An external resistor is used to Program the Output Current (50 to 1000mA) and can be used as a current monitor.

where

• I_OUT is the desired fast charge current;
• K_ISET is a gain factor found in the electrical specification

For greater accuracy at lower currents, part of the sense FET is disabled to give better resolution. Figure 7-1 shows the transition from low current to higher current. Going from higher currents to low currents, there is hysteresis and the transition occurs around 0.15A.

The ISET resistor is short protected and will detect a resistance lower than ≉340Ω. The detection requires at least 80mA of output current. If a “short” is detected, then the IC will latch off and can only be reset by cycling the power. The OUT current is internally clamped to a maximum current between 1.05A and 1.4A and is independent of the ISET short detection circuitry, as shown in Figure 8-5. Also, see Figure 9-14 and Figure 9-15.

Figure 8-4 Operation Over TS Bias Voltage (BQ24040)

Figure 8-5 Programmed/Clamped Out Current (BQ24040)