Battery Charging Algorithm; Stage 0: Trickle Charging; Stage 1: Full Constant Current - Analog Devices LINEAR LT8491 Manual

LT8491
OPERATION
STAGE 0
TRICKLE CHARGE
V
S1_S2
V
S2_S1
V
S3_S0
V
BAT
V
S0_S1
V
S1_S0
V
UV_S0
V DROP CAUSES TRANSITION TO UNDERVOLTAGE
BAT
V
S0_UV
I
OUT

BATTERY CHARGING ALGORITHM

The LT8491 implements a CCCV charging algorithm.
The idealized charging profile is shown in Figure 7 and
assumes constant temperature and adequate input power.
As battery temperature and illumination conditions on the
panel change, the actual current and voltage seen by the
battery will vary accordingly.
Figure 8 illustrates a flow chart for the charging algorithm.
Many options are available to configure the algorithm as
needed. Options include...
• Stage 3 is enabled or not
• Stop charging when I
OUT
• Timer expiration indicates a fault or not
• Various automatic restart options
Footnotes at the bottom of Figure 8 indicate configurable
aspects of the algorithm and the related thresholds.
20
STAGE 1
CONSTANT CURRENT
STAGE 2 VOLTAGE
REGULATION
V DROP CAUSES TRANSITION TO STAGE 0
BAT
Figure 7. Typical Battery Charging Cycle
< C/10 or not
For more information
STAGE 2
CONSTANT VOLTAGE
V DROP CAUSES TRANSITION TO STAGE 1
BAT
STAGE 1 OUTPUT
CURRENT LIMIT
STAGE 2 LOWER OUTPUT
CURRENT LIMIT
Stage 0: Trickle Charging
In Stage 0 the LT8491 charges the battery with a reduced
constant current that is hardware configurable (see HW
Config: Output Current Sense and Limit section). This
stage typically occurs for battery voltages between 35%
to 70% of the Stage 2 battery voltage limit (V
the Stage 0 battery thresholds are I
discussed in the Configure V
tion. Stage 0 charging is indicated in the STAT_CHARGER
register when the CHRG_STAGE bits are 000b and the
CHRG_LOGIC_ON bit is 1.
Stage 1: Full Constant Current
At higher battery voltage, the LT8491 enters Stage 1 and
charges the battery with full constant current (see HW
Config: Output Current Sense and Limit section). Stage 1
typically occurs for battery voltages between 70% to 98%
of the Stage 2 battery voltage limit. The threshold for
2
entering Stage 1 is I C configurable as discussed in the
www.analog.com
STAGE 3
FLOAT VOLTAGE
STAGE 3 VOLTAGE
REGULATION
VOLTAGES BELOW OR
CURRENTS ABOVE PRESET
LEVELS DURING STAGE 3 CAUSES
TRANSITION TO STAGE 0
C/5
C/10
). However,
S2
2
C configurable as
for Stages 0, 1 and 3 sec-
BAT
Rev. 0
8491 F07