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Hybrid Power Boost (HPB) and Narrow VDC (NVDC) Combo Battery Charger with SMBus Interface

Product Status: Mass Production


The ISL95521B is a highly versatile combo battery charger configurable for operating as either a Hybrid Power Boost (HPB) charger or a Narrow VDC (NVDC) charger, supporting 2-, 3-, or 4-cell batteries. Both configurations allow the battery to work with the adapter to supply the system load when it exceeds the adapter capability, referred to as system Turbo mode. The HPB charger configuration reverse-boosts battery energy to the system bus to help the adapter provide the system power in Turbo mode. The NVDC charger configuration quickly turns on BGATE to enable the battery to help the adapter provide the system power in Turbo mode.

The ISL95521B uses N-channel MOSFETs (NFETs) for all the switches to achieve the best performance and lowest BOM cost. The internal charge pump is capable of turning on all the NFETs fast or slow, depending on the circumstance or the need. The ability to quickly turn on NFETs prevents system bus voltage drop when the battery is suddenly removed in Turbo mode or in Battery Learn mode.

The ISL95521B provides many protection features including a PROCHOT# indicator for system low voltage, adapter overcurrent, battery overcurrent, or overheating, with an array of SMBus programmable parameters for maximum flexibility. It also features a hardware-based adapter-current limit and battery-current limit in addition to SMBus programmable limits.

The ISL95521B provides a high accuracy adapter current monitor, battery current monitor, and system power monitor outputs. To provide maximum flexibility for working with high and low power systems, it provides several configurable current-sense resistor value options to achieve the best trade-off of current sensing accuracy vs power loss.

The ISL95521B uses the Renesas Robust Ripple Regulator (R3™) modulation scheme to provide excellent light-load efficiency and fast dynamic response. It is available in a 32 Ld 4x4mm2 QFN package.


  • Configurable as an HPB charger or NVDC charger
  • Compliant with Intel PROCHOT# and PSYS requirements
  • Adapter current monitor and battery discharging current monitor
  • Uses NFET for all the switches
  • Supports battery removal during Battery Learn mode
  • Actively controlled inrush current to prevent FET damage
  • SMBus programmable settings and high accuracy
  • Comprehensive protection features include:
  • PROCHOT# indicator for system low voltage, adapter overcurrent, battery overcurrent, or system overheating
  • Hardware-based adapter current and battery current limits
  • Supports sudden battery removal in system Turbo mode
  • 16 switching frequency options from 350kHz to 1MHz
  • Low quiescent current
  • SMBus and auto-increment I2C compatible
  • Renesas Robust Ripple Regulator (R3) modulation scheme provides excellent light-load efficiency and fast dynamic response
  • 32 Ld 4x4mm2 QFN package
  • Pb-free (RoHS compliant)


 Block Diagram


Basic Information
Production Status
Mass Production
Input Voltage Min (V)
Input Voltage Max (V)
Input Current Limit Accuracy (%)
Battery Charge Voltage (V)
2-4 cell battery, 16mV step
Charging Voltage Accuracy Max (%)
Battery Charge Voltage Adjust (%)
16mV steps
Charge Current Limit Accuracy (%)
Trickle Charge Current Limit Accuracy (%)
256mA, 128mA or 64mA
Automatic Trickle Charge Typ (V)
Set by user
Battery Leakage Current Max (μA)
Automatic Power Source Selection
DC Adapter Detection
R3 modulator
Switching Frequency Typ (kHz)
350 to 1000
Audible Noise
Thermal Shutdown (°C)
155 °C
Battery Chemistry
Multi-Cell Li+/Polymer
Qualification Level
Input Voltage Range (V)
4.75 to 25
Can Sample
Temperature Range
-40 to +85

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