Table of Contents
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FEATURES
V
Range: 6V to 80V
n
IN
V
Range: 1.3V to 80V
n
BAT
Single Inductor Allows V
n
to V
BAT
Automatic MPPT for Solar Powered Charging
n
Automatic Temperature Compensation
n
2
I
C Telemetry and Configuration
n
Internal EEPROM for Configuration Storage
n
Operation from Solar Panel or DC Supply
n
Four Integrated Feedback Loops
n
Synchronizable Fixed Frequency: 100kHz to 400kHz
n
64-Lead (7mm × 11mm × 0.75mm) QFN Package
n
APPLICATIONS
Solar Powered Battery Chargers
n
Multiple Types of Lead-Acid Battery Charging
n
Li-Ion Battery Charger
n
Battery Equipped Industrial or Portable Military
n
Equipment
TYPICAL APPLICATION
Simplified Solar Powered Battery Charger Schematic
SOLAR PANEL
2
I
C INTERFACE
TELEMETRY
STATUS CONTROL
CONFIGURATION
GATEV
´
CC
Document Feedback
High Voltage Buck-Boost Battery Charge
Controller with Maximum Power Point
Above, Below, or Equal
IN
GATEV
´
CC
TG1 BOOST1
SW1 BG1 CSP CSN
BG2 SW2 BOOST2 TG2
CSNIN
CSPIN
V
IN
LT8491
SDA
SCL
GATEV
CC
INTV
STATUS
CA
CC
AV
AV
DD
DD
For more information
Tracking (MPPT) and I
DESCRIPTION
The
LT
8491
is a buck-boost switching regulator battery
®
charger that implements a constant-current constant-
voltage (CCCV) charging profile used for most battery
types, including sealed lead-acid (SLA), flooded, gel and
lithium-ion.
The device operates from input voltages above, below or
equal to the output voltage and can be powered by a solar
panel or a DC power supply. On-chip logic provides auto-
matic maximum power point tracking (MPPT) for solar
powered applications. The LT8491 can perform automatic
temperature compensation by sensing an external therm-
istor thermally coupled to the battery. The STATUS pin
can be used to drive an LED indicator lamp. The device is
available in a low profile (0.75mm) 7mm × 11mm 64-lead
QFN package.
All registered trademarks and trademarks are the property of their respective owners.
GATEV
´
CC
V
BAT
CSPOUT
+
CSNOUT
EXTV
CC
RECHARGABLE
BATTERY
AV
DD
THERMISTOR
TEMPSENSE
GND
www.analog.com
Maximum Power
Point Tracking
FULL PANEL SCAN
LOAD
V
PANEL
6V/DIV
–
PERTURB AND
OBSERVE
IMON_IN
0.2V/DIV
0.5s/DIV
8491 TA01a
LT8491
2
C
PERTURB
AND
OBSERVE
8491 TA01b
Rev. 0
1
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Table of Contents
Related Manuals for Analog Devices LINEAR LT8491
Summary of Contents for Analog Devices LINEAR LT8491
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Page 1: Features
LT8491 High Voltage Buck-Boost Battery Charge Controller with Maximum Power Point Tracking (MPPT) and I FEATURES DESCRIPTION Range: 6V to 80V 8491 is a buck-boost switching regulator battery ® Range: 1.3V to 80V charger that implements a constant-current constant- Single Inductor Allows V Above, Below, or Equal voltage (CCCV) charging profile used for most battery to V... -
Page 2: Table Of Contents
LT8491 TABLE OF CONTENTS Features ............. 1 C Register Map .......... 27 Applications ..........1 C Register Descriptions ........ 30 Telemetry Registers ..........30 Typical Application ........1 TELE_TBAT ..............30 Description..........1 TELE_POUT ..............31 Absolute Maximum Ratings ......4 TELE_PIN ..............31 Order Information .......... - Page 3 LT8491 Applications Information ........ 61 Configure V for Stages 0, 1 and 3 ......46 Hardware Configuration .......... 61 CFG_VS3_25C ............46 HW Config: Input Voltage Sensing and Modulation .. 61 CFG_UV_S0 ..............47 HW Config: VINR Pin Connections ......61 CFG_S0_UV ..............47 HW Config: Solar Panel Powered Charging ....
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Page 4: Absolute Maximum Ratings
LT8491 ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION (Note 1) TOP VIEW – V – V CSPIN CSNIN – V ........–0.3V to 0.3V CSPOUT CSNOUT SS, CLKOUT, CSP, CSN Voltage ....–0.3V to 3V Voltage (Note 2) ........–0.3V to 2.2V LDO33, V , AV , Voltage...... -
Page 5: Electrical Characteristics
LT8491 ELECTRICAL CHARACTERISTICS denotes the specifications which apply over the full operating temperature range, otherwise specifications are at T = 25°C. V = 12V, V = AV = 3.3V, SHDN = 3V unless otherwise noted. (Note 3) PARAMETER CONDITIONS UNITS Voltage Supply and Regulators Operating Voltage Range (Note 7) Quiescent Current... - Page 6 LT8491 ELECTRICAL CHARACTERISTICS denotes the specifications which apply over the full operating temperature range, otherwise specifications are at T = 25°C. V = 12V, V = AV = 3.3V, SHDN = 3V unless otherwise noted. (Note 3) PARAMETER CONDITIONS UNITS Switching Regulator Oscillator (OSC1) Switch Frequency Range Syncing or Free Running...
- Page 7 LT8491 ELECTRICAL CHARACTERISTICS denotes the specifications which apply over the full operating temperature range, otherwise specifications are at T = 25°C. V = 12V, V = AV = 3.3V, SHDN = 3V unless otherwise noted. (Note 3) PARAMETER CONDITIONS UNITS EEPROM Characteristics Endurance (Note 8) 0°C <...
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Page 8: Typical Performance Characteristics
LT8491 TYPICAL PERFORMANCE CHARACTERISTICS Solar Powered Charging Solar Powered Charging Solar Powered Charging Lithium- Lead-Acid Battery Lithium-Ion Battery Ion Battery – C/10 Termination 17.5 PARTLY CLOUDY PARTLY CLOUDY PARTLY CLOUDY 15.0 STAGE 1 STAGE 1 STAGE 2 STAGE 2 12.5 10.0 SUNSET STATUS... - Page 9 LT8491 TYPICAL PERFORMANCE CHARACTERISTICS Max Power Point Tracking Perturb and Observe Perturb and Observe PANEL PANEL 5V/DIV 5V/DIV PERTURB AND OBSERVE PANEL 5V/DIV IMON_OUT IMON_OUT 100mV/DIV 200mV/DIV IMON_OUT 500mV/DIV 30s/DIV 8491 G09 0.5s/DIV 8491 G10 0.5s/DIV 8491 G11 FIGURE 37 APPLICATION FIGURE 37 APPLICATION FIGURE 37 APPLICATION Perturb and Observe Max Power...
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Page 10: Pin Functions
LT8491 PIN FUNCTIONS FBIR (Pin 1): A/D Input Pin. Connects to FBIN pin to mea- SHDN (Pin 11): Shutdown Pin. In conjunction with the sure input voltage. UVLO (undervoltage lockout) circuit, this pin is used to enable/disable the chip. Do not float this pin. CA (Pin 2): A/D Input Pin. - Page 11 LT8491 PIN FUNCTIONS SYNC (Pin 21): To synchronize the switching frequency SRVO_FBOUT (Pin 38): Open-Drain Logic Output. This to an outside clock, simply drive this pin with a clock. The pin is pulled to ground when the output voltage feedback high voltage level of the clock needs to exceed 1.3V, and loop is active.
- Page 12 LT8491 PIN FUNCTIONS NC (Pins 52, 60): Not connected. (Pin 58): A/D Positive Reference Pin. Tie this pin to and LDO33. IIR (Pin 53): A/D Input Pin. Connects to IMON_IN to read input current. Used to manage MPPT and for telemetry. SDA (Pin 61): I C Bidirectional Data Pin.
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Page 13: Block Diagram
LT8491 BLOCK DIAGRAM BOOST1 – – MODE 2.5V GATEV UV_INTV CI_IN OI_OUT BUCK-BOOST LOGIC START-UP AND FAULT LOGIC UV_LD033 UV_V UV_GATEV – 1.234V SHDN SYNC – BOOST2 OSC1 6.4V CLKOUT EXTV – 305k CLKDET 6.35V REG 6.35V REG INTV INTERNAL SWEN SUPPLY1 3.3V REG... -
Page 14: Operation
LT8491 OPERATION OVERVIEW The LT8491 also includes a TEMPSENSE pin, which can be connected to an NTC resistor divider network ther- The LT8491 is a powerful and easy to use battery charging mally coupled to the battery pack. The TEMPSENSE pin controller with automatic maximum power point track- can facilitate several functions including temperature ing (MPPT), temperature compensation and an I... -
Page 15: I 2 C: Chip Addressing
LT8491 OPERATION A6 - A0 B7 - B0 B7 - B0 1 - 7 1 - 7 1 - 7 START CHIP DATA DATA STOP CONDITION ADDRESS CONDITION 8491 F02 Figure 2. Data Transfer Over I C Bus from the slave, the master pulls down the SDA line during The word-read transaction, shown in Figure 5, should be the clock pulse to indicate receipt of the data. -
Page 16: I 2 C Data
LT8491 OPERATION CHIP ADDR REG ADDR DATA A6:A0 b7:b0 b7:b0 8491 F03 FROM MASTER TO SLAVE A: ACKNOWLEDGE (LOW) A: NOT ACKNOWLEDGE (HIGH) R: READ BIT (HIGH) FROM SLAVE TO MASTER W: WRITE BIT (LOW) S: START CONDITION P: STOP CONDITION Figure 3. -
Page 17: Data: Bytes, Words And Long Words
LT8491 OPERATION Boot Region: The boot data is stored in non-volatile Reading TELE_IOUT with the word-read transaction from EEPROM and is copied into the configuration registers register address 0x08 returns two bytes, DATA0 (0x9A) during startup or after the CTRL_RESTART_CHIP register and then DATA1 (0x14) indicating 5.274 Amps. -
Page 18: Startup Sequence
LT8491 OPERATION Table 4. Register Access Permissions (Except Control Region) MEMORY REGION REGISTER NAME C REG ADDRESS RANGE READ ACCESS WRITE ACCESS Telemetry 0x00-0x11 Always Never Status 0x12-0x1F Always Never Configuration 0x28-0x5B Always Only when CHRG_LOGIC_ON=0 CTRL_EE_WRT_EN≠0xCC and SYSTEM_BUSY=b00 Manufacturer 0x5D-0x61 Always Never 1, 2... - Page 19 LT8491 OPERATION until the CRC check passes. More information about the Subsequently, CTRL_CHRG_EN is preset with the value CRC checking is discussed in the CRC Operation section. read from BOOT_MISC in the EEPROM. This determines if the charging starts automatically, at the end of the When the boot CRC and the factory CRC check passes, sequence, or not.
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Page 20: Battery Charging Algorithm
LT8491 OPERATION STAGE 0 STAGE 1 STAGE 2 STAGE 3 TRICKLE CHARGE CONSTANT CURRENT CONSTANT VOLTAGE FLOAT VOLTAGE STAGE 2 VOLTAGE REGULATION S1_S2 STAGE 3 VOLTAGE REGULATION S2_S1 S3_S0 DROP CAUSES TRANSITION TO STAGE 1 S0_S1 DROP CAUSES TRANSITION TO STAGE 0 VOLTAGES BELOW OR S1_S0 CURRENTS ABOVE PRESET... -
Page 21: Stage 2: Constant Voltage
LT8491 OPERATION Configure V for Stages 0, 1 and 3 section. Stage 1 is Done Charging often referred to as bulk charging in the battery charging When done charging, the power stage is disabled, and community. However, this stage will continue to be called charging is complete. - Page 22 LT8491 OPERATION CHRG_EN*=0 CHARGE LOGIC OFF POWER STAGE OFF ALL FAULT BITS CLEARED CHRG_EN* SET TO 1 CHARGE LOGIC ON < V BATUV_S0 RESET STAGE TIMERS SET CHARGE_STAGE < V S0_BATUV > V BATUV_S0 (STAT_TS0_REMAIN =0x00 AND STAGE 0 (TS0_EXPIRED_FLT S0_TMR_TERM_EN 4,10 TRICKLE CHARGE CURRENT...
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Page 23: Maximum Power Point Tracking
LT8491 OPERATION Any active fault causes the charging to stop, the stage initiated. The TELE_VBAT register and the LOW_VBAT_ timers to pause their countdown, and the status to be FLT bit are updated with each new V measurement. reported as follows: During a stage timer fault, if CFG_RSTRT_IN_ •... -
Page 24: Telemetry: Configuration Settings
LT8491 OPERATION Telemetry: Configuration Settings measure telemetry. This is because the output feedback divider is (optionally) disconnected and the output current All of the telemetry measurements, except for TELE_TBAT sense amplifier is disabled to reduce discharge current and TELE_VINR, first require that valid PCB resistor val- from the battery. -
Page 25: Eeprom Operation
LT8491 OPERATION Table 7. Summary of CRC-Related Registers MEMORY C REG REGION REGISTER NAME ADDRESS DESCRIPTION OF CRC OPERATION PAGE Status STAT_SYSTEM 0x13 Indicates startup CRC calculation errors and startup CRC calculation status. STAT_BOOT_CRC 0x1C Result of most recent CRC, calculated by the LT8491, from the boot region. STAT_CFG_CRC 0x1E Result of most recent CRC, calculated by the LT8491, from the configuration... - Page 26 LT8491 OPERATION Copy the Configuration Registers to the EEPROM: The Restore Factory Defaults: The boot data can be restored configuration register contents are copied to the boot to the factory defaults by writing 0x57 to the CTRL_WRT_ region of the EEPROM by writing 0x30 to the CTRL_ TO_BOOT register.
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Page 27: I 2 C Register Map
LT8491 C REGISTER MAP Summary Table MEMORY C REG DEFAULT REGION REGISTER NAME ADDR SIZE PG. BRIEF REG. DESCRIPTION VALUE DESCRIPTION OF DEFAULT VALUE Telemetry TELE_TBAT 0x00 Word Battery temperature 0x7FFF Indicates that the value has not been measured yet. TELE_POUT 0x02 Word... - Page 28 LT8491 C REGISTER MAP MEMORY C REG DEFAULT REGION REGISTER NAME ADDR SIZE PG. BRIEF REG. DESCRIPTION VALUE DESCRIPTION OF DEFAULT VALUE Configuration CFG_RSENSE1 0x28 Word PCB resistor value Copied from EEPROM during startup. See Boot registers in this table for the factory settings. CFG_RIMON_OUT 0x2A Word...
- Page 29 LT8491 C REGISTER MAP MEMORY C REG DEFAULT REGION REGISTER NAME ADDR SIZE PG. BRIEF REG. DESCRIPTION VALUE DESCRIPTION OF DEFAULT VALUE Boot BOOT_RSENSE1 0x88 Word PCB resistor value 0x0000 Must be configured by user. (EEPROM) BOOT_RIMON_OUT 0x8A Word PCB resistor value 0x0000 Must be configured by user.
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Page 30: I 2 C Register Descriptions
LT8491 C REGISTER MAP Note: I C register addresses 0x62 through 0x87 and 0xBE through 0xFF are reserved locations. Byte read, or Word read of these locations return manufacturer reserved values. If the user writes these locations with new values they will not be stored. C REGISTER DESCRIPTIONS TELEMETRY REGISTERS The telemetry registers, summarized in Table 9 and in the I... -
Page 31: Tele_Pout
LT8491 C REGISTER DESCRIPTIONS TELE_POUT C REG ADDRESS BIT(S) UNITS FORMAT EXAMPLES DESCRIPTION 0x02 [15:0] Watts • 100 Unsigned Integer 210.6W = 0x5244 Calculated power delivered out of the charger. 5.3W = 0x0212 This register contains the most recently measured power delivered out of the charger. The value is in Watts multiplied by 100 in an unsigned integer format. -
Page 32: Tele_Iout
LT8491 C REGISTER DESCRIPTIONS TELE_IOUT C REG ADDRESS BIT(S) UNITS FORMAT EXAMPLES DESCRIPTION 0x08 [15:0] Milliamps Unsigned Integer 5.274A = 0x149A Output current to V 0.039A = 0x0027 This register contains the most recently measured current flowing out of the charger through the R resistor. -
Page 33: Tele_Vin
LT8491 C REGISTER DESCRIPTIONS TELE_VIN C REG ADDRESS BIT(S) UNITS FORMAT EXAMPLES DESCRIPTION 0x0E [15:0] Volts • 100 Unsigned Integer 27.42V = 0x0AB6 V voltage measured from the FBIR pin. This register contains the most recently measured V voltage as measured at the FBIR pin. The value is in Volts multiplied by 100 in an unsigned integer format. -
Page 34: Status Registers
LT8491 C REGISTER DESCRIPTIONS STATUS REGISTERS The following read-only registers, shown in Table 10, indicate status information about the charger. Detailed informa- tion about each register and its respective data follows this table. Table 10. Summary of Status Registers C REGISTER REGISTER NAME SIZE ADDRESS DESCRIPTION... -
Page 35: Stat_System
LT8491 C REGISTER DESCRIPTIONS C REGISTER ADDRESS BIT NAME BIT(S) DESCRIPTION 0x12 CHARGING 1 indicates that battery charging is ongoing in one of the 4 charging stages (Stage 0 to 3). 0 indicates that the charging is not active, and the power stage has been turned off. 0 (not charging) is indicated due to any of the following conditions: •... -
Page 36: Stat_Supply
LT8491 C REGISTER DESCRIPTIONS STAT_SUPPLY C REGISTER ADDRESS BIT NAME BIT(S) DESCRIPTION 0x14 Reserved [7:5] Reserved VIN_UVLO When powered by a panel: 1 indicates that the input voltage is below 10 Volts if Low Power Mode is enabled, otherwise input voltage is below 5.7 Volts. -
Page 37: Stat_Chrg_Faults
LT8491 C REGISTER DESCRIPTIONS The time remaining is approximately 4.47 minutes multiplied by the register value. For example, 0x0D represents 58 minutes remaining. The countdown for each timer pauses when not charging (STAT_CHARGER→CHARGING=0) or a temperature fault occurs. The countdown for a timer also pauses when charging proceeds to the next stage. If either a battery disconnect fault or a low V fault is detected, all countdown timer values are reset. -
Page 38: Stat_Version
LT8491 C REGISTER DESCRIPTIONS C REGISTER ADDRESS BIT NAME BIT(S) DESCRIPTION 0x19 LOW_VBAT_FLT 1 indicates that the low battery voltage fault has been detected. The V thresholds for this fault and V ) are configured in the CFG_UV_S0 and CFG_S0_UV registers. S0_UV UV_S0 This fault bit is cleared to 0:... -
Page 39: Control The Eeprom
LT8491 C REGISTER DESCRIPTIONS CONTROL THE EEPROM The following registers are used to initiate and monitor EEPROM write operations. Write access permissions are detailed in the Data: Access Permissions section. CTRL_WRT_TO_BOOT C REGISTER ADDRESS BIT NAME BIT(S) DESCRIPTION 0x20 Reserved [7:3] Reserved WRITE_FAIL Read of this bit returns a 1 if the most recent attempt to write the EEPROM boot region failed. -
Page 40: Control Other Functions
LT8491 C REGISTER DESCRIPTIONS CONTROL OTHER FUNCTIONS The following registers, shown in Table 11, can be written to control various functions of the LT8491. Write access permissions are detailed in the Data: Access Permissions section. Detailed information about each register and its respective function follow this table. -
Page 41: Ctrl_Restart_Chip
LT8491 C REGISTER DESCRIPTIONS • The supply status register STAT_SUPPLY→SOLAR_STATE bits [2:0] clear to 000b. • The fault register STAT_CHRG_FAULTS holds its last value reported before CHRG_EN=0. • The ECON pin is driven low (see Optional: EXTV Disconnect section). • Some registers cannot be written until the CHRG_LOGIC_ON bit clears in the STAT_CHARGER register. Be sure to poll the CHRG_LOGIC_ON bit before attempting subsequent register writes. -
Page 42: Configure The Telemetry
LT8491 C REGISTER DESCRIPTIONS Writing 0xAA to this register initiates a telemetry update. It can be written when the charging logic is off and telemetry is not otherwise being acquired (see Telemetry: Acquisition). Reading back the BUSY_RDY bit indicates the status of the update which typically requires approximately 20ms to complete. -
Page 43: Cfg_Rimon_Out
LT8491 C REGISTER DESCRIPTIONS multiplied by 100 in an unsigned integer format. See the examples above. The default value is 0x0000 indicating that this value has not been configured. Related Data Sheet Section: See HW Config: Input Current Sense and Limit for information about R SENSE1 CFG_RIMON_OUT C REG ADDRESS BIT(S) -
Page 44: Cfg_Rfbout1
LT8491 C REGISTER DESCRIPTIONS CFG_RFBOUT1 C REG ADDRESS BIT(S) UNITS FORMAT EXAMPLES DESCRIPTION 0x30 [15:0] kΩ • 10 Unsigned Integer 442kΩ = 0x1144 Value of R . Required to calculate telemetry for FBOUT1 274kΩ = 0x0AB4 TELE_VBAT, TELE_POUT, TELE_EFF. The LT8491 uses this register value to calculate telemetry for the TELE_VBAT, TELE_POUT, and TELE_EFF registers. CFG_RFBOUT1 is not used for any other purpose and does not affect charging in any way. -
Page 45: Cfg_Rfbin2
LT8491 C REGISTER DESCRIPTIONS CFG_RFBIN2 C REG ADDRESS BIT(S) UNITS FORMAT EXAMPLES DESCRIPTION 0x36 [15:0] kΩ • 100 Unsigned Integer 10kΩ = 0x03E8 Value of R . Required to calculate telemetry for TELE_VIN. FBIN2 20kΩ = 0x07D0 Also required for TELE_PIN and TELE_EFF telemetry when powered by a DC power supply. -
Page 46: Configure V Bat
LT8491 C REGISTER DESCRIPTIONS CONFIGURE V FOR STAGES 0, 1 AND 3 The following registers configure the battery voltages for some of the charging stage transitions. These are set as a percentage of V which is initially configured with external resistors as discussed in the HW Config: V in Stage 2 ) section. -
Page 47: Cfg_Uv_S0
LT8491 C REGISTER DESCRIPTIONS Related Data Sheet Sections: Battery Charging Algorithm, HW Config: V in Stage 2 (V ), Configure Temp. Compensation, CFG_CHRG_MISC CFG_UV_S0 C REG ADDRESS BIT(S) UNITS FORMAT EXAMPLES MIN VALUE MAX VALUE DESCRIPTION 0x3C [7:0] 200 • (% of V ) Unsigned 30% = 0x3C 0% = 0x00 90% = 0xB4 Configure V... -
Page 48: Cfg_S0_S1
LT8491 C REGISTER DESCRIPTIONS This register is used to set V , the falling V threshold to exit Stage 0 charging and enter the low V fault con- S0_UV dition. V is a percentage of the Stage 2 voltage V . -
Page 49: Cfg_S1_S0
LT8491 C REGISTER DESCRIPTIONS Example: Presume that V is set to 14.2V and we wish to configure V = 9.94V. Set CFG_S0_S1 as follows: S0_S1 9.94V ⎡ ⎤ CFG_S0_S1= 200 • •100% ⎣ ⎢ ⎦ ⎥ 14.2V = 200 •[70%] = 140 (decimal) = 0x8C (hexadecimal) Therefore, writing CFG_S0_S1 to 0x8C configures V... -
Page 50: Configure Temperature Fault Limits
LT8491 C REGISTER DESCRIPTIONS CONFIGURE TEMPERATURE FAULT LIMITS The following two registers set the battery temperature operating range by setting the upper and lower temperature fault limits. The register values are stored in °C as two’s complement, signed integers. Table 15. Summary of Battery Temperature Configuration Registers C REGISTER C BOOT READ REGISTER NAME... -
Page 51: Configure Stage Timeout Limits
LT8491 C REGISTER DESCRIPTIONS CONFIGURE STAGE TIMEOUT LIMITS In power supply mode the user can set finite charging time limits for each stage separately by properly configuring the following register values. Charging time limits are not recommended for use when a load is present on the battery due to the unpredictable amount of time required to achieve full charge. -
Page 52: Configure Automatic Restart
LT8491 C REGISTER DESCRIPTIONS CONFIGURE AUTOMATIC RESTART The following registers in Table 17 configure some of the conditions under which the charging will automatically restart or resume after stopping. The LT8491 employs many features and checks that may cause the charger to stop until more favorable operating conditions return. - Page 53 LT8491 C REGISTER DESCRIPTIONS A specific use case for the CFG_RSTRT_IN_FLT register is when a dead battery needs to be replaced. The user may want the charger to remain off until the battery is exchanged. A voltage measurement might be required prior to start- ing the charger.
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Page 54: Cfg_Rstrt_In_Donea
LT8491 C REGISTER DESCRIPTIONS CFG_RSTRT_IN_DONEA C REGISTER ADDRESS BIT NAME BIT(S) DESCRIPTION 0x47 RSTRT_IN_DONE_ON_VOLTS Setting this bit causes the battery charging to automatically restart, if in the done charging stage, when the V voltage is detected to be below the voltage configured in the RSTRT_IN_ DONE_SET_VOLTS bits. -
Page 55: Cfg_Rstrt_In_Doneb
LT8491 C REGISTER DESCRIPTIONS CFG_RSTRT_IN_DONEB C REGISTER ADDRESS BIT NAME BIT(S) DESCRIPTION 0x48 Reserved [7:6] Reserved RSTRT_IN_DONE_HRS [5:0] By setting these bits to a non-zero value, the charger will wait for a delay time after reaching the done charging stage (see Figure 8), then automatically restart the charging in Stage 0. These bits set the delay in ½... -
Page 56: Configure Misc
LT8491 C REGISTER DESCRIPTIONS CONFIGURE MISC. Table 18. Summary of Miscellaneous Configuration Registers C REGISTER C BOOT READ REGISTER NAME SIZE ADDRESS ADDRESS DESCRIPTION PAGE CFG_SCAN_RATE_LP BYTE 0x4B 0xAB Configures timed full panel scan frequency in solar low power mode. CFG_SCAN_RATE BYTE 0x4C 0xAC... -
Page 57: Cfg_Chrg_Misc
LT8491 C REGISTER DESCRIPTIONS CFG_CHRG_MISC C REGISTER ADDRESS BIT NAME BIT(S) DESCRIPTION 0x4D Reserved [7:5] Reserved USE_VS3_IN_STAGE2 Reduces the Stage 2 battery charging voltage to the value set in CFG_VS3_25C. See below for details. LPMODE_EN Setting this bit enables low power mode as discussed in the Optional: Low Power Mode section. PS_S3_ENABLE When powered by a DC power supply, 1 permits the use of Stage 3 charging and 0 disables the use of Stage 3. -
Page 58: Configure Temperature Compensation
LT8491 C REGISTER DESCRIPTIONS CONFIGURE TEMPERATURE COMPENSATION Table 19. Summary of Temperature Compensation Configuration Registers C REGISTER C BOOT READ REGISTER NAME SIZE ADDRESS ADDRESS DESCRIPTION PAGE CFG_CHRG_MISC BYTE 0x4D 0xAD Contains bit to enable temperature compensation. CFG_TC3 LONG-WORD 0x4E 0xAE 3rd order coefficient for Stage 2 and 3 temperature compensation. -
Page 59: Cfg_Tc3, Cfg_Tc2, Cfg_Tc1
LT8491 C REGISTER DESCRIPTIONS The curve in Figure 10 can be modified via the CFG_TCx registers if needed. Note that hardware limitations restrict ) and V ) to the range of approximately 82% to 123.5% of V (25°C). For proper charger operation, V must always be set lower than V CFG_TC3, CFG_TC2, CFG_TC1 C REG ADDRESS REGISTER NAME... -
Page 60: Manufacturer Data
LT8491 C REGISTER DESCRIPTIONS MANUFACTURER DATA Table 21. Manufacturer CRC C REGISTER REGISTER NAME SIZE ADDRESS DESCRIPTION PAGE MFR_DATA1 WORD 0x5C Manufacturer data. MFR_DATA2 WORD 0x5E Manufacturer data. MFR_DATA3 WORD 0X60 Manufacturer data. MFR_DATA1 C REGISTER ADDRESS BIT NAME BIT(S) DESCRIPTION 0x5C [15:0] Manufacturer data. -
Page 61: Applications Information
LT8491 APPLICATIONS INFORMATION HARDWARE CONFIGURATION where V is the greater of V and V with OCMAX DCMAX some additional margin. The resistors should have a 1% HW Config: Input Voltage Sensing and Modulation tolerance or better. The passive component network shown in Figure 11 is Due to the granularity of standard resistor values, simply required to modulate the solar panel voltage. -
Page 62: Hw Config: Solar Panel Powered Charging
LT8491 APPLICATIONS INFORMATION measured to determine the absolute panel voltage and Timers are disabled when solar powered due to the check for under voltage conditions. As such, VINR must inability to guarantee full charging current during the be connected to the resistor divider network shown in entire charging cycle when panel illumination conditions Figure 12. -
Page 63: Hw Config: Dc Supply Powered Charging
LT8491 APPLICATIONS INFORMATION HW Config: Input Voltage Sensing and Modulation sec- voltage source. This is done by pulling the VINR pin low, tion. Maximum charging current can reduce as FBIN or to ground, as discussed in the HW Config: VINR Pin gets closer to its regulation voltage of 1.205V (typical). -
Page 64: Hw Config: Input Current Sense And Limit
LT8491 APPLICATIONS INFORMATION Setting the Stage 2 Battery Voltage (V ): The resistor X = 1.211• network shown in Figure 14 is used to set the Stage 2 ⎡ ⎤ ⎛ ⎞ ⎛ ⎞ battery voltage and to measure V via the FBOR pin DACO1 DACO2 DACO1... -
Page 65: Hw Config: Output Current Sense And Limit
LT8491 APPLICATIONS INFORMATION In addition, note that the LT8491 uses the same circuit or better. Using this information, the appropriate value for (shown in Figure 15) to measure the input current as to can be calculated using the following equation: SENSE1 limit it. -
Page 66: Hw Config: Current Sense Filtering
LT8491 APPLICATIONS INFORMATION . For cases where I it is FROM OUT(MAX) OUT(MAX) OUT(MAXS0) SENSE2 TO BATTERY CONTROLLER OK to exclude R from the PCB and float the IOW pin. OUT1 OUTPUT must be at least 20% of I OUT(MAXS0) OUT(MAX) CURRENT reduces IMON_OUT ripple and stabilizes the... -
Page 67: Hw Config: Battery Temperature And Disconnect Sensing
LT8491 APPLICATIONS INFORMATION bias currents of the C and C pins. This repre- The LT8491 detects if the battery has been disconnected SNOUT SNIN sents a ~0.5% reduction in the maximum current limit from the charger by monitoring the TEMPSENSE pin which typically occurs with ~50mV across R . -
Page 68: Hw Config: Driving An Led With The Status Pin
LT8491 APPLICATIONS INFORMATION the external circuit discussed in the Optional: EXTV Disconnect section. Finally, a 305k (typical) resistor is connected from EXTV to ground inside the LT8491. This resistor draws draw current from the battery unless EXTV is disconnected. See the Optional: EXTV Disconnect section for a way to automatically disconnect EXTV SENSE... -
Page 69: Hw Config: I 2 C Chip Address Pin
LT8491 APPLICATIONS INFORMATION To properly set the resistors shown in Figure 22, use the Table 24. I C Address Resistor Values following equation: C ADDRESS 0x10 100k (Pull-Up) – ≅ Ω 0x19 71.5k 110k 0x20 187k 107k where I is the desired bias current through the LED. 0x29 –... -
Page 70: Hot-Plugging Considerations
LT8491 APPLICATIONS INFORMATION The arrow in Figure 24 shows the proper disconnect point While the LT8491 is operating, the STATUS pin toggles on if removing the battery from the charger in an in-situ bat- a 2 Sec (typical) interval as shown in Figure 25. The three tery charging application. -
Page 71: Lead-Acid Battery Charging
LT8491 APPLICATIONS INFORMATION LEAD-ACID BATTERY CHARGING Table 26. Lithium-Ion Battery Register Settings REGISTER NAME C REG ADDR VALUE The LT8491 can be used to charge lead-acid batteries. Table 27 shows a sample configuration that puts the CFG_TBAT_MIN 0x40 0x00 → (0°C) LT8491 into a typical setup for lead-acid battery charging. -
Page 72: Optional Features
LT8491 APPLICATIONS INFORMATION OPTIONAL FEATURES Exiting Low Power Mode: The charger will automatically exit low power mode and resume normal charging after Optional: Low Power Mode adequate input power is detected. The charger typically requires the input current to exceed 2.5% to 3% of the When current from the solar panel is not high enough to maximum input current limit to make a valid power point reliably measure the maximum power point, the LT8491... -
Page 73: Optional: Extv Cc Disconnect
LT8491 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 V . The circuits shown in Figure 30 and Figure 31. -
Page 74: Optional: Remote Battery Voltage Sensing
LT8491 APPLICATIONS INFORMATION low, as discussed in the HW Config: MODE Pin – Current CHARGE Conduction Mode section, eliminates most of the current TO CHARGER OUT – AT R SENSE2 LT8491 draw from EXTV when the charging current becomes low. However, there is a 305kΩ (typical) path from EXTV FBOUT FBOR CABLE... - Page 75 LT8491 APPLICATIONS INFORMATION Selecting R3 as a 100Ω resistor is often a good choice. TO CHARGER OUT CABLE AT R SENSE2 During normal operation, the voltage across R3 is about the same as across R . However, R3 may experience CABLE voltage up to V –...
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Page 76: Optional: Dc Supply Detection Circuit
LT8491 APPLICATIONS INFORMATION an NPN that can pull VINR below the Power Supply Mode CABLE TO CHARGER OUT AT R SENSE2 threshold before fully saturating. Alternatively, Q6 can be replaced with an NMOS device with proper care taken to avoid overvoltage of the NMOS gate. R˝... - Page 77 LT8491 APPLICATIONS INFORMATION • Following the calculation of R , solve for R • Iterations of the previous step are performed that FBOUT1 DACO1 and C according to the following formulas: include adjustments to R and R DACO2 DACO FBOUT1 DAC01 DAC02 until the following standard value feedback resistors...
- Page 78 LT8491 APPLICATIONS INFORMATION Choose R = 5.76k which is the closest standard • The 10A maximum charge current limit and 2.5A trickle DACI2 value. charge current limit are set by choosing R SENSE2 and R using the following formulas: IMON_OUT Ω...
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Page 79: Typical Applications
LT8491 TYPICAL APPLICATIONS Rev. 0 For more information www.analog.com... - Page 80 LT8491 TYPICAL APPLICATIONS Rev. 0 For more information www.analog.com...
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Page 81: Package Description
Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications For more information www.analog.com subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. -
Page 82: Typical Application
High Voltage, High Current Controller for Battery Charger with MPPC and V Range = 3V to 60V, MPPC LTC4200 55V V Buck-Boost Multi-Chemistry Battery Charging Controller Li-Ion and Lead-Acid Algorithms, MPPC Rev. 0 01/20 www.analog.com ANALOG DEVICES, INC. 2020...
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