limit for DPM
• High-Accuracy Voltage and Current Regulation
  • ±0.5% Charge Voltage Accuracy
  • ±3% Charge Current Accuracy
  • ±3% Adapter Current Accuracy
  • ±2% Input Current Sense Amp Accuracy
• 150 mA Trickle-charge Current with ±33% Accuracy Down to Zero Battery Voltage
• Safety Protection
  • Input Overvoltage Protection
  • Battery Overvoltage Protection
  • Charger Overcurrent Protection
  • Thermal Shutdown Protection
• Status and Monitoring Outputs
  • Adapter Present Indicator
  • Programmable Input Power Detect with Adjustable Threshold
  • Dynamic Power Management (DPM) with Status Indicator
  • Current Drawn from Input Source
• Charge Enable Pin
• Internal Soft-Start
• Internal Loop Compensation
• 25 ns Minimum Driver Dead-Time and 99.5% Maximum Effective Duty Cycle
• 28-pin, 5x5-mm² QFN package
• Energy Star Low I_q
  • < 10 µA Off-State Battery Discharge Current
  • < 1.5 mA Off-State Input Quiescent Current
• APPLICATIONS
  • Notebook and Ultra-Mobile Computers
  • Portable Data Capture Terminals
  • Portable Printers
  • Medical Diagnostics Equipment
  • Battery Bay Chargers
  • Battery Back-up Systems

Description

The bq24741 is a high-efficiency, synchronous battery charger with integrated compensation, offering low component count for space-constrained Li-ion or Li-polymer battery charging applications. Ratiometric charge current and voltage programming allows high regulation accuracies, and can be either hardwired with resistors or programmed by the system power-management microcontroller using a DAC or GPIOs.

The bq24741 charges two, three, or four series Li+ cells, supporting up to 10 A of charge current, and is available in a 28-pin, 5x5-mm² thin QFN package.

The bq24741 features resistor-programmable PWM switching frequency and accurate 150mA trickle charge (with 20 m sensing resistor), which can be enabled via the TRICKLE pin. The bq24741 also features Dynamic Power Management (DPM) and input power limiting. These features reduce battery charge current when the input power limit is reached to avoid overloading the AC adapter when supplying the load and the battery charger simultaneously. A high-accuracy current sense amplifier enables accurate measurement of input current from the AC adapter, allowing monitoring the overall system power. If the adapter current is above the programmed low-power threshold, a signal is sent to host so that the system optimizes its power performance according to what is available from the adapter.

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