LM3570
Description
The LM3570 device provides a plete LED driver solution for wireless handsets and other portable devices using a display and keypad. With three constant current sources, up to three white LEDs can be used for display lighting with excellent current matching (0.3% typ.). The regulated 4.35V output voltage is perfect for driving auxiliary keypad LEDs in voltage mode. The LM3570 utilizes a high efficiency 3/2 CMOS chargepump with a pre-regulation loop that minimizes conducted noise on the input. It accepts an input voltage range from 2.7V to 5.5V and maintains a constant current determined by the current through an external RSET resistor. The device supplies up to 80m A of total load current to acmodate any bination of up to three white LEDs, and additional current from VOUT. The switching frequency is set at 500k Hz. (typ.) to keep the conducted noise spectrum away from sensitive frequencies within portable RF devices. By applying a pulse width modulated (PWM) signal to the PWM...
