LTC4015_15 Datasheet, PDF (57/76 Pages) Linear Technology – Multichemistry Buck Battery Charger Controller with Digital Telemetry System

LTC4015
DETAILED Register Descriptions
VBAT_LO_ALERT_LIMIT (Sub-Address 0x01, Bits 15:0, R/W),
VBAT_HI_ALERT_LIMIT (Sub-Address 0x02, Bits 15:0, R/W)
These 16-bit words set upper and lower limits that can be used to trigger an SMBALERT based on the BATSENS pin
voltage out of range. The values use the same two’s complement format as VBAT. For lithium chemistries, BATSENS/
cellcount voltage HI/LO alert limit = [VBAT_xx_ALERT_LIMIT] • 192.264µV. For lead-acid batteries, BATSENS/cellcount
voltage HI/LO alert limit = [VBAT_xx_ALERT_LIMIT] • 128.176µV
VIN_LO_ALERT_LIMIT (Sub-Address 0x03, Bits 15:0, R/W),
VIN_HI_ALERT_LIMIT (Sub-Address 0x04, Bits 15:0, R/W)
These 16-bit words set upper and lower limits that can be used to trigger an SMBALERT based on input voltage at
the V_IN pin out of range. The values use the same two’s complement format as VIN. Input voltage HI/LO alert limit =
[VIN_xx_ALERT_LIMIT] • 1.648mV.
VSYS_LO_ALERT_LIMIT (Sub-Address 0x05, Bits 15:0, R/W),
VSYS_HI_ALERT_LIMIT (Sub-Address 0x06, Bits 15:0, R/W)
These 16-bit words set upper and lower limits that can be used to trigger an SMBALERT based on system voltage at
the SYS pin out of range. The values use the same two’s complement format as VSYS. System voltage HI/LO alert
limit = [VSYS_xx_ALERT_LIMIT] • 1.648mV.
IIN_HI_ALERT_LIMIT (Sub-Address 0x07, Bits 15:0, R/W)
This 16-bit word sets an upper limit that can be used to trigger an SMBALERT based on input current above a certain
value. IIN_HI_ALERT_LIMIT uses the same two’s complement format as IIN. Input current high alert limit = [IIN_HI_
ALERT_LIMIT] • 1.46487µV/R_SNSI.
IBAT_LO_ALERT_LIMIT (Sub-Address 0x08, Bits 15:0, R/W)
This 16-bit word sets an upper limit that can be used to trigger an SMBALERT based on charge current below a certain
value. IBAT_LO_ALERT_LIMIT uses the same two’s complement format as IBAT with battery discharge current being
negative. Battery current low alert limit = [IBAT_LO_ALERT_LIMIT] • 1.46487µV/R_SNSB.
DIE_TEMP_HI_ALERT_LIMIT (Sub-Address 0x09, Bits 15:0, R/W)
This 16-bit word sets an upper limit that can be used to trigger an SMBALERT based on high die temperature. DIE_
TEMP_HI_ALERT_LIMIT uses the same two’s complement format as DIE_TEMP. LTC4015 temperature = (DIE_TEMP
– 12010)/45.6°C
BSR_HI_ALERT_LIMIT (Sub-Address 0x0A, Bits 15:0, R/W)
This 16-bit word sets an upper limit that can be used to trigger an SMBALERT based on high battery series resistance.
BSR_HI_ALERT_LIMIT uses the same format as BSR. The battery series resistance is a function of R_SNSB, and can be
computed as Ω/cellcount = [BSR/500] • R_SNSB (lithium chemistries), or Ω/cellcount = [BSR/750] • R_SNSB (lead-acid).
NTC_RATIO_HI_ALERT_LIMIT (Sub-Address 0x0B, Bits 15:0,R/W),
NTC_RATIO_LO_ALERT_LIMIT (Sub-Address 0x0C, Bits 15:0, R/W)
These 16-bit words set upper and lower limits that can be used to trigger an SMBALERT based on thermistor value out
of range. The values use the same two’s complement format as NTC_RATIO. The thermistor value can be determined
by the expression R_NTC = R_NTCBIAS • NTC_RATIO/(21,845 – NTC_RATIO). Recall that the thermistor has a negative
temperature coefficient so higher temperatures correspond to lower NTC_RATIO readings and vice-versa. Thus,
NTC_RATIO_HI_ALERT_LIMIT sets an upper alert limit for the value of NTC_RATIO which corresponds to a low (cold)
temperature for the thermistor, and NTC_RATIO_LO_ALERT_LIMIT sets a lower alert limit for the value of NTC_RATIO
which corresponds to a high (hot) temperature for the thermistor.
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