BQ24232HA Datasheet, PDF (15/36 Pages) Texas Instruments – USB-Friendly Lithium-Ion Battery Charger

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bq24232HA
SLUSCG4 – MAY 2016
Feature Description (continued)
The input current limit selection is controlled by the state of the EN1 and EN2 pins as shown in Table 1. When
using the resistor-programmable current limit, the input current limit is set by the value of the resistor connected
from the ILIM pin to VSS and is given by the Equation 1:
I_IN-MAX = K_ILIM/R_ILIM
(1)
The input current limit is adjustable up to 500 mA. The valid resistor range is 2.75 kΩ to 8.4 kΩ.
When the IN source is connected, priority is given to the system load. The DPPM and Battery Supplement
modes are used to maintain the system load. Figure 11 illustrates examples of the DPPM and supplement
modes. These modes are explained in detail in the following sections.
7.3.3.1.1 Input Voltage Dynamic Power Management, (V_{IN_DPM})
The bq24232HA uses the V_{IN_DPM} mode for operation from current-limited sources (including USB ports). The
input voltage is monitored and compared to the V_IN-DPM threshold (nominally ~ 4.5V). If the adaptor input voltage
begins to collapse, the input current limit is reduced to prevent the supply voltage from falling further. This
prevents the bq24232HA from crashing the external power source in case of a current-limited supply regardless
of the input current limit setting (USB100, USB500, or external resistor-set ILIM mode)..
7.3.3.1.2 Dynamic Power Path Management (DPPM)
When the sum of the charging (BAT) and system (OUT) currents exceeds the preset maximum input current
(programmed with EN1, EN2, and ILIM pins), the voltage at the OUT pin decreases. Once the voltage on the
OUT pin falls to the VDPPM limit, the bq24232HA enters DPPM mode. In this mode, the charging current is
reduced and power to the system is prioritized. Battery termination is disabled and the charge timer period is
extended while in DPPM mode, because the charging current is less than the programmed value.
7.3.3.1.3 Battery Supplement Mode
If the system load current demand exceeds the input current limit, even with charging current reduced to zero,
the OUT voltage continues to drop. When the OUT pin voltage drops below V_BSUP1, the partially charged battery
supplements the external power source to provide current to the system. When the OUT pin voltage increases
above V_BSUP2 the device exits battery supplement mode and all system current is drawn from the external power
source.
During supplement mode, the battery supplement current is not regulated; however, a short-circuit protection
circuit is built in. If during battery supplement mode, the voltage at OUT drops 250 mV below the BAT voltage,
the OUT output is turned off if the overload exists after t_DGL(SC2). The short-circuit recovery timer then starts
counting. After t_REC(SC2), OUT turns on and attempts to restart. If the short circuit remains, OUT is turned off and
the counter restarts. Battery termination is disabled while in supplement mode.
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