ACE4704
Fully 5A, 4cell Standalone Li-ion Battery Charger
When control signal is high, N-channel MOSFET M1 is turned on, the voltage at TEMP pin is pulled
down to GND, which will disable the charging;
When control signal is low, N-channel MOSFET is turned off, the voltage at TEMP pin is determined by
NTC thermistor, which performs normal battery temperature monitoring function.
About Battery Current In Sleep Mode
In the typical application circuit shown in Figure 1, when input voltage is powered off or lower than
battery voltage, ACE4704 will enter sleep mode. In sleep mode, the battery current includes:
(1) The current into BAT pin and CSP pin, which is about 14uA(VBAT＝16.8V).
(2) The current from battery to VCC pin via diode D1, which is determined by D1’s leakage current.
The current will charge capacitance C1 at VCC pin, which will make VCC voltage a bit higher. To avoid
erratic operation, a resistor in parallel with capacitance C1 may be needed to discharge the
capacitance, the resistor value is determined by diode D1’s leakage, generally speaking, a 20KΩ
resistor can achieve the task.
The current from battery to GND via diode D2, which is also determined by D2’s leakage current.
PCB Layout Considerations
When laying out the printed circuit board, the following considerations should be taken to ensure proper
operation of the IC.
(1) To minimize radiation, the 2 diodes, pass transistor, inductor and the input bypass capacitor traces
should be kept as short as possible. The positive side of the input capacitor should be close to the
source of the P-channel MOSFET; it provides the AC current to the pass transistor. The connection
between the catch diode and the pass transistor should also be kept as short as possible.
(2) The compensation capacitor connected at the COM1, COM2 and COM3 pins should return to the
analog ground pin of the IC. This will prevent ground noise from disrupting the loop stability.
(3) Output capacitor ground connections need to feed into same copper that connects to the input
capacitor ground before tying back into system ground.
(4) Analog ground and power ground(or switching ground) should return to system ground separately.
(5) The ground pins also works as a heat sink, therefore use a generous amount of copper around the
ground pins. This is especially important for high VCC and/or high gate capacitance applications.
(6) Place the charge current sense resistor RCS right next to the inductor output but oriented such that
the IC’s CSP and BAT traces going to RCS are not long. The 2 traces need to be routed together as a
single pair on the same layer at any given time with smallest trace spacing possible.
(7) The CSP and BAT pins should be connected directly to the current sense resistor (Kelvin sensing) for
best charge current accuracy. See Figure 4 as an example.
VER 1.2
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ACE [ ACE TECHNOLOGY CO., LTD. ]
