Datasheet

ILIM
ILIM
IN _ LIM
K
R
I
=
0mA
0mA
V
OUT
3.7V
3.5V
~3.1V
DPPM loop active
Supplement
Mode
I
BAT
I
IN
I
OUT
800mA
1800mA
2000mA
-200mA
1A
1500mA
~850mA
0mA
bq24278
www.ti.com SLUSB04 –JUNE 2012
Figure 3. Example DPPM Response (V
Supply
=5V, V
BAT
= 3.1V, 1.5A Input current limit)
If the V
BAT(REG)
threshold is ever less than the battery voltage, the battery FET is turned off to allow the battery to
relax down to V
BAT(REG)
and the SYS output is regulated to V
SYSREG(FETOFF)
. If the battery is ever above V
BOVP
, the
battery OVP circuit shuts the PWM converter off and the battery FET is turned on to discharge the battery to safe
operating levels.
The input current limit for IN is programmable using the ILIM input. Connect a resistor from ILIM to GND to set
the maximum input current limit. The programmable range for the IN input current limit is 1000mA to 2.5A. R
ILIM
is calculated using Equation 2:
(2)
Where I
IN_LIM
is the programmed input current limit and K
ILIM
is the programming factor found in the Electrical
Characteristics table.
Battery Only Connected
When the battery is connected with no input source, the battery FET is turned on similar to supplement mode. In
this mode, the current is not regulated; however, there is a short circuit current limit. If the short circuit limit is
reached, the battery FET is turned off for the deglitch time. After the deglitch time, the battery FET is turned on to
test and see if the short has been removed. If it has not, the FET turns off and the process repeats until the short
is removed.
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