LTC4015_15 Datasheet, PDF (63/76 Pages) Linear Technology – Multichemistry Buck Battery Charger Controller with Digital Telemetry System

LTC4015
DETAILED Register Descriptions
VABSORB_DELTA (Sub-Address 0x2A, bits 5:0, Fixed: R, Programmable: R/W)
This register controls the absorb adder voltage for LiFePO₄ and lead-acid batteries in absorb charge phase. The absorb
charge phase battery voltage servo level is based on the sum of the absorb adder voltage and the charge voltage level.
For Li-Ion batteries, VABSORB_DELTA is ignored.
For LiFePO₄ batteries, only the lower five bits (4:0) are active, and the absorb voltage level is given by (VABSORB_DELTA
+ VCHARGE_SETTING)/80 + 3.4125 V/cell, limited to a maximum of 3.8 V/cell. Setting VABSORB_DELTA=0 disables
the absorb phase. See the section LiFePO₄ Absorb Charge for more information.
For lead-acid batteries, if en_lead_acid_temp_comp=1, the absorb voltage level is given by (VABSORB_DELTA +
VCHARGE_SETTING)/105.0 + 2.0V/cell at 25°C when a thermistor with a b value of 3490k is used. See the section
Lead-Acid Temperature Compensated Charging for more information. If en_lead_acid_temp_comp=0, the absorb
voltage level is given by (VABSORB_DELTA + VCHARGE_SETTING)/105.0 + 2.0V/cell, regardless of temperature. To
maintain inherent over charge protection, the maximum lead-acid absorb voltage level is 2.6 V/cell.
VEQUALIZE_DELTA (Sub-Address 0x2C, Bits 5:0, Fixed: R, Programmable: R/W)
These six bits control the equalize adder voltage for lead-acid batteries in equalize charge phase. The equalize charge
phase battery voltage servo level is based on the sum of the equalize adder voltage and the vcharge level.
For lead-acid batteries, if en_lead_acid_temp_comp=1, the equalize voltage level is given by (VEQUALIZE_DELTA +
VCHARGE_SETTING) / 105.0 + 2.0 V/cell at 25°C when a typical curve two thermistor is used. See the section Lead-Acid
Temperature Compensated Charging for more information. If en_lead_acid_temp_comp=0, the equalize voltage level
is given by ((VEQUALIZE_DELTA + VCHARGE_SETTING)/105.0 + 2.0)V/cell, regardless of temperature. To maintain
inherent over charge protection, the maximum lead-acid equalize voltage level is 2.6V/cell.
For lithium chemistries, VEQUALIZE_DELTA is ignored.
C_OVER_X_THRESHOLD (Sub-Address 0x1C, Bits 15:0, Fixed: R, Programmable: R/W)
This 16-bit word sets the IBAT value used to qualify C/x detection for charge phase termination/transition. C_OVER_X_
THRESHOLD uses the same format as IBAT, and the C/x current level is given by C_OVER_X_THRESHOLD/(R_SNSB
• 21845.0/0.032V). The default value for C_OVER_X_THRESHOLD is 2184, which corresponds to 10% (3.2mV) of a
32mV/ R_SNSB full-scale charge current. C/x detection is disabled if C_OVER_X_THRESHOLD is set to zero.
For Li-Ion batteries, if en_c_over_x_term=1 (0 by default), C/x charge termination occurs after the battery reaches the
charge voltage level and IBAT drops below C_OVER_X_THRESHOLD. See the section C/x Termination.
For LiFePO₄ batteries, if en_c_over_x_term=1 (0 by default), C/x charge termination occurs after the battery reaches
vcharge level and IBAT drops below C_OVER_X_THRESHOLD during CC-CV charge phase. See the section C/x Termination.
If the optional LiFePO₄ absorb charge phase is employed and if C_OVER_X_THRESHOLD is set to a non-zero value,
the absorb phase ends if the battery voltage reaches absorb level and IBAT drops below C_OVER_X_THRESHOLD,
and CC-CV phase begins. See the section LiFePO₄ Absorb Charge.
For lead-acid batteries, if C_OVER_X_THRESHOLD is non-zero, absorb charge phase ends after the battery voltage
reaches absorb level and IBAT drops below C_OVER_X_THRESHOLD, and the CC-CV charge phase continues indefinitely.
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