LTC4015_15 Datasheet, PDF (72/76 Pages) Linear Technology – Multichemistry Buck Battery Charger Controller with Digital Telemetry System

LTC4015
DETAILED Register Descriptions
IIN (Sub-Address 0x3E, Bits 15:0, R)
This 16-bit word indicates the A/D measurement of 37.5 • (V_CLP – V_CLN) at the CLP, CLN pins. Input current = [IIN] •
1.46487µV/R_SNSI
DIE_TEMP (Sub-Address 0x3F, Bits 15:0, R)
This 16-bit two’s complement word indicates the A/D measurement result for LTC4015 die temperature. LTC4015
temperature = (DIE_TEMP – 12010)/45.6°C
NTC_RATIO (Sub-Address 0x40, Bits 15:0, R)
This 16-bit two’s complement word indicates the A/D measurement result for R_NTC/(R_NTC + R_NTCBIAS). The thermistor
value can be determined by the expression R_NTC = R_NTCBIAS • NTC_RATIO/(21,845.0 – NTC_RATIO). Recall that the
thermistor has a negative temperature coefficient so higher temperatures correspond to lower NTC_RATIO readings
and vice-versa.
BSR (Sub-Address 0x41, Bits 15:0, R)
This 16-bit word indicates the calculated per cell battery series resistance. The battery series resistance is proportional
to the battery charge current setting resistor, R_SNSB, and can be computed in Ω from [BSR/500] • R_SNSB for lithium
chemistries, or [BSR/750] • R_SNSB for lead-acid chemistries. Multiply this value by the total number of cells to calculate
total battery series resistance. ICHARGE_BSR is the value of IBAT used in the BSR calculation.
JEITA_ REGION (Sub-Address 0x42, Bits 2:0, R)
For lithium chemistries, this register indicates the JEITA battery temperature region as determined by the A/D
measurement result NTC_RATIO and the values of the JEITA_Tn registers. Recall that the thermistor has a negative
temperature coefficient so higher temperatures make lower NTC_RATIO readings and vice-versa. See the section JEITA
Temperature Qualified Charging for a diagram of the temperature regions.
CHEM_AND_CELLS (Sub-Address 0x43, Bits 11:0, R)
This register indicates the state of the CHEMn and CELLSn pins. See the sections Chemistry Selection and Cells Selec-
tion for more information on defining the pin states.
chem (Sub-Address 0x43, Bits 11:8, R)
These four bits indicate the chemistry algorithm set by the CHEMn pins, as shown in the following table. For ad-
ditional safety, these bits can be checked during test and/or by the application software to ensure that LTC4015 is
connected properly on the circuit board.
chem:
0x0
0x1
0x2
0x3
0x4
0x5
0x6
0x7
0x8
CHEM1,CHEM0:
L, L
H, H
L, Z
Z, L
L, H
H, Z
Z, H
Z, Z
H, L
Chemistry Algorithm:
Li-Ion Programmable
Li-Ion Fixed 4.2V/cell
Li-Ion Fixed 4.1V/cell
Li-Ion Fixed 4.0V/cell
LiFePO₄ Programmable
LiFePO₄ Fixed Fast Charge
LiFePO₄ Fixed 3.6V/cell
Lead-Acid Fixed
Lead-Acid Programmable
cells (Sub-Address 0x43, Bits 3:0, R)
These four bits indicate the battery cell count set by the CELLSn pins. For additional safety, these bits can be checked
during test and/or by the application software to ensure that LTC4015 is connected properly on the circuit board.
4015f
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