STLD20D Datasheet | STMicroelectronics

.. ® WHITE LED POWER SUPPLY PRELIMINARY DATA ASD™ Features - - - - - - - - - - - - - - - APPLICATION - - - - High efficiency above 80% Can drive up to 4 LEDs in series from 2.8V supply Constant LED current regulation Integrated LED disconnect switch that cuts the LEDs branch in shutdown mode Constant switching frequency Stable current regulation across the total input voltage range Supply voltage rejection Inherent soft start by limiting the peak inductor current Peak inductor current adjustability (STLD20DC8 only) Shutdown pin with possibility of PWM dimming control Over voltage and over temperature protection with automatic restart Low shutdown current < 1µA Small external inductor (10µH, height < 2mm) Tiny ceramic external capacitor Can be supplied by a Li-ion battery - VIN range: 2.5Vdc to 5Vdc White Led supply for LCD backlight Mobile phone PDA and organizers Any handsets powered from 2.8V to 4.2V DESCRIPTION The STLD20D is a constant switching frequency boost regulator with specific Features to supply up to 4 white LEDs in series. A stable LED current regulation, from 2.8V to 4.2V, is achieved by sensing the LED current through a low ohmic shunt resistor RLED (see figure 1). The device also includes a supply rejection circuit that prevent any kind of flickering effect on the display during dynamic supply voltage variation. A LED disconnect switch cut the LED branch to reduce the current consumption in shutdown mode. The maximum peak inductor current can be programmed. The STLD20D includes often numerous Features and innovative design circuit that allows getting an efficiency above 80% across the total supply voltage range. Figure 2: Efficiency versus input voltage (ILED=20m A; Tamb=25°C) Efficiency (%) Figure 1: Basic connection VBATT L = 10µH 87 86 Cin = 2.2µF Cout = 1µF 85 84 83 VOUT RSET (- ) RSET ILED = 20m A 82 81 80 79 FB...