BQ24040_16 Datasheet, PDF (17/38 Pages) Texas Instruments – Single Cell Li-Ion and Li-Pol Battery Charger With Auto Start

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SLUS941F – SEPTEMBER 2009 – REVISED MARCH 2015
8.4.3 IN-DPM (V_IN-DPM or IN-DPM)
The IN-DPM feature is used to detect an input source voltage that is folding back (voltage dropterminalg),
reaching its current limit due to excessive load. When the input voltage drops to the V_IN-DPM threshold the internal
pass FET starts to reduce the current until there is no further drop in voltage at the input. This would prevent a
source with voltage less than V_IN-DPM to power the out terminal. This works well with current limited adaptors and
USB ports as long as the nominal voltage is above 4.3V and 4.4V respectively. This is an added safety feature
that helps protect the source from excessive loads.
8.4.4 OUT
The Charger’s OUT terminal 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 terminal 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.
8.4.5 ISET
An external resistor is used to Program the Output Current (50 to 1000mA) and can be used as a current
monitor.
R_ISET = K_ISET ÷ I_OUT
(1)
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 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 12. Also, see Figure 28 and Figure 29.
4.5
For < 45^oC, 4.2V Regulation
4
3.5
60^oC to 45^oC
HOT TEMP
3
4.06V
Regulation
2.5
V_OUT
2
No Operation
During Cold
Fault
< 48^oC
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 11. Operation Over TS Bias Voltage
1.8
1.6
1.4
1.2
I_OUT Internal Clamp Range
1
0.8
max
0.6
I_SET Short
0.4
Fault
Range
0.2
min
I_OUT Programmed
Non Restricted
Operating Area
0
100
1000
I_SET - W
10000
Figure 12. Programmed/Clamped Out Current
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