Forensic Data Logging (Readable via SMBus)

Power Modes

OPERATION

bq6400

• Maximum/minimum cell temperature

• Maximum/minimum pack voltage

• Maximum/minimum cell voltages

• Maximum discharge power

• Last known full capacity of the battery

• Capacity (or SOC) at the time of failure

• Cycle count and/or cumulative number of Ah delivered by the battery

• Battery pack status; being charged, discharged or at rest

• Balancing effort required by each bank of cells to maintain balance

• Cell bank impedance information

• Last ten (10) previous failures causing primary (first level) safety action

• Degree days histogram (time that the battery has spent in a temperature range)

• Voltage Hours – Time for each cell measurement spent above/below safety limits

• Forensic data up-loadable to Host CPU via SMBus (see below)

• Forensic data recording of anomalies and events

• Normal Mode: The bq6400 performs measurements and calculations, makes decisions, and updates internal

data at approximately once per second. All safety circuitry is fully functional in this mode.

• Standby Mode: The bq6400 performs as in normal mode, but at a reduced measurement rate to lower power

consumption at times when the host computer is inactive or the pack is removed from the system. All safety

circuitry remains fully functional in this mode.

• Ship Mode: The bq6400 disables (opens) all the protection MOSFETs, and continues to monitor temperature

and voltage, but at a reduced measurement rate to dramatically lower power consumption. Environmental

data is saved in flash as a part of the historical record. Safety circuitry is disabled in this mode. The device

does not enter this power state as a part of normal operation – it is intended for use after factory

programming and test. Entry occurs only after a unique SMBus command is issued and then only when the

SMBus lines are set to logic low. Exit occurs when the SMBus lines return to an active state.

• Extreme Cell Under-Voltage (ECUV) Shutdown Mode: In this mode, the bq6400 draws minimal current and

the Charge and Discharge protection MOSFETs are disabled (opened). The Pre-Charge MOSFET remains

enabled when a charge voltage is present. Safety circuitry is disabled in this mode. The device does not enter

this mode as a part of normal operation: It enters this state during extreme cell under-voltage conditions

(ECUV). The ECUV threshold is fully programmable below 2.7V.

CURRENT DRAW

STATE

OVER-CURRENT

ENTRY CONDITION

EXIT CONDITION

(TYP)

Active

< 250

µA

Fully active

Normal operation as determined

Firmware directed to operating

by firmware

modes below

Standby

< 150

µA

Fully active

No load current flowing for

Load activity

predetermined time

Ship

< 40

µA

Not active

Protected SMBus command and

Either SMBus line high

SMBus then off (low)

Extreme Cell

< 1

µA

Not active (Pre-Charge

Enabled when Vcell < ECUV

Vcell charge above ECUV

Under-Voltage

enabled)

recovery threshold (2.7V/cell

typical)

The bq6400 Battery Management Controller serves as the master controller for a Li-Ion battery system consisting

of three or four cells in series. Any number may be connected in parallel; other system or safety issues will limit

this to a more practical number. The bq6400 provides extraordinarily precise State-of-Charge gas gauging, and

first and second level pack safety functions. Voltage and current measurements are performed synchronously

and simultaneously for all cells in the pack allowing a level of precision not previously possible in battery

10

Submit Documentation Feedback

Copyright © 2008, Texas Instruments Incorporated

Product Folder Link(s) :bq6400