ACE4704
Fully 5A, 4cell Standalone Li-ion Battery Charger
Where:
Pd is the power dissipation of the power MOSFET
VBAT is the maximum battery voltage
VCC is the minimum input voltage
Rds(on) is the power MOSFET’s on resistance at room temperature
ICH is the charge current
dT is the temperature difference between actual ambient temperature and room temperature(25℃)
In addition to the I2Rds(on) loss, the power MOSFET still has transition loss, which are highest at the
highest input voltage. Generally speaking, for VIN＜20V, the I2Rds(on) loss may be dominant, so the
MOSFET with lower Rds(on) should be selected for better efficiency; for VIN＞20V, the transition loss
may be dominant, so the MOSFET with lower CRSS can provide better efficiency. CRSS is usually specified
in the MOSFET characteristics; if not, then CRSS can be calculated using CRSS = QGD/ΔVDS.
The MOSFETs such as AO4459, STM9435(or WT9435), AO3407A can be used. The part numbers
listed above are for reference only, the users can select the right MOSFET based on their requirements.
Diode Selection
The diodes D1 and D2 in Figure 1 are schottky diode, the current rating of the diodes should be at least
the charge current limit, the voltage rating of the diode should exceed the maximum expected input
voltage. The diode that is much larger than that is sufficient can result in larger transition losses due to
their larger junction capacitance.
Disable Charging with TEMP Pin
The charging can be disabled with TEMP pin, as shown in Figure 3：
ACE4704
Note: M1 is N-Channel MOSFET
Figure 3 Disable Charging With TEMP Pin
VER 1.2
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ACE [ ACE TECHNOLOGY CO., LTD. ]
