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bq27320

SLUSCG9A – FEBRUARY 2016 – REVISED MARCH 2016

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Copyright © 2016, Texas Instruments Incorporated

9.2.1 Design Requirements

Several key parameters must be updated to align with a given application's battery characteristics. For highest

accuracy gauging, it is important to follow-up this initial configuration with a learning cycle to optimize resistance

and maximum chemical capacity (Qmax) values prior to sealing and shipping systems to the field. Successful

and accurate configuration of the fuel gauge for a target application can be used as the basis for creating a

"golden" gas gauge (.fs) file that can be written to all gauges, assuming identical pack design and Li-ion cell

origin (chemistry, lot, and so on). Calibration data is included as part of this golden GG file to cut down on

system production time. If going this route, it is recommended to average the voltage and current measurement

calibration data from a large sample size and use these in the golden file. Table 3, Key Data Flash Parameters

for Configuration, shows the items that should be configured to achieve reliable protection and accurate gauging

with minimal initial configuration.

Table 3. Key Data Flash Parameters for Configuration

NAME

DEFAULT

UNIT

RECOMMENDED SETTING

Design Capacity

1000

mAh

Set based on the nominal pack capacity as interpreted from cell manufacturer's

datasheet. If multiple parallel cells are used, should be set to N × Cell Capacity.

Design Energy Scale

1

—

Set to 10 to convert all power values to cWh or to 1 for mWh. Design Energy

is divided by this value.

Reserve Capacity-mAh

0

mAh

Set to desired runtime remaining (in seconds / 3600) × typical applied load

between reporting 0% SOC and reaching Terminate Voltage, if needed.

Chem ID

0100

hex

Should be configured using TI-supplied Battery Management Studio software.

Default open-circuit voltage and resistance tables are also updated in

conjunction with this step. Do not attempt to manually update reported Device

Chemistry as this does not change all chemistry information! Always update

chemistry using the appropriate software tool (that is, bqStudio).

Load Mode

1

—

Set to applicable load model, 0 for constant current or 1 for constant power.

Load Select

1

—

Set to load profile which most closely matches typical system load.

Qmax Cell 0

1000

mAh

Set to initial configured value for Design Capacity. The gauge will update this

parameter automatically after the optimization cycle and for every regular

Qmax update thereafter.

Cell0 V at Chg Term

4200

mV

Set to nominal cell voltage for a fully charged cell. The gauge will update this

parameter automatically each time full charge termination is detected.

Terminate Voltage

3200

mV

Set to empty point reference of battery based on system needs. Typical is

between 3000 and 3200 mV.

Ra Max Delta

44

m

Ω

Set to 15% of Cell0 R_a 4 resistance after an optimization cycle is completed.

Charging Voltage

4200

mV

Set based on nominal charge voltage for the battery in normal conditions

(25°C, etc). Used as the reference point for offsetting by Taper Voltage for full

charge termination detection.

Taper Current

100

mA

Set to the nominal taper current of the charger + taper current tolerance to

ensure that the gauge will reliably detect charge termination.

Taper Voltage

100

mV

Sets the voltage window for qualifying full charge termination. Can be set

tighter to avoid or wider to ensure possibility of reporting 100% SOC in outer

JEITA temperature ranges that use derated charging voltage.

Dsg Current Threshold

60

mA

Sets threshold for gauge detecting battery discharge. Should be set lower than

minimal system load expected in the application and higher than Quit Current.

Chg Current Threshold

75

mA

Sets the threshold for detecting battery charge. Can be set higher or lower

depending on typical trickle charge current used. Also should be set higher

than Quit Current.

Quit Current

40

mA

Sets threshold for gauge detecting battery relaxation. Can be set higher or

lower depending on typical standby current and exhibited in the end system.

Avg I Last Run

–299

mA

Current profile used in capacity simulations at onset of discharge or at all times

if Load Select = 0. Should be set to nominal system load. Is automatically

updated by the gauge every cycle.

Avg P Last Run

–1131

mW

Power profile used in capacity simulations at onset of discharge or at all times

if Load Select = 0. Should be set to nominal system power. Is automatically

updated by the gauge every cycle.

Sleep Current

15

mA

Sets the threshold at which the fuel gauge enters SLEEP mode. Take care in

setting above typical standby currents else entry to SLEEP may be

unintentionally blocked.