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BQ78350-R1A

SLUSE05 – DECEMBER 2019

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Feature Description (continued)

8.3.7.2 Voltage

The BQ78350-R1A device updates the individual series cell voltages through the BQ769x0 at 1-s intervals. The

BQ78350-R1A device 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-R1A device where they

are scaled and translated into unit mV. The maximum supported input range of the ADC is 6.075 V.

The BQ78350-R1A device 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-R1A 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.

8.3.7.3 Temperature

The BQ78350-R1A device 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.

8.4 Device Functional Modes

The BQ78350-R1A device supports three power modes to optimize the power consumption:

•

In NORMAL mode, the device performs measurements, calculations, protection decisions, and data updates

in 1-s intervals. Between these intervals, the device is in a reduced power mode.

•

In SLEEP mode, the device performs measurements, calculations, protection decisions, and data updates in

adjustable time intervals. Between these intervals, the device is in a reduced power mode.

•

In SHUTDOWN mode, the device is completely powered down.

The device 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 device.

8.5 Programming

8.5.1 Physical Interface

The device uses SMBus 1.1 with packet error checking (PEC) as an option and is used as a slave only.

8.5.2 SMBus Address

The device determines its SMBus 1.1 slave address through a voltage on SMBA, Pin 30. The voltage is set with

a pair of high-value resistors if an alternate address is required and is measured either upon exit of POR or when

system present is detected. ADREN, Pin 29, may be used to disable the voltage divider after use to reduce

power consumption.

8.5.3 SMBus On and Off State

The device detects an SMBus off state when SMBC and SMBD are logic-low for

≥ 2 seconds. Clearing this state

requires either SMBC or SMBD to transition high. Within 1 ms, the communication bus is available.