Hw Config: I 2 C Chip Address Pin; In-Situ Battery Charging - Analog Devices LINEAR LT8491 Manual

APPLICATIONS INFORMATION
To properly set the resistors shown in Figure 22, use the
following equation:
2.6
R ≅ Ω
E
I
D
where I is the desired bias current through the LED.
D
V
IN
D
S
Q1
R
E
Q1: MMBT5550L
Figure 22. Higher Current Drive for STATUS LED
2
HW Config: I C Chip Address Pin
The CA pin on the LT8491 is a resistor programmable
ADC input used to select one of four possible I
addresses for the LT8491.
Figure 23 shows a sample configuration for a desired I
Address of 0x19 (7-bit).
AV
DD
R1
71.5k
R2
110k
Figure 23. Chip Address Select Circuit
Use the recommended resistor values stated in Table 24.
The given resistor value combinations select the proper
function and yield low current consumption.
LT8491
V
IN
STATUS
8491 F22
2
C chip
LT8491
CA
GND
8491 F23
For more information
2
Table 24. I C Address Resistor Values
2
I C ADDRESS
0x10
0x19
0x20
0x29

IN-SITU BATTERY CHARGING

The LT8491 can be used to charge a battery while the
battery is powering a load. The load should be directly
connected to the battery terminals as shown in Figure 24.
The variable nature of some loads can make charging
times unpredictable. Due to this unpredictability, it is
recommended that charging time limits be disabled (see
Configure Stage Timeout Limits section).
LT8491
BASED
CHARGER
2
C
Figure 24. Load Connection to Battery in LT8491 Application
Because a load connected to the battery may draw more
power than provided by the charger, the battery may
discharge while the LT8491 is charging the battery. If
this case occurs and the battery voltage falls below the
V threshold (31% default) of the Stage 2 voltage
S0_UV
limit, the undervoltage fault will become active and the
charger will halt until the battery voltage rises above the
V threshold (35% default) of the Stage 2 voltage
UV_S0
limit. Note that these thresholds are configurable. See
Configure V for Stages 0, 1, and 3. Consider disabling
BAT
the load current if the battery depletes below an unac-
ceptably low voltage.
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LT8491
R1 R2
100k (Pull-Up) –
71.5k 110k
187k 107k
– 100k (Pull-Down)
+
V LOAD
BAT
CABLE
–
TO/FROM
CHARGER
8491 F24
Rev. 0
69