MPF42791DRT-0B-0000-P

MPF42791 2 to 16 Stacked Cells Battery Pack Fuel Gauge with Resistance Detection and Thermal Model DESCRIPTION FEATURES The MPF42791 is a drop-in solution to provide comprehensive status information on lithium-ion battery strings up to 16 series cells. The MPF42791 estimates the internal state-ofcharge (SOC) and state-of-health (SOH) for each cell, as well as the full pack. The MPF42791 also determines impedance, remaining runtime, charge time, and instantaneous available power. On-board memory enables the lifetime logging of key parameters. • The MPF42791 is simple to use and supports a variety of lithium cell chemistries and cell sizes. A few basic configurations allow for quick set-up, and advanced configuration capabilities can fine-tune the device for specific applications. When paired with an MP279x battery monitor, the MPF42791 can achieve SOC accuracy within 2.5% across the temperature range. The MPF42791 can also be paired with other analog front-end (AFE) or battery stack monitors. The 400kHz I2C interface provides standard, robust communication. The 5-level LED drivers provide a simple, cost-effective charge level indicator for the device. The MPF42791 is available in a TQFN-32 (4mmx4mm) package. MINIMUM SYSTEM REQUIREMENTS • • BMS AFE Providing Individual Cell Voltages, Pack Currents, and Temperatures M0 System MCU with I2C and Interrupt, 48KB of Flash and 4KB of RAM • • • • • • • • • • Compatible with Commonly Used Battery Monitors for Up to 16 Series Cells o ±2.5% State-of-Charge (SOC) Accuracy when Paired with MP279x Battery Monitors Provides Critical Battery Information: o Pack and Cell SOC o Pack and Cell State-of-Health (SOH) o Remaining Runtime and Charge Time o Instantaneous Available Power Supports a Wide Variety of Lithium Cells Adaptive Learning Can Be Enabled to: o Refine Initial Charge Settings o Refine Initial Discharge Settings o Update Individual Cells’ State-of-Health (SOH) to Track Degradation o Update Equivalent Series Resistance (ESR) to Track Degradation Provides Lifetime Logging Supports 5-Level LED SOC Indicator with Push-Button Trigger 2.5V Minimum Supply Voltage Low Current Consumption: 6µA in Disabled Mode and 135µA (Average) in Operating Mode during Rest Supports Up to 400kHz I2C with CRC for Robust Communication Available in a Compact TQFN-32 (4mmx4mm) Package Available in Turn-Key MPS BMS Module: o MBM1xS-P50-B and MBM1xS-P100-B APPLICATIONS • • • • Light EVs: Scooters, Bikes, and Golf Carts Energy Storage: Uninterruptable Power Supplies (UPS) and Renewable Energy Industrial Robots, Floor Cleaners, and Forklifts Cordless Tools and Gardening Equipment All MPS parts are lead-free, halogen-free, and adhere to the RoHS directive. For MPS green status, please visit the MPS website under Quality Assurance. “MPS”, the MPS logo, and “Simple, Easy Solutions” are trademarks of Monolithic Power Systems, Inc. or its subsidiaries. MPF42791 Rev. 1.0 MonolithicPower.com 9/19/2022 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2022 MPS. All Rights Reserved. 1 MPF42791 – 2 TO 16 BATTERY PACK FG W/ R DETECTION AND THERMAL MODEL TYPICAL APPLICATION I2C MP279x SCL SDA MPF42791 MCU CE 3.3V IRQ VDD nRST VCC 3.3V Figure 1: MPF42791 with MP279x AFE Typical Electrical Diagram MPF42791 Rev. 1.0 MonolithicPower.com 9/19/2022 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2022 MPS. All Rights Reserved. 2 MPF42791 – 2 TO 16 STACKED CELL BATTERY PACK FUEL GAUGE W/ LEVEL LEDS ORDERING INFORMATION Part Number* MPF42791DRT-0B-yyyy** EVKT_MPF42791 EVKT-MBM16S-P50-B Package TQFN-32 (4mmx4mm) Evaluation kit Evaluation kit Top Marking See Below - MSL Rating 3 - * For Tape & Reel, add suffix -Z (e.g. MPF42791DRT-0B-yyyy-Z). ** “-yyyy” refers to the default configuration identifier (“-0000” by default), where each “y” is a hexadecimal value between 0 and F. Work with an MPS FAE to obtain a customized default configuration. TOP MARKING MPF4279X Family generic version MPS: MPS prefix Y: Year code WW: Week code M4279X: Family part number* LLLLLL: Lot number * The specific part number is in the IC_VER register. EVALUATION KITS EVKT-MBM1XS-P50-B (MP279X BMS) EVKT-MBM16S-P50-B EVKT-MBM16S-P50-B kit contents (items below can be ordered separately): # Part Number 1 MBM16S-P50-B 2 3 EVKT-USB_RS232/I2C-01 Online resources Item MPF42791DRT-0B-0001 and MP2797DFP-0001 reference design and evaluation board USB to RS232 / I2C adapter Include datasheet, user guide, product brief, and GUI Quantity 1 1 1 EVKT-MBM14S-P50-B EVKT-MBM14S-P50-B kit contents (items below can be ordered separately): # Part Number 1 MBM14S-P50-B 2 3 EVKT-USB_RS232/I2C-01 Online resources Item MPF42791DRT-0B-0001 and MP2791DFP-0001 reference design and evaluation board USB to RS232 / I2C adapter Include datasheet, user guide, product brief, and GUI Quantity 1 1 1 Order directly from MonolithicPower.com or our distributors. MPF42791 Rev. 1.0 MonolithicPower.com 9/19/2022 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2022 MPS. All Rights Reserved. 3 MPF42791 – 2 TO 16 BATTERY PACK FG W/ R DETECTION AND THERMAL MODEL Figure 2: MBM1xS-P50-B Evaluation Kit Set-Up PACKAGE REFERENCE 25 IRQ 26 NC 28 CHSL 27 NC 30 SDAMON 29 SCLMON 32 GND 31 VCC TOP VIEW PB 1 24 SDA LED1 2 23 SCL LED2 3 22 NC LED3 4 LED4 5 LED5 6 19 NC N/C 7 18 NC N/C 8 17 NC 21 NC NC 16 CE 15 NC 13 20 NC NC 14 GND 11 nRST 12 9 LDO VDD 10 GND 33 Pin 33 (GND) is an exposed pad that requires a GND connection TQFN-32 (4mmx4mm) MPF42791 Rev. 1.0 MonolithicPower.com 9/19/2022 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2022 MPS. All Rights Reserved. 4 MPF42791 – 2 TO 16 BATTERY PACK FG W/ R DETECTION AND THERMAL MODEL PIN FUNCTIONS Pin # Name I/O Description 1 2 3 4 5 6 7 8 PB LED1 LED2 LED3 LED4 LED5 NC NC I O O O O O - 9 LDO Power 10 VDD Power 11 12 13 14 GND nRST NC NC Power I - 15 CE I 16 17 18 19 20 21 22 23 24 25 26 27 NC NC NC NC NC NC NC SCL SDA IRQ NC NC I/O I/O O - 28 CHSL I 29 SCLMON I/O 30 SDAMON I/O 31 VCC Power 32 33 GND GND Power Power Push-button. Triggers state-of-charge (SOC) LED indicator. LED 1 driver. The LED1 pin reports the SOC with a 330Ω resistor in series. LED 2 driver. The LED2 pin reports the SOC with a 330Ω resistor in series. LED 3 driver. The LED3 pin reports the SOC with a 330Ω resistor in series. LED 4 driver. The LED4 pin reports the SOC with a 330Ω resistor in series. LED 5 driver. The LED5 pin reports the SOC with a 330Ω resistor in series. No connection. No connection. Internal LDO. Bypass the LDO pin with a 2.2μF + 100nF ceramic capacitor connected to ground. Power supply input. Bypass VDD with a 2.2μF ceramic capacitor connected to ground. Ground pin. IC reset control. No connection. No connection. Chip enabled. Set the CE pin to stop fuel gauge updates and disable the communication interface to minimize current consumption. No connection. No connection. No connection. No connection. No connection. No connection. No connection. I2C interface clock. Connect the SCL pin to the logic rail through a 10kΩ resistor. I2C interface data. Connect the SDA pin to the logic rail through a 10kΩ resistor. Interrupt request pin. The IRQ pin is the interrupt going to the host system(s). No connection. No connection. Channel selection. The CHSL pin selects which I2C channel is capable of writing data into the fuel gauge memory. Pull CHSL high to write data using the secondary I2C. Secondary I2C interface clock. Connect the SCLMON pin to the logic rail through a 10kΩ resistor. Secondary I2C interface data. Connect the SDAMON pin to the logic rail through a 10kΩ resistor. 3V to 3.3V power supply input. Bypass the VCC pin with a 2.2µF ceramic capacitor connected to ground. Ground pin. Ground pin. MPF42791 Rev. 1.0 MonolithicPower.com 9/19/2022 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2022 MPS. All Rights Reserved. 5 MPF42791 – 2 TO 16 BATTERY PACK FG W/ R DETECTION AND THERMAL MODEL θJA θJC ABSOLUTE MAXIMUM RATINGS (1) Thermal Resistance (4) VCC supply voltage (VCC) ........................... 3.6V VDD supply voltage (VDD) ........................... 3.6V nRST pin......................................-0.3V to +3.6V All other pins ........................ -0.3V to VCC + 0.3V Total power dissipation (TA = 25°C) (2) …………………………………………….. 500mW Storage temperature ................ -55°C to +150°C Junction temperature ............... -55°C to +150°C TQFN-32 (4mmx4mm)...........47…...4.5…°C/W ESD Ratings Human body model (HBM) .................... ±4000V Recommended Operating Conditions (3) Supply voltage (VDD) .......................... 3V to 3.6V All other pins ........................ -0.3V to VCC + 0.3V Operating junction temp (TJ) ...... -40°C to +85°C Notes: 1) Exceeding these ratings may damage the device. 2) The maximum allowable power dissipation is a function of the maximum junction temperature, TJ (MAX), the junction-toambient thermal resistance, θJA, and the ambient temperature, TA. The maximum allowable continuous power dissipation at any ambient temperature is calculated by PD (MAX) = (TJ (MAX) - TA) / θJA. Exceeding the maximum allowable power dissipation can produce an excessive die temperature, and the regulator may go into thermal shutdown. Internal thermal shutdown circuitry protects the device from permanent damage. 3) The device is not guaranteed to function outside of its operating conditions. 4) Measured on JESD51-7, 4-layer PCB. MPF42791 Rev. 1.0 MonolithicPower.com 9/19/2022 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2022 MPS. All Rights Reserved. 6 MPF42791 – 2 TO 16 BATTERY PACK FG W/ R DETECTION AND THERMAL MODEL ELECTRICAL CHARACTERISTICS VCC = 3.3V, TA = 25°C, unless otherwise noted. Parameters Symbol Condition Min Typ Max Units State-of-Charge (SOC) Performance MPS MP279x AFE family, 15°C ≤ TA ≤ 35°C, ICHG ≤ 0.5C, -2 0 +2 % IDIS ≤ 0.5C MPS MP279x AFE family, Pack state-of-charge (SOC) θERR 10°C ≤ TA ≤ 50°C, ICHG ≤ 1C, -3 0 +3 % (5) accuracy IDIS ≤ 1C MPS MP279x AFE family, 10°C ≤ TA ≤ 50°C, ICHG ≤ 2C, -4 0 +4 % IDIS ≤ 2C Power Supply VDD operating voltage range VDD 2.5 3.3 3.6 V VCC operating voltage range VCC 2.5 3.3 3.6 V VDD = 3.3V, LEDs off, fuel Total active current IDD_ACTIVE 4.3 mA gauge updating IDD_ VDD = 3.3V, LEDs off, fuel Total standby current 50 μA gauge idle STANDBY VDD = 3.3V, LEDs off, Average operating current IDD_ EXE_TIME = 4s, 476 μA during CHG or DSG NCELLS_SER = 10, with I2C CHG/DSG traffic VDD = 3.3V, LEDs off, NCELLS_SER = 10, Average operating current IDD_REST EXE_TIME = 4s, 192 μA during rest WEXE_TIME_REST = 4, with I2C traffic Total disabled current IDD_DIS VDD = 3.3V 6 μA Power-On Reset (POR) Release threshold of POR VROT VDD rising 1.66 1.79 1.9 V nRST Pin nRST pin threshold voltage VRST 0.2 x VDD 0.9 x VDD V Minimum pulse width on tRST VDD = 3.3V 700 ns nRST pin Timeout after reset tTOUT 64 128 ms CE Low input voltage VOL_CE IOL = 5mA -0.3 0.35 x VDD V High input voltage VOH_CE 0.65 x VDD 0.3V + VDD V I CE_LKG_ Low leakage current VCE = 3.3V 3 μA LOW High leakage current IRQ Low output voltage High output voltage PB Low input voltage High input voltage CHSL Low input voltage High input voltage ICE_LKG_ HIGH VIRQL VIRQH VCE = 3.3V Sink = 4mA Source = 4mA 3 μA 0.4 V V VDD - 0.4 VPBL VPBH -0.3 0.65 x VDD 0.35 x VDD 0.3V + VDD V V VPBL VPBH -0.3 0.65 x VDD 0.35 x VDD 0.3V + VDD V V MPF42791 Rev. 1.0 MonolithicPower.com 9/19/2022 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2022 MPS. All Rights Reserved. 7 MPF42791 – 2 TO 16 BATTERY PACK FG W/ R DETECTION AND THERMAL MODEL ELECTRICAL CHARACTERISTICS (continued) VDD = 3.3V, TA = 25°C, unless otherwise noted. Parameters LEDs Symbol Condition High-level output voltage VOH_LED Output current = 4 mA High-level output current I2C DC Characteristics IOH_LED VLEDx = VDD - 0.4V Min Typ Max VDD 0.4V 4 High input voltage VIH SCL, SDA 0.7 x VDD Low input voltage VIL SCL, SDA -0.5 Low output voltage I2C Timing Characteristics Spikes suppressed by input filter Operating frequency range SCL clock low period SCL clock high period SCL and SDA falling time SCL and SDA rising time Data hold time Data set-up time Data valid time Set-up time for a repeated start condition Hold time for a repeated start condition Set-up time for a stop condition VOL SDA, sink current = 3mA 0 Units V mA 0.3V + VDD 0.3 x VDD 0.4 50 400 V V V tSP fSCL tLOW tHIGH tFALL tRISE 1.125 1.125 tHD_DAT tSU_DAT tV_DAT 0 125 475 ns kHz μs μs μs μs ns ns ns tSU_STA 125 ns tHD_STA 0 ns tSU_STO 125 ns 0.34 0.34 Note: 5) Validated on a 10S1P Samsung INR18650 25R pack (see the Typical Performance Characteristics section on page 9 for more details). Similar results can be achieved with other cell/pack types after characterization. MPF42791 Rev. 1.0 MonolithicPower.com 9/19/2022 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2022 MPS. All Rights Reserved. 8 MPF42791 – 2 TO 16 BATTERY PACK FG W/ R DETECTION AND THERMAL MODEL TYPICAL PERFORMANCE CHARACTERISTICS The MPF42791 fuel gauge performance depends on multiple factors, such as the accuracy of the measurements, the correctness of the configuration, and the fidelity of the cell mathematical model. This means that fuel gauge performance may vary depending on the battery operating conditions. This section shows examples of the MPS MPF42791 fuel gauge pack’s SOC performance when paired with MPS’s MP279x AFE family. Constant-Current/Constant-Voltage (CC/CV) Charge and Dynamic Discharge Cycle The next scenarios consist of charging a 10S1P (6) battery using the typical CC/CV method, followed by a highly dynamic discharge at different ambient temperatures. The charge constant current rate is 1C, while the charge termination current in this example is 0.1C. The highly dynamic discharge corresponds to a typical e-bike’s current profile, with an average current of 1C and maximum peak currents up to 2.8C. Figure 3 shows the current profile of the complete cycle at 25°C. 1 Current C-Rate 0.5 0 -0.5 -1 -1.5 -2 -2.5 -3 0 20 40 0 0 100 120 140 1 0 Time min Figure 3: CC/CV Charge and Dynamic Discharge Current Profile Figure 4 shows the MPF42791’s performance for the CC/CV charge and dynamic discharge cycle at an ambient temperature of 25°C. During charge, the root-mean-squared (7) and maximum pack SOC error are 0.61% and 1.03%, respectively. During discharge, the root-mean-squared and pack SOC error are 0.78% and 1.94%, respectively. Notes: 6) 10S1P refers to the battery configuration. There are 10 groups of 1 parallel cell connected in series. ̂ 2 ∑𝑁 𝑛=1(𝜃𝑛 −𝜃𝑛 ) 𝑁 , where θ is the actual SOC, 𝜃̂ is the estimated SOC, and N is the number of samples. 100 10 MPF42791 Reference Error 0 State-Of-Charge 3 5 SOC Error ound 0 0 40 -3 SOC Error ound -5 20 0 0 20 40 0 0 100 120 140 State-Of-Charge Error 7) The RMS error is equal to √ -10 1 0 Time min Figure 4: MPF42791 Performance for a CC/CV Charge and Dynamic Discharge (Ambient Temperature = 25°C) MPF42791 Rev. 1.0 MonolithicPower.com 9/19/2022 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2022 MPS. All Rights Reserved. 9 MPF42791 – 2 TO 16 BATTERY PACK FG W/ R DETECTION AND THERMAL MODEL Figure 5 shows the MPF42791’s performance for the CC/CV charge and dynamic discharge cycle at an ambient temperature of 0°C. During charge, the root-mean-squared and maximum pack SOC error are 0.68% and 1.22%, respectively. During discharge, the root-mean-squared and pack SOC error are 1.15% and 2.97%, respectively. 100 10 MPF42791 Reference Error State-Of-Charge 3 5 SOC Error ound State-Of-Charge Error 0 0 0 40 -3 SOC Error ound -5 20 0 0 50 100 -10 150 Time min Figure 5: MPF42791 Performance for a CC/CV Charge and Dynamic Discharge (Ambient Temperature = 0°C) Figure 6 shows the MPF42791’s performance for the CC/CV charge and dynamic discharge cycle at 40°C ambient temperature. During charge, the root-mean-squared and maximum pack SOC error are 0.40% and 0.60%, respectively. During discharge, the root-mean-squared and pack SOC error are 0.77% and 1.89%, respectively. 100 10 0 State-Of-Charge 3 5 SOC Error ound 0 0 40 -3 SOC Error ound -5 20 0 0 50 100 150 State-Of-Charge Error MPF42791 Reference Error -10 Time min Figure 6: MPF42791 Performance for a CC/CV Charge and Dynamic Discharge (Ambient Temperature = 40°C) Performance Summary This section provides a summary of the MPF42791’s real-world performance. Table 2Error! Reference source not found. shows a summary of the pack SOC performance metrics for a 10S1P battery. Table 2: MPF42791 SOC Root-Mean-Squared (and Maximum) Error Test Case CC/CV charge Dynamic discharge 0°C 0.68% (1.22%) 1.15% (2.97%) 25°C 0.61% (1.03%) 0.78% (1.94%) 40°C 0.40% (0.60%) 0.77% (1.89%) MPF42791 Rev. 1.0 MonolithicPower.com 9/19/2022 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2022 MPS. All Rights Reserved. 10 MPF42791 – 2 TO 16 BATTERY PACK FG W/ R DETECTION AND THERMAL MODEL OPERATION The MPF42791 relies on a host microcontroller (MCU) to periodically update the fuel gauge’s required inputs. This includes the cell voltages (via the VRDG_CELLxx registers), current (via the IRDG_CELLxx registers), and temperature (via the TRDG_TSx registers). The host MCU is responsible for synchronizing the input data to the fuel gauge’s execution time (EXE_TIME). The host MCU sends the EXE_CMD command to trigger the fuel gauge execution and waits until the iteration is completed (FG_EXE_FLAG = 0). Then the host MCU can read back the fuel gauge’s output registers, such as the pack state-of-charge (SOC). The interrupt request (IRQ) pin can be configured to notify several events, such as a completed iteration or other conditions (see the xx_INTR_EN registers starting on page 56 for details). Operating Modes Active In active mode, the fuel gauge is either updating the battery internal states or communicating via the I2C bus. Standby In standby mode, the fuel gauge is idle, which means that all triggered updates have been completed and the fuel gauge is waiting for activity on the SDA line to transition to active mode. See the I2C Communication Interface section on page 12 for more details. Disabled In disabled mode, the chip enable (CE) pin is low. I2C communication is not available, and the fuel gauge achieves minimal current consumption but still retains all internal state variables in its memory. Configuration and Data Exchange Configuration Mode In the configuration mode, the MPF42791 is set to receive configuration parameters. However, the device will stop operating. This mode is enabled by sending the CONFIG_MODE_CMD and can be confirmed by reading the CONFIG_MODE_FLAG register. After the fuel gauge configurations are successfully updated, the host system must send the CONFIG_EXIT_CMD command to save the configuration into non-volatile memory (NVM). This ensures that the configuration remains after a hardware reset (cycling the device’s power or cycling power on the nRST pin). Editing Mode As an alternative to the configuration mode, the edit mode allows for partial configuration changes. In this mode, the fuel gauge settings can be updated, but not changes to the fuel gauge cell model. Configuration mode is required to change the fuel gauge cell model. In this mode, the fuel gauge operation does not stop, which allows for on-the-fly configurations. This mode is enabled by sending the EDIT_CONFIG_CMD command and can be confirmed by reading the EDIT_SETTINGS_FLAG. The host system can exit this mode by sending the END_EDIT_CONFIG_CMD or CONFIG_EXIT_CMD command, which store the updated configuration in the MPF42791’s NVM. LED Control The MPF42791 can drive five external LEDs that report the pack SOC. There are 2 methods for controlling the LEDs, direct control or manual control, which is configured using the LEDS_ON_MAN register. Note that the LED settings can be written at any time during active or standby operating modes without having to enter configuration or edit modes. Direct Control With direct LED control, the fuel gauge directly controls the LEDs based on the pack SOC (see Table 1 on page 12). When the PB pin is pulled low (if the LEDS_ON_BTN register is enabled), or when the battery pack is charging (if LEDS_ON_CHG is enabled), the LEDs display pack SOC. The deglitch time between charge and discharge can be configured via the LED_TRANS register. The LED turn-on time can be configured via the LEDS_ON_TIME register. MPF42791 Rev. 1.0 MonolithicPower.com 9/19/2022 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2022 MPS. All Rights Reserved. 11 MPF42791 – 2 TO 16 BATTERY PACK FG W/ R DETECTION AND THERMAL MODEL Table 1: LED State-of-Charge Indicator Map LED Status Pack SOC 1 2 4 4 5 SOC > 90% On On On On On 90% ≥ SOC > On On On On Off 70% 70% ≥ SOC > On On On Off Off 50% 50% ≥ SOC > On On Off Off Off 30% 30% ≥ SOC > On Off Off Off Off 10% 10% ≥ SOC Off Off Off Off Off Manual LED Control With manual LED control, the host manually controls each LED via the corresponding LEDx_ON register. I2C COMMUNICATION INTERFACE The MPF42791 has two I2C-compatible interfaces. The primary I2C channel communicates with the host MCU which extracts the data from the AFE. The secondary I2C channel is designed to monitor the fuel gauge status in real time and configure the fuel gauge using the MPF4279x graphic user interface (GUI). Note that write operations are only accepted from one channel at a time (the primary channel by default). To write to the fuel gauge using the secondary I2C channel, the CHSL pin must be pulled high; otherwise, write operations from this channel are ignored. I2C The is a bidirectional, two-wire serial interface. Only two bus lines are required: a serial data line (SDA) and a serial clock line (SCL). The device can be considered a master or a slave when performing data transfers. A device that initiates a data transfer on the bus and generates the clock signals to permit the transfer is considered a master. Any device that the master addresses is considered a slave. Both MPF42791 I2C interfaces operate as slave devices with a configurable address (0x08 by default). They receive control inputs from the master device and ignore general call addresses. The I2C interface supports both standard mode (up to 100kbits), and fast mode (up to 400kbits). The SDA and SCL lines are bidirectional with open drain outputs that should be connected to the positive supply voltage via a current source or pull-up resistor. When the bus is free, both lines are high. The data on the SDA line must be stable during the high period of the clock. the high or low state of the data line can only change when the clock signal on the SCL line is low. Note that a single clock pulse is generated for each data bit transferred (see Figure 7). Figure 7: Bit Transfer on the I2C Bus All transactions must begin with a start (S) command and can be terminated with a stop (P) command. Start and stop commands are always generated by the master. A start command is defined by a high-to-low transition on the SDA line while SCL is high (see Figure 8). A stop command is defined by a low-to-high transition on the SDA line while the SCL is high (see Figure 8). The bus is considered busy after a start command and free after a stop command. Figure 8: I2C Start (S) and Stop (P) Commands Every byte on the SDA line must be 8 bits long and must be followed by an acknowledge bit (ACK). Note that data is transferred with the most significant bit (MSB) first. A slave cannot receive or transmit a complete byte of data while performing other tasks, but it can hold the SCL line low to force the master into a wait state (clock stretching). Then, when the slave is ready, data transfer continues, and the clock line (SCL) is released. Figure 9 shows a complete data transfer. The acknowledgement takes place after every byte and allows the receiver to signal to the transmitter that the byte was successfully received. All clock pulses are generated by the master, including the 9th clock pulse (ACK). The transmitter releases the SDA line during the ACK clock pulse so that the receiver pulls the MPF42791 Rev. 1.0 MonolithicPower.com 9/19/2022 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2022 MPS. All Rights Reserved. 12 MPF42791 – 2 TO 16 BATTERY PACK FG W/ R DETECTION AND THERMAL MODEL SDA line low. If the SDA line remains high during the acknowledge clock pulse, it is not acknowledged (NACK). Then the master can generate a stop command to abort the transfer, or it can generate a repeated start (Sr) command to start a new transfer. After the start command, a 7-bit slave address is sent, followed by the read/write (R/W) bit. A 0 represents a write transmission (W), while a 1 indicates a read request (R). Figure 9 shows a complete data transfer. Figure 9: Complete Data Transfer Active Mode The MPF42791 must be in active mode to communicate (see Operating Modes for additional detail). To transition to active mode, the SDA line must be pulled low. There is a 20ms timeout before starting operation, or the device transitions back to standby mode. After the operations are completed (e.g. I2C communication or fuel gauge updates) there is a 5ms timeout. A low 5ms pulse on the SDA line is recommended to transition to active mode. Note that it may take a few additional milliseconds for the MPF42791 to reach active mode and for the I2C to be ready. To verify that the MPF42791 is ready for communication, an I2C header with the start command, the device address, and the R/W bit can be sent. The device responds with an ACK signal if it is ready for communication. Protocol Layer The MPF42791 uses a protocol where 2 bytes are used for the register and command addresses. A length field is also provided to declare the number of bytes in each read or write transaction. The maximum allowed transaction length is 82 bytes of data (not including the register address, length byte, or CRC bytes). A Cyclic Redundancy Check (CRC) can be used to ensure the transaction’s integrity. When enabled, the last 4 bytes of the transaction correspond to the CRC. Figure 10 and Figure 11 show an example of read and write transactions with CRC, respectively. Figure 10: I2C Read Transaction with CRC Figure 11: I2C Write Transaction with CRC If CRC is disabled, a write transaction can optionally include the correct CRC bytes to be accepted. During a read, the MPF42791 does not include the CRC, so the NACK signal and stop command from the master come after DATA[x]. I2C operations using any address outside of the register map are invalid, even if they are partially valid addresses. An invalid read operation returns a 0 as the data and correct CRC (if enabled), and an invalid write operation is ignored. Cyclic Redundancy Check (CRC) The CRC spans the register address, length, and data payload. It is generated in blocks of 4 bytes. If the number of bytes is not a multiple of 4, the MPF42791 Rev. 1.0 MonolithicPower.com 9/19/2022 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2022 MPS. All Rights Reserved. 13 MPF42791 – 2 TO 16 BATTERY PACK FG W/ R DETECTION AND THERMAL MODEL block is padded with 0x00. The algorithm to generate the CRC is listed below. unsigned long crc32 (unsigned short Reg_Address, unsigned char len, unsigned char *data){ short i; unsigned long crc = 0xffffffff; unsigned char dataTemp[4]; To disable CRC and configure the slave address as 0x08, send the following message: {0x00, 0x41, 0x01, 0x08, 0x94, 0xA0, 0xDE, 0xDD} (Address = 0x4100, Length = 0x01, Data = 0x08, CRC = 0xDDDE A094). for (i=-1; i>8; dataTemp[3]=0; } else dataTemp[i%4]=data[i]; if((i%4)==3 || i == len-1 || i == -1) { for (char j=0; j