BQ24165 Datasheet, PDF (17/35 Pages) Texas Instruments – 2.5A, Dual-Input, Single Cell Switch Mode Li-Ion Battery Charger with Power Path

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bq24165
bq24166
bq24167
SLUSAP4A – DECEMBER 2011 – REVISED MARCH 2012
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:
R_ILIM
=
K _{ILI M}
I_{IN_LIM}
(2)
Where I_{IN_LIM} is the programmed input current limit and K_ILIM is the programming factor found in the Electrical
Characteristics table.
The bq24165/6/7 manages the dual input supply paths as well. The IN input has precedence when valid supplies
are connected to both inputs. The two inputs are always isolated from one another. The bq24165/6/7 always
seeks to charge from a valid source. For example, if a valid source is connected to USB and a source is
connected to IN that is greater than the OVP threshold, the USB source is used to charge the battery. In this
case, both the USB source and the battery would be isolated from the OVP source connected to the IN input.
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.
EXTERNAL BATTERY DISCHARGE FET (BGATE)
The bq24165/6/7 contains a MOSFET driver to drive an external P-Channel MOSFET between the battery and
the system output. This external FET provides a low impedance path to supply the system from the battery.
Connect BGATE to the gate of the external discharge MOSFET. BGATE is on under the following conditions:
1. No valid input supply connected.
2. IUSB1=IUSB2=IUSB3=high (High Impedance Mode)
This FET is optional and runs in parallel with the internal charge FET during discharge. Note that this FET is not
protected by the short circuit current limit.
SAFETY TIMER
At the beginning of charging process, the bq24165/6/7 starts the 6 hour safety timer. This timer is active during
the entire charging process. If charging has not terminated before the safety timer expires, the charge cycle is
terminated and the battery FET is turned off. A new charge cycle must be entered using CE1 and CE2 (bq24165)
or CE(bq24166/7) or High Impedance mode or input power must be toggled in order to clear the safety timer
fault.
During the fast charge phase, several events increase the timer durations.
1. The system load current reduces the available charging current.
2. The input current is reduced because the V_INDPM loop is preventing the supply from crashing.
3. The device has entered thermal regulation because the IC junction temperature has exceeded T_J(REG).
4. The battery voltage is less than V_BATSHORT.
During these events, the timer is slowed by half to extend the timer and prevent any false timer faults. Starting a
new charge cycle by toggling inputs, toggling the CE1/CE2(bq24165) or CE(bq24166/7) pins to disable/enable
charge, resets the safety timer. Additionally, thermal shutdown events cause the safety timer to reset.
Copyright © 2011–2012, Texas Instruments Incorporated
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