MIKROE Charger 16 Click is a compact add-on board that represents a single-cell battery charger. This board features the LT1571, a constant-current/constant-voltage battery charger with preset voltage and termination flag from Analog Devices. Powering up from an external power supply rated up to 20V, this Click board™ has an onboard current sense resistor which allows simple charge current programming to within 5% accuracy. The internal switch is capable of delivering a 1.5A DC (2A peak current). It also comes with an indication for battery near full-charge state, when the charge current drops to 20% of the programmed value, and selectable constant voltage for 4.1V or 4.2V per cell with 0.6% accuracy. This Click board™ is suitable as a Li-Ion, NiMH, NiCd battery charger for portable devices and accessories, power tools, and more.
Charger 16 Click as its foundation uses the LT1571, a current-mode PWM step-down (buck) charger from Analog Devices. This battery charger represents a simple, efficient solution to fast-charge rechargeable batteries, including lithium-ion (Li-Ion), nickel-metal-hydride (NiMH), and nickel-cadmium (NiCd) using constant-current and/or constant-voltage control. The internal switch is capable of delivering a 1.5A DC (2A peak current). A saturating switch operates at 500kHz, which provides high efficiency and a small charger size.
Charger 16 Click communicates with MCU using two GPIO pins. The Enable pin, labeled as EN and routed to the CS pin of the mikroBUS™ socket, optimizes power consumption and is used for power ON/OFF purposes (driver operation permission). The onboard current sense resistor (R7) allows simple charge current programming to within 5% accuracy. Charge current can be programmed with the PWM from the mikroBUS™ socket by pulse width modulating current on a PROG pin with a switch Q2 to R7 at a frequency higher than a few kHz. Charge current will be proportional to the duty cycle of Q2 with full-current at 100% duty cycle.
This Click board™ also comes with an indication, red LED labeled as CHARGE, for battery near full-charge state, when the charge current drops to 20% of the programmed value, and selectable constant voltage for 4.1V or 4.2V per cell with 0.6% accuracy. Selection can be performed by onboard SMD jumper labeled as CELL SEL. Besides, the charge termination-flag threshold can be reduced from the default 20% level to as low as 7.5% of the programmed full charge current by positioning an onboard R5 resistor of appropriate value.
The Charger 16 Click supports an external power supply for the LT1571, which can be connected to the input terminal labeled as VIN and should be within the range of 8V to 20V. When the input voltage is removed, its supply voltage pin drops to 0.7V below the battery voltage forcing the charger into a low-battery drain (5mA typical) Sleep mode.
This Click board™ operates only with a 5V logic voltage level. The board must perform appropriate logic voltage level conversion before use with MCUs with different logic levels. However, the Click board™ comes equipped with a library containing functions and an example code that can be used, as a reference, for further development.
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