bq78350-R1

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SLUSCD0 – AUGUST 2015

To calculate the External Temp Model coefficients, use the bq78350-R1 Family Thermistor Coefficient

Calculator shown in the application note, Using the bq78350 (SLUA726).

For improved accuracy, offset calibration is available for this value and can be managed through the bqSTUDIO

tool. The procedure for calibration is described in the bq78350-R1 Technical Reference Manual (SLUUBD3) in

the "Calibration" chapter.

10.2.3.2 Gas Gauging

The default battery chemistry (Chem ID) is 1210, which is a Li-CoO2 type chemistry. Other secondary Li-Ion

based Chem IDs can be obtained from MathCAD Chemistry Selection Tool (SLUC138).

The default maximum capacity of the battery is 4400 mAh and this should be changed based on the cell and

battery configuration chosen.

QMAX = Design Capacity of the Cell × # of parallel cells

Where: Design Capacity of the Cell can be taken from the manufacturer data sheet.

The CEDV gas gauging algorithm requires seven coefficients to enable accurate gas gauging. The default values

are generic for Li-CoO2 chemistry, but for accurate gas gauging these coefficients should be re-calculated. The

procedure

to

gather

the

required

data

and

generate

the

coefficients

can

be

found

at

http://www.ti.com/tool/GAUGEPARCAL.

10.2.3.3 Charging

The charging algorithm in the bq78350-R1 is configured to support Constant Voltage/Constant Current (CC/CV)

charging of a nominal 18-V, 4400-mAh battery.

10.2.3.3.1

Fast Charging Voltage

The charging voltage is configured (Fast Charging: Voltage) based on an individual cell basis (for example, 4200

mV), but the ChargingVoltage() is reported as the required battery voltage (for example, 4200 mV × 5 =

21000 mV).

10.2.3.3.2

Fast Charging Current

The fast charging current is configured to 2000 mA (Fast Charging: Current) by default, which is conservative for

the majority of 4400-mAh battery applications. This should be configured based on the battery configuration, cell

manufacturer's data sheet, and system power design requirements.

10.2.3.3.3

Other Charging Modes

The bq78350-R1 is configured to limit, through external components, and report either low or 0

ChargingVoltage() and ChargingCurrent(), based on temperature, voltage, and fault status information.

The "Charge Algorithm" section of the bq78350-R1 Technical Reference Manual (SLUUBD3) details these

features and settings.

10.2.3.4 Protection

The safety features and settings of the bq78350-R1 are configured conservatively and are suitable for bench

evaluation. However, in many cases, users will need to change these values to meet system requirements.

These values should not be changed to exceed the safe operating limits provided by the cell manufacturer and

any industry standard.

For details on the safety features and settings, see the "Protections" and "Permanent Fail" sections of the

bq78350-R1Technical Reference Manual (SLUUBD3).

10.2.3.5 Peripheral Features

10.2.3.5.1

LED Display

The bq78350-R1 is configured by default to display up to five LEDs in a bar graph configuration based on the

value of RemainingStateOfCharge() (RSOC). Each LED represents 20% of RSOC and is illuminated when the

bq78350-R1 DISP pin transitions low, and remains on for a programmable period of time.

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