MAX1577V/MAX1577Z driving white LED circuit diagram

The MAX1577/MAX1577Z charge pump is suitable for driving high-power white LEDs, such as camera flashes, with a maximum regulation current of 1.2A (guaranteed 800mA). Even if the battery input voltage is very low, its extremely low open-loop impedance can still ensure high flash brightness. Its adaptive 1x voltage mode and 2x voltage mode working methods can provide high efficiency (maximum 92%) in flash mode or backlight. Because it uses high-speed (1MHz) switching, small external components can be used.

The MAX1577Y/MAX1577Z use an external resistor to set the full-scale white LED current. Two enable inputs (EN1 and EN2) provide simple on/off control and 20% of the white LED full-scale current. When the voltage across the external resistor is less than 24mV, the output The voltage will be regulated. The MAX1577Z has a fixed 5.1V output voltage, while the MAX1577Y provides 3.4V, 4.6V, or 5.1V output voltages for logic control for backlight, keypad, and RGB applications, respectively.

(1)Technical characteristics of MAX1577Y/MAX1577Z

The main technical characteristics of MAX1577Y/MAX1577Z are as follows.

①Maximum output drive capability of 1.2A (guaranteed 800mA).

②In flash mode, the maximum (η=PLED/PBAT) efficiency is 92%.

③Flexible brightness control.

④ Two-bit logic can achieve 100%, 33%, 20% brightness control and shutdown control.

⑤20%~100% PWM control.

⑥3% current adjustment to adapt to cable and temperature changes.

⑦ Voltage or current adjustment of flash and backlight (NIAXISTTY).

⑧Flash current adjustment (MAX1577Z).

⑨Low ripple and EMI.

⑩Input voltage range of 2.7~5.5V.

④It has soft start function to limit the surge current.

②Output voltage adjustment mode.

⑩Thermal shutdown protection.

(11) All come in an 8-pin, 3mm×3mm TDFN package (maximum height 0.8mm).

(2)Typical application circuit

The MAX1577Z charge pump drives white LED circuit as shown in the figure.

Figure MAX1577Z charge pump driving white LED circuit