BQ24040 Datasheet, PDF (19/31 Pages) Texas Instruments – 800mA Single-Input Single Cell Li-Ion Battery Charger With Auto Start

bq24040
bq24041
www.ti.com.................................................................................................................................... SLUS941A – SEPTEMBER 2009 – REVISED SEPTEMBER 2009
OUT
The Charger’s OUT pin provides current to the battery and to the system, if present. This IC can be used to
charge the battery plus power the system, charge just the battery or just power the system (TTDM) assuming the
loads do not exceed the available current. The OUT pin is a current limited source and is inherently protected
against shorts. If the system load ever exceeds the output programmed current threshold, the output will be
discharged unless there is sufficient capacitance or a charged battery present to supplement the excessive load.
ISET
An external resistor is used to Program the Output Current (50 to 800mA) and can be used as a current monitor.
R_ISET = K_ISET ÷ I_OUT
(0)
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 19
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 1.1A and 1.35A and is independent
of the ISET short detection circuitry, as shown in Figure 27. Also, see Figure 13 and Figure 14.
4.5
For < 45^oC, 4.2V Regulation
4
3.5
60^oC to 45^oC
HOT TEMP
3
4.06V
Regulation
V_OUT
No Operation
During Cold
Fault
2.5
< 48^oC
2
1.5
60^oC
10^oC
0^oC
100% of Programmed
1
Current
0.5
I_OUT
0
0
0.2
0.4
0.6
0.8
50%
Cold
Fault
1
1.2
1.4
1.6
1.8
V_TS - Voltage - V
Figure 26. Operation Over TS Bias Voltage
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