Datasheet LT8491 (Analog Devices) - 73
| Manufacturer | Analog Devices |
| Description | High Voltage Buck-Boost Battery Charge Controller with Maximum Power Point Tracking (MPPT) and I2C |
| Pages / Page | 82 / 73 — APPLICATIONS INFORMATION. Figure 30. Optional Feedback Resistor … |
| File Format / Size | PDF / 2.1 Mb |
| Document Language | English |
APPLICATIONS INFORMATION. Figure 30. Optional Feedback Resistor Disconnect Circuit #1. Optional: EXTVCC Disconnect
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APPLICATIONS INFORMATION
If desired, the resistors can be automatically disconnected Selecting Q3: This NPN must have a collector to emitter from the battery when charging stops by using one of the breakdown voltage greater than the maximum VBAT. The circuits shown in Figure 30 and Figure 31. The circuits MMBT5550L is also suitable for most applications due to are controlled by the SWENO signal from the LT8491 and its 140V breakdown rating. connect the resistor feedback network when charging is Selecting R taking place. When charging stops, the network is dis- LIM3: Using VGS(ON) and setting RVGS1 to 100k connected and current draw from the battery becomes ⎛ R ⎞ VGS1 negligible. RLIM3 = ⎜ V ⎟ •2.6V Ω ⎝ GS(ON) ⎠ TO CHARGER OUT AT RSENSE2 where VGS(ON) is the desired gate to source voltage needed to turn on M5. If M5 is not properly selected, the RVGS1 Z1 100k on resistance may be large enough to cause a significant (OPT.) M5 LT8491 voltage drop across the drain-source terminals of this FBOUT + device. Check this voltage drop to determine if the appli- OPTIONAL R FBOR FBOUT1 FEEDBACK cation can tolerate this error. RDACO1 RDACO2 RESISTOR FBOW V DISCONNECT BAT CIRCUIT Selecting Z1: Due to the transients that may occur during C R DACO FBOUT2 – hot-plugging of a battery, this Zener diode is recommended SWEN SWENO Q3 to protect device M5 from excessive gate to source volt- GND age. If using device Z1, the reverse breakdown voltage 200k RLIM3 26.1k should be selected such that VGS(ON) < VZ1(BREAKDOWN) 8491 F30 < VGSMAX where VGSMAX is the maximum rated gate to source voltage specified by the device manufacturer. The
Figure 30. Optional Feedback Resistor Disconnect Circuit #1
BZT52C13 has a reverse breakdown voltage of 13V mak- ing it suitable for the RLIM3 value shown in Figure 30. TO CHARGER OUT AT RSENSE2 Alternate Circuit: For lower battery voltages (< 20V), Q3 in Figure 30 may saturate. To avoid this, consider connecting RVGS1 100k the emitter of Q3 directly to ground by removing RLIM3 M5 LT8491 and adding resistor RLIM4 to the base of Q3 as shown in FBOUT + Figure 31. Employing the optional feedback resistor dis- OPTIONAL R FBOR FBOUT1 FEEDBACK connect at arbitrarily low battery voltages will be limited RDACO1 RDACO2 RESISTOR FBOW V DISCONNECT BAT by the required gate to source voltage of M5. C R CIRCUIT DACO FBOUT2 – Use the following equation to properly set R SWEN LIM4: SWENO Q3 RLIM4 R GND R VGS1 200k LIM4 = 91• VBAT 8491 F31
Optional: EXTVCC Disconnect Figure 31. Optional Feedback Resistor Disconnect Circuit #2
It is often desirable to connect EXTVCC to the battery to Selecting M5: This PMOS must have a drain to source reduce power loss (increase efficiency) and heating in breakdown voltage greater than the maximum V the LT8491. However, the LT8491 draws current into the BAT. The ZVP3310F is rated for 100V making it suitable for most EXTVCC pin that can drain the battery when charging cur- applications. rents are low or when charging stops. Tying the MODE pin Rev. 0 For more information www.analog.com 73 Document Outline Features Applications Typical Application Description Absolute Maximum Ratings Order Information Pin Configuration Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Overview I2C Serial Interface I2C: START and STOP Conditions I2C: ACKnowledge I2C: Chip Addressing I2C: Clock Stretching I2C: Data Transfer Transactions I2C: Powering the Interface I2C Data Data: Memory Regions Data: Bytes, Words and Long Words Data: Min/Max Register Values Data: Access Permissions Startup Sequence Battery Charging Algorithm Stage 0: Trickle Charging Stage 1: Full Constant Current Stage 2: Constant Voltage Stage 3: (Optional) Reduced Constant Voltage Done Charging Charging Faults Maximum Power Point Tracking Telemetry Operation Telemetry: Configuration Settings Telemetry: Acquisition CRC Operation EEPROM Operation EEPROM: Startup EEPROM: Reading EEPROM: Writing I2C Register Map I2C Register Descriptions Telemetry Registers TELE_TBAT TELE_POUT TELE_PIN TELE_EFF TELE_IOUT TELE_IIN TELE_VBAT TELE_VIN TELE_VINR Status Registers STAT_CHARGER STAT_SYSTEM STAT_SUPPLY STAT_TSx_REMAIN STAT_CHRG_FAULTS STAT_VERSION STAT_BOOT_CRC STAT_CFG_CRC Control The EEPROM CTRL_WRT_TO_BOOT CTRL_EE_WRT_EN Control Other Functions CTRL_HALT_STARTUP CTRL_CHRG_EN CTRL_RESTART_CHIP CTRL_RESET_FLAG CTRL_UPDATE_TELEM Configure The Telemetry CFG_RSENSE1 CFG_RIMON_OUT CFG_RSENSE2 CFG_RDACO CFG_RFBOUT1 CFG_RFBOUT2 CFG_RDACI CFG_RFBIN2 CFG_RFBIN1 Configure Initial Charger Enable CFG_INIT_CHRG_EN Configure VBAT for Stages 0, 1 and 3 CFG_VS3_25C CFG_UV_S0 CFG_S0_UV CFG_S0_S1 CFG_S1_S0 Configure Temperature Fault Limits CFG_TBAT_MIN CFG_TBAT_MAX Configure Stage Timeout Limits CFG_TMR_S0 CFG_TMR_S1 CFG_TMR_S2 CFG_TMR_S3 Configure Automatic Restart CFG_RSTRT_IN_FLT CFG_RSTRT_IN_DONEA CFG_RSTRT_IN_DONEB CFG_RSTRT_IN_S3 Configure Charge Termination CFG_TERMINATE Configure Misc. CFG_SCAN_RATE_LP CFG_SCAN_RATE CFG_CHRG_MISC Configure Temperature Compensation CFG_TC3, CFG_TC2, CFG_TC1 Configure User Code CFG_USER_CODE Manufacturer Data MFR_DATA1 MFR_DATA2 MFR_DATA3 Applications Information Hardware Configuration HW Config: Input Voltage Sensing and Modulation HW Config: VINR Pin Connections HW Config: Solar Panel Powered Charging HW Config: DC Supply Powered Charging HW Config: VBAT in Stage 2 (VS2) HW Config: Input Current Sense and Limit HW Config: Output Current Sense and Limit HW Config: Current Sense Filtering HW Config: Battery Temperature and Disconnect Sensing HW Config: SHDN Pin Connections HW Config: MODE Pin – Current Conduction Mode HW Config: Driving an LED with the STATUS Pin HW Config: I2C Chip Address Pin In-Situ Battery Charging Hot-Plugging Considerations STATUS Indicator Pin Lithium-Ion Battery Charging Lead-Acid Battery Charging Optional Features Optional: Low Power Mode Optional: Output Feedback Resistor Disconnect Optional: EXTVCC Disconnect Optional: Remote Battery Voltage Sensing Optional: DC Supply Detection Circuit Board Layout Considerations Design Example Typical Applications Package Description Typical Application Related Parts
APPLICATIONS INFORMATION
If desired, the resistors can be automatically disconnected Selecting Q3: This NPN must have a collector to emitter from the battery when charging stops by using one of the breakdown voltage greater than the maximum VBAT. The circuits shown in Figure 30 and Figure 31. The circuits MMBT5550L is also suitable for most applications due to are controlled by the SWENO signal from the LT8491 and its 140V breakdown rating. connect the resistor feedback network when charging is Selecting R taking place. When charging stops, the network is dis- LIM3: Using VGS(ON) and setting RVGS1 to 100k connected and current draw from the battery becomes ⎛ R ⎞ VGS1 negligible. RLIM3 = ⎜ V ⎟ •2.6V Ω ⎝ GS(ON) ⎠ TO CHARGER OUT AT RSENSE2 where VGS(ON) is the desired gate to source voltage needed to turn on M5. If M5 is not properly selected, the RVGS1 Z1 100k on resistance may be large enough to cause a significant (OPT.) M5 LT8491 voltage drop across the drain-source terminals of this FBOUT + device. Check this voltage drop to determine if the appli- OPTIONAL R FBOR FBOUT1 FEEDBACK cation can tolerate this error. RDACO1 RDACO2 RESISTOR FBOW V DISCONNECT BAT CIRCUIT Selecting Z1: Due to the transients that may occur during C R DACO FBOUT2 – hot-plugging of a battery, this Zener diode is recommended SWEN SWENO Q3 to protect device M5 from excessive gate to source volt- GND age. If using device Z1, the reverse breakdown voltage 200k RLIM3 26.1k should be selected such that VGS(ON) < VZ1(BREAKDOWN) 8491 F30 < VGSMAX where VGSMAX is the maximum rated gate to source voltage specified by the device manufacturer. The
Figure 30. Optional Feedback Resistor Disconnect Circuit #1
BZT52C13 has a reverse breakdown voltage of 13V mak- ing it suitable for the RLIM3 value shown in Figure 30. TO CHARGER OUT AT RSENSE2 Alternate Circuit: For lower battery voltages (< 20V), Q3 in Figure 30 may saturate. To avoid this, consider connecting RVGS1 100k the emitter of Q3 directly to ground by removing RLIM3 M5 LT8491 and adding resistor RLIM4 to the base of Q3 as shown in FBOUT + Figure 31. Employing the optional feedback resistor dis- OPTIONAL R FBOR FBOUT1 FEEDBACK connect at arbitrarily low battery voltages will be limited RDACO1 RDACO2 RESISTOR FBOW V DISCONNECT BAT by the required gate to source voltage of M5. C R CIRCUIT DACO FBOUT2 – Use the following equation to properly set R SWEN LIM4: SWENO Q3 RLIM4 R GND R VGS1 200k LIM4 = 91• VBAT 8491 F31
Optional: EXTVCC Disconnect Figure 31. Optional Feedback Resistor Disconnect Circuit #2
It is often desirable to connect EXTVCC to the battery to Selecting M5: This PMOS must have a drain to source reduce power loss (increase efficiency) and heating in breakdown voltage greater than the maximum V the LT8491. However, the LT8491 draws current into the BAT. The ZVP3310F is rated for 100V making it suitable for most EXTVCC pin that can drain the battery when charging cur- applications. rents are low or when charging stops. Tying the MODE pin Rev. 0 For more information www.analog.com 73 Document Outline Features Applications Typical Application Description Absolute Maximum Ratings Order Information Pin Configuration Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Overview I2C Serial Interface I2C: START and STOP Conditions I2C: ACKnowledge I2C: Chip Addressing I2C: Clock Stretching I2C: Data Transfer Transactions I2C: Powering the Interface I2C Data Data: Memory Regions Data: Bytes, Words and Long Words Data: Min/Max Register Values Data: Access Permissions Startup Sequence Battery Charging Algorithm Stage 0: Trickle Charging Stage 1: Full Constant Current Stage 2: Constant Voltage Stage 3: (Optional) Reduced Constant Voltage Done Charging Charging Faults Maximum Power Point Tracking Telemetry Operation Telemetry: Configuration Settings Telemetry: Acquisition CRC Operation EEPROM Operation EEPROM: Startup EEPROM: Reading EEPROM: Writing I2C Register Map I2C Register Descriptions Telemetry Registers TELE_TBAT TELE_POUT TELE_PIN TELE_EFF TELE_IOUT TELE_IIN TELE_VBAT TELE_VIN TELE_VINR Status Registers STAT_CHARGER STAT_SYSTEM STAT_SUPPLY STAT_TSx_REMAIN STAT_CHRG_FAULTS STAT_VERSION STAT_BOOT_CRC STAT_CFG_CRC Control The EEPROM CTRL_WRT_TO_BOOT CTRL_EE_WRT_EN Control Other Functions CTRL_HALT_STARTUP CTRL_CHRG_EN CTRL_RESTART_CHIP CTRL_RESET_FLAG CTRL_UPDATE_TELEM Configure The Telemetry CFG_RSENSE1 CFG_RIMON_OUT CFG_RSENSE2 CFG_RDACO CFG_RFBOUT1 CFG_RFBOUT2 CFG_RDACI CFG_RFBIN2 CFG_RFBIN1 Configure Initial Charger Enable CFG_INIT_CHRG_EN Configure VBAT for Stages 0, 1 and 3 CFG_VS3_25C CFG_UV_S0 CFG_S0_UV CFG_S0_S1 CFG_S1_S0 Configure Temperature Fault Limits CFG_TBAT_MIN CFG_TBAT_MAX Configure Stage Timeout Limits CFG_TMR_S0 CFG_TMR_S1 CFG_TMR_S2 CFG_TMR_S3 Configure Automatic Restart CFG_RSTRT_IN_FLT CFG_RSTRT_IN_DONEA CFG_RSTRT_IN_DONEB CFG_RSTRT_IN_S3 Configure Charge Termination CFG_TERMINATE Configure Misc. CFG_SCAN_RATE_LP CFG_SCAN_RATE CFG_CHRG_MISC Configure Temperature Compensation CFG_TC3, CFG_TC2, CFG_TC1 Configure User Code CFG_USER_CODE Manufacturer Data MFR_DATA1 MFR_DATA2 MFR_DATA3 Applications Information Hardware Configuration HW Config: Input Voltage Sensing and Modulation HW Config: VINR Pin Connections HW Config: Solar Panel Powered Charging HW Config: DC Supply Powered Charging HW Config: VBAT in Stage 2 (VS2) HW Config: Input Current Sense and Limit HW Config: Output Current Sense and Limit HW Config: Current Sense Filtering HW Config: Battery Temperature and Disconnect Sensing HW Config: SHDN Pin Connections HW Config: MODE Pin – Current Conduction Mode HW Config: Driving an LED with the STATUS Pin HW Config: I2C Chip Address Pin In-Situ Battery Charging Hot-Plugging Considerations STATUS Indicator Pin Lithium-Ion Battery Charging Lead-Acid Battery Charging Optional Features Optional: Low Power Mode Optional: Output Feedback Resistor Disconnect Optional: EXTVCC Disconnect Optional: Remote Battery Voltage Sensing Optional: DC Supply Detection Circuit Board Layout Considerations Design Example Typical Applications Package Description Typical Application Related Parts
