Table of Contents Table of Contents Read This First...................................7 1.1 About This Manual................................1.2 Formatting conventions used in this document:.........................7 1.3 Related Documentation from Texas Instruments....................... 1.4 Trademarks..................................1 General Description................................9 1.1 Gas Gauging..................................1.1.1 CEDV Gas Gauging Operational Overview.......................10 1.1.2 Main Fuel Gauge...
Read This First 1.1 About This Manual This manual discusses the modules and peripherals of the BQ27220 device, and how each is used to build a complete battery pack fuel gauge solution. For further information, refer to the BQ27220 System-Side CEDV Fuel Gauge Data Sheet (SLUSCB7).
Chapter 1 General Description The BQ27220 fuel gauge, using compensated end-of-discharge voltage (CEDV) technology, accurately predicts the battery capacity and other operational characteristics of a single series, Li-based rechargeable cell. It can be interrogated by a system processor to provide cell information such as time-to-empty (TTE), state-of-charge (SOC), and the SOC interrupt signal to the host.
DCR to update the FCC register if the battery undergoes a qualified discharge from nearly full to a low battery level. In this way, the BQ27220 device learns the true discharge capacity of the battery under-system use conditions.
1.1.3 Capacity Learning (FCC Update) and Qualified Discharge The BQ27220 device updates FCC with an amount based on the value in the DCR if a qualified discharge occurs. The new value for FCC equals the DCR value plus the programmable Near Full and low battery levels, per the following equation: FCC (new) = DCR (final) = DCR (initial) + Measured Discharge to EDV2 + (FCC ×...
If [FCC_LIMIT] is set in CEDV Gauging Configuration then FCC cannot learn above the Design Capacity mAh. The BQ27220 device saves the new FCC value to the data flash within 4 s of being updated. 1.1.4 End-of-Discharge Thresholds and Capacity Correction The BQ27220 device monitors the battery for three low-voltage thresholds: EDV0, EDV1, and EDV2.
Various Loads 1.1.6 EDV Age Factor The EDV Age Factor allows the BQ27220 device to correct the EDV detection algorithm to compensate for cell aging. This parameter scales cell impedances as the cycle count increases. This new factor is used to accommodate for much higher impedances observed in larger capacity and/or aged cells.
EDV0, EDV1, and EDV2 thresholds based on rate, temperature, and capacity. If the bit is cleared, the BQ27220 device uses the fixed values programmed in data flash for EDV0, EDV1, and EDV2. If the bit is set, the BQ27220 device calculates EDV_CMP EDV0, EDV1, and EDV2.
Design Capacity mAh data flash value. 1.1.13 CEDV Smoothing The BQ27220 device has the ability to smooth the RemainingCapacity() during discharge in order to avoid a drop in RelativeStateOfCharge() when the EDV thresholds are reached. This feature is enabled by setting the Smoothing Config [SMEN] = 1 and configuring the Smoothing Start Voltage and Smoothing Delta Voltage.
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Smoothing to EDV0 if calculated EDV2/EDV1 is less than EDV0. The BQ27220 device can also add smoothing during charging. In situations when the FCC is not updated during a discharge cycle or on a subsequent charge cycle, if the valid charge termination is reached, RSOC is synced to 100% regardless of the true RSOC.
Chapter 2 Standard Data Commands 2.1 Standard Commands The BQ27220 fuel gauge uses a series of 2-byte standard commands to enable system reading and writing of battery information. Each standard command has an associated command-code pair, as indicated in Table 2-1.
(see Section 4.2.1, Pin Function Code (PFC) Descriptions). WAKE_EN,WK_TH1,WK_TH0 = These bits configure the current wake function. See the BQ27220 System-Side CEDV Fuel Gauge Data Sheet (SLUSCB7) for threshold values. 4.1.3 Operation Configuration B (Operation Config B) Register Table 4-3. Operation Config B Register Bit Definitions...
Note Because the BQ27220 device does not support HIBERNATE mode, it is highly recommended to set Hibernate I to 0. To set Hibernate I to 0, do the following set of commands: 1. Write 0x0090 to 0x3E (enter CONFIG UPDATE mode), and wait 1100 ms for it to fully enter CONFIG UPDATE mode.
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This value is the desired reserved battery capacity remaining at EDV0. 4.9.22 Age Factor This value allows the BQ27220 device to correct the EDV detection algorithm to compensate for cell aging. 4.9.23 Fixed EDV0 This value is the EDV0 threshold if [CEDV] is clear in CEDV Config.
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Low % ÷ 100. The firmware default value is 15232, which corresponds to a Battery Low % = 703 (.01 %). 4.9.38 Cycle Count The default value of CycleCount() is stored in Cycle Count and copied upon BQ27220 initialization. When the value changes Cycle Count is also updated.
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During Primary Charge Termination detection, one of the three requirements is that the accumulated change in capacity > 0.25 mAh per Current Taper Window for the BQ27220 device to start trying to qualify a termination. It must be above this Min Taper Capacity before BQ27220 starts trying to detect a primary charge termination.
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During Primary Charge Termination detection, one of the three requirements is that Voltage must be above (Charging Voltage – Taper Voltage) for the BQ27220 device to start trying to qualify a termination. It must be above this voltage before BQ27220 starts trying to detect a primary charge termination.
4.9.62.1 OT Charge Time If the [OTC] condition exists for a time that exceeds the OT Chg Time period, the BQ27220 device goes into an overtemperature charge condition. This function is disabled if OT Chg Time is set to 0.
DeviceName() (0x63 through 0x69). 4.9.69 System Down Set Voltage The BQ27220 device goes into SYSTEM DOWN mode if the battery pack Voltage() is equal to or less than SysDown Set Voltage Threshold for SysDown Set Volt Time.
5.1 I C Interface The BQ27220 fuel gauge supports the standard I C read, incremental read, quick read, one byte write, and incremental write functions. The 7-bit device address (ADDR) is the most significant 7 bits of the hex address and is fixed as 1010101.
0x01 0x36; //Two-byte incremental method wr 0x00 0xFF 0xFF; wr 0x00 0xFF 0xFF; The BQ27220 boots up in UNSEAL, but not in FULL ACCESS. Enter //Alternative single byte method FULL ACCESS to gain access to the Data Memory. wr 0x00 0xFF;...
1. Download the configuration/profile to BQ27220 RAM on power up. The BQ27220 fuel gauge has RAM-based data memory parameters that can be updated if needed by the host processor. This prevents external communication access to the fuel gauge to allow updating with external tools.
SOFT_RESET subcommand from the host. The memory of the BQ27220 device is separated into memory subclasses defined in this document. The memory cannot be directly addressed, but is updated through a sequence of extended commands that can access each block of memory indirectly.
The BQ27220 fuel gauge has two One-Time Programmable (OTP) areas for custom CEDV profile programming. In cases where the user does not want to program the RAM in the BQ27220 device every time on a power up, there is a provision to program the custom CEDV profiles in the OTP area of the BQ27220 device. Once programmed, the fuel gauge automatically uses the OTP profile the next time the gauge is powered up.
C instructions (with data) on how to program the OTP with the values that were just setup in RAM. Step 5: Use the ot.fs file with the SmartFlash programming tool; the OTP on the BQ27220 device can be programmed. 8.4 General Setup and Software Installation to Program OTP 1.
Updating BQ27220 Configuration Parameters 8.6 Load .GG File This procedure imports the fuel gauge data or the data memory image to the device. 1. Browse to a desired template or sample *.GG parameter file. (Example: BQ27220.gg.csv in Figure 8-4.) 2. Click Open button.
Updating BQ27220 Configuration Parameters www.ti.com 8.8 Save .OTFS File 1. Click the GoldenImage icon. 2. From the GoldenImage panel, enter the desired .OTFS base file name (example, BQ27220.ot.fs). Note No Options changes are required. 3. Click Create Image File. 4. Exit BQStudio software.
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