bq78350-R1

SLUSCD0 – AUGUST 2015

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Feature Description (continued)

9.3.7.1 Current and Coulomb Counting

The integrating delta-sigma ADC (CC) in the companion bq769x0 AFE measures the charge/discharge flow of

the battery by measuring the voltage drop across a small-value sense resistor between the SRP and SRN pins.

The 15-bit integrating ADC measures bipolar signals from –0.20 V to 0.20 V with 15-µV resolution. The AFE

is negative. The bq78350-R1 continuously monitors the measured current and integrates the digital signal from

the AFE over time, using an internal counter.

To support large battery configurations, the current data can be scaled to ensure accurate reporting through the

SMBus. The data reported is scaled based on the setting of the SpecificationInfo() command.

9.3.7.2 Voltage

The bq78350-R1 updates the individual series cell voltages through the bq769x0 at 1-s intervals. The bq78350-

R1 configures the bq769x0 to connect to the selected cells in sequence and uses this information for cell

balancing and individual cell fault functions. The internal 14-bit ADC of the bq769x0 measures each cell voltage

value, which is then communicated digitally to the bq78350-R1 where they are scaled and translated into unit

mV. The maximum supported input range of the ADC is 6.075 V.

The bq78350-R1 also separately measures the average cell voltage through an external translation circuit at the

BAT pin. This value is specifically used for the fuel gauge algorithm. The external translation circuit is controlled

via the VEN pin so that the translation circuit is only enabled when required to reduce overall power

consumption. For correct operation, VEN requires an external pull-up to VCC, typically 100 k.

In addition to the voltage measurements used by the bq78350-R1 algorithms, there is an optional auxiliary

voltage measurement capability via the VAUX pin. This feature measures the input on a 1-s update rate and

provides the programmable scaled value through an SMBus command.

To support large battery configurations, the voltage data can be scaled to ensure accurate reporting through the

SMBus. The data reported is scaled based on the setting of the SpecificationInfo() command.

9.3.7.3 Temperature

The bq78350-R1 receives temperature information from external or internal temperature sensors in the bq769x0

AFE. Depending on the number of series cells supported, the AFE will provide one, two, or three external

thermistor measurements.

9.4 Device Functional Modes

The bq78350-R1 supports three power modes to optimize the power consumption:

•

In NORMAL mode, the bq78350-R1 performs measurements, calculations, protection decisions, and data

updates in 1-s intervals. Between these intervals, the bq78350-R1 is in a reduced power mode.

•

In SLEEP mode, the bq78350-R1 performs measurements, calculations, protection decisions, and data

updates in adjustable time intervals. Between these intervals, the bq78350-R1 is in a reduced power mode.

•

In SHUTDOWN mode, the bq78350-R1 is completely powered down.

The bq78350-R1 indicates through the PWRM pin which power mode it is in. This enables other circuits to

change based on the power mode detection criteria of the bq78350-R1.

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