IC Does Management for 14 Series-Connected Li-ion Battery Cells

Renesas Electronics has announced its fourth-generation lithium-ion (Li-ion) battery management IC that offers unmatched lifetime accuracy. The ISL78714 provides accurate cell voltage and temperature monitoring, along with cell balancing and extensive system diagnostics to protect 14-cell Li-ion battery packs while maximizing driving time and range for hybrid and electric vehicles (HEV/MHEV/PHEV/BEV).

The feature-rich ISL78714 monitors and balances up to 14 series connected cells with ±2mV accuracy across automotive temperature ranges, letting system designers make informed decisions based on absolute voltage levels. The ISL78714 includes a precision 14-bit analog-to-digital converter and associated data acquisition circuitry. The device also offers up to six external temperature inputs (two available from GPIOs) and includes fault detection and diagnostics for all key internal functions.

The ISL78714 meets the stringent reliability and performance requirements of battery pack systems for all EV variants including HEV/PHEV, with safety features enabling automotive manufacturers to achieve the ISO 26262 automotive safety integrity level (ASIL D). In addition, the ISL78714 monitors and reads back over/under voltage, temperature, open wire conditions, and fault status for 112 cells in less than 10 ms, or 70 cells in 6.5 ms.

Multiple ISL78714’s can be connected together via a proprietary daisy chain that supports systems up to 420 cells (30 ICs) that provide industry-leading transient and EMC/EMI immunity, exceeding automotive requirements. The ISL78714’s daisy-chain architecture uses low-cost capacitive or transformer isolation, or a combination of both, with twisted pair wiring to stack multiple battery packs together while protecting against hot plug and high voltage transients. A watchdog timer automatically shuts down a daisy-chained IC if communications is lost with the master MCU.

Key Features:

  • Monitors and manages up to 14 cell voltages with ±2mV measurement accuracy
  • Robust two-wire daisy chain communications system using capacitor or transformer coupling up to 1 Mbps
  • Fully differential cell input range of ±5V accommodates fuel cell and bus bar measurement requirements for aging battery packs
  • 15-year board level accuracy (long term drift) of ±6mV at ±6σ
  • High diagnostic coverage for cell voltage and temperature measurements
  • AEC-Q100 Grade-2 qualified and specified for operation from -40°C to +105°C

A battery management system (BMS) reference design is available, which includes five ISL78714 ICs and a RH850/P1M MCU to form a complete 70-cell evaluation platform for external balancing. The reference design kit provides setup and data logging via CAN and UART. Also provided is a GUI, Altium layout files and low-level drivers for the RH850 peripherals and ISL78714. Hardware, software, and interface reference manuals are included, along with an EMC report.

Mass production quantities of the ISL78714 Li-ion battery management IC are available now in a 64-lead TQFP package.

Renesas Electronics | www.renesas.com

 

Bidirectional Buck-Boost Controller Targets Autonomous Vehicles

Analog Devices has announced the Power by Linear LT8708/-1, a 98% efficient bidirectional buck-boost switching regulator controller that operates between two batteries that have the same voltage. This makes them well-suited for redundancy in self-driving cars. The LT8708/-1 operates from an input voltage that can be above, below or equal to the output voltage, making it well suited for two each 12 V, 24 V or 48 V batteries commonly found in electric and hybrid vehicles. It operates between two batteries and prevents system shutdown should one of the batteries fail. The LT8708/-1 can also be used in 48V/12V and 48V/24V dual battery systems.

The LT8708/-1 operates with a single inductor over a 2.8 V to 80 V input voltage range and can produce an output voltage from 1.3 V to 80 V, delivering up to several kilowatts of power depending on the choice of external components and number of phases. It simplifies bidirectional power conversion in battery/capacitor backup systems that need regulation of VOUT, VIN, and/or IOUT, IIN, both in the forward or reverse direction. This device’s six independent forms of regulation allow it to be used in numerous applications.

The LT8708-1 is used in parallel with the LT8708 to add power and phases. The LT8708-1 always operates as a slave to the master LT8708, can be clocked out-of-phase and has the capability to deliver as much power as the master. One or more slaves can be connected to a single master, proportionally increasing power and current capability of the system.

Another application is for an input voltage to power a load, where this same input voltage is used to power a LT8708/-1 circuit that charges a battery or bank of supercapacitors. When the input voltage goes away, the load maintains power without disruption from the battery or supercaps by way of the LT8708’s bidirectional capability.

Forward and reverse current can be monitored and limited for the input and output sides of the converter. All four current limits (forward input, reverse input, forward output and reverse output) can be set independently using four resistors. In combination with the DIR (direction) pin, the chip can be configured to process power from VIN to VOUT or from VOUT to VIN ideal for automotive, solar, telecom and battery-powered systems.

The LT8708 is available in a 5 mm × 8 mm QFN-40 package. Three temperature grades are available, with operation from –40 to 125°C for the extended and industrial grades and a high temp automotive range of –40°C to 150°C.

Pricing for the LT8708/-1 starts at $6.60 (1,000s).

Analog Devices | www.analog.com