QT3300 is a PFM boost battery charging control integrated circuit that operates from 4V to 28V. The QT3300 integrates a reference voltage source, +5V voltage modulation unit, inductor current detection unit, battery voltage detection circuit and off-chip N-channel MOSFET drive circuit, etc., which are very suitable
The charging control of lithium batteries, lithium iron phosphate batteries and lead-acid batteries has the advantages of fewer external components and simple circuits. When the input power is turned on, QT3300 enters the charging state, controls the off-chip N-channel MOSFET to turn on, the inductor current rises, and the energy in the output capacitor is transferred to the battery. When the inductor current rises to the upper limit set by the external current detection resistor, the off-chip N-channel MOSFET is turned off, the inductor current decreases, and the energy in the inductor is transferred to the output capacitor and battery. When the inductor current drops to the lower limit set by the external current detection resistor, the off-chip N-channel MOSFET turns on again, and so on. The battery voltage is fed back to the FB pin through the resistor divider network. When the FB pin voltage reaches 1.205V (typical value), the charging process ends, the off-chip N-channel MOSFET is turned off, and the charging end state is entered. In the end-of-charge state, no current flows from the input to the battery. When the FB pin voltage drops to the recharge threshold 1.155V (typical value), QT3300 enters the charging state again. The maximum operating frequency of QT3300 can reach 1MHz.