MAX1516 charge pump driver circuit diagram

The MAX1516 charge pump can drive up to 8 self-illuminating LEDs and has a constant current adjustment function to achieve uniform light intensity. It can drive each group of LEDs with a current of 30mA and is mostly used for backlighting. The flash group LEDs (LED5~LED8) are individually controlled and can drive each LED at 100mA (400mA total). By using an adaptive 1×, 1.5×, and 2× mode charge pump and an ultra-low dropout current regulator, the MAX1576 is able to achieve high efficiency over the entire voltage range of a single Li-ion battery. Due to the fixed switching frequency of 1MHz, only very small external components are used and the regulation scheme is optimized to ensure low EMI and low input ripple.

The MAX1576 uses two external resistors to set the maximum (100%) current for the main LED and flash LED. The ENM1 and ENM2 pins set the main LED current to 10%, 30% or 100% of the maximum current. The ENF1 and ENF2 pins set the flash LED current to 20%, 40% or 100% of the maximum current. Additionally, single-wire, serial pulse brightness control can be achieved by connecting each pair of control pins together.

(1)Main technical characteristics of MAX1576

①Drive up to 8 LEDs. 30mA driver is used for backlighting and 400mA driver is used for flash.

② An average efficiency of 85% can be achieved during the entire lithium-ion battery discharge process, and the current matching accuracy of the LED is 0.7%.

③Adaptive 1×, 1.5×, 2× mode switching, flexible brightness control.

④Single wire, serial pulse interface (5%~100%), 2-bit (3-level) logarithmic logic.

⑤Low input ripple and EMI, 0.1μA low shutdown current.

⑥The power supply voltage range is 2.7~5.5V.

⑦ It has soft start to limit surge current, output overvoltage protection and thermal shutdown protection functions.

⑧MAX1576 is available in a 24 -pin 4mm×4mm thin QFN package (maximum thickness is 0.8mm).

(2)Typical application circuit

The circuit of MAX1576 charge pump driving white LED is shown in the figure.