BQ27441-G1 — Single-Cell Li-Ion Fuel Gauge with Impedance Track
UnreviewedTexas Instruments system-side fuel gauge for single-cell Li-Ion batteries. Reports remaining capacity, state-of-charge, and battery voltage over I2C using the patented Impedance Track algorithm. 12-pi
Source: Texas Instruments Datasheet (SLUSBH1C)
Manufacturer: Texas Instruments
Part Number: BQ27441-G1
Document: SLUSBH1C — November 2013, Revised December 2014
Description
The Texas Instruments bq27441-G1 fuel gauge is a microcontroller peripheral that provides system-side fuel gauging for single-cell Li-Ion batteries. The device requires minimal user configuration and system microcontroller firmware development.
The bq27441-G1 battery fuel gauge uses the patented Impedance Track™ algorithm for fuel gauging, and provides information such as remaining battery capacity (mAh), state-of-charge (%), and battery voltage (mV).
Battery fuel gauging with the bq27441-G1 fuel gauge requires connections only to PACK+ (P+) and PACK– (P–) for a removable battery pack or embedded battery circuit. The tiny, 12-pin, 2.50 mm × 4.00 mm, small outline no-lead (SON) package is ideal for space-constrained applications.
Features
- Single Series Cell Li-Ion Battery Fuel Gauge
- Resides on System Board
- Supports Embedded or Removable Batteries
- Powered Directly from Battery with Integrated LDO
- Supports a Low-Value Sense Resistor (10 mΩ)
- Battery Fuel Gauging Based on Patented Impedance Track™ Technology
- Reports Remaining Capacity and State-of-Charge (SOC) with Smoothing Filter
- Automatically Adjusts for Battery Aging, Self-discharge, Temperature, and Rate Changes
- Battery State-of-Health (Aging) Estimation
- Microcontroller Peripheral Support
- 400-kHz I²C Serial Interface
- Configurable SOC Interrupt or Battery Low Digital Output Warning
- Internal Temperature Sensor or Host-Reported Temperature
Applications
- Smartphones, Feature Phones, and Tablets
- Digital Still and Video Cameras
- Handheld Terminals
- MP3 or Multimedia Players
Key Specifications
| Parameter | Value |
|---|---|
| Supply Voltage (V_BAT) | –0.3 V to 6 V |
| Regulated LDO Output (V_DD) | 1.8 V |
| LDO Wake-up Threshold (V_WU+) | 1.2 V (min) |
| Normal Mode Current | 93 µA (typ) |
| Sleep Mode Current | 21 µA (typ) |
| Hibernate Mode Current | 9 µA (typ) |
| Shutdown Mode Current | 0.6 µA (typ) |
| I²C Clock Frequency | 100 kHz (Standard) / 400 kHz (Fast) |
| Coulomb-Counter ADC Resolution | 16 bits |
| BAT Voltage ADC Resolution | 15 bits |
| Sense Resistor (recommended) | 10 mΩ, 1 %, 50 ppm, 1 W |
| Operating Temperature | –40 °C to 85 °C |
| Storage Temperature | –65 °C to 150 °C |
| Package | 12-pin VSON (DRZ), 2.50 mm × 4.00 mm |
Pin Configuration
| Pin | Name | Type | Description |
|---|---|---|---|
| 1 | SDA | DIO | I²C serial data (open-drain). 10-kΩ pullup required. Pull down through 1 MΩ to V_SS if host disconnects during low-power operation. |
| 2 | SCL | DIO | I²C serial clock (open-drain). 10-kΩ pullup required. Pull down through 1 MΩ to V_SS if host disconnects during low-power operation. |
| 3 | V_SS | P | Ground pin. |
| 4 | NC | — | No internal connection. May be left floating or tied to V_SS. |
| 5 | V_DD | P | 1.8-V regulator output. Bypass with a 0.47-µF ceramic capacitor to V_SS. Do not use this pin to provide power for other devices. |
| 6 | BAT | PI, AI | LDO regulator input and battery voltage measurement input. Kelvin sense-connect to positive battery terminal (PACKP). Place a 0.1-µF capacitor between BAT and V_SS. |
| 7 | SRN | AI | Coulomb-counter differential input, negative side. Expects external ≈10-mΩ sense resistor in the high-side current path. |
| 8 | SRP | AI | Coulomb-counter differential input, positive side. |
| 9 | NC | — | No internal connection. |
| 10 | BIN | DI | Battery insertion detect input. Configurable behavior through OpConfig. Typically a 10-kΩ pullup to V_DD with a battery-present pulldown resistor. |
| 11 | NC | — | No internal connection. |
| 12 | GPOUT | DO | Open-drain general-purpose output. Configurable as BAT_LOW interrupt (default) or SOC interrupt via OpConfig [BATLOWEN]. Controlled by [GPIOPOL]. Also serves as SHUTDOWN wake-up input. |
Absolute Maximum Ratings
Over operating free-air temperature range (unless otherwise noted).
| Symbol | Parameter | Min | Max | Unit |
|---|---|---|---|---|
| V_BAT | BAT pin input voltage range | –0.3 | 6 | V |
| V_IN | SRP and SRN pin input voltage range | –0.3 | V_BAT + 0.3 | V |
| Differential voltage across SRP and SRN, ABS(SRP – SRN) | 2 | V | ||
| V_DD | V_DD pin supply voltage range (LDO output) | –0.3 | 2 | V |
| V_IOD | Open-drain I/O pins (SDA, SCL) | –0.3 | 6 | V |
| V_IOPP | Push-pull I/O pins (BIN) | –0.3 | V_DD + 0.3 | V |
| T_A | Operating free-air temperature range | –40 | 85 | °C |
| T_stg | Storage temperature range | –65 | 150 | °C |
Recommended Operating Conditions
| Symbol | Parameter | Test Conditions | Min | Typ | Max | Unit |
|---|---|---|---|---|---|---|
| C_BAT | External input capacitor for internal LDO between BAT and V_SS | Nominal capacitor values specified. Recommend a 5 %, ceramic, X5R type capacitor located close to the device. | 0.1 | µF | ||
| C_LDO18 | External input capacitor for internal LDO between V_DD and V_SS | 0.47 | µF | |||
| V_PU | External pullup voltage for open-drain pins (SDA, SCL, GPOUT) | 1.62 | 3.6 | V |
Electrical Characteristics
Supply Current
T_A = 30 °C and V_REGIN = 3.6 V (unless otherwise noted).
| Symbol | Parameter | Test Conditions | Typ | Unit |
|---|---|---|---|---|
| I_CC | NORMAL mode current | I_LOAD > Sleep Current | 93 | µA |
| I_SLP | SLEEP mode current | I_LOAD < Sleep Current | 21 | µA |
| I_HIB | HIBERNATE mode current | I_LOAD < Hibernate Current | 9 | µA |
| I_SD | SHUTDOWN mode current | Fuel gauge in host-commanded SHUTDOWN mode (LDO regulator output disabled). | 0.6 | µA |
Digital Input and Output DC Characteristics
T_A = –40 °C to 85 °C, typical values at T_A = 30 °C and V_REGIN = 3.6 V (unless otherwise noted).
| Symbol | Parameter | Test Conditions | Min | Max | Unit |
|---|---|---|---|---|---|
| V_IH(OD) | Input voltage high, open drain | External pullup resistor to V_PU | V_PU – 0.7 | V | |
| V_IH(PP) | Input voltage high, push-pull | 1.4 | V | ||
| V_IL | Input voltage low, open drain | 0.6 | V | ||
| V_OL | Output voltage low, open drain | 0.6 | V | ||
| I_OH | Output source current, high (push-pull) | 0.5 | mA | ||
| I_OL(OD) | Output sink current, low (open drain) | –3 | mA | ||
| C_IO | Input capacitance | 5 | pF | ||
| I_lkg | Input leakage current (SCL, SDA, BIN / GPOUT) | 0.1 / 1 | µA |
LDO Regulator, Wake-up, and Auto-Shutdown DC Characteristics
| Symbol | Parameter | Min | Typ | Max | Unit |
|---|---|---|---|---|---|
| V_BAT | BAT pin regulator input voltage | 2.45 | 4.5 | V | |
| V_DD | Regulator output voltage | 1.8 | V | ||
| UVLO_F | V_BAT undervoltage lockout, falling threshold | 2 | V | ||
| UVLO_R | V_BAT undervoltage lockout, rising threshold | 1.95 | V | ||
| V_WU+ | LDO Wake-up from SHUTDOWN (GPOUT rising edge threshold) | 1.2 | V |
LDO Regulator, Wake-up, and Auto-shutdown AC Characteristics
| Symbol | Parameter | Test Conditions | Typ | Unit |
|---|---|---|---|---|
| t_SHDN | SHUTDOWN entry time | Time delay from SHUTDOWN command before LDO output disable | 250 | ms |
| t_SHUP | SHUTDOWN GPOUT low time | Minimum low time of GPOUT (input) in SHUTDOWN before WAKEUP | 10 | µs |
| t_VDD | Initial V_DD output delay | 13 | ms | |
| t_WUVDD | Wake-up V_DD output delay | Time delay from rising edge of GPOUT (input) to nominal V_DD output | 8 | ms |
| t_PUCD | Power-up communication delay | Time delay from rising edge of REGIN to the Active state. Includes firmware initialization time. | 250 | ms |
ADC (Temperature and Cell Measurement) Characteristics
| Symbol | Parameter | Test Conditions | Min | Typ | Max | Unit |
|---|---|---|---|---|---|---|
| V_IN(BAT) | BAT pin voltage measurement range | Voltage divider enabled | 2.45 | 4.5 | V | |
| t_ADC_CONV | Conversion time | 125 | ms | |||
| Effective resolution | 15 | bits |
Integrating ADC (Coulomb Counter) Characteristics
| Symbol | Parameter | Test Conditions | Value | Unit |
|---|---|---|---|---|
| V_SR | Input voltage range from BAT to SRN pins | BAT ± 25 | mV | |
| t_SR_CONV | Conversion time | Single conversion | 1 | s |
| Effective resolution | Single conversion | 16 | bits |
Thermal Information
T_A = 30 °C and V_REGIN = 3.6 V (unless otherwise noted).
| Thermal Metric | DRZ (12 pins) | Unit |
|---|---|---|
| R_θJA — Junction-to-ambient thermal resistance | 64.1 | °C/W |
| R_θJC(top) — Junction-to-case (top) | 59.8 | °C/W |
| R_θJB — Junction-to-board | 52.7 | °C/W |
| ψ_JT — Junction-to-top characterization parameter | 0.3 | °C/W |
| ψ_JB — Junction-to-board characterization parameter | 28.3 | °C/W |
| R_θJC(bot) — Junction-to-case (bottom) | 2.4 | °C/W |
Communication Interface
The bq27441-G1 communicates over a two-wire I²C-compatible bus in either standard (100 kHz) or fast (400 kHz) mode. All transactions that write to Data Memory must use single-byte write commands at ≤100 kHz; other transaction types are supported at 400 kHz.
I²C-Compatible Interface Timing Characteristics
T_A = –40 °C to 85 °C; V_REGIN = 3.6 V (unless otherwise noted).
| Symbol | Parameter | Test Conditions | Min | Typ | Max | Unit |
|---|---|---|---|---|---|---|
| Standard Mode (100 kHz) | ||||||
| t_r(SDA) | Start to first falling edge of SCL | 4 | µs | |||
| t_w(H) | SCL pulse duration (high) | 4.7 | µs | |||
| t_w(L) | SCL pulse duration (low) | 4 | µs | |||
| t_su(STA) | Setup for repeated start | 4.7 | µs | |||
| t_su(DAT) | Data setup time | Host drives SDA | 250 | ns | ||
| t_h(DAT) | Data hold time | Host drives SDA | 0 | ns | ||
| t_su(STOP) | Setup time for stop | 4 | µs | |||
| t_BUF | Bus free time between stop and start | Includes Command Waiting Time | 66 | µs | ||
| t_f | SCL or SDA fall time | 300 | ns | |||
| t_r | SCL or SDA rise time | 300 | ns | |||
| f_SCL | Clock frequency | 100 | kHz | |||
| Fast Mode (400 kHz) | ||||||
| t_r(SDA) | Start to first falling edge of SCL | 600 | ns | |||
| t_w(H) | SCL pulse duration (high) | 1300 | ns | |||
| t_w(L) | SCL pulse duration (low) | 600 | ns | |||
| t_su(STA) | Setup for repeated start | 600 | ns | |||
| t_su(DAT) | Data setup time | Host drives SDA | 100 | ns | ||
| t_h(DAT) | Data hold time | Host drives SDA | 0 | ns | ||
| t_su(STOP) | Setup time for stop | 600 | ns | |||
| t_BUF | Bus free time between stop and start | Includes Command Waiting Time | 66 | µs | ||
| t_f | SCL or SDA fall time | 300 | ns | |||
| t_r | SCL or SDA rise time | 300 | ns | |||
| f_SCL | Clock frequency | 400 | kHz |
Software API
Standard Commands (Table 1)
The fuel gauge uses a series of 2-byte standard commands to enable reading and writing battery information. Each command consists of two bytes of data; two consecutive I²C transmissions must be executed both to initiate and to read/write the corresponding two bytes of data.
| Name | Command Code | Unit | Sealed Access |
|---|---|---|---|
| Control() | 0x00 and 0x01 | NA | RW |
| Temperature() | 0x02 and 0x03 | 0.1 K | RW |
| Voltage() | 0x04 and 0x05 | mV | R |
| Flags() | 0x06 and 0x07 | NA | R |
| NominalAvailableCapacity() | 0x08 and 0x09 | mAh | R |
| FullAvailableCapacity() | 0x0A and 0x0B | mAh | R |
| RemainingCapacity() | 0x0C and 0x0D | mAh | R |
| FullChargeCapacity() | 0x0E and 0x0F | mAh | R |
| AverageCurrent() | 0x10 and 0x11 | mA | R |
| StandbyCurrent() | 0x12 and 0x13 | mA | R |
| MaxLoadCurrent() | 0x14 and 0x15 | mA | R |
| AveragePower() | 0x18 and 0x19 | mW | R |
| StateOfCharge() | 0x1C and 0x1D | % | R |
| InternalTemperature() | 0x1E and 0x1F | 0.1 K | R |
| StateOfHealth() | 0x20 and 0x21 | num / % | R |
| RemainingCapacityUnfiltered() | 0x28 and 0x29 | mAh | R |
| RemainingCapacityFiltered() | 0x2A and 0x2B | mAh | R |
| FullChargeCapacityUnfiltered() | 0x2C and 0x2D | mAh | R |
| FullChargeCapacityFiltered() | 0x2E and 0x2F | mAh | R |
| StateOfChargeUnfiltered() | 0x30 and 0x31 | % | R |
| TrueRemainingCapacity() | 0x6A and 0x6B | mAh | R |
Control() Subcommands (Table 2)
Issuing a Control() command requires a subsequent 2-byte subcommand. These additional bytes specify the particular control function desired.
| CNTL Function | CNTL Data | Sealed Access | Description |
|---|---|---|---|
| CONTROL_STATUS | 0x0000 | Yes | Reports the status of device. |
| FW_VERSION | 0x0002 | Yes | Reports the firmware version of the device. |
| DM_CODE | 0x0004 | Yes | Reports the Data Memory Code number stored in NVM. |
| PREV_MACWRITE | 0x0007 | Yes | Returns previous MAC command code. |
| CHEM_ID | 0x0008 | Yes | Reports the chemical identifier of the battery profile used by the fuel gauge. |
| BAT_INSERT | 0x000C | Yes | Forces the Flags() [BAT_DET] bit set when the OpConfig [BIE] bit is 0. |
| BAT_REMOVE | 0x000D | Yes | Forces the Flags() [BAT_DET] bit clear when the OpConfig [BIE] bit is 0. |
| SET_HIBERNATE | 0x0011 | Yes | Forces CONTROL_STATUS [HIBERNATE] to 1. |
| CLEAR_HIBERNATE | 0x0012 | Yes | Forces CONTROL_STATUS [HIBERNATE] to 0. |
| SET_CFGUPDATE | 0x0013 | No | Forces CONTROL_STATUS [CFGUPMODE] to 1 and gauge enters CONFIG UPDATE mode. |
| SHUTDOWN_ENABLE | 0x001B | No | Enables device SHUTDOWN mode. |
| SHUTDOWN | 0x001C | No | Commands the device to enter SHUTDOWN mode. |
| SEALED | 0x0020 | No | Places the device in SEALED access mode. |
| TOGGLE_GPOUT | 0x0023 | Yes | Commands the device to toggle the GPOUT pin for 1 ms. |
| RESET | 0x0041 | No | Gauge exits CONFIG UPDATE mode. |
| SOFT_RESET | 0x0042 | No | Gauge exits CONFIG UPDATE mode. |
| EXIT_CFGUPDATE | 0x0043 | No | Exits CONFIG UPDATE mode without an OCV measurement and without resimulating to update StateOfCharge(). |
| EXIT_RESIM | 0x0044 | No | Exits CONFIG UPDATE mode without an OCV measurement and resimulates with updated configuration data to update StateOfCharge(). |
Extended Commands (Table 3)
Extended data commands offer additional functionality beyond the standard set of commands. They are used in the same manner; however, unlike standard commands, extended commands are not limited to 2-byte words. The number of command bytes for a given extended command ranges in size from single to multiple bytes, as specified in the table.
| Name | Command Code | Unit | Sealed Access | Unsealed Access |
|---|---|---|---|---|
| OpConfig() | 0x3A and 0x3B | NA | R | R |
| DesignCapacity() | 0x3C and 0x3D | mAh | R | R |
| DataClass() | 0x3E | NA | NA | RW |
| DataBlock() | 0x3F | NA | RW | RW |
| BlockData() | 0x40 through 0x5F | NA | RW | RW |
| BlockDataCheckSum() | 0x60 | NA | NA | RW |
| BlockDataControl() | 0x61 | NA | NA | RW |
| Reserved | 0x62 through 0x7F | NA | R | R |
Applications
Typical Application
The bq27441-G1 fuel gauge is a microcontroller peripheral that provides system-side fuel gauging for single-cell Li-Ion batteries. The device requires minimal configuration and uses One Time Programmable (OTP) Non-Volatile Memory (NVM). Battery fuel gauging with the fuel gauge requires connections only to PACK+ and PACK– for a removable battery pack or embedded battery circuit. To allow for optimal performance in the end application, special considerations must be taken to ensure minimization of measurement error through proper printed circuit board (PCB) board layout.
Design Requirements
- bq27441-G1 parameters in OTP NVM are left in the unprogrammed state (zero). With some parameters directly associated with the CHEMID are preprogrammed.
- This partially-programmed configuration facilitates customization for each application. Upon device reset, the contents of the OTP are copied to associated volatile RAM-based Data Memory blocks.
- For proper operation, all parameters in RAM-based Data Memory require initialization — either by updating Data Memory parameters in a table-evaluation situation or by programming the OTP for customer production.
BAT Voltage Sense Input
A ceramic capacitor at the input to the BAT pin is used to bypass AC voltage ripple to ground, greatly reducing its influence on battery voltage measurements. It proves most effective in applications with load profiles that exhibit high-frequency current pulses (e.g., cell phones), but is recommended for use in all applications to reduce noise on this sensitive high-impedance measurement node.
Integrated LDO Capacitor
The fuel gauge has an integrated LDO with an output on the V_DD pin of approximately 1.8 V. A capacitor of value at least 0.47 µF should be connected between the V_DD pin and V_SS. The capacitor should be placed close to the gauge IC and have short traces to both the V_DD pin and V_SS.
Sense Resistor Selection
Any variation encountered in the resistance present between the SRP and SRN pins of the fuel gauge will affect the resulting differential voltage, and derived current, it senses. As such, it is recommended to select a sense resistor with minimal tolerance and temperature coefficient of resistance (TCR) characteristics. The standard recommendation based on best compromise between performance and price is a 1 % tolerance, 50 ppm drift sense resistor with a 1-W power rating.
Layout Guidelines
- A capacitor of a value of at least 0.47 µF is connected between the V_DD pin and V_SS. The capacitor should be placed close to the gauge IC and have short traces to both the V_DD pin and V_SS.
- It is required to have a capacitor of at least 1.0 µF connected between the BAT pin and V_SS. If the connection between the battery pack and the gauge BAT pin has the potential to pick up noise, the capacitor should be placed close to the gauge IC and have short traces to both the V_DD pin and V_SS.
- If the external pullup resistors on the SCL and SDA lines will be disconnected from the host during low-power operation, it is recommended to use external 1-MΩ pulldown resistors to V_SS to avoid floating inputs to the I²C engine.
- The value of the SCL and SDA pullup resistors should take into consideration the pullup voltage and the bus capacitance. Some recommended values, assuming a bus capacitance of 10 pF, are given in the table below.
Recommended Values for SCL and SDA Pullup Resistors
| VPU | 1.8 V Range | 1.8 V Typical | 3.3 V Range | 3.3 V Typical |
|---|---|---|---|---|
| R_PU | 400 Ω ≤ R_PU ≤ 37.6 kΩ | 10 kΩ | 900 Ω ≤ R_PU ≤ 29.2 kΩ | 5.1 kΩ |
Packages
- Package: 12-pin VSON (Very thin Small Outline No-lead), TI designator DRZ
- Body size: 2.50 mm × 4.00 mm
- Height: 1.00 mm maximum
- Device variants:
- bq27441DRZR-G1A — LiCoO₂ chemistry, 4.2 V max charge (CHEM_ID = 0x0128, DM_CODE = 0x48)
- bq27441DRZT-G1A — LiCoO₂ chemistry, 4.2 V max charge (CHEM_ID = 0x0128, DM_CODE = 0x48)
- bq27441DRZR-G1B — LiCoO₂ chemistry, 4.3 V to 4.35 V max charge (CHEM_ID = 0x0312, DM_CODE = 0x58)
- bq27441DRZT-G1B — LiCoO₂ chemistry, 4.3 V to 4.35 V max charge (CHEM_ID = 0x0312, DM_CODE = 0x58)
- Firmware version (all variants): 1.09 (0x0109)