The ISL95521A 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 together 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 system bus in order to help the adapter provide the system power in Turbo mode. NVDC charger configuration quickly turns on BGATE to enable the battery to help the adapter provide the system power in Turbo mode. The ISL95521A 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 ISL95521A 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 hardware-based adapter current limit and battery-current limit in addition to SMBus programmable limits. The ISL95521A provides a high accuracy adapter current monitor, battery current monitor and system power monitor outputs. To provide maximum flexibility for working with high power 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 ISL95521A 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 4 x 4mm2QFN package.