Configure The Telemetry; Cfg_Rsense1 - Analog Devices LINEAR LT8491 Manual

LT8491
2
I 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. Writes to this register are only accepted if
STAT_CHARGER→CHRG_LOGIC_ON=0, CTRL_EE_WRT_EN≠0xCC and STAT_SYSTEM→SYSTEM_BUSY=00b. Reads
are permitted any time that the I
This telemetry update operation causes the LT8491 to measure telemetry and update the following registers: TELE_
TBAT, TELE_PIN, TELE_IIN, TELE_VBAT, TELE_VIN, TELE_VINR. The remaining telemetry registers are not updated
because the charger is off. Note that if the TEMPSENSE pin measurement detects a disconnected battery condition,
TELE_TBAT will become 0x7777 indicating the disconnect condition. Also note that in order to minimize battery dis-
charge, the V feedback divider is optionally disconnected when the charging is off (see the Optional: Output Feedback
BAT
Resistor Disconnect section). Updating the telemetry, by writing to CTRL_UPDATE_TELEM, temporarily reconnects
the feedback divider to measure the battery voltage.
Related Data Sheet Sections: Telemetry: Acquisition, HW Config: Battery Temperature and Disconnect Sensing, Optional:
Output Feedback Resistor Disconnect, Data: Access Permissions

CONFIGURE THE TELEMETRY

The registers in Table 12 must contain valid data before the LT8491 can properly calculate telemetry for volts, amps,
power and efficiency. The contents of these registers don't affect any aspect of the charger's operation, including
MPPT scanning, V , V
S2 S3
to calculate the read-only telemetry values found between I
CHARGER→GT_C10 bit.
Table 12. Summary of Telemetry Configuration Registers
REGISTER NAME SIZE

CFG_RSENSE1

WORD
CFG_RIMON_OUT WORD
CFG_RSENSE2 WORD
CFG_RDACO WORD
CFG_RFBOUT1 WORD
CFG_RFBOUT2 WORD
CFG_RDACI WORD
CFG_RFBIN2 WORD
CFG_RFBIN1 WORD
CFG_RSENSE1
2
I C REG ADDRESS BIT(S)
0x28 [15:0]
The LT8491 uses this register value to calculate telemetry for the TELE_PIN, TELE_EFF and TELE_IIN registers. CFG_
RSENSE1 is not used for any other purpose and does not affect charging in any way. Write this register to indicate the
value of the R input current sense resistor. The value written to this register should be R
SENSE1
42
2
C interface is operational.
, temperature calculation etc. The contents of these registers are only used by the LT8491
2 2
I C REGISTER I C BOOT READ
ADDRESS ADDRESS
0x28 0x88
0x2A 0x8A
0x2C 0x8C
0x2E 0x8E
0x30 0x90
0x32 0x92
0x34 0x94
0x36 0x96
0x38 0x98
UNITS FORMAT
mΩ • 100 Unsigned Integer 4.7mΩ = 0x01D6
For more information
2
C addresses 0x02 and 0x0E and to set/clear the STAT_
DESCRIPTION
Indicate the R resistor value.
SENSE1
Indicate the R resistor value.
IMON_OUT
Indicate the R resistor value.
SENSE2
Indicate the total value of R
DACO1
Indicate the R resistor value.
FBOUT1
Indicate the R resistor value.
FBOUT2
Indicate the total value of R
DACI1
Indicate the R resistor value.
FBIN2
Indicate the R resistor value.
FBIN1
EXAMPLES DESCRIPTION
R resistor value. Required to calculate telemetry for
SENSE1
10mΩ = 0x03E8 TELE_PIN, TELE_EFF, TELE_IIN.
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+ R .
DACO2
+ R .
DACI2
, in milliohms,
SENSE1
REF
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