PowerLAN Communications

Operation Modes

COMPLEMENTARY PRODUCTS

PowerLAN Master Gateway Battery Controller

bq76PL102

PowerLAN communications technology is a patented serial network and protocol designed specifically for battery

management in a multicell environment. PowerLAN is used to initiate and report measurements of cell voltage

and temperature, as well as control cell balancing. Using only a capacitor, PowerLAN isolates voltages from

adjacent bq76PL102 parts to permit high-voltage stack assemblies without compromising precision and

accuracy. PowerLAN is expandable to support up to 12 cells in series, with each bq76PL102 handling two series

cells. PowerLAN provides high ESD standoff and high immunity to noise generated by nearby digital circuitry or

switching currents. Each bq76PL102 has both a PowerLAN serial input and serial output pin. Received data is

buffered and retransmitted, permitting high numbers of nodes without loss of signal fidelity. Signals are

capacitor-coupled between nodes to provide high dc isolation.

The bq76PL102 normally operates in one of two modes: active or standby. The bq76PL102 is normally in

standby mode and consumes typically less than 50

µA. The low-dropout regulator output is still functional in this

mode, as are internal system protection functions (undervoltage, communications timeout, etc.)

When a PowerLAN communications event occurs, then the bq76PL102 transitions to active mode and current

drain increases to 250

µA typically. The bq76PL102 stays in this mode to complete any measurements or

cell-balancing pumping operations. Once activity in this mode ceases, the return to standby is automatic, thus

reducing overall power consumption.

An undervoltage ultralow-current mode is also available when initiated by the bq78PL114 master-gateway battery

controller and when the cell voltages drop below a preset threshold. This mode is used to preserve battery

capacity during long periods of non-use and therefore has a current drain of approximately 1

µA.

Note that cell balancing currents are external to the bq76PL102 and may be sized according to the needs of the

application (typically 10 mA to 1 A). These currents are fixed by the cell-balancing circuitry and only enabled or

disabled by the bq76PL102 (under control of the bq78PL114) to achieve the necessary cell-balance operations.

The bq78PL114 master-gateway battery-management controller with PowerPump cell balancing from Texas

Instruments is the central controller for a complete multicell battery system.

This advanced master-gateway battery controller works with up to 12 series cells monitored by bq76PL102 cell

monitors to provide battery voltage, temperature, current and safety monitoring; state-of-charge and

state-of-health information; system-wide internal PowerLAN communications; as well as external communications

of battery parameters via the industry-standard SMBus interface.

Copyright © 2008–2009, Texas Instruments Incorporated

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