Texas Instruments BQ25123, Manual

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9.3.13 Input Current Limit Programming by External Components (ILIM)
The input current limit threshold is user programmable through an external resistor or through registers over
I
2
C. Set the input current limit using the ILIM pin by connecting a resistor from ILIM to GND using Table 9-4 for
guidance. If no ILIM resistor is connected and the pin is tied to GND, the default ILIM register value is used. The
external value is not valid once the device enters host mode.
Table 9-4. ILIM Resistor Settings
ILIM KILIM RILIM
(STANDARD 1%
VALUES)
UNIT
MIN TYP MAX MIN TYP MAX
0.048469388 0.051020408 0.053571429 190 200 210 3920 Ω
0.09047619 0.095238095 0.1 190 200 210 2100 Ω
0.146153846 0.153846154 0.161538462 190 200 210 1300 Ω
0.19 0.2 0.21 190 200 210 1000 Ω
0.285714286 0.30075188 0.315789474 190 200 210 665 Ω
0.380761523 0.400801603 0.420841683 190 200 210 499 Ω
The device has register programmable input current limits from 50 mA to 400 mA in 50-mA steps. The device is
USB-IF compliant for inrush current testing, assuming that the input capacitance to the device is selected to be
small enough to prevent a violation (<10 µF), as this current is not limited.
9.3.14 Charge Current Programming by External Components (ISET)
The fast charge current is user programmable through an external resistor or through registers over I
2
C. Set the
fast charge current by connecting a resistor from ISET to GND. If no ISET resistor is connected and the pin is
tied to GND, the default ISET register value is used. While charging, if the charge current is using the externally
programmed value, the voltage at ISET reflects the actual charging current and can be used to monitor charge
current. The current out of ISET is 1/100 (±10%) of the charge current. The charge current can be calculated by
using
Table 9-5 for guidance:
Table 9-5. ISET Resistor Settings
ISET KISET RISET
(STANDARD 1%
VALUES)
UNIT
MIN TYP MAX MIN TYP MAX
0.285714286 0.30075188 0.315789474 190 200 210 665 Ω
0.19 0.2 0.21 190 200 210 1000 Ω
0.126666667 0.133333333 0.14 190 200 210 1500 Ω
0.095 0.1 0.105 190 200 210 2000 Ω
0.06462585 0.068027211 0.071428571 190 200 210 2940 Ω
0.048469388 0.051020408 0.053571429 190 200 210 3920 Ω
0.038076152 0.04008016 0.042084168 190 200 210 4990 Ω
0.031456954 0.033112583 0.034768212 190 200 210 6040 Ω
0.025956284 0.027322404 0.028688525 190 200 210 7320 Ω
0.019 0.02 0.021 190 200 210 10000 Ω
0.012666667 0.013333333 0.014 190 200 210 15000 Ω
0.0095 0.01 0.0105 190 200 210 20000 Ω
0.006462585 0.006802721 0.007142857 190 200 210 29400 Ω
0.004846939 0.005102041 0.005357143 190 200 210 39200 Ω
9.3.15 Safety Timer and Watchdog Timer
At the beginning of the charge cycle, the device starts the safety timer. If charging has not terminated before
the programmed safety time, t
MAXCHG
, expires, the device enters idle mode and charging is disabled. The
pre-charge safety time, t
PRECHG
, is 10% of t
MAXCHG
. When a safety timer fault occurs, a single 128 µs pulse
is sent on the INT pin and the STAT and FAULT bits of the status registers are updated over I
2
C. The CD pin
or power must be toggled in order to clear the safety timer fault. The safety timer duration is programmable
BQ25123
SLUSCZ6A – JANUARY 2018 – REVISED MAY 2021
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