The BQ2085 -V1P3 SBS standard fuel gauge IC is installed and maintained in a battery pack or system to accurately record the available charge in Li-ion or Li-polymer cells. The BQ2085-V1P3 monitors key parameters of the battery pack such as capacity and reports the information communication bus provided to the system host controller via the serial port. It is designed to maximize functionality and safety with the BQ29311 analog front end (AFE) protection IC minimizing component count and cost of smart battery circuits. Using the information from the BQ2085-V1P3, the host controller can manage the remaining battery power to extend the system runtime as much as possible.

The BQ2085-V1P3 uses an integrating converter to continuously sample and measure battery charge and discharge currents. Optimized for coulomb counting in portable applications, the resolution of the self-calibrating integrating converter is better than 3-nVh offset measurement error is less than 1-µV (typical). For voltage and temperature reporting, the BQ2085-V1P3 uses a 16-bit A/D converter. The use of the BQ29311 in conjunction with the on-board ADC to monitor the individual cell voltages in the battery pack allows the BQ2085-V1P3 to generate the control signals necessary for cell balancing and safety chemicals required for Li-ion and Li-polymer batteries.

The BQ2085-V1P3 supports Smart Battery Data (SBData) commands and charging control functions. It transmits data using the System Management Bus (SMBus) 2-wire protocol. Available data includes remaining battery capacity, temperature, voltage, current and remaining runtime forecast. The BQ2085-V1P3 provides LED drivers and buttons

Enter to change remaining battery capacity from full to empty in 20%, 25% or 33% increments with 3, 4 or 3 5-segment displays.

The BQ2085-V1P3 contains 512 bytes of internal data flash memory for storing configuration information. This information includes nominal capacity and voltage, self-discharge rate, rate compensation factor, etc. Programmable cell modeling factors are used to accurately adjust remaining capacity based on usage conditions

time, speed and temperature. The BQ2085-V1P3 is also self-calibrating or learning the true battery capacity during a programmable near full to near empty level during electrical cycling.

The BQ29311 AFE protection IC supplies power from the bq2085-V1P3 of the 3 or 4 series Li-Ion battery stack without the need for an external voltage regulator circuit.

Functional block diagram

feature

Provides accurate available measurements for Li-ion and Li-polymer battery charging.

Support Smart Battery Specification (SBS) V1.1.

The integrated time base eliminates the need for external crystals.

A complete package is available for the TI bq29311 analog front end (AFE) protection IC.

Electronics for 10.8 V or 14.4 V battery packs with few external components

Based on powerful low power RISC CPU

Core and High-Performance Peripherals

Integrated flash eliminates the need

EEPROM for external configuration

Measuring Charge Flow Using High Voltage

Resolution 16-bit integrating converter

Better than 3-nVh resolution

self-calibration

Offset error less than 1µV

Using a 16-bit Delta Sigma converter

Accurate voltage and temperature

Measurement

Programmable cell modeling maximizes

Battery Fuel Gauge Accuracy

3-segment, 4-segment or 5-segment LED display for the driver

Remaining capacity indication

38-pin TSSOP (DBT)

application

laptop

Medical and Test Equipment

Portable Meter

TSSOP Packaging Diagram

SMBus Timing Diagram

SCLKACK is the master-generated clock pulse associated with the acknowledgment

Function Description

Internal oscillator function

The internal oscillator performance also depends on the tolerance of the connected 113kΩ resistor between RSOC (Pin 33) and VSSA (Pin 34). It is recommended that this resistor be as close as possible to the bq2085-V1P3, which has a specification of ±0.1% tolerance and ±50 ppm temperature drift or better. The layout of the PCBA is also another factor in performance degradation.

The average temperature drift error of the oscillator function over a learned charge or discharge cycle introduces an equal capacity prediction error in the learned full charge capacity (FCC.

General operation

The BQ2085-V1P3 determines battery capacity by monitoring the amount of power input or removed from a rechargeable battery. In addition to measuring charge and discharge, the BQ2085-V1P3 can measure battery charge voltage, temperature, and current, estimate battery self-discharge, and monitor the battery's low-voltage threshold. The BQ2085-V1P3 measures charging and discharging by monitoring the voltage across a small value series sense resistor between the negative terminal and the negative terminal of the active battery pack. The available battery charge measurement environment and operating conditions are determined by monitoring this voltage and correcting the voltage.

The BQ2085-V1P3 interfaces with the bq29311 to perform battery protection, battery balancing and voltage translation functions.

The BQ2085-V1P3 can accept any NTC thermistor (Semitec 103AT by default) for temperature measurement or can be configured to use its internal temperature sensor. The BQ2085-V1P3 uses temperature for monitoring the battery pack and compensating for self-discharge estimation.

Measurement

The BQ2085-V1P3 uses an integrated sigma-delta analog-to-digital converter (ADC) for current measurements and a second sigma delta ADC for battery voltage and temperature measurements. Voltage, current and temperature measurements are made every second.

charge and discharge count

The integrating ADC measures the charge and discharge flow of the battery by monitoring the small sense of the resistance between the SR1 and SR2 pins as shown in the schematic. The integrating ADC measures bipolar signals from -0.3 to 1.0 V. The BQ2085-V1P3 detects charging activity when VSR = V(SR1) - V(SR2) is positive. Discharge is active when VSR = V(SR1) - V(SR2) is negative. The BQ2085-V1P3 continuously integrates signals over time using an internal counter. The base rate of the counter is 2.6 nVh. The BQ2085-V1P3 updates the remaining capacity, accumulating a charge or discharge every second in this internal counter.

offset calibration

The BQ2085-V1P3 provides an auto-calibration function that removes voltage offset errors on SR1 and SR2 for maximum charge measurement accuracy. The BQ2085-V1P3 performs auto-calibration while SMBus and the lines remain low for at least 20 seconds. The BQ2085-V1P3 is capable of automatic offset calibration down to 1µV.

digital filter

The BQ2085-V1P3 does not measure charge or discharge counts below the digital filter threshold. The digitizing filter threshold is programmed in Digital Filter DF 0x2b. Set it high enough to prevent false signal detection without charging or discharging current through the sense resistor.

Voltage

While monitoring the charge and discharge currents of SR1 and SR2, the BQ2085-V1P3 monitors the individual series battery voltage through the bq29311. The BQ2085-V1P3 configures the bq29311 to display the selected cell to the VCELL pin of the BQ29311. Therefore, connect the VCELL pin to the VIN of the BQ2085-V1P3. The internal ADC of the BQ2085-V1P3 then measures the voltage and adjusts it appropriately. The BQ2085-V1P3 then reports the Voltage and individual battery voltages in VCELL1, VCELL2, VCELL3 and VCELL4 in 0x3c-0x3f.

current

The BQ2085-V1P3 uses the SR1 and SR2 inputs to measure and calculate the current represented in the battery charge and discharge data register Current().

temperature

TS input of BQ2085-V1P3 together with NTC thermistor to measure battery temperature

The BQ2085-V1P3 reports the temperature of the temperature. The BQ2085-V1P3 can also be configured to configure DF 0x2a with its internal temperature sensor by setting the IT bit in Misc. Data Flash locations DF 0xa4 to DF 0xad must also be changed to the values specified when the Internal Temperature Sensor option is selected.

BQ2085-V1P3 Operation Overview Diagram

The BQ2085-V1P3 accumulates a measure of charge and discharge current and estimates the self-discharged battery. The BQ2085-V1P3 temperature-compensated charge current and temperature-compensated charge current measure the state of charge of the battery. The BQ2085-V1P3 also estimates temperature based on adjusted self-discharge. The main charge counter RemainingCapacity (RM) represents the available capacity or energy in the battery at any given time. The BQ2085-V1P3 can adjust the charge, self-discharge and other compensation factors of the RM. The information in the RM registers can be accessed through the SMBus interface and can also be represented by the LED display as follows. The FullChargeCapacity (FCC) register indicates that the battery was fully discharged at the last measurement. It is used as a reference for battery full charge as a relative capacity indication. The BQ2085-V1P3 updates the FCC battery for qualified discharge, from near full battery to low battery. FCC can interface through SMBus. The Discharge Count Register (DCR) is an inaccessible register that tracks the discharge of the battery. The BQ2085-V1P3 uses the DCR register to update the FCC register from almost full to low battery level if the battery has undergone a qualifying discharge. In this way, the BQ2085-V1P3 can obtain the true discharge capacity of the battery under system usage conditions.

RemainingCapacity (RM)

RM represents the remaining capacity of the battery. The bq2085-V1P3 calculates RM in mAh or 10 mWh, depending on the selected mode. About device configuration. The RM counts to the maximum value of the FCC during charge and drops during discharge and self-discharges to a. In addition to charge and self-discharge compensation, the BQ2085-V1P3 also calibrates the RM to 3 low battery voltage thresholds, EDV2, EDV1 and EDV0 and three Programmable IF thresholds VOC25, VOC50 and VOC75. This provides voltage-based calibration for the RM counter.

DesignCapacity (DC)

DC is the user specified battery full capacity. It is calculated from Pack Capacity DF 0x31-0x32 and expressed in mAh or 10mWh. It also represents the full battery reference mode of the absolute display.

FullChargeCapacity (FCC)

FCC is the last measured battery discharge capacity. It is expressed in mAh or 10 mWh, depending on the selected mode. When initialized, the BQ2085-V1P3 sets the FCC to the value stored in the Last measurement discharge DF 0x35-0x36. During the subsequent discharge process, the BQ2085-V1P3 updates the discharge capacity of the battery last measured by the FCC. The last measured battery discharge is based on the value in the DCR register after a qualifying discharge has occurred. After the update, the BQ2085-V1P3 will write the new FCC data flashing in milliamps until the last measured discharge. FCC stands for Complete Battery Reference Relative Display Mode and Relative State of Charge Calculations.

Discharge Count Register (DCR)

The DCR register counts up during discharge, independent of RM. DCR calculates discharge activity, battery load estimates and self-discharge increments. The BQ2085-V1P3 initializes the DCR at the start of discharge, to FCC - RM when the RM is within the programmed value in Near Full DF 0x2f. DCR Initial Value for FCC - If SC = 1 (bit 5 in meter configuration), then RM is decreased by FCC/128, if SC = 0, then RM is decreased. DCR stops counting when battery voltage reaches EDV2 threshold while discharging.

Capacity Learning (FCC Update) and Qualified Dismissal

If a qualifying discharge occurs, the bq2085-V1P3 updates the FCC based on the value in the DCR. The new value for FCC is equal to the DCR value plus the programmable near-full and low battery levels, according to the following equation:

FCC (new) DCR (final) DCR (initial) measured discharge to EDV2 (FCC battery low %) battery low % = (value stored in DF 0x2e) ÷ 2.56, if battery from RM ≥ FIN - close to full charge Discharge to the EDV2 voltage threshold, a qualifying discharge occurs when the following conditions are met:

No valid charging activity occurs during discharge. The effective charge is defined as a 10 mAh charge cell. During discharge, no self-discharge or battery load estimation beyond 256 mAh occurs. The temperature will not fall below the low temperature threshold programmed in the learning low temperature DF, which is 0x9b during discharge. The battery voltage reaches the EDV2 threshold during discharge and the voltage is greater than or equal to the EDV2 threshold minus 256 mV when the BQ2085-V1P3 detects EDV2. No IF voltage correction occurs during discharge. When reaching EDV2 or low battery %, the current is still ≥ 3C/32. There is no overload condition when EDV2 threshold is reached or RM drops to low battery %*FCC.

When the qualified discharge begins, the BQ2085-V1P3 sets VDQ = 1 in the packaged state. BQ2085-V1P3 Kit VDQ = 0 if any non-qualified condition occurs. The FCC cannot reduce more than 256 mAh or increase it by more than 512 mAh in any single refresh cycle. The BQ2085-V1P3 saves the new FCC value to the data and flashes within 4 seconds after the update.