ISL9208
Multi-Cell Li-ion Battery Pack OCP/Analog Front End

Key Features

• Software selectable overcurrent protection levels and variable protect detection times
• 4 discharge overcurrent thresholds
• 4 short circuit thresholds
• 4 charge overcurrent thresholds
• 8 overcurrent delay times (Charge)
• 8 overcurrent delay times (Discharge)
• 2 short circuit delay times (Discharge)
• Automatic FET turn-off and cell balance disable on reaching external (battery) or internal (IC) temperature limit.
• Automatic override of cell balance on reaching internal (IC) temperature limit.
• Fast short circuit pack shutdown
• Can use current sense resistor, FET r_DS(ON), or Sense FET for overcurrent detection.
• Four battery backed software controlled flags.
• Allows three different FET controls:
• Back-to-back N-Channel FETs for charge and discharge control
• Single N-Channel discharge FET.
• Single N-Channel FET for discharge, with separate, optional (smaller) back-to-back N-channel FETs for charge.
• Integrated Charge/Discharge FET Drive Circuitry with 200µA (typ) turn-on current and 150mA (typ) Discharge FET turn-off current.
• 10% Accurate 3.3V voltage regulator (minimum 25mA out with external NPN transistor having current gain of 70).
• Monitored cell voltage output stable in 100µs.
• Internal Cell balancing FETs handle up to 200mA of balancing current for each cell (with the number of cells being balanced limited by the maximum package power dissipation of 400mW).
• Simple I²C host interface
• Sleep operation with programmable negative edge or positive edge wake-up.
• <10µA Sleep Mode
• Pb-free (RoHS compliant)

Description

The ISL9208 is an overcurrent protection device and analog front end for a microcontroller in a multi-cell Li-ion battery pack. The ISL9208 supports battery pack configurations consisting of 5-cells to 7-cells in series and 1 or more cells in parallel. The ISL9208 provides integral overcurrent protection circuitry, short circuit protection, an internal 3.3V voltage regulator, internal cell balancing switches, cell voltage monitor level shifters, and drive circuitry for external FET devices for control of pack charge and discharge.

Selectable overcurrent and short circuit thresholds reside in internal RAM registers. An external microcontroller sets the thresholds by setting register values through an I²C serial interface. Internal registers also contain the detection delays for overcurrent and short circuit conditions.

Using an internal analog multiplexer the ISL9208 provides monitoring of each cell voltage plus internal and external temperature by a separate microcontroller with an A/D converter. Software on this microcontroller implements all battery pack control functionality, except for overcurrent and short circuit shutdown.

Applications

• Power Tools
• Battery Backup Systems
• E-Bikes
• Portable Test Equipment
• Medical Systems
• Hybrid Vehicle
• Military Electronics